Add m-esr52 at 52.6.0

1 files changed, 4133 insertions, 0 deletions

diff --git a/js/src/jsstr.cpp b/js/src/jsstr.cpp
new file mode 100644
index 000000000..32a85dc13
--- /dev/null
+++ b/js/src/jsstr.cpp
@@ -0,0 +1,4133 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "jsstr.h"
+
+#include "mozilla/Attributes.h"
+#include "mozilla/Casting.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/FloatingPoint.h"
+#include "mozilla/PodOperations.h"
+#include "mozilla/Range.h"
+#include "mozilla/TypeTraits.h"
+#include "mozilla/Unused.h"
+
+#include <ctype.h>
+#include <limits>
+#include <string.h>
+
+#include "jsapi.h"
+#include "jsarray.h"
+#include "jsatom.h"
+#include "jsbool.h"
+#include "jscntxt.h"
+#include "jsgc.h"
+#include "jsnum.h"
+#include "jsobj.h"
+#include "jsopcode.h"
+#include "jstypes.h"
+#include "jsutil.h"
+
+#include "builtin/Intl.h"
+#include "builtin/RegExp.h"
+#include "jit/InlinableNatives.h"
+#include "js/Conversions.h"
+#include "js/UniquePtr.h"
+#if ENABLE_INTL_API
+#include "unicode/unorm.h"
+#endif
+#include "vm/GlobalObject.h"
+#include "vm/Interpreter.h"
+#include "vm/Opcodes.h"
+#include "vm/Printer.h"
+#include "vm/RegExpObject.h"
+#include "vm/RegExpStatics.h"
+#include "vm/StringBuffer.h"
+#include "vm/Unicode.h"
+
+#include "vm/Interpreter-inl.h"
+#include "vm/String-inl.h"
+#include "vm/StringObject-inl.h"
+#include "vm/TypeInference-inl.h"
+
+using namespace js;
+using namespace js::gc;
+
+using JS::Symbol;
+using JS::SymbolCode;
+using JS::ToInt32;
+using JS::ToUint32;
+
+using mozilla::AssertedCast;
+using mozilla::CheckedInt;
+using mozilla::IsNaN;
+using mozilla::IsNegativeZero;
+using mozilla::IsSame;
+using mozilla::Move;
+using mozilla::PodCopy;
+using mozilla::PodEqual;
+using mozilla::RangedPtr;
+
+using JS::AutoCheckCannotGC;
+
+static JSLinearString*
+ArgToRootedString(JSContext* cx, const CallArgs& args, unsigned argno)
+{
+    if (argno >= args.length())
+        return cx->names().undefined;
+
+    JSString* str = ToString<CanGC>(cx, args[argno]);
+    if (!str)
+        return nullptr;
+
+    args[argno].setString(str);
+    return str->ensureLinear(cx);
+}
+
+/*
+ * Forward declarations for URI encode/decode and helper routines
+ */
+static bool
+str_decodeURI(JSContext* cx, unsigned argc, Value* vp);
+
+static bool
+str_decodeURI_Component(JSContext* cx, unsigned argc, Value* vp);
+
+static bool
+str_encodeURI(JSContext* cx, unsigned argc, Value* vp);
+
+static bool
+str_encodeURI_Component(JSContext* cx, unsigned argc, Value* vp);
+
+/*
+ * Global string methods
+ */
+
+
+/* ES5 B.2.1 */
+template <typename CharT>
+static Latin1Char*
+Escape(JSContext* cx, const CharT* chars, uint32_t length, uint32_t* newLengthOut)
+{
+    static const uint8_t shouldPassThrough[128] = {
+         0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+         0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+         0,0,0,0,0,0,0,0,0,0,1,1,0,1,1,1,       /*    !"#$%&'()*+,-./  */
+         1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,       /*   0123456789:;<=>?  */
+         1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,       /*   @ABCDEFGHIJKLMNO  */
+         1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,1,       /*   PQRSTUVWXYZ[\]^_  */
+         0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,       /*   `abcdefghijklmno  */
+         1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,       /*   pqrstuvwxyz{\}~  DEL */
+    };
+
+    /* Take a first pass and see how big the result string will need to be. */
+    uint32_t newLength = length;
+    for (size_t i = 0; i < length; i++) {
+        char16_t ch = chars[i];
+        if (ch < 128 && shouldPassThrough[ch])
+            continue;
+
+        /* The character will be encoded as %XX or %uXXXX. */
+        newLength += (ch < 256) ? 2 : 5;
+
+        /*
+         * newlength is incremented by at most 5 on each iteration, so worst
+         * case newlength == length * 6. This can't overflow.
+         */
+        static_assert(JSString::MAX_LENGTH < UINT32_MAX / 6,
+                      "newlength must not overflow");
+    }
+
+    Latin1Char* newChars = cx->pod_malloc<Latin1Char>(newLength + 1);
+    if (!newChars)
+        return nullptr;
+
+    static const char digits[] = "0123456789ABCDEF";
+
+    size_t i, ni;
+    for (i = 0, ni = 0; i < length; i++) {
+        char16_t ch = chars[i];
+        if (ch < 128 && shouldPassThrough[ch]) {
+            newChars[ni++] = ch;
+        } else if (ch < 256) {
+            newChars[ni++] = '%';
+            newChars[ni++] = digits[ch >> 4];
+            newChars[ni++] = digits[ch & 0xF];
+        } else {
+            newChars[ni++] = '%';
+            newChars[ni++] = 'u';
+            newChars[ni++] = digits[ch >> 12];
+            newChars[ni++] = digits[(ch & 0xF00) >> 8];
+            newChars[ni++] = digits[(ch & 0xF0) >> 4];
+            newChars[ni++] = digits[ch & 0xF];
+        }
+    }
+    MOZ_ASSERT(ni == newLength);
+    newChars[newLength] = 0;
+
+    *newLengthOut = newLength;
+    return newChars;
+}
+
+static bool
+str_escape(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    JSLinearString* str = ArgToRootedString(cx, args, 0);
+    if (!str)
+        return false;
+
+    ScopedJSFreePtr<Latin1Char> newChars;
+    uint32_t newLength = 0;  // initialize to silence GCC warning
+    if (str->hasLatin1Chars()) {
+        AutoCheckCannotGC nogc;
+        newChars = Escape(cx, str->latin1Chars(nogc), str->length(), &newLength);
+    } else {
+        AutoCheckCannotGC nogc;
+        newChars = Escape(cx, str->twoByteChars(nogc), str->length(), &newLength);
+    }
+
+    if (!newChars)
+        return false;
+
+    JSString* res = NewString<CanGC>(cx, newChars.get(), newLength);
+    if (!res)
+        return false;
+
+    newChars.forget();
+    args.rval().setString(res);
+    return true;
+}
+
+template <typename CharT>
+static inline bool
+Unhex4(const RangedPtr<const CharT> chars, char16_t* result)
+{
+    char16_t a = chars[0],
+             b = chars[1],
+             c = chars[2],
+             d = chars[3];
+
+    if (!(JS7_ISHEX(a) && JS7_ISHEX(b) && JS7_ISHEX(c) && JS7_ISHEX(d)))
+        return false;
+
+    *result = (((((JS7_UNHEX(a) << 4) + JS7_UNHEX(b)) << 4) + JS7_UNHEX(c)) << 4) + JS7_UNHEX(d);
+    return true;
+}
+
+template <typename CharT>
+static inline bool
+Unhex2(const RangedPtr<const CharT> chars, char16_t* result)
+{
+    char16_t a = chars[0],
+             b = chars[1];
+
+    if (!(JS7_ISHEX(a) && JS7_ISHEX(b)))
+        return false;
+
+    *result = (JS7_UNHEX(a) << 4) + JS7_UNHEX(b);
+    return true;
+}
+
+template <typename CharT>
+static bool
+Unescape(StringBuffer& sb, const mozilla::Range<const CharT> chars)
+{
+    /*
+     * NB: use signed integers for length/index to allow simple length
+     * comparisons without unsigned-underflow hazards.
+     */
+    static_assert(JSString::MAX_LENGTH <= INT_MAX, "String length must fit in a signed integer");
+    int length = AssertedCast<int>(chars.length());
+
+    /*
+     * Note that the spec algorithm has been optimized to avoid building
+     * a string in the case where no escapes are present.
+     */
+
+    /* Step 4. */
+    int k = 0;
+    bool building = false;
+
+    /* Step 5. */
+    while (k < length) {
+        /* Step 6. */
+        char16_t c = chars[k];
+
+        /* Step 7. */
+        if (c != '%')
+            goto step_18;
+
+        /* Step 8. */
+        if (k > length - 6)
+            goto step_14;
+
+        /* Step 9. */
+        if (chars[k + 1] != 'u')
+            goto step_14;
+
+#define ENSURE_BUILDING                                      \
+        do {                                                 \
+            if (!building) {                                 \
+                building = true;                             \
+                if (!sb.reserve(length))                     \
+                    return false;                            \
+                sb.infallibleAppend(chars.begin().get(), k); \
+            }                                                \
+        } while(false);
+
+        /* Step 10-13. */
+        if (Unhex4(chars.begin() + k + 2, &c)) {
+            ENSURE_BUILDING;
+            k += 5;
+            goto step_18;
+        }
+
+      step_14:
+        /* Step 14. */
+        if (k > length - 3)
+            goto step_18;
+
+        /* Step 15-17. */
+        if (Unhex2(chars.begin() + k + 1, &c)) {
+            ENSURE_BUILDING;
+            k += 2;
+        }
+
+      step_18:
+        if (building && !sb.append(c))
+            return false;
+
+        /* Step 19. */
+        k += 1;
+    }
+
+    return true;
+#undef ENSURE_BUILDING
+}
+
+/* ES5 B.2.2 */
+static bool
+str_unescape(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    /* Step 1. */
+    RootedLinearString str(cx, ArgToRootedString(cx, args, 0));
+    if (!str)
+        return false;
+
+    /* Step 3. */
+    StringBuffer sb(cx);
+    if (str->hasTwoByteChars() && !sb.ensureTwoByteChars())
+        return false;
+
+    if (str->hasLatin1Chars()) {
+        AutoCheckCannotGC nogc;
+        if (!Unescape(sb, str->latin1Range(nogc)))
+            return false;
+    } else {
+        AutoCheckCannotGC nogc;
+        if (!Unescape(sb, str->twoByteRange(nogc)))
+            return false;
+    }
+
+    JSLinearString* result;
+    if (!sb.empty()) {
+        result = sb.finishString();
+        if (!result)
+            return false;
+    } else {
+        result = str;
+    }
+
+    args.rval().setString(result);
+    return true;
+}
+
+#if JS_HAS_UNEVAL
+static bool
+str_uneval(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    JSString* str = ValueToSource(cx, args.get(0));
+    if (!str)
+        return false;
+
+    args.rval().setString(str);
+    return true;
+}
+#endif
+
+static const JSFunctionSpec string_functions[] = {
+    JS_FN(js_escape_str,             str_escape,                1, JSPROP_RESOLVING),
+    JS_FN(js_unescape_str,           str_unescape,              1, JSPROP_RESOLVING),
+#if JS_HAS_UNEVAL
+    JS_FN(js_uneval_str,             str_uneval,                1, JSPROP_RESOLVING),
+#endif
+    JS_FN(js_decodeURI_str,          str_decodeURI,             1, JSPROP_RESOLVING),
+    JS_FN(js_encodeURI_str,          str_encodeURI,             1, JSPROP_RESOLVING),
+    JS_FN(js_decodeURIComponent_str, str_decodeURI_Component,   1, JSPROP_RESOLVING),
+    JS_FN(js_encodeURIComponent_str, str_encodeURI_Component,   1, JSPROP_RESOLVING),
+
+    JS_FS_END
+};
+
+static const unsigned STRING_ELEMENT_ATTRS = JSPROP_ENUMERATE | JSPROP_READONLY | JSPROP_PERMANENT;
+
+static bool
+str_enumerate(JSContext* cx, HandleObject obj)
+{
+    RootedString str(cx, obj->as<StringObject>().unbox());
+    RootedValue value(cx);
+    for (size_t i = 0, length = str->length(); i < length; i++) {
+        JSString* str1 = NewDependentString(cx, str, i, 1);
+        if (!str1)
+            return false;
+        value.setString(str1);
+        if (!DefineElement(cx, obj, i, value, nullptr, nullptr,
+                           STRING_ELEMENT_ATTRS | JSPROP_RESOLVING))
+        {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+static bool
+str_mayResolve(const JSAtomState&, jsid id, JSObject*)
+{
+    // str_resolve ignores non-integer ids.
+    return JSID_IS_INT(id);
+}
+
+static bool
+str_resolve(JSContext* cx, HandleObject obj, HandleId id, bool* resolvedp)
+{
+    if (!JSID_IS_INT(id))
+        return true;
+
+    RootedString str(cx, obj->as<StringObject>().unbox());
+
+    int32_t slot = JSID_TO_INT(id);
+    if ((size_t)slot < str->length()) {
+        JSString* str1 = cx->staticStrings().getUnitStringForElement(cx, str, size_t(slot));
+        if (!str1)
+            return false;
+        RootedValue value(cx, StringValue(str1));
+        if (!DefineElement(cx, obj, uint32_t(slot), value, nullptr, nullptr,
+                           STRING_ELEMENT_ATTRS | JSPROP_RESOLVING))
+        {
+            return false;
+        }
+        *resolvedp = true;
+    }
+    return true;
+}
+
+static const ClassOps StringObjectClassOps = {
+    nullptr, /* addProperty */
+    nullptr, /* delProperty */
+    nullptr, /* getProperty */
+    nullptr, /* setProperty */
+    str_enumerate,
+    str_resolve,
+    str_mayResolve
+};
+
+const Class StringObject::class_ = {
+    js_String_str,
+    JSCLASS_HAS_RESERVED_SLOTS(StringObject::RESERVED_SLOTS) |
+    JSCLASS_HAS_CACHED_PROTO(JSProto_String),
+    &StringObjectClassOps
+};
+
+/*
+ * Perform the initial |RequireObjectCoercible(thisv)| and |ToString(thisv)|
+ * from nearly all String.prototype.* functions.
+ */
+static MOZ_ALWAYS_INLINE JSString*
+ToStringForStringFunction(JSContext* cx, HandleValue thisv)
+{
+    JS_CHECK_RECURSION(cx, return nullptr);
+
+    if (thisv.isString())
+        return thisv.toString();
+
+    if (thisv.isObject()) {
+        RootedObject obj(cx, &thisv.toObject());
+        if (obj->is<StringObject>()) {
+            StringObject* nobj = &obj->as<StringObject>();
+            Rooted<jsid> id(cx, NameToId(cx->names().toString));
+            if (ClassMethodIsNative(cx, nobj, &StringObject::class_, id, str_toString))
+                return nobj->unbox();
+        }
+    } else if (thisv.isNullOrUndefined()) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_CANT_CONVERT_TO,
+                                  thisv.isNull() ? "null" : "undefined", "object");
+        return nullptr;
+    }
+
+    return ToStringSlow<CanGC>(cx, thisv);
+}
+
+MOZ_ALWAYS_INLINE bool
+IsString(HandleValue v)
+{
+    return v.isString() || (v.isObject() && v.toObject().is<StringObject>());
+}
+
+#if JS_HAS_TOSOURCE
+
+MOZ_ALWAYS_INLINE bool
+str_toSource_impl(JSContext* cx, const CallArgs& args)
+{
+    MOZ_ASSERT(IsString(args.thisv()));
+
+    Rooted<JSString*> str(cx, ToString<CanGC>(cx, args.thisv()));
+    if (!str)
+        return false;
+
+    str = QuoteString(cx, str, '"');
+    if (!str)
+        return false;
+
+    StringBuffer sb(cx);
+    if (!sb.append("(new String(") || !sb.append(str) || !sb.append("))"))
+        return false;
+
+    str = sb.finishString();
+    if (!str)
+        return false;
+    args.rval().setString(str);
+    return true;
+}
+
+static bool
+str_toSource(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    return CallNonGenericMethod<IsString, str_toSource_impl>(cx, args);
+}
+
+#endif /* JS_HAS_TOSOURCE */
+
+MOZ_ALWAYS_INLINE bool
+str_toString_impl(JSContext* cx, const CallArgs& args)
+{
+    MOZ_ASSERT(IsString(args.thisv()));
+
+    args.rval().setString(args.thisv().isString()
+                              ? args.thisv().toString()
+                              : args.thisv().toObject().as<StringObject>().unbox());
+    return true;
+}
+
+bool
+js::str_toString(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    return CallNonGenericMethod<IsString, str_toString_impl>(cx, args);
+}
+
+/*
+ * Java-like string native methods.
+ */
+
+JSString*
+js::SubstringKernel(JSContext* cx, HandleString str, int32_t beginInt, int32_t lengthInt)
+{
+    MOZ_ASSERT(0 <= beginInt);
+    MOZ_ASSERT(0 <= lengthInt);
+    MOZ_ASSERT(uint32_t(beginInt) <= str->length());
+    MOZ_ASSERT(uint32_t(lengthInt) <= str->length() - beginInt);
+
+    uint32_t begin = beginInt;
+    uint32_t len = lengthInt;
+
+    /*
+     * Optimization for one level deep ropes.
+     * This is common for the following pattern:
+     *
+     * while() {
+     *   text = text.substr(0, x) + "bla" + text.substr(x)
+     *   test.charCodeAt(x + 1)
+     * }
+     */
+    if (str->isRope()) {
+        JSRope* rope = &str->asRope();
+
+        /* Substring is totally in leftChild of rope. */
+        if (begin + len <= rope->leftChild()->length())
+            return NewDependentString(cx, rope->leftChild(), begin, len);
+
+        /* Substring is totally in rightChild of rope. */
+        if (begin >= rope->leftChild()->length()) {
+            begin -= rope->leftChild()->length();
+            return NewDependentString(cx, rope->rightChild(), begin, len);
+        }
+
+        /*
+         * Requested substring is partly in the left and partly in right child.
+         * Create a rope of substrings for both childs.
+         */
+        MOZ_ASSERT(begin < rope->leftChild()->length() &&
+                   begin + len > rope->leftChild()->length());
+
+        size_t lhsLength = rope->leftChild()->length() - begin;
+        size_t rhsLength = begin + len - rope->leftChild()->length();
+
+        Rooted<JSRope*> ropeRoot(cx, rope);
+        RootedString lhs(cx, NewDependentString(cx, ropeRoot->leftChild(), begin, lhsLength));
+        if (!lhs)
+            return nullptr;
+
+        RootedString rhs(cx, NewDependentString(cx, ropeRoot->rightChild(), 0, rhsLength));
+        if (!rhs)
+            return nullptr;
+
+        return JSRope::new_<CanGC>(cx, lhs, rhs, len);
+    }
+
+    return NewDependentString(cx, str, begin, len);
+}
+
+template <typename CharT>
+static JSString*
+ToLowerCase(JSContext* cx, JSLinearString* str)
+{
+    // Unlike toUpperCase, toLowerCase has the nice invariant that if the input
+    // is a Latin1 string, the output is also a Latin1 string.
+    UniquePtr<CharT[], JS::FreePolicy> newChars;
+    size_t length = str->length();
+    {
+        AutoCheckCannotGC nogc;
+        const CharT* chars = str->chars<CharT>(nogc);
+
+        // Look for the first upper case character.
+        size_t i = 0;
+        for (; i < length; i++) {
+            char16_t c = chars[i];
+            if (!IsSame<CharT, Latin1Char>::value) {
+                if (unicode::IsLeadSurrogate(c) && i + 1 < length) {
+                    char16_t trail = chars[i + 1];
+                    if (unicode::IsTrailSurrogate(trail)) {
+                        if (unicode::CanLowerCaseNonBMP(c, trail))
+                            break;
+
+                        i++;
+                        continue;
+                    }
+                }
+            }
+            if (unicode::CanLowerCase(c))
+                break;
+        }
+
+        // If all characters are lower case, return the input string.
+        if (i == length)
+            return str;
+
+        newChars = cx->make_pod_array<CharT>(length + 1);
+        if (!newChars)
+            return nullptr;
+
+        PodCopy(newChars.get(), chars, i);
+
+        for (; i < length; i++) {
+            char16_t c = chars[i];
+            if (!IsSame<CharT, Latin1Char>::value) {
+                if (unicode::IsLeadSurrogate(c) && i + 1 < length) {
+                    char16_t trail = chars[i + 1];
+                    if (unicode::IsTrailSurrogate(trail)) {
+                        trail = unicode::ToLowerCaseNonBMPTrail(c, trail);
+                        newChars[i] = c;
+                        newChars[i + 1] = trail;
+                        i++;
+                        continue;
+                    }
+                }
+            }
+
+            c = unicode::ToLowerCase(c);
+            MOZ_ASSERT_IF((IsSame<CharT, Latin1Char>::value), c <= JSString::MAX_LATIN1_CHAR);
+            newChars[i] = c;
+        }
+
+        newChars[length] = 0;
+    }
+
+    JSString* res = NewStringDontDeflate<CanGC>(cx, newChars.get(), length);
+    if (!res)
+        return nullptr;
+
+    mozilla::Unused << newChars.release();
+    return res;
+}
+
+static inline bool
+ToLowerCaseHelper(JSContext* cx, const CallArgs& args)
+{
+    RootedString str(cx, ToStringForStringFunction(cx, args.thisv()));
+    if (!str)
+        return false;
+
+    JSLinearString* linear = str->ensureLinear(cx);
+    if (!linear)
+        return false;
+
+    if (linear->hasLatin1Chars())
+        str = ToLowerCase<Latin1Char>(cx, linear);
+    else
+        str = ToLowerCase<char16_t>(cx, linear);
+    if (!str)
+        return false;
+
+    args.rval().setString(str);
+    return true;
+}
+
+bool
+js::str_toLowerCase(JSContext* cx, unsigned argc, Value* vp)
+{
+    return ToLowerCaseHelper(cx, CallArgsFromVp(argc, vp));
+}
+
+bool
+js::str_toLocaleLowerCase(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    /*
+     * Forcefully ignore the first (or any) argument and return toLowerCase(),
+     * ECMA has reserved that argument, presumably for defining the locale.
+     */
+    if (cx->runtime()->localeCallbacks && cx->runtime()->localeCallbacks->localeToLowerCase) {
+        RootedString str(cx, ToStringForStringFunction(cx, args.thisv()));
+        if (!str)
+            return false;
+
+        RootedValue result(cx);
+        if (!cx->runtime()->localeCallbacks->localeToLowerCase(cx, str, &result))
+            return false;
+
+        args.rval().set(result);
+        return true;
+    }
+
+    return ToLowerCaseHelper(cx, args);
+}
+
+template <typename DestChar, typename SrcChar>
+static void
+ToUpperCaseImpl(DestChar* destChars, const SrcChar* srcChars, size_t firstLowerCase, size_t length)
+{
+    MOZ_ASSERT(firstLowerCase < length);
+
+    for (size_t i = 0; i < firstLowerCase; i++)
+        destChars[i] = srcChars[i];
+
+    for (size_t i = firstLowerCase; i < length; i++) {
+        char16_t c = srcChars[i];
+        if (!IsSame<DestChar, Latin1Char>::value) {
+            if (unicode::IsLeadSurrogate(c) && i + 1 < length) {
+                char16_t trail = srcChars[i + 1];
+                if (unicode::IsTrailSurrogate(trail)) {
+                    trail = unicode::ToUpperCaseNonBMPTrail(c, trail);
+                    destChars[i] = c;
+                    destChars[i + 1] = trail;
+                    i++;
+                    continue;
+                }
+            }
+        }
+        c = unicode::ToUpperCase(c);
+        MOZ_ASSERT_IF((IsSame<DestChar, Latin1Char>::value), c <= JSString::MAX_LATIN1_CHAR);
+        destChars[i] = c;
+    }
+
+    destChars[length] = '\0';
+}
+
+template <typename CharT>
+static JSString*
+ToUpperCase(JSContext* cx, JSLinearString* str)
+{
+    typedef UniquePtr<Latin1Char[], JS::FreePolicy> Latin1CharPtr;
+    typedef UniquePtr<char16_t[], JS::FreePolicy> TwoByteCharPtr;
+
+    mozilla::MaybeOneOf<Latin1CharPtr, TwoByteCharPtr> newChars;
+    size_t length = str->length();
+    {
+        AutoCheckCannotGC nogc;
+        const CharT* chars = str->chars<CharT>(nogc);
+
+        // Look for the first lower case character.
+        size_t i = 0;
+        for (; i < length; i++) {
+            char16_t c = chars[i];
+            if (!IsSame<CharT, Latin1Char>::value) {
+                if (unicode::IsLeadSurrogate(c) && i + 1 < length) {
+                    char16_t trail = chars[i + 1];
+                    if (unicode::IsTrailSurrogate(trail)) {
+                        if (unicode::CanUpperCaseNonBMP(c, trail))
+                            break;
+
+                        i++;
+                        continue;
+                    }
+                }
+            }
+            if (unicode::CanUpperCase(c))
+                break;
+        }
+
+        // If all characters are upper case, return the input string.
+        if (i == length)
+            return str;
+
+        // If the string is Latin1, check if it contains the MICRO SIGN (0xb5)
+        // or SMALL LETTER Y WITH DIAERESIS (0xff) character. The corresponding
+        // upper case characters are not in the Latin1 range.
+        bool resultIsLatin1;
+        if (IsSame<CharT, Latin1Char>::value) {
+            resultIsLatin1 = true;
+            for (size_t j = i; j < length; j++) {
+                Latin1Char c = chars[j];
+                if (c == 0xb5 || c == 0xff) {
+                    MOZ_ASSERT(unicode::ToUpperCase(c) > JSString::MAX_LATIN1_CHAR);
+                    resultIsLatin1 = false;
+                    break;
+                } else {
+                    MOZ_ASSERT(unicode::ToUpperCase(c) <= JSString::MAX_LATIN1_CHAR);
+                }
+            }
+        } else {
+            resultIsLatin1 = false;
+        }
+
+        if (resultIsLatin1) {
+            Latin1CharPtr buf = cx->make_pod_array<Latin1Char>(length + 1);
+            if (!buf)
+                return nullptr;
+
+            ToUpperCaseImpl(buf.get(), chars, i, length);
+            newChars.construct<Latin1CharPtr>(Move(buf));
+        } else {
+            TwoByteCharPtr buf = cx->make_pod_array<char16_t>(length + 1);
+            if (!buf)
+                return nullptr;
+
+            ToUpperCaseImpl(buf.get(), chars, i, length);
+            newChars.construct<TwoByteCharPtr>(Move(buf));
+        }
+    }
+
+    JSString* res;
+    if (newChars.constructed<Latin1CharPtr>()) {
+        res = NewStringDontDeflate<CanGC>(cx, newChars.ref<Latin1CharPtr>().get(), length);
+        if (!res)
+            return nullptr;
+
+        mozilla::Unused << newChars.ref<Latin1CharPtr>().release();
+    } else {
+        res = NewStringDontDeflate<CanGC>(cx, newChars.ref<TwoByteCharPtr>().get(), length);
+        if (!res)
+            return nullptr;
+
+        mozilla::Unused << newChars.ref<TwoByteCharPtr>().release();
+    }
+
+    return res;
+}
+
+static bool
+ToUpperCaseHelper(JSContext* cx, const CallArgs& args)
+{
+    RootedString str(cx, ToStringForStringFunction(cx, args.thisv()));
+    if (!str)
+        return false;
+
+    JSLinearString* linear = str->ensureLinear(cx);
+    if (!linear)
+        return false;
+
+    if (linear->hasLatin1Chars())
+        str = ToUpperCase<Latin1Char>(cx, linear);
+    else
+        str = ToUpperCase<char16_t>(cx, linear);
+    if (!str)
+        return false;
+
+    args.rval().setString(str);
+    return true;
+}
+
+bool
+js::str_toUpperCase(JSContext* cx, unsigned argc, Value* vp)
+{
+    return ToUpperCaseHelper(cx, CallArgsFromVp(argc, vp));
+}
+
+bool
+js::str_toLocaleUpperCase(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    /*
+     * Forcefully ignore the first (or any) argument and return toUpperCase(),
+     * ECMA has reserved that argument, presumably for defining the locale.
+     */
+    if (cx->runtime()->localeCallbacks && cx->runtime()->localeCallbacks->localeToUpperCase) {
+        RootedString str(cx, ToStringForStringFunction(cx, args.thisv()));
+        if (!str)
+            return false;
+
+        RootedValue result(cx);
+        if (!cx->runtime()->localeCallbacks->localeToUpperCase(cx, str, &result))
+            return false;
+
+        args.rval().set(result);
+        return true;
+    }
+
+    return ToUpperCaseHelper(cx, args);
+}
+
+#if !EXPOSE_INTL_API
+bool
+js::str_localeCompare(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    RootedString str(cx, ToStringForStringFunction(cx, args.thisv()));
+    if (!str)
+        return false;
+
+    RootedString thatStr(cx, ToString<CanGC>(cx, args.get(0)));
+    if (!thatStr)
+        return false;
+
+    if (cx->runtime()->localeCallbacks && cx->runtime()->localeCallbacks->localeCompare) {
+        RootedValue result(cx);
+        if (!cx->runtime()->localeCallbacks->localeCompare(cx, str, thatStr, &result))
+            return false;
+
+        args.rval().set(result);
+        return true;
+    }
+
+    int32_t result;
+    if (!CompareStrings(cx, str, thatStr, &result))
+        return false;
+
+    args.rval().setInt32(result);
+    return true;
+}
+#endif
+
+#if EXPOSE_INTL_API
+/* ES6 20140210 draft 21.1.3.12. */
+bool
+js::str_normalize(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    // Steps 1-3.
+    RootedString str(cx, ToStringForStringFunction(cx, args.thisv()));
+    if (!str)
+        return false;
+
+    // Step 4.
+    UNormalizationMode form;
+    if (!args.hasDefined(0)) {
+        form = UNORM_NFC;
+    } else {
+        // Steps 5-6.
+        RootedLinearString formStr(cx, ArgToRootedString(cx, args, 0));
+        if (!formStr)
+            return false;
+
+        // Step 7.
+        if (EqualStrings(formStr, cx->names().NFC)) {
+            form = UNORM_NFC;
+        } else if (EqualStrings(formStr, cx->names().NFD)) {
+            form = UNORM_NFD;
+        } else if (EqualStrings(formStr, cx->names().NFKC)) {
+            form = UNORM_NFKC;
+        } else if (EqualStrings(formStr, cx->names().NFKD)) {
+            form = UNORM_NFKD;
+        } else {
+            JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INVALID_NORMALIZE_FORM);
+            return false;
+        }
+    }
+
+    // Step 8.
+    AutoStableStringChars stableChars(cx);
+    if (!str->ensureFlat(cx) || !stableChars.initTwoByte(cx, str))
+        return false;
+
+    static const size_t INLINE_CAPACITY = 32;
+
+    const UChar* srcChars = Char16ToUChar(stableChars.twoByteRange().begin().get());
+    int32_t srcLen = AssertedCast<int32_t>(str->length());
+    Vector<char16_t, INLINE_CAPACITY> chars(cx);
+    if (!chars.resize(INLINE_CAPACITY))
+        return false;
+
+    UErrorCode status = U_ZERO_ERROR;
+    int32_t size = unorm_normalize(srcChars, srcLen, form, 0,
+                                   Char16ToUChar(chars.begin()), INLINE_CAPACITY,
+                                   &status);
+    if (status == U_BUFFER_OVERFLOW_ERROR) {
+        if (!chars.resize(size))
+            return false;
+        status = U_ZERO_ERROR;
+#ifdef DEBUG
+        int32_t finalSize =
+#endif
+        unorm_normalize(srcChars, srcLen, form, 0,
+                        Char16ToUChar(chars.begin()), size,
+                        &status);
+        MOZ_ASSERT(size == finalSize || U_FAILURE(status), "unorm_normalize behaved inconsistently");
+    }
+    if (U_FAILURE(status))
+        return false;
+
+    JSString* ns = NewStringCopyN<CanGC>(cx, chars.begin(), size);
+    if (!ns)
+        return false;
+
+    // Step 9.
+    args.rval().setString(ns);
+    return true;
+}
+#endif
+
+bool
+js::str_charAt(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    RootedString str(cx);
+    size_t i;
+    if (args.thisv().isString() && args.length() != 0 && args[0].isInt32()) {
+        str = args.thisv().toString();
+        i = size_t(args[0].toInt32());
+        if (i >= str->length())
+            goto out_of_range;
+    } else {
+        str = ToStringForStringFunction(cx, args.thisv());
+        if (!str)
+            return false;
+
+        double d = 0.0;
+        if (args.length() > 0 && !ToInteger(cx, args[0], &d))
+            return false;
+
+        if (d < 0 || str->length() <= d)
+            goto out_of_range;
+        i = size_t(d);
+    }
+
+    str = cx->staticStrings().getUnitStringForElement(cx, str, i);
+    if (!str)
+        return false;
+    args.rval().setString(str);
+    return true;
+
+  out_of_range:
+    args.rval().setString(cx->runtime()->emptyString);
+    return true;
+}
+
+bool
+js::str_charCodeAt_impl(JSContext* cx, HandleString string, HandleValue index, MutableHandleValue res)
+{
+    RootedString str(cx);
+    size_t i;
+    if (index.isInt32()) {
+        i = index.toInt32();
+        if (i >= string->length())
+            goto out_of_range;
+    } else {
+        double d = 0.0;
+        if (!ToInteger(cx, index, &d))
+            return false;
+        // check whether d is negative as size_t is unsigned
+        if (d < 0 || string->length() <= d )
+            goto out_of_range;
+        i = size_t(d);
+    }
+    char16_t c;
+    if (!string->getChar(cx, i , &c))
+        return false;
+    res.setInt32(c);
+    return true;
+
+out_of_range:
+    res.setNaN();
+    return true;
+}
+
+bool
+js::str_charCodeAt(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    RootedString str(cx);
+    RootedValue index(cx);
+    if (args.thisv().isString()) {
+        str = args.thisv().toString();
+    } else {
+        str = ToStringForStringFunction(cx, args.thisv());
+        if (!str)
+            return false;
+    }
+    if (args.length() != 0)
+        index = args[0];
+    else
+        index.setInt32(0);
+
+    return js::str_charCodeAt_impl(cx, str, index, args.rval());
+}
+
+/*
+ * Boyer-Moore-Horspool superlinear search for pat:patlen in text:textlen.
+ * The patlen argument must be positive and no greater than sBMHPatLenMax.
+ *
+ * Return the index of pat in text, or -1 if not found.
+ */
+static const uint32_t sBMHCharSetSize = 256; /* ISO-Latin-1 */
+static const uint32_t sBMHPatLenMax   = 255; /* skip table element is uint8_t */
+static const int      sBMHBadPattern  = -2;  /* return value if pat is not ISO-Latin-1 */
+
+template <typename TextChar, typename PatChar>
+static int
+BoyerMooreHorspool(const TextChar* text, uint32_t textLen, const PatChar* pat, uint32_t patLen)
+{
+    MOZ_ASSERT(0 < patLen && patLen <= sBMHPatLenMax);
+
+    uint8_t skip[sBMHCharSetSize];
+    for (uint32_t i = 0; i < sBMHCharSetSize; i++)
+        skip[i] = uint8_t(patLen);
+
+    uint32_t patLast = patLen - 1;
+    for (uint32_t i = 0; i < patLast; i++) {
+        char16_t c = pat[i];
+        if (c >= sBMHCharSetSize)
+            return sBMHBadPattern;
+        skip[c] = uint8_t(patLast - i);
+    }
+
+    for (uint32_t k = patLast; k < textLen; ) {
+        for (uint32_t i = k, j = patLast; ; i--, j--) {
+            if (text[i] != pat[j])
+                break;
+            if (j == 0)
+                return static_cast<int>(i);  /* safe: max string size */
+        }
+
+        char16_t c = text[k];
+        k += (c >= sBMHCharSetSize) ? patLen : skip[c];
+    }
+    return -1;
+}
+
+template <typename TextChar, typename PatChar>
+struct MemCmp {
+    typedef uint32_t Extent;
+    static MOZ_ALWAYS_INLINE Extent computeExtent(const PatChar*, uint32_t patLen) {
+        return (patLen - 1) * sizeof(PatChar);
+    }
+    static MOZ_ALWAYS_INLINE bool match(const PatChar* p, const TextChar* t, Extent extent) {
+        MOZ_ASSERT(sizeof(TextChar) == sizeof(PatChar));
+        return memcmp(p, t, extent) == 0;
+    }
+};
+
+template <typename TextChar, typename PatChar>
+struct ManualCmp {
+    typedef const PatChar* Extent;
+    static MOZ_ALWAYS_INLINE Extent computeExtent(const PatChar* pat, uint32_t patLen) {
+        return pat + patLen;
+    }
+    static MOZ_ALWAYS_INLINE bool match(const PatChar* p, const TextChar* t, Extent extent) {
+        for (; p != extent; ++p, ++t) {
+            if (*p != *t)
+                return false;
+        }
+        return true;
+    }
+};
+
+template <typename TextChar, typename PatChar>
+static const TextChar*
+FirstCharMatcherUnrolled(const TextChar* text, uint32_t n, const PatChar pat)
+{
+    const TextChar* textend = text + n;
+    const TextChar* t = text;
+
+    switch ((textend - t) & 7) {
+        case 0: if (*t++ == pat) return t - 1; MOZ_FALLTHROUGH;
+        case 7: if (*t++ == pat) return t - 1; MOZ_FALLTHROUGH;
+        case 6: if (*t++ == pat) return t - 1; MOZ_FALLTHROUGH;
+        case 5: if (*t++ == pat) return t - 1; MOZ_FALLTHROUGH;
+        case 4: if (*t++ == pat) return t - 1; MOZ_FALLTHROUGH;
+        case 3: if (*t++ == pat) return t - 1; MOZ_FALLTHROUGH;
+        case 2: if (*t++ == pat) return t - 1; MOZ_FALLTHROUGH;
+        case 1: if (*t++ == pat) return t - 1;
+    }
+    while (textend != t) {
+        if (t[0] == pat) return t;
+        if (t[1] == pat) return t + 1;
+        if (t[2] == pat) return t + 2;
+        if (t[3] == pat) return t + 3;
+        if (t[4] == pat) return t + 4;
+        if (t[5] == pat) return t + 5;
+        if (t[6] == pat) return t + 6;
+        if (t[7] == pat) return t + 7;
+        t += 8;
+    }
+    return nullptr;
+}
+
+static const char*
+FirstCharMatcher8bit(const char* text, uint32_t n, const char pat)
+{
+#if  defined(__clang__)
+    return FirstCharMatcherUnrolled<char, char>(text, n, pat);
+#else
+    return reinterpret_cast<const char*>(memchr(text, pat, n));
+#endif
+}
+
+static const char16_t*
+FirstCharMatcher16bit(const char16_t* text, uint32_t n, const char16_t pat)
+{
+#if defined(XP_DARWIN) || defined(XP_WIN)
+    /*
+     * Performance of memchr is horrible in OSX. Windows is better,
+     * but it is still better to use UnrolledMatcher.
+     */
+    return FirstCharMatcherUnrolled<char16_t, char16_t>(text, n, pat);
+#else
+    /*
+     * For linux the best performance is obtained by slightly hacking memchr.
+     * memchr works only on 8bit char but char16_t is 16bit. So we treat char16_t
+     * in blocks of 8bit and use memchr.
+     */
+
+    const char* text8 = (const char*) text;
+    const char* pat8 = reinterpret_cast<const char*>(&pat);
+
+    MOZ_ASSERT(n < UINT32_MAX/2);
+    n *= 2;
+
+    uint32_t i = 0;
+    while (i < n) {
+        /* Find the first 8 bits of 16bit character in text. */
+        const char* pos8 = FirstCharMatcher8bit(text8 + i, n - i, pat8[0]);
+        if (pos8 == nullptr)
+            return nullptr;
+        i = static_cast<uint32_t>(pos8 - text8);
+
+        /* Incorrect match if it matches the last 8 bits of 16bit char. */
+        if (i % 2 != 0) {
+            i++;
+            continue;
+        }
+
+        /* Test if last 8 bits match last 8 bits of 16bit char. */
+        if (pat8[1] == text8[i + 1])
+            return (text + (i/2));
+
+        i += 2;
+    }
+    return nullptr;
+#endif
+}
+
+template <class InnerMatch, typename TextChar, typename PatChar>
+static int
+Matcher(const TextChar* text, uint32_t textlen, const PatChar* pat, uint32_t patlen)
+{
+    const typename InnerMatch::Extent extent = InnerMatch::computeExtent(pat, patlen);
+
+    uint32_t i = 0;
+    uint32_t n = textlen - patlen + 1;
+    while (i < n) {
+        const TextChar* pos;
+
+        if (sizeof(TextChar) == 2 && sizeof(PatChar) == 2)
+            pos = (TextChar*) FirstCharMatcher16bit((char16_t*)text + i, n - i, pat[0]);
+        else if (sizeof(TextChar) == 1 && sizeof(PatChar) == 1)
+            pos = (TextChar*) FirstCharMatcher8bit((char*) text + i, n - i, pat[0]);
+        else
+            pos = (TextChar*) FirstCharMatcherUnrolled<TextChar, PatChar>(text + i, n - i, pat[0]);
+
+        if (pos == nullptr)
+            return -1;
+
+        i = static_cast<uint32_t>(pos - text);
+        if (InnerMatch::match(pat + 1, text + i + 1, extent))
+            return i;
+
+        i += 1;
+     }
+     return -1;
+ }
+
+
+template <typename TextChar, typename PatChar>
+static MOZ_ALWAYS_INLINE int
+StringMatch(const TextChar* text, uint32_t textLen, const PatChar* pat, uint32_t patLen)
+{
+    if (patLen == 0)
+        return 0;
+    if (textLen < patLen)
+        return -1;
+
+#if defined(__i386__) || defined(_M_IX86) || defined(__i386)
+    /*
+     * Given enough registers, the unrolled loop below is faster than the
+     * following loop. 32-bit x86 does not have enough registers.
+     */
+    if (patLen == 1) {
+        const PatChar p0 = *pat;
+        const TextChar* end = text + textLen;
+        for (const TextChar* c = text; c != end; ++c) {
+            if (*c == p0)
+                return c - text;
+        }
+        return -1;
+    }
+#endif
+
+    /*
+     * If the text or pattern string is short, BMH will be more expensive than
+     * the basic linear scan due to initialization cost and a more complex loop
+     * body. While the correct threshold is input-dependent, we can make a few
+     * conservative observations:
+     *  - When |textLen| is "big enough", the initialization time will be
+     *    proportionally small, so the worst-case slowdown is minimized.
+     *  - When |patLen| is "too small", even the best case for BMH will be
+     *    slower than a simple scan for large |textLen| due to the more complex
+     *    loop body of BMH.
+     * From this, the values for "big enough" and "too small" are determined
+     * empirically. See bug 526348.
+     */
+    if (textLen >= 512 && patLen >= 11 && patLen <= sBMHPatLenMax) {
+        int index = BoyerMooreHorspool(text, textLen, pat, patLen);
+        if (index != sBMHBadPattern)
+            return index;
+    }
+
+    /*
+     * For big patterns with large potential overlap we want the SIMD-optimized
+     * speed of memcmp. For small patterns, a simple loop is faster. We also can't
+     * use memcmp if one of the strings is TwoByte and the other is Latin1.
+     *
+     * FIXME: Linux memcmp performance is sad and the manual loop is faster.
+     */
+    return
+#if !defined(__linux__)
+        (patLen > 128 && IsSame<TextChar, PatChar>::value)
+            ? Matcher<MemCmp<TextChar, PatChar>, TextChar, PatChar>(text, textLen, pat, patLen)
+            :
+#endif
+              Matcher<ManualCmp<TextChar, PatChar>, TextChar, PatChar>(text, textLen, pat, patLen);
+}
+
+static int32_t
+StringMatch(JSLinearString* text, JSLinearString* pat, uint32_t start = 0)
+{
+    MOZ_ASSERT(start <= text->length());
+    uint32_t textLen = text->length() - start;
+    uint32_t patLen = pat->length();
+
+    int match;
+    AutoCheckCannotGC nogc;
+    if (text->hasLatin1Chars()) {
+        const Latin1Char* textChars = text->latin1Chars(nogc) + start;
+        if (pat->hasLatin1Chars())
+            match = StringMatch(textChars, textLen, pat->latin1Chars(nogc), patLen);
+        else
+            match = StringMatch(textChars, textLen, pat->twoByteChars(nogc), patLen);
+    } else {
+        const char16_t* textChars = text->twoByteChars(nogc) + start;
+        if (pat->hasLatin1Chars())
+            match = StringMatch(textChars, textLen, pat->latin1Chars(nogc), patLen);
+        else
+            match = StringMatch(textChars, textLen, pat->twoByteChars(nogc), patLen);
+    }
+
+    return (match == -1) ? -1 : start + match;
+}
+
+static const size_t sRopeMatchThresholdRatioLog2 = 5;
+
+bool
+js::StringHasPattern(JSLinearString* text, const char16_t* pat, uint32_t patLen)
+{
+    AutoCheckCannotGC nogc;
+    return text->hasLatin1Chars()
+           ? StringMatch(text->latin1Chars(nogc), text->length(), pat, patLen) != -1
+           : StringMatch(text->twoByteChars(nogc), text->length(), pat, patLen) != -1;
+}
+
+int
+js::StringFindPattern(JSLinearString* text, JSLinearString* pat, size_t start)
+{
+    return StringMatch(text, pat, start);
+}
+
+// When an algorithm does not need a string represented as a single linear
+// array of characters, this range utility may be used to traverse the string a
+// sequence of linear arrays of characters. This avoids flattening ropes.
+class StringSegmentRange
+{
+    // If malloc() shows up in any profiles from this vector, we can add a new
+    // StackAllocPolicy which stashes a reusable freed-at-gc buffer in the cx.
+    Rooted<StringVector> stack;
+    RootedLinearString cur;
+
+    bool settle(JSString* str) {
+        while (str->isRope()) {
+            JSRope& rope = str->asRope();
+            if (!stack.append(rope.rightChild()))
+                return false;
+            str = rope.leftChild();
+        }
+        cur = &str->asLinear();
+        return true;
+    }
+
+  public:
+    explicit StringSegmentRange(JSContext* cx)
+      : stack(cx, StringVector(cx)), cur(cx)
+    {}
+
+    MOZ_MUST_USE bool init(JSString* str) {
+        MOZ_ASSERT(stack.empty());
+        return settle(str);
+    }
+
+    bool empty() const {
+        return cur == nullptr;
+    }
+
+    JSLinearString* front() const {
+        MOZ_ASSERT(!cur->isRope());
+        return cur;
+    }
+
+    MOZ_MUST_USE bool popFront() {
+        MOZ_ASSERT(!empty());
+        if (stack.empty()) {
+            cur = nullptr;
+            return true;
+        }
+        return settle(stack.popCopy());
+    }
+};
+
+typedef Vector<JSLinearString*, 16, SystemAllocPolicy> LinearStringVector;
+
+template <typename TextChar, typename PatChar>
+static int
+RopeMatchImpl(const AutoCheckCannotGC& nogc, LinearStringVector& strings,
+              const PatChar* pat, size_t patLen)
+{
+    /* Absolute offset from the beginning of the logical text string. */
+    int pos = 0;
+
+    for (JSLinearString** outerp = strings.begin(); outerp != strings.end(); ++outerp) {
+        /* Try to find a match within 'outer'. */
+        JSLinearString* outer = *outerp;
+        const TextChar* chars = outer->chars<TextChar>(nogc);
+        size_t len = outer->length();
+        int matchResult = StringMatch(chars, len, pat, patLen);
+        if (matchResult != -1) {
+            /* Matched! */
+            return pos + matchResult;
+        }
+
+        /* Try to find a match starting in 'outer' and running into other nodes. */
+        const TextChar* const text = chars + (patLen > len ? 0 : len - patLen + 1);
+        const TextChar* const textend = chars + len;
+        const PatChar p0 = *pat;
+        const PatChar* const p1 = pat + 1;
+        const PatChar* const patend = pat + patLen;
+        for (const TextChar* t = text; t != textend; ) {
+            if (*t++ != p0)
+                continue;
+
+            JSLinearString** innerp = outerp;
+            const TextChar* ttend = textend;
+            const TextChar* tt = t;
+            for (const PatChar* pp = p1; pp != patend; ++pp, ++tt) {
+                while (tt == ttend) {
+                    if (++innerp == strings.end())
+                        return -1;
+
+                    JSLinearString* inner = *innerp;
+                    tt = inner->chars<TextChar>(nogc);
+                    ttend = tt + inner->length();
+                }
+                if (*pp != *tt)
+                    goto break_continue;
+            }
+
+            /* Matched! */
+            return pos + (t - chars) - 1;  /* -1 because of *t++ above */
+
+          break_continue:;
+        }
+
+        pos += len;
+    }
+
+    return -1;
+}
+
+/*
+ * RopeMatch takes the text to search and the pattern to search for in the text.
+ * RopeMatch returns false on OOM and otherwise returns the match index through
+ * the 'match' outparam (-1 for not found).
+ */
+static bool
+RopeMatch(JSContext* cx, JSRope* text, JSLinearString* pat, int* match)
+{
+    uint32_t patLen = pat->length();
+    if (patLen == 0) {
+        *match = 0;
+        return true;
+    }
+    if (text->length() < patLen) {
+        *match = -1;
+        return true;
+    }
+
+    /*
+     * List of leaf nodes in the rope. If we run out of memory when trying to
+     * append to this list, we can still fall back to StringMatch, so use the
+     * system allocator so we don't report OOM in that case.
+     */
+    LinearStringVector strings;
+
+    /*
+     * We don't want to do rope matching if there is a poor node-to-char ratio,
+     * since this means spending a lot of time in the match loop below. We also
+     * need to build the list of leaf nodes. Do both here: iterate over the
+     * nodes so long as there are not too many.
+     *
+     * We also don't use rope matching if the rope contains both Latin1 and
+     * TwoByte nodes, to simplify the match algorithm.
+     */
+    {
+        size_t threshold = text->length() >> sRopeMatchThresholdRatioLog2;
+        StringSegmentRange r(cx);
+        if (!r.init(text))
+            return false;
+
+        bool textIsLatin1 = text->hasLatin1Chars();
+        while (!r.empty()) {
+            if (threshold-- == 0 ||
+                r.front()->hasLatin1Chars() != textIsLatin1 ||
+                !strings.append(r.front()))
+            {
+                JSLinearString* linear = text->ensureLinear(cx);
+                if (!linear)
+                    return false;
+
+                *match = StringMatch(linear, pat);
+                return true;
+            }
+            if (!r.popFront())
+                return false;
+        }
+    }
+
+    AutoCheckCannotGC nogc;
+    if (text->hasLatin1Chars()) {
+        if (pat->hasLatin1Chars())
+            *match = RopeMatchImpl<Latin1Char>(nogc, strings, pat->latin1Chars(nogc), patLen);
+        else
+            *match = RopeMatchImpl<Latin1Char>(nogc, strings, pat->twoByteChars(nogc), patLen);
+    } else {
+        if (pat->hasLatin1Chars())
+            *match = RopeMatchImpl<char16_t>(nogc, strings, pat->latin1Chars(nogc), patLen);
+        else
+            *match = RopeMatchImpl<char16_t>(nogc, strings, pat->twoByteChars(nogc), patLen);
+    }
+
+    return true;
+}
+
+/* ES6 draft rc4 21.1.3.7. */
+bool
+js::str_includes(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    // Steps 1, 2, and 3
+    RootedString str(cx, ToStringForStringFunction(cx, args.thisv()));
+    if (!str)
+        return false;
+
+    // Steps 4 and 5
+    bool isRegExp;
+    if (!IsRegExp(cx, args.get(0), &isRegExp))
+        return false;
+
+    // Step 6
+    if (isRegExp) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INVALID_ARG_TYPE,
+                                  "first", "", "Regular Expression");
+        return false;
+    }
+
+    // Steps 7 and 8
+    RootedLinearString searchStr(cx, ArgToRootedString(cx, args, 0));
+    if (!searchStr)
+        return false;
+
+    // Steps 9 and 10
+    uint32_t pos = 0;
+    if (args.hasDefined(1)) {
+        if (args[1].isInt32()) {
+            int i = args[1].toInt32();
+            pos = (i < 0) ? 0U : uint32_t(i);
+        } else {
+            double d;
+            if (!ToInteger(cx, args[1], &d))
+                return false;
+            pos = uint32_t(Min(Max(d, 0.0), double(UINT32_MAX)));
+        }
+    }
+
+    // Step 11
+    uint32_t textLen = str->length();
+
+    // Step 12
+    uint32_t start = Min(Max(pos, 0U), textLen);
+
+    // Steps 13 and 14
+    JSLinearString* text = str->ensureLinear(cx);
+    if (!text)
+        return false;
+
+    args.rval().setBoolean(StringMatch(text, searchStr, start) != -1);
+    return true;
+}
+
+/* ES6 20120927 draft 15.5.4.7. */
+bool
+js::str_indexOf(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    // Steps 1, 2, and 3
+    RootedString str(cx, ToStringForStringFunction(cx, args.thisv()));
+    if (!str)
+        return false;
+
+    // Steps 4 and 5
+    RootedLinearString searchStr(cx, ArgToRootedString(cx, args, 0));
+    if (!searchStr)
+        return false;
+
+    // Steps 6 and 7
+    uint32_t pos = 0;
+    if (args.hasDefined(1)) {
+        if (args[1].isInt32()) {
+            int i = args[1].toInt32();
+            pos = (i < 0) ? 0U : uint32_t(i);
+        } else {
+            double d;
+            if (!ToInteger(cx, args[1], &d))
+                return false;
+            pos = uint32_t(Min(Max(d, 0.0), double(UINT32_MAX)));
+        }
+    }
+
+   // Step 8
+    uint32_t textLen = str->length();
+
+    // Step 9
+    uint32_t start = Min(Max(pos, 0U), textLen);
+
+    // Steps 10 and 11
+    JSLinearString* text = str->ensureLinear(cx);
+    if (!text)
+        return false;
+
+    args.rval().setInt32(StringMatch(text, searchStr, start));
+    return true;
+}
+
+template <typename TextChar, typename PatChar>
+static int32_t
+LastIndexOfImpl(const TextChar* text, size_t textLen, const PatChar* pat, size_t patLen,
+                size_t start)
+{
+    MOZ_ASSERT(patLen > 0);
+    MOZ_ASSERT(patLen <= textLen);
+    MOZ_ASSERT(start <= textLen - patLen);
+
+    const PatChar p0 = *pat;
+    const PatChar* patNext = pat + 1;
+    const PatChar* patEnd = pat + patLen;
+
+    for (const TextChar* t = text + start; t >= text; --t) {
+        if (*t == p0) {
+            const TextChar* t1 = t + 1;
+            for (const PatChar* p1 = patNext; p1 < patEnd; ++p1, ++t1) {
+                if (*t1 != *p1)
+                    goto break_continue;
+            }
+
+            return static_cast<int32_t>(t - text);
+        }
+      break_continue:;
+    }
+
+    return -1;
+}
+
+// ES2017 draft rev 6859bb9ccaea9c6ede81d71e5320e3833b92cb3e
+// 21.1.3.9 String.prototype.lastIndexOf ( searchString [ , position ] )
+bool
+js::str_lastIndexOf(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    // Steps 1-2.
+    RootedString str(cx, ToStringForStringFunction(cx, args.thisv()));
+    if (!str)
+        return false;
+
+    // Step 3.
+    RootedLinearString searchStr(cx, ArgToRootedString(cx, args, 0));
+    if (!searchStr)
+        return false;
+
+    // Step 6.
+    size_t len = str->length();
+
+    // Step 8.
+    size_t searchLen = searchStr->length();
+
+    // Steps 4-5, 7.
+    int start = len - searchLen; // Start searching here
+    if (args.hasDefined(1)) {
+        if (args[1].isInt32()) {
+            int i = args[1].toInt32();
+            if (i <= 0)
+                start = 0;
+            else if (i < start)
+                start = i;
+        } else {
+            double d;
+            if (!ToNumber(cx, args[1], &d))
+                return false;
+            if (!IsNaN(d)) {
+                d = JS::ToInteger(d);
+                if (d <= 0)
+                    start = 0;
+                else if (d < start)
+                    start = int(d);
+            }
+        }
+    }
+
+    if (searchLen > len) {
+        args.rval().setInt32(-1);
+        return true;
+    }
+
+    if (searchLen == 0) {
+        args.rval().setInt32(start);
+        return true;
+    }
+    MOZ_ASSERT(0 <= start && size_t(start) < len);
+
+    JSLinearString* text = str->ensureLinear(cx);
+    if (!text)
+        return false;
+
+    // Step 9.
+    int32_t res;
+    AutoCheckCannotGC nogc;
+    if (text->hasLatin1Chars()) {
+        const Latin1Char* textChars = text->latin1Chars(nogc);
+        if (searchStr->hasLatin1Chars())
+            res = LastIndexOfImpl(textChars, len, searchStr->latin1Chars(nogc), searchLen, start);
+        else
+            res = LastIndexOfImpl(textChars, len, searchStr->twoByteChars(nogc), searchLen, start);
+    } else {
+        const char16_t* textChars = text->twoByteChars(nogc);
+        if (searchStr->hasLatin1Chars())
+            res = LastIndexOfImpl(textChars, len, searchStr->latin1Chars(nogc), searchLen, start);
+        else
+            res = LastIndexOfImpl(textChars, len, searchStr->twoByteChars(nogc), searchLen, start);
+    }
+
+    args.rval().setInt32(res);
+    return true;
+}
+
+bool
+js::HasSubstringAt(JSLinearString* text, JSLinearString* pat, size_t start)
+{
+    MOZ_ASSERT(start + pat->length() <= text->length());
+
+    size_t patLen = pat->length();
+
+    AutoCheckCannotGC nogc;
+    if (text->hasLatin1Chars()) {
+        const Latin1Char* textChars = text->latin1Chars(nogc) + start;
+        if (pat->hasLatin1Chars())
+            return PodEqual(textChars, pat->latin1Chars(nogc), patLen);
+
+        return EqualChars(textChars, pat->twoByteChars(nogc), patLen);
+    }
+
+    const char16_t* textChars = text->twoByteChars(nogc) + start;
+    if (pat->hasTwoByteChars())
+        return PodEqual(textChars, pat->twoByteChars(nogc), patLen);
+
+    return EqualChars(pat->latin1Chars(nogc), textChars, patLen);
+}
+
+/* ES6 draft rc3 21.1.3.18. */
+bool
+js::str_startsWith(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    // Steps 1, 2, and 3
+    RootedString str(cx, ToStringForStringFunction(cx, args.thisv()));
+    if (!str)
+        return false;
+
+    // Steps 4 and 5
+    bool isRegExp;
+    if (!IsRegExp(cx, args.get(0), &isRegExp))
+        return false;
+
+    // Step 6
+    if (isRegExp) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INVALID_ARG_TYPE,
+                                  "first", "", "Regular Expression");
+        return false;
+    }
+
+    // Steps 7 and 8
+    RootedLinearString searchStr(cx, ArgToRootedString(cx, args, 0));
+    if (!searchStr)
+        return false;
+
+    // Steps 9 and 10
+    uint32_t pos = 0;
+    if (args.hasDefined(1)) {
+        if (args[1].isInt32()) {
+            int i = args[1].toInt32();
+            pos = (i < 0) ? 0U : uint32_t(i);
+        } else {
+            double d;
+            if (!ToInteger(cx, args[1], &d))
+                return false;
+            pos = uint32_t(Min(Max(d, 0.0), double(UINT32_MAX)));
+        }
+    }
+
+    // Step 11
+    uint32_t textLen = str->length();
+
+    // Step 12
+    uint32_t start = Min(Max(pos, 0U), textLen);
+
+    // Step 13
+    uint32_t searchLen = searchStr->length();
+
+    // Step 14
+    if (searchLen + start < searchLen || searchLen + start > textLen) {
+        args.rval().setBoolean(false);
+        return true;
+    }
+
+    // Steps 15 and 16
+    JSLinearString* text = str->ensureLinear(cx);
+    if (!text)
+        return false;
+
+    args.rval().setBoolean(HasSubstringAt(text, searchStr, start));
+    return true;
+}
+
+/* ES6 draft rc3 21.1.3.6. */
+bool
+js::str_endsWith(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    // Steps 1, 2, and 3
+    RootedString str(cx, ToStringForStringFunction(cx, args.thisv()));
+    if (!str)
+        return false;
+
+    // Steps 4 and 5
+    bool isRegExp;
+    if (!IsRegExp(cx, args.get(0), &isRegExp))
+        return false;
+
+    // Step 6
+    if (isRegExp) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INVALID_ARG_TYPE,
+                                  "first", "", "Regular Expression");
+        return false;
+    }
+
+    // Steps 7 and 8
+    RootedLinearString searchStr(cx, ArgToRootedString(cx, args, 0));
+    if (!searchStr)
+        return false;
+
+    // Step 9
+    uint32_t textLen = str->length();
+
+    // Steps 10 and 11
+    uint32_t pos = textLen;
+    if (args.hasDefined(1)) {
+        if (args[1].isInt32()) {
+            int i = args[1].toInt32();
+            pos = (i < 0) ? 0U : uint32_t(i);
+        } else {
+            double d;
+            if (!ToInteger(cx, args[1], &d))
+                return false;
+            pos = uint32_t(Min(Max(d, 0.0), double(UINT32_MAX)));
+        }
+    }
+
+    // Step 12
+    uint32_t end = Min(Max(pos, 0U), textLen);
+
+    // Step 13
+    uint32_t searchLen = searchStr->length();
+
+    // Step 15 (reordered)
+    if (searchLen > end) {
+        args.rval().setBoolean(false);
+        return true;
+    }
+
+    // Step 14
+    uint32_t start = end - searchLen;
+
+    // Steps 16 and 17
+    JSLinearString* text = str->ensureLinear(cx);
+    if (!text)
+        return false;
+
+    args.rval().setBoolean(HasSubstringAt(text, searchStr, start));
+    return true;
+}
+
+template <typename CharT>
+static void
+TrimString(const CharT* chars, bool trimLeft, bool trimRight, size_t length,
+           size_t* pBegin, size_t* pEnd)
+{
+    size_t begin = 0, end = length;
+
+    if (trimLeft) {
+        while (begin < length && unicode::IsSpace(chars[begin]))
+            ++begin;
+    }
+
+    if (trimRight) {
+        while (end > begin && unicode::IsSpace(chars[end - 1]))
+            --end;
+    }
+
+    *pBegin = begin;
+    *pEnd = end;
+}
+
+static bool
+TrimString(JSContext* cx, const CallArgs& args, bool trimLeft, bool trimRight)
+{
+    RootedString str(cx, ToStringForStringFunction(cx, args.thisv()));
+    if (!str)
+        return false;
+
+    JSLinearString* linear = str->ensureLinear(cx);
+    if (!linear)
+        return false;
+
+    size_t length = linear->length();
+    size_t begin, end;
+    if (linear->hasLatin1Chars()) {
+        AutoCheckCannotGC nogc;
+        TrimString(linear->latin1Chars(nogc), trimLeft, trimRight, length, &begin, &end);
+    } else {
+        AutoCheckCannotGC nogc;
+        TrimString(linear->twoByteChars(nogc), trimLeft, trimRight, length, &begin, &end);
+    }
+
+    str = NewDependentString(cx, str, begin, end - begin);
+    if (!str)
+        return false;
+
+    args.rval().setString(str);
+    return true;
+}
+
+bool
+js::str_trim(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    return TrimString(cx, args, true, true);
+}
+
+bool
+js::str_trimLeft(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    return TrimString(cx, args, true, false);
+}
+
+bool
+js::str_trimRight(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    return TrimString(cx, args, false, true);
+}
+
+// Utility for building a rope (lazy concatenation) of strings.
+class RopeBuilder {
+    JSContext* cx;
+    RootedString res;
+
+    RopeBuilder(const RopeBuilder& other) = delete;
+    void operator=(const RopeBuilder& other) = delete;
+
+  public:
+    explicit RopeBuilder(JSContext* cx)
+      : cx(cx), res(cx, cx->runtime()->emptyString)
+    {}
+
+    inline bool append(HandleString str) {
+        res = ConcatStrings<CanGC>(cx, res, str);
+        return !!res;
+    }
+
+    inline JSString* result() {
+        return res;
+    }
+};
+
+namespace {
+
+template <typename CharT>
+static uint32_t
+FindDollarIndex(const CharT* chars, size_t length)
+{
+    if (const CharT* p = js_strchr_limit(chars, '$', chars + length)) {
+        uint32_t dollarIndex = p - chars;
+        MOZ_ASSERT(dollarIndex < length);
+        return dollarIndex;
+    }
+    return UINT32_MAX;
+}
+
+} /* anonymous namespace */
+
+static JSString*
+BuildFlatReplacement(JSContext* cx, HandleString textstr, HandleString repstr,
+                     size_t match, size_t patternLength)
+{
+    RopeBuilder builder(cx);
+    size_t matchEnd = match + patternLength;
+
+    if (textstr->isRope()) {
+        /*
+         * If we are replacing over a rope, avoid flattening it by iterating
+         * through it, building a new rope.
+         */
+        StringSegmentRange r(cx);
+        if (!r.init(textstr))
+            return nullptr;
+
+        size_t pos = 0;
+        while (!r.empty()) {
+            RootedString str(cx, r.front());
+            size_t len = str->length();
+            size_t strEnd = pos + len;
+            if (pos < matchEnd && strEnd > match) {
+                /*
+                 * We need to special-case any part of the rope that overlaps
+                 * with the replacement string.
+                 */
+                if (match >= pos) {
+                    /*
+                     * If this part of the rope overlaps with the left side of
+                     * the pattern, then it must be the only one to overlap with
+                     * the first character in the pattern, so we include the
+                     * replacement string here.
+                     */
+                    RootedString leftSide(cx, NewDependentString(cx, str, 0, match - pos));
+                    if (!leftSide ||
+                        !builder.append(leftSide) ||
+                        !builder.append(repstr))
+                    {
+                        return nullptr;
+                    }
+                }
+
+                /*
+                 * If str runs off the end of the matched string, append the
+                 * last part of str.
+                 */
+                if (strEnd > matchEnd) {
+                    RootedString rightSide(cx, NewDependentString(cx, str, matchEnd - pos,
+                                                                  strEnd - matchEnd));
+                    if (!rightSide || !builder.append(rightSide))
+                        return nullptr;
+                }
+            } else {
+                if (!builder.append(str))
+                    return nullptr;
+            }
+            pos += str->length();
+            if (!r.popFront())
+                return nullptr;
+        }
+    } else {
+        RootedString leftSide(cx, NewDependentString(cx, textstr, 0, match));
+        if (!leftSide)
+            return nullptr;
+        RootedString rightSide(cx);
+        rightSide = NewDependentString(cx, textstr, match + patternLength,
+                                       textstr->length() - match - patternLength);
+        if (!rightSide ||
+            !builder.append(leftSide) ||
+            !builder.append(repstr) ||
+            !builder.append(rightSide))
+        {
+            return nullptr;
+        }
+    }
+
+    return builder.result();
+}
+
+template <typename CharT>
+static bool
+AppendDollarReplacement(StringBuffer& newReplaceChars, size_t firstDollarIndex,
+                        size_t matchStart, size_t matchLimit, JSLinearString* text,
+                        const CharT* repChars, size_t repLength)
+{
+    MOZ_ASSERT(firstDollarIndex < repLength);
+
+    /* Move the pre-dollar chunk in bulk. */
+    newReplaceChars.infallibleAppend(repChars, firstDollarIndex);
+
+    /* Move the rest char-by-char, interpreting dollars as we encounter them. */
+    const CharT* repLimit = repChars + repLength;
+    for (const CharT* it = repChars + firstDollarIndex; it < repLimit; ++it) {
+        if (*it != '$' || it == repLimit - 1) {
+            if (!newReplaceChars.append(*it))
+                return false;
+            continue;
+        }
+
+        switch (*(it + 1)) {
+          case '$': /* Eat one of the dollars. */
+            if (!newReplaceChars.append(*it))
+                return false;
+            break;
+          case '&':
+            if (!newReplaceChars.appendSubstring(text, matchStart, matchLimit - matchStart))
+                return false;
+            break;
+          case '`':
+            if (!newReplaceChars.appendSubstring(text, 0, matchStart))
+                return false;
+            break;
+          case '\'':
+            if (!newReplaceChars.appendSubstring(text, matchLimit, text->length() - matchLimit))
+                return false;
+            break;
+          default: /* The dollar we saw was not special (no matter what its mother told it). */
+            if (!newReplaceChars.append(*it))
+                return false;
+            continue;
+        }
+        ++it; /* We always eat an extra char in the above switch. */
+    }
+
+    return true;
+}
+
+/*
+ * Perform a linear-scan dollar substitution on the replacement text,
+ * constructing a result string that looks like:
+ *
+ *      newstring = string[:matchStart] + dollarSub(replaceValue) + string[matchLimit:]
+ */
+static JSString*
+BuildDollarReplacement(JSContext* cx, JSString* textstrArg, JSLinearString* repstr,
+                       uint32_t firstDollarIndex, size_t matchStart, size_t patternLength)
+{
+    RootedLinearString textstr(cx, textstrArg->ensureLinear(cx));
+    if (!textstr)
+        return nullptr;
+
+    size_t matchLimit = matchStart + patternLength;
+
+    /*
+     * Most probably:
+     *
+     *      len(newstr) >= len(orig) - len(match) + len(replacement)
+     *
+     * Note that dollar vars _could_ make the resulting text smaller than this.
+     */
+    StringBuffer newReplaceChars(cx);
+    if (repstr->hasTwoByteChars() && !newReplaceChars.ensureTwoByteChars())
+        return nullptr;
+
+    if (!newReplaceChars.reserve(textstr->length() - patternLength + repstr->length()))
+        return nullptr;
+
+    bool res;
+    if (repstr->hasLatin1Chars()) {
+        AutoCheckCannotGC nogc;
+        res = AppendDollarReplacement(newReplaceChars, firstDollarIndex, matchStart, matchLimit,
+                                      textstr, repstr->latin1Chars(nogc), repstr->length());
+    } else {
+        AutoCheckCannotGC nogc;
+        res = AppendDollarReplacement(newReplaceChars, firstDollarIndex, matchStart, matchLimit,
+                                      textstr, repstr->twoByteChars(nogc), repstr->length());
+    }
+    if (!res)
+        return nullptr;
+
+    RootedString leftSide(cx, NewDependentString(cx, textstr, 0, matchStart));
+    if (!leftSide)
+        return nullptr;
+
+    RootedString newReplace(cx, newReplaceChars.finishString());
+    if (!newReplace)
+        return nullptr;
+
+    MOZ_ASSERT(textstr->length() >= matchLimit);
+    RootedString rightSide(cx, NewDependentString(cx, textstr, matchLimit,
+                                                  textstr->length() - matchLimit));
+    if (!rightSide)
+        return nullptr;
+
+    RopeBuilder builder(cx);
+    if (!builder.append(leftSide) || !builder.append(newReplace) || !builder.append(rightSide))
+        return nullptr;
+
+    return builder.result();
+}
+
+template <typename StrChar, typename RepChar>
+static bool
+StrFlatReplaceGlobal(JSContext *cx, JSLinearString *str, JSLinearString *pat, JSLinearString *rep,
+                     StringBuffer &sb)
+{
+    MOZ_ASSERT(str->length() > 0);
+
+    AutoCheckCannotGC nogc;
+    const StrChar *strChars = str->chars<StrChar>(nogc);
+    const RepChar *repChars = rep->chars<RepChar>(nogc);
+
+    // The pattern is empty, so we interleave the replacement string in-between
+    // each character.
+    if (!pat->length()) {
+        CheckedInt<uint32_t> strLength(str->length());
+        CheckedInt<uint32_t> repLength(rep->length());
+        CheckedInt<uint32_t> length = repLength * (strLength - 1) + strLength;
+        if (!length.isValid()) {
+            ReportAllocationOverflow(cx);
+            return false;
+        }
+
+        if (!sb.reserve(length.value()))
+            return false;
+
+        for (unsigned i = 0; i < str->length() - 1; ++i, ++strChars) {
+            sb.infallibleAppend(*strChars);
+            sb.infallibleAppend(repChars, rep->length());
+        }
+        sb.infallibleAppend(*strChars);
+        return true;
+    }
+
+    // If it's true, we are sure that the result's length is, at least, the same
+    // length as |str->length()|.
+    if (rep->length() >= pat->length()) {
+        if (!sb.reserve(str->length()))
+            return false;
+    }
+
+    uint32_t start = 0;
+    for (;;) {
+        int match = StringMatch(str, pat, start);
+        if (match < 0)
+            break;
+        if (!sb.append(strChars + start, match - start))
+            return false;
+        if (!sb.append(repChars, rep->length()))
+            return false;
+        start = match + pat->length();
+    }
+
+    if (!sb.append(strChars + start, str->length() - start))
+        return false;
+
+    return true;
+}
+
+// This is identical to "str.split(pattern).join(replacement)" except that we
+// do some deforestation optimization in Ion.
+JSString *
+js::str_flat_replace_string(JSContext *cx, HandleString string, HandleString pattern,
+                            HandleString replacement)
+{
+    MOZ_ASSERT(string);
+    MOZ_ASSERT(pattern);
+    MOZ_ASSERT(replacement);
+
+    if (!string->length())
+        return string;
+
+    RootedLinearString linearRepl(cx, replacement->ensureLinear(cx));
+    if (!linearRepl)
+        return nullptr;
+
+    RootedLinearString linearPat(cx, pattern->ensureLinear(cx));
+    if (!linearPat)
+        return nullptr;
+
+    RootedLinearString linearStr(cx, string->ensureLinear(cx));
+    if (!linearStr)
+        return nullptr;
+
+    StringBuffer sb(cx);
+    if (linearStr->hasTwoByteChars()) {
+        if (!sb.ensureTwoByteChars())
+            return nullptr;
+        if (linearRepl->hasTwoByteChars()) {
+            if (!StrFlatReplaceGlobal<char16_t, char16_t>(cx, linearStr, linearPat, linearRepl, sb))
+                return nullptr;
+        } else {
+            if (!StrFlatReplaceGlobal<char16_t, Latin1Char>(cx, linearStr, linearPat, linearRepl, sb))
+                return nullptr;
+        }
+    } else {
+        if (linearRepl->hasTwoByteChars()) {
+            if (!sb.ensureTwoByteChars())
+                return nullptr;
+            if (!StrFlatReplaceGlobal<Latin1Char, char16_t>(cx, linearStr, linearPat, linearRepl, sb))
+                return nullptr;
+        } else {
+            if (!StrFlatReplaceGlobal<Latin1Char, Latin1Char>(cx, linearStr, linearPat, linearRepl, sb))
+                return nullptr;
+        }
+    }
+
+    JSString *str = sb.finishString();
+    if (!str)
+        return nullptr;
+
+    return str;
+}
+
+JSString*
+js::str_replace_string_raw(JSContext* cx, HandleString string, HandleString pattern,
+                           HandleString replacement)
+{
+    RootedLinearString repl(cx, replacement->ensureLinear(cx));
+    if (!repl)
+        return nullptr;
+
+    RootedAtom pat(cx, AtomizeString(cx, pattern));
+    if (!pat)
+        return nullptr;
+
+    size_t patternLength = pat->length();
+    int32_t match;
+    uint32_t dollarIndex;
+
+    {
+        AutoCheckCannotGC nogc;
+        dollarIndex = repl->hasLatin1Chars()
+                      ? FindDollarIndex(repl->latin1Chars(nogc), repl->length())
+                      : FindDollarIndex(repl->twoByteChars(nogc), repl->length());
+    }
+
+    /*
+     * |string| could be a rope, so we want to avoid flattening it for as
+     * long as possible.
+     */
+    if (string->isRope()) {
+        if (!RopeMatch(cx, &string->asRope(), pat, &match))
+            return nullptr;
+    } else {
+        match = StringMatch(&string->asLinear(), pat, 0);
+    }
+
+    if (match < 0)
+        return string;
+
+    if (dollarIndex != UINT32_MAX)
+        return BuildDollarReplacement(cx, string, repl, dollarIndex, match, patternLength);
+    return BuildFlatReplacement(cx, string, repl, match, patternLength);
+}
+
+// ES 2016 draft Mar 25, 2016 21.1.3.17 steps 4, 8, 12-18.
+static JSObject*
+SplitHelper(JSContext* cx, HandleLinearString str, uint32_t limit, HandleLinearString sep,
+            HandleObjectGroup group)
+{
+    size_t strLength = str->length();
+    size_t sepLength = sep->length();
+    MOZ_ASSERT(sepLength != 0);
+
+    // Step 12.
+    if (strLength == 0) {
+        // Step 12.a.
+        int match = StringMatch(str, sep, 0);
+
+        // Step 12.b.
+        if (match != -1)
+            return NewFullyAllocatedArrayTryUseGroup(cx, group, 0);
+
+        // Steps 12.c-e.
+        RootedValue v(cx, StringValue(str));
+        return NewCopiedArrayTryUseGroup(cx, group, v.address(), 1);
+    }
+
+    // Step 3 (reordered).
+    AutoValueVector splits(cx);
+
+    // Step 8 (reordered).
+    size_t lastEndIndex = 0;
+
+    // Step 13.
+    size_t index = 0;
+
+    // Step 14.
+    while (index != strLength) {
+        // Step 14.a.
+        int match = StringMatch(str, sep, index);
+
+        // Step 14.b.
+        //
+        // Our match algorithm differs from the spec in that it returns the
+        // next index at which a match happens.  If no match happens we're
+        // done.
+        //
+        // But what if the match is at the end of the string (and the string is
+        // not empty)?  Per 14.c.i this shouldn't be a match, so we have to
+        // specially exclude it.  Thus this case should hold:
+        //
+        //   var a = "abc".split(/\b/);
+        //   assertEq(a.length, 1);
+        //   assertEq(a[0], "abc");
+        if (match == -1)
+            break;
+
+        // Step 14.c.
+        size_t endIndex = match + sepLength;
+
+        // Step 14.c.i.
+        if (endIndex == lastEndIndex) {
+            index++;
+            continue;
+        }
+
+        // Step 14.c.ii.
+        MOZ_ASSERT(lastEndIndex < endIndex);
+        MOZ_ASSERT(sepLength <= strLength);
+        MOZ_ASSERT(lastEndIndex + sepLength <= endIndex);
+
+        // Step 14.c.ii.1.
+        size_t subLength = size_t(endIndex - sepLength - lastEndIndex);
+        JSString* sub = NewDependentString(cx, str, lastEndIndex, subLength);
+
+        // Steps 14.c.ii.2-4.
+        if (!sub || !splits.append(StringValue(sub)))
+            return nullptr;
+
+        // Step 14.c.ii.5.
+        if (splits.length() == limit)
+            return NewCopiedArrayTryUseGroup(cx, group, splits.begin(), splits.length());
+
+        // Step 14.c.ii.6.
+        index = endIndex;
+
+        // Step 14.c.ii.7.
+        lastEndIndex = index;
+    }
+
+    // Step 15.
+    JSString* sub = NewDependentString(cx, str, lastEndIndex, strLength - lastEndIndex);
+
+    // Steps 16-17.
+    if (!sub || !splits.append(StringValue(sub)))
+        return nullptr;
+
+    // Step 18.
+    return NewCopiedArrayTryUseGroup(cx, group, splits.begin(), splits.length());
+}
+
+// Fast-path for splitting a string into a character array via split("").
+static JSObject*
+CharSplitHelper(JSContext* cx, HandleLinearString str, uint32_t limit, HandleObjectGroup group)
+{
+    size_t strLength = str->length();
+    if (strLength == 0)
+        return NewFullyAllocatedArrayTryUseGroup(cx, group, 0);
+
+    js::StaticStrings& staticStrings = cx->staticStrings();
+    uint32_t resultlen = (limit < strLength ? limit : strLength);
+
+    AutoValueVector splits(cx);
+    if (!splits.reserve(resultlen))
+        return nullptr;
+
+    for (size_t i = 0; i < resultlen; ++i) {
+        JSString* sub = staticStrings.getUnitStringForElement(cx, str, i);
+        if (!sub)
+            return nullptr;
+        splits.infallibleAppend(StringValue(sub));
+    }
+
+    return NewCopiedArrayTryUseGroup(cx, group, splits.begin(), splits.length());
+}
+
+// ES 2016 draft Mar 25, 2016 21.1.3.17 steps 4, 8, 12-18.
+JSObject*
+js::str_split_string(JSContext* cx, HandleObjectGroup group, HandleString str, HandleString sep, uint32_t limit)
+
+{
+    RootedLinearString linearStr(cx, str->ensureLinear(cx));
+    if (!linearStr)
+        return nullptr;
+
+    RootedLinearString linearSep(cx, sep->ensureLinear(cx));
+    if (!linearSep)
+        return nullptr;
+
+    if (linearSep->length() == 0)
+        return CharSplitHelper(cx, linearStr, limit, group);
+
+    return SplitHelper(cx, linearStr, limit, linearSep, group);
+}
+
+/*
+ * Python-esque sequence operations.
+ */
+bool
+js::str_concat(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    JSString* str = ToStringForStringFunction(cx, args.thisv());
+    if (!str)
+        return false;
+
+    for (unsigned i = 0; i < args.length(); i++) {
+        JSString* argStr = ToString<NoGC>(cx, args[i]);
+        if (!argStr) {
+            RootedString strRoot(cx, str);
+            argStr = ToString<CanGC>(cx, args[i]);
+            if (!argStr)
+                return false;
+            str = strRoot;
+        }
+
+        JSString* next = ConcatStrings<NoGC>(cx, str, argStr);
+        if (next) {
+            str = next;
+        } else {
+            RootedString strRoot(cx, str), argStrRoot(cx, argStr);
+            str = ConcatStrings<CanGC>(cx, strRoot, argStrRoot);
+            if (!str)
+                return false;
+        }
+    }
+
+    args.rval().setString(str);
+    return true;
+}
+
+static const JSFunctionSpec string_methods[] = {
+#if JS_HAS_TOSOURCE
+    JS_FN(js_toSource_str,     str_toSource,          0,0),
+#endif
+
+    /* Java-like methods. */
+    JS_FN(js_toString_str,     str_toString,          0,0),
+    JS_FN(js_valueOf_str,      str_toString,          0,0),
+    JS_FN("toLowerCase",       str_toLowerCase,       0,0),
+    JS_FN("toUpperCase",       str_toUpperCase,       0,0),
+    JS_INLINABLE_FN("charAt",  str_charAt,            1,0, StringCharAt),
+    JS_INLINABLE_FN("charCodeAt", str_charCodeAt,     1,0, StringCharCodeAt),
+    JS_SELF_HOSTED_FN("substring", "String_substring", 2,0),
+    JS_SELF_HOSTED_FN("padStart", "String_pad_start", 2,0),
+    JS_SELF_HOSTED_FN("padEnd", "String_pad_end", 2,0),
+    JS_SELF_HOSTED_FN("codePointAt", "String_codePointAt", 1,0),
+    JS_FN("includes",          str_includes,          1,0),
+    JS_FN("indexOf",           str_indexOf,           1,0),
+    JS_FN("lastIndexOf",       str_lastIndexOf,       1,0),
+    JS_FN("startsWith",        str_startsWith,        1,0),
+    JS_FN("endsWith",          str_endsWith,          1,0),
+    JS_FN("trim",              str_trim,              0,0),
+    JS_FN("trimLeft",          str_trimLeft,          0,0),
+    JS_FN("trimRight",         str_trimRight,         0,0),
+    JS_FN("toLocaleLowerCase", str_toLocaleLowerCase, 0,0),
+    JS_FN("toLocaleUpperCase", str_toLocaleUpperCase, 0,0),
+#if EXPOSE_INTL_API
+    JS_SELF_HOSTED_FN("localeCompare", "String_localeCompare", 1,0),
+#else
+    JS_FN("localeCompare",     str_localeCompare,     1,0),
+#endif
+    JS_SELF_HOSTED_FN("repeat", "String_repeat",      1,0),
+#if EXPOSE_INTL_API
+    JS_FN("normalize",         str_normalize,         0,0),
+#endif
+
+    /* Perl-ish methods (search is actually Python-esque). */
+    JS_SELF_HOSTED_FN("match", "String_match",        1,0),
+    JS_SELF_HOSTED_FN("search", "String_search",      1,0),
+    JS_SELF_HOSTED_FN("replace", "String_replace",    2,0),
+    JS_SELF_HOSTED_FN("split",  "String_split",       2,0),
+    JS_SELF_HOSTED_FN("substr", "String_substr",      2,0),
+
+    /* Python-esque sequence methods. */
+    JS_FN("concat",            str_concat,            1,0),
+    JS_SELF_HOSTED_FN("slice", "String_slice",        2,0),
+
+    /* HTML string methods. */
+    JS_SELF_HOSTED_FN("bold",     "String_bold",       0,0),
+    JS_SELF_HOSTED_FN("italics",  "String_italics",    0,0),
+    JS_SELF_HOSTED_FN("fixed",    "String_fixed",      0,0),
+    JS_SELF_HOSTED_FN("strike",   "String_strike",     0,0),
+    JS_SELF_HOSTED_FN("small",    "String_small",      0,0),
+    JS_SELF_HOSTED_FN("big",      "String_big",        0,0),
+    JS_SELF_HOSTED_FN("blink",    "String_blink",      0,0),
+    JS_SELF_HOSTED_FN("sup",      "String_sup",        0,0),
+    JS_SELF_HOSTED_FN("sub",      "String_sub",        0,0),
+    JS_SELF_HOSTED_FN("anchor",   "String_anchor",     1,0),
+    JS_SELF_HOSTED_FN("link",     "String_link",       1,0),
+    JS_SELF_HOSTED_FN("fontcolor","String_fontcolor",  1,0),
+    JS_SELF_HOSTED_FN("fontsize", "String_fontsize",   1,0),
+
+    JS_SELF_HOSTED_SYM_FN(iterator, "String_iterator", 0,0),
+    JS_FS_END
+};
+
+// ES6 rev 27 (2014 Aug 24) 21.1.1
+bool
+js::StringConstructor(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    RootedString str(cx);
+    if (args.length() > 0) {
+        if (!args.isConstructing() && args[0].isSymbol())
+            return js::SymbolDescriptiveString(cx, args[0].toSymbol(), args.rval());
+
+        str = ToString<CanGC>(cx, args[0]);
+        if (!str)
+            return false;
+    } else {
+        str = cx->runtime()->emptyString;
+    }
+
+    if (args.isConstructing()) {
+        RootedObject proto(cx);
+        RootedObject newTarget(cx, &args.newTarget().toObject());
+        if (!GetPrototypeFromConstructor(cx, newTarget, &proto))
+            return false;
+
+        StringObject* strobj = StringObject::create(cx, str, proto);
+        if (!strobj)
+            return false;
+        args.rval().setObject(*strobj);
+        return true;
+    }
+
+    args.rval().setString(str);
+    return true;
+}
+
+static bool
+str_fromCharCode_few_args(JSContext* cx, const CallArgs& args)
+{
+    MOZ_ASSERT(args.length() <= JSFatInlineString::MAX_LENGTH_TWO_BYTE);
+
+    char16_t chars[JSFatInlineString::MAX_LENGTH_TWO_BYTE];
+    for (unsigned i = 0; i < args.length(); i++) {
+        uint16_t code;
+        if (!ToUint16(cx, args[i], &code))
+            return false;
+        chars[i] = char16_t(code);
+    }
+    JSString* str = NewStringCopyN<CanGC>(cx, chars, args.length());
+    if (!str)
+        return false;
+    args.rval().setString(str);
+    return true;
+}
+
+bool
+js::str_fromCharCode(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    MOZ_ASSERT(args.length() <= ARGS_LENGTH_MAX);
+
+    // Optimize the single-char case.
+    if (args.length() == 1)
+        return str_fromCharCode_one_arg(cx, args[0], args.rval());
+
+    // Optimize the case where the result will definitely fit in an inline
+    // string (thin or fat) and so we don't need to malloc the chars. (We could
+    // cover some cases where args.length() goes up to
+    // JSFatInlineString::MAX_LENGTH_LATIN1 if we also checked if the chars are
+    // all Latin1, but it doesn't seem worth the effort.)
+    if (args.length() <= JSFatInlineString::MAX_LENGTH_TWO_BYTE)
+        return str_fromCharCode_few_args(cx, args);
+
+    char16_t* chars = cx->pod_malloc<char16_t>(args.length() + 1);
+    if (!chars)
+        return false;
+    for (unsigned i = 0; i < args.length(); i++) {
+        uint16_t code;
+        if (!ToUint16(cx, args[i], &code)) {
+            js_free(chars);
+            return false;
+        }
+        chars[i] = char16_t(code);
+    }
+    chars[args.length()] = 0;
+    JSString* str = NewString<CanGC>(cx, chars, args.length());
+    if (!str) {
+        js_free(chars);
+        return false;
+    }
+
+    args.rval().setString(str);
+    return true;
+}
+
+static inline bool
+CodeUnitToString(JSContext* cx, uint16_t ucode, MutableHandleValue rval)
+{
+    if (StaticStrings::hasUnit(ucode)) {
+        rval.setString(cx->staticStrings().getUnit(ucode));
+        return true;
+    }
+
+    char16_t c = char16_t(ucode);
+    JSString* str = NewStringCopyN<CanGC>(cx, &c, 1);
+    if (!str)
+        return false;
+
+    rval.setString(str);
+    return true;
+}
+
+bool
+js::str_fromCharCode_one_arg(JSContext* cx, HandleValue code, MutableHandleValue rval)
+{
+    uint16_t ucode;
+
+    if (!ToUint16(cx, code, &ucode))
+        return false;
+
+    return CodeUnitToString(cx, ucode, rval);
+}
+
+static MOZ_ALWAYS_INLINE bool
+ToCodePoint(JSContext* cx, HandleValue code, uint32_t* codePoint)
+{
+    // String.fromCodePoint, Steps 5.a-b.
+    double nextCP;
+    if (!ToNumber(cx, code, &nextCP))
+        return false;
+
+    // String.fromCodePoint, Steps 5.c-d.
+    if (JS::ToInteger(nextCP) != nextCP || nextCP < 0 || nextCP > unicode::NonBMPMax) {
+        ToCStringBuf cbuf;
+        if (char* numStr = NumberToCString(cx, &cbuf, nextCP))
+            JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_NOT_A_CODEPOINT, numStr);
+        return false;
+    }
+
+    *codePoint = uint32_t(nextCP);
+    return true;
+}
+
+bool
+js::str_fromCodePoint_one_arg(JSContext* cx, HandleValue code, MutableHandleValue rval)
+{
+    // Steps 1-4 (omitted).
+
+    // Steps 5.a-d.
+    uint32_t codePoint;
+    if (!ToCodePoint(cx, code, &codePoint))
+        return false;
+
+    // Steps 5.e, 6.
+    if (!unicode::IsSupplementary(codePoint))
+        return CodeUnitToString(cx, uint16_t(codePoint), rval);
+
+    char16_t chars[] = { unicode::LeadSurrogate(codePoint), unicode::TrailSurrogate(codePoint) };
+    JSString* str = NewStringCopyNDontDeflate<CanGC>(cx, chars, 2);
+    if (!str)
+        return false;
+
+    rval.setString(str);
+    return true;
+}
+
+static bool
+str_fromCodePoint_few_args(JSContext* cx, const CallArgs& args)
+{
+    MOZ_ASSERT(args.length() <= JSFatInlineString::MAX_LENGTH_TWO_BYTE / 2);
+
+    // Steps 1-2 (omitted).
+
+    // Step 3.
+    char16_t elements[JSFatInlineString::MAX_LENGTH_TWO_BYTE];
+
+    // Steps 4-5.
+    unsigned length = 0;
+    for (unsigned nextIndex = 0; nextIndex < args.length(); nextIndex++) {
+        // Steps 5.a-d.
+        uint32_t codePoint;
+        if (!ToCodePoint(cx, args[nextIndex], &codePoint))
+            return false;
+
+        // Step 5.e.
+        unicode::UTF16Encode(codePoint, elements, &length);
+    }
+
+    // Step 6.
+    JSString* str = NewStringCopyN<CanGC>(cx, elements, length);
+    if (!str)
+        return false;
+
+    args.rval().setString(str);
+    return true;
+}
+
+// ES2017 draft rev 40edb3a95a475c1b251141ac681b8793129d9a6d
+// 21.1.2.2 String.fromCodePoint(...codePoints)
+bool
+js::str_fromCodePoint(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    // Optimize the single code-point case.
+    if (args.length() == 1)
+        return str_fromCodePoint_one_arg(cx, args[0], args.rval());
+
+    // Optimize the case where the result will definitely fit in an inline
+    // string (thin or fat) and so we don't need to malloc the chars. (We could
+    // cover some cases where |args.length()| goes up to
+    // JSFatInlineString::MAX_LENGTH_LATIN1 / 2 if we also checked if the chars
+    // are all Latin1, but it doesn't seem worth the effort.)
+    if (args.length() <= JSFatInlineString::MAX_LENGTH_TWO_BYTE / 2)
+        return str_fromCodePoint_few_args(cx, args);
+
+    // Steps 1-2 (omitted).
+
+    // Step 3.
+    static_assert(ARGS_LENGTH_MAX < std::numeric_limits<size_t>::max() / 2,
+                  "|args.length() * 2 + 1| does not overflow");
+    char16_t* elements = cx->pod_malloc<char16_t>(args.length() * 2 + 1);
+    if (!elements)
+        return false;
+
+    // Steps 4-5.
+    unsigned length = 0;
+    for (unsigned nextIndex = 0; nextIndex < args.length(); nextIndex++) {
+        // Steps 5.a-d.
+        uint32_t codePoint;
+        if (!ToCodePoint(cx, args[nextIndex], &codePoint)) {
+            js_free(elements);
+            return false;
+        }
+
+        // Step 5.e.
+        unicode::UTF16Encode(codePoint, elements, &length);
+    }
+    elements[length] = 0;
+
+    // Step 6.
+    JSString* str = NewString<CanGC>(cx, elements, length);
+    if (!str) {
+        js_free(elements);
+        return false;
+    }
+
+    args.rval().setString(str);
+    return true;
+}
+
+static const JSFunctionSpec string_static_methods[] = {
+    JS_INLINABLE_FN("fromCharCode", js::str_fromCharCode, 1, 0, StringFromCharCode),
+    JS_INLINABLE_FN("fromCodePoint", js::str_fromCodePoint, 1, 0, StringFromCodePoint),
+
+    JS_SELF_HOSTED_FN("raw",             "String_static_raw",           2,JSFUN_HAS_REST),
+    JS_SELF_HOSTED_FN("substring",       "String_static_substring",     3,0),
+    JS_SELF_HOSTED_FN("substr",          "String_static_substr",        3,0),
+    JS_SELF_HOSTED_FN("slice",           "String_static_slice",         3,0),
+
+    JS_SELF_HOSTED_FN("match",           "String_generic_match",        2,0),
+    JS_SELF_HOSTED_FN("replace",         "String_generic_replace",      3,0),
+    JS_SELF_HOSTED_FN("search",          "String_generic_search",       2,0),
+    JS_SELF_HOSTED_FN("split",           "String_generic_split",        3,0),
+
+    JS_SELF_HOSTED_FN("toLowerCase",     "String_static_toLowerCase",   1,0),
+    JS_SELF_HOSTED_FN("toUpperCase",     "String_static_toUpperCase",   1,0),
+    JS_SELF_HOSTED_FN("charAt",          "String_static_charAt",        2,0),
+    JS_SELF_HOSTED_FN("charCodeAt",      "String_static_charCodeAt",    2,0),
+    JS_SELF_HOSTED_FN("includes",        "String_static_includes",      2,0),
+    JS_SELF_HOSTED_FN("indexOf",         "String_static_indexOf",       2,0),
+    JS_SELF_HOSTED_FN("lastIndexOf",     "String_static_lastIndexOf",   2,0),
+    JS_SELF_HOSTED_FN("startsWith",      "String_static_startsWith",    2,0),
+    JS_SELF_HOSTED_FN("endsWith",        "String_static_endsWith",      2,0),
+    JS_SELF_HOSTED_FN("trim",            "String_static_trim",          1,0),
+    JS_SELF_HOSTED_FN("trimLeft",        "String_static_trimLeft",      1,0),
+    JS_SELF_HOSTED_FN("trimRight",       "String_static_trimRight",     1,0),
+    JS_SELF_HOSTED_FN("toLocaleLowerCase","String_static_toLocaleLowerCase",1,0),
+    JS_SELF_HOSTED_FN("toLocaleUpperCase","String_static_toLocaleUpperCase",1,0),
+#if EXPOSE_INTL_API
+    JS_SELF_HOSTED_FN("normalize",       "String_static_normalize",     1,0),
+#endif
+    JS_SELF_HOSTED_FN("concat",          "String_static_concat",        2,0),
+
+    JS_SELF_HOSTED_FN("localeCompare",   "String_static_localeCompare", 2,0),
+    JS_FS_END
+};
+
+/* static */ Shape*
+StringObject::assignInitialShape(ExclusiveContext* cx, Handle<StringObject*> obj)
+{
+    MOZ_ASSERT(obj->empty());
+
+    return obj->addDataProperty(cx, cx->names().length, LENGTH_SLOT,
+                                JSPROP_PERMANENT | JSPROP_READONLY);
+}
+
+JSObject*
+js::InitStringClass(JSContext* cx, HandleObject obj)
+{
+    MOZ_ASSERT(obj->isNative());
+
+    Rooted<GlobalObject*> global(cx, &obj->as<GlobalObject>());
+
+    Rooted<JSString*> empty(cx, cx->runtime()->emptyString);
+    RootedObject proto(cx, global->createBlankPrototype(cx, &StringObject::class_));
+    if (!proto || !proto->as<StringObject>().init(cx, empty))
+        return nullptr;
+
+    /* Now create the String function. */
+    RootedFunction ctor(cx);
+    ctor = global->createConstructor(cx, StringConstructor, cx->names().String, 1,
+                                     AllocKind::FUNCTION, &jit::JitInfo_String);
+    if (!ctor)
+        return nullptr;
+
+    if (!LinkConstructorAndPrototype(cx, ctor, proto))
+        return nullptr;
+
+    if (!DefinePropertiesAndFunctions(cx, proto, nullptr, string_methods) ||
+        !DefinePropertiesAndFunctions(cx, ctor, nullptr, string_static_methods))
+    {
+        return nullptr;
+    }
+
+    /*
+     * Define escape/unescape, the URI encode/decode functions, and maybe
+     * uneval on the global object.
+     */
+    if (!JS_DefineFunctions(cx, global, string_functions))
+        return nullptr;
+
+    if (!GlobalObject::initBuiltinConstructor(cx, global, JSProto_String, ctor, proto))
+        return nullptr;
+
+    return proto;
+}
+
+const char*
+js::ValueToPrintable(JSContext* cx, const Value& vArg, JSAutoByteString* bytes, bool asSource)
+{
+    RootedValue v(cx, vArg);
+    JSString* str;
+    if (asSource)
+        str = ValueToSource(cx, v);
+    else
+        str = ToString<CanGC>(cx, v);
+    if (!str)
+        return nullptr;
+    str = QuoteString(cx, str, 0);
+    if (!str)
+        return nullptr;
+    return bytes->encodeLatin1(cx, str);
+}
+
+template <AllowGC allowGC>
+JSString*
+js::ToStringSlow(ExclusiveContext* cx, typename MaybeRooted<Value, allowGC>::HandleType arg)
+{
+    /* As with ToObjectSlow, callers must verify that |arg| isn't a string. */
+    MOZ_ASSERT(!arg.isString());
+
+    Value v = arg;
+    if (!v.isPrimitive()) {
+        if (!cx->shouldBeJSContext() || !allowGC)
+            return nullptr;
+        RootedValue v2(cx, v);
+        if (!ToPrimitive(cx->asJSContext(), JSTYPE_STRING, &v2))
+            return nullptr;
+        v = v2;
+    }
+
+    JSString* str;
+    if (v.isString()) {
+        str = v.toString();
+    } else if (v.isInt32()) {
+        str = Int32ToString<allowGC>(cx, v.toInt32());
+    } else if (v.isDouble()) {
+        str = NumberToString<allowGC>(cx, v.toDouble());
+    } else if (v.isBoolean()) {
+        str = BooleanToString(cx, v.toBoolean());
+    } else if (v.isNull()) {
+        str = cx->names().null;
+    } else if (v.isSymbol()) {
+        if (cx->shouldBeJSContext() && allowGC) {
+            JS_ReportErrorNumberASCII(cx->asJSContext(), GetErrorMessage, nullptr,
+                                      JSMSG_SYMBOL_TO_STRING);
+        }
+        return nullptr;
+    } else {
+        MOZ_ASSERT(v.isUndefined());
+        str = cx->names().undefined;
+    }
+    return str;
+}
+
+template JSString*
+js::ToStringSlow<CanGC>(ExclusiveContext* cx, HandleValue arg);
+
+template JSString*
+js::ToStringSlow<NoGC>(ExclusiveContext* cx, const Value& arg);
+
+JS_PUBLIC_API(JSString*)
+js::ToStringSlow(JSContext* cx, HandleValue v)
+{
+    return ToStringSlow<CanGC>(cx, v);
+}
+
+static JSString*
+SymbolToSource(JSContext* cx, Symbol* symbol)
+{
+    RootedString desc(cx, symbol->description());
+    SymbolCode code = symbol->code();
+    if (code != SymbolCode::InSymbolRegistry && code != SymbolCode::UniqueSymbol) {
+        // Well-known symbol.
+        MOZ_ASSERT(uint32_t(code) < JS::WellKnownSymbolLimit);
+        return desc;
+    }
+
+    StringBuffer buf(cx);
+    if (code == SymbolCode::InSymbolRegistry ? !buf.append("Symbol.for(") : !buf.append("Symbol("))
+        return nullptr;
+    if (desc) {
+        desc = StringToSource(cx, desc);
+        if (!desc || !buf.append(desc))
+            return nullptr;
+    }
+    if (!buf.append(')'))
+        return nullptr;
+    return buf.finishString();
+}
+
+JSString*
+js::ValueToSource(JSContext* cx, HandleValue v)
+{
+    JS_CHECK_RECURSION(cx, return nullptr);
+    assertSameCompartment(cx, v);
+
+    if (v.isUndefined())
+        return cx->names().void0;
+    if (v.isString())
+        return StringToSource(cx, v.toString());
+    if (v.isSymbol())
+        return SymbolToSource(cx, v.toSymbol());
+    if (v.isPrimitive()) {
+        /* Special case to preserve negative zero, _contra_ toString. */
+        if (v.isDouble() && IsNegativeZero(v.toDouble())) {
+            /* NB: _ucNstr rather than _ucstr to indicate non-terminated. */
+            static const char16_t js_negzero_ucNstr[] = {'-', '0'};
+
+            return NewStringCopyN<CanGC>(cx, js_negzero_ucNstr, 2);
+        }
+        return ToString<CanGC>(cx, v);
+    }
+
+    RootedValue fval(cx);
+    RootedObject obj(cx, &v.toObject());
+    if (!GetProperty(cx, obj, obj, cx->names().toSource, &fval))
+        return nullptr;
+    if (IsCallable(fval)) {
+        RootedValue v(cx);
+        if (!js::Call(cx, fval, obj, &v))
+            return nullptr;
+
+        return ToString<CanGC>(cx, v);
+    }
+
+    return ObjectToSource(cx, obj);
+}
+
+JSString*
+js::StringToSource(JSContext* cx, JSString* str)
+{
+    return QuoteString(cx, str, '"');
+}
+
+bool
+js::EqualChars(JSLinearString* str1, JSLinearString* str2)
+{
+    MOZ_ASSERT(str1->length() == str2->length());
+
+    size_t len = str1->length();
+
+    AutoCheckCannotGC nogc;
+    if (str1->hasTwoByteChars()) {
+        if (str2->hasTwoByteChars())
+            return PodEqual(str1->twoByteChars(nogc), str2->twoByteChars(nogc), len);
+
+        return EqualChars(str2->latin1Chars(nogc), str1->twoByteChars(nogc), len);
+    }
+
+    if (str2->hasLatin1Chars())
+        return PodEqual(str1->latin1Chars(nogc), str2->latin1Chars(nogc), len);
+
+    return EqualChars(str1->latin1Chars(nogc), str2->twoByteChars(nogc), len);
+}
+
+bool
+js::EqualStrings(JSContext* cx, JSString* str1, JSString* str2, bool* result)
+{
+    if (str1 == str2) {
+        *result = true;
+        return true;
+    }
+
+    size_t length1 = str1->length();
+    if (length1 != str2->length()) {
+        *result = false;
+        return true;
+    }
+
+    JSLinearString* linear1 = str1->ensureLinear(cx);
+    if (!linear1)
+        return false;
+    JSLinearString* linear2 = str2->ensureLinear(cx);
+    if (!linear2)
+        return false;
+
+    *result = EqualChars(linear1, linear2);
+    return true;
+}
+
+bool
+js::EqualStrings(JSLinearString* str1, JSLinearString* str2)
+{
+    if (str1 == str2)
+        return true;
+
+    size_t length1 = str1->length();
+    if (length1 != str2->length())
+        return false;
+
+    return EqualChars(str1, str2);
+}
+
+static int32_t
+CompareStringsImpl(JSLinearString* str1, JSLinearString* str2)
+{
+    size_t len1 = str1->length();
+    size_t len2 = str2->length();
+
+    AutoCheckCannotGC nogc;
+    if (str1->hasLatin1Chars()) {
+        const Latin1Char* chars1 = str1->latin1Chars(nogc);
+        return str2->hasLatin1Chars()
+               ? CompareChars(chars1, len1, str2->latin1Chars(nogc), len2)
+               : CompareChars(chars1, len1, str2->twoByteChars(nogc), len2);
+    }
+
+    const char16_t* chars1 = str1->twoByteChars(nogc);
+    return str2->hasLatin1Chars()
+           ? CompareChars(chars1, len1, str2->latin1Chars(nogc), len2)
+           : CompareChars(chars1, len1, str2->twoByteChars(nogc), len2);
+}
+
+int32_t
+js::CompareChars(const char16_t* s1, size_t len1, JSLinearString* s2)
+{
+    AutoCheckCannotGC nogc;
+    return s2->hasLatin1Chars()
+           ? CompareChars(s1, len1, s2->latin1Chars(nogc), s2->length())
+           : CompareChars(s1, len1, s2->twoByteChars(nogc), s2->length());
+}
+
+bool
+js::CompareStrings(JSContext* cx, JSString* str1, JSString* str2, int32_t* result)
+{
+    MOZ_ASSERT(str1);
+    MOZ_ASSERT(str2);
+
+    if (str1 == str2) {
+        *result = 0;
+        return true;
+    }
+
+    JSLinearString* linear1 = str1->ensureLinear(cx);
+    if (!linear1)
+        return false;
+
+    JSLinearString* linear2 = str2->ensureLinear(cx);
+    if (!linear2)
+        return false;
+
+    *result = CompareStringsImpl(linear1, linear2);
+    return true;
+}
+
+int32_t
+js::CompareAtoms(JSAtom* atom1, JSAtom* atom2)
+{
+    return CompareStringsImpl(atom1, atom2);
+}
+
+bool
+js::StringEqualsAscii(JSLinearString* str, const char* asciiBytes)
+{
+    size_t length = strlen(asciiBytes);
+#ifdef DEBUG
+    for (size_t i = 0; i != length; ++i)
+        MOZ_ASSERT(unsigned(asciiBytes[i]) <= 127);
+#endif
+    if (length != str->length())
+        return false;
+
+    const Latin1Char* latin1 = reinterpret_cast<const Latin1Char*>(asciiBytes);
+
+    AutoCheckCannotGC nogc;
+    return str->hasLatin1Chars()
+           ? PodEqual(latin1, str->latin1Chars(nogc), length)
+           : EqualChars(latin1, str->twoByteChars(nogc), length);
+}
+
+size_t
+js_strlen(const char16_t* s)
+{
+    const char16_t* t;
+
+    for (t = s; *t != 0; t++)
+        continue;
+    return (size_t)(t - s);
+}
+
+int32_t
+js_strcmp(const char16_t* lhs, const char16_t* rhs)
+{
+    while (true) {
+        if (*lhs != *rhs)
+            return int32_t(*lhs) - int32_t(*rhs);
+        if (*lhs == 0)
+            return 0;
+        ++lhs, ++rhs;
+    }
+}
+
+int32_t
+js_fputs(const char16_t* s, FILE* f)
+{
+    while (*s != 0) {
+        if (fputwc(wchar_t(*s), f) == WEOF)
+            return WEOF;
+        s++;
+    }
+    return 1;
+}
+
+UniqueChars
+js::DuplicateString(js::ExclusiveContext* cx, const char* s)
+{
+    size_t n = strlen(s) + 1;
+    auto ret = cx->make_pod_array<char>(n);
+    if (!ret)
+        return ret;
+    PodCopy(ret.get(), s, n);
+    return ret;
+}
+
+UniqueTwoByteChars
+js::DuplicateString(js::ExclusiveContext* cx, const char16_t* s)
+{
+    size_t n = js_strlen(s) + 1;
+    auto ret = cx->make_pod_array<char16_t>(n);
+    if (!ret)
+        return ret;
+    PodCopy(ret.get(), s, n);
+    return ret;
+}
+
+UniqueChars
+js::DuplicateString(const char* s)
+{
+    return UniqueChars(js_strdup(s));
+}
+
+UniqueChars
+js::DuplicateString(const char* s, size_t n)
+{
+    UniqueChars ret(js_pod_malloc<char>(n + 1));
+    if (!ret)
+        return nullptr;
+    PodCopy(ret.get(), s, n);
+    ret[n] = 0;
+    return ret;
+}
+
+UniqueTwoByteChars
+js::DuplicateString(const char16_t* s)
+{
+    return DuplicateString(s, js_strlen(s));
+}
+
+UniqueTwoByteChars
+js::DuplicateString(const char16_t* s, size_t n)
+{
+    UniqueTwoByteChars ret(js_pod_malloc<char16_t>(n + 1));
+    if (!ret)
+        return nullptr;
+    PodCopy(ret.get(), s, n);
+    ret[n] = 0;
+    return ret;
+}
+
+template <typename CharT>
+const CharT*
+js_strchr_limit(const CharT* s, char16_t c, const CharT* limit)
+{
+    while (s < limit) {
+        if (*s == c)
+            return s;
+        s++;
+    }
+    return nullptr;
+}
+
+template const Latin1Char*
+js_strchr_limit(const Latin1Char* s, char16_t c, const Latin1Char* limit);
+
+template const char16_t*
+js_strchr_limit(const char16_t* s, char16_t c, const char16_t* limit);
+
+char16_t*
+js::InflateString(ExclusiveContext* cx, const char* bytes, size_t* lengthp)
+{
+    size_t nchars;
+    char16_t* chars;
+    size_t nbytes = *lengthp;
+
+    nchars = nbytes;
+    chars = cx->pod_malloc<char16_t>(nchars + 1);
+    if (!chars)
+        goto bad;
+    for (size_t i = 0; i < nchars; i++)
+        chars[i] = (unsigned char) bytes[i];
+    *lengthp = nchars;
+    chars[nchars] = 0;
+    return chars;
+
+  bad:
+    // For compatibility with callers of JS_DecodeBytes we must zero lengthp
+    // on errors.
+    *lengthp = 0;
+    return nullptr;
+}
+
+template <typename CharT>
+bool
+js::DeflateStringToBuffer(JSContext* maybecx, const CharT* src, size_t srclen,
+                          char* dst, size_t* dstlenp)
+{
+    size_t dstlen = *dstlenp;
+    if (srclen > dstlen) {
+        for (size_t i = 0; i < dstlen; i++)
+            dst[i] = char(src[i]);
+        if (maybecx) {
+            AutoSuppressGC suppress(maybecx);
+            JS_ReportErrorNumberASCII(maybecx, GetErrorMessage, nullptr,
+                                      JSMSG_BUFFER_TOO_SMALL);
+        }
+        return false;
+    }
+    for (size_t i = 0; i < srclen; i++)
+        dst[i] = char(src[i]);
+    *dstlenp = srclen;
+    return true;
+}
+
+template bool
+js::DeflateStringToBuffer(JSContext* maybecx, const Latin1Char* src, size_t srclen,
+                          char* dst, size_t* dstlenp);
+
+template bool
+js::DeflateStringToBuffer(JSContext* maybecx, const char16_t* src, size_t srclen,
+                          char* dst, size_t* dstlenp);
+
+#define ____ false
+
+/*
+ * Identifier start chars:
+ * -      36:    $
+ * -  65..90: A..Z
+ * -      95:    _
+ * - 97..122: a..z
+ */
+const bool js_isidstart[] = {
+/*       0     1     2     3     4     5     6     7     8     9  */
+/*  0 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  1 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  2 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  3 */ ____, ____, ____, ____, ____, ____, true, ____, ____, ____,
+/*  4 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  5 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  6 */ ____, ____, ____, ____, ____, true, true, true, true, true,
+/*  7 */ true, true, true, true, true, true, true, true, true, true,
+/*  8 */ true, true, true, true, true, true, true, true, true, true,
+/*  9 */ true, ____, ____, ____, ____, true, ____, true, true, true,
+/* 10 */ true, true, true, true, true, true, true, true, true, true,
+/* 11 */ true, true, true, true, true, true, true, true, true, true,
+/* 12 */ true, true, true, ____, ____, ____, ____, ____
+};
+
+/*
+ * Identifier chars:
+ * -      36:    $
+ * -  48..57: 0..9
+ * -  65..90: A..Z
+ * -      95:    _
+ * - 97..122: a..z
+ */
+const bool js_isident[] = {
+/*       0     1     2     3     4     5     6     7     8     9  */
+/*  0 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  1 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  2 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  3 */ ____, ____, ____, ____, ____, ____, true, ____, ____, ____,
+/*  4 */ ____, ____, ____, ____, ____, ____, ____, ____, true, true,
+/*  5 */ true, true, true, true, true, true, true, true, ____, ____,
+/*  6 */ ____, ____, ____, ____, ____, true, true, true, true, true,
+/*  7 */ true, true, true, true, true, true, true, true, true, true,
+/*  8 */ true, true, true, true, true, true, true, true, true, true,
+/*  9 */ true, ____, ____, ____, ____, true, ____, true, true, true,
+/* 10 */ true, true, true, true, true, true, true, true, true, true,
+/* 11 */ true, true, true, true, true, true, true, true, true, true,
+/* 12 */ true, true, true, ____, ____, ____, ____, ____
+};
+
+/* Whitespace chars: '\t', '\n', '\v', '\f', '\r', ' '. */
+const bool js_isspace[] = {
+/*       0     1     2     3     4     5     6     7     8     9  */
+/*  0 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, true,
+/*  1 */ true, true, true, true, ____, ____, ____, ____, ____, ____,
+/*  2 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  3 */ ____, ____, true, ____, ____, ____, ____, ____, ____, ____,
+/*  4 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  5 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  6 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  7 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  8 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  9 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/* 10 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/* 11 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/* 12 */ ____, ____, ____, ____, ____, ____, ____, ____
+};
+
+/*
+ * Uri reserved chars + #:
+ * - 35: #
+ * - 36: $
+ * - 38: &
+ * - 43: +
+ * - 44: ,
+ * - 47: /
+ * - 58: :
+ * - 59: ;
+ * - 61: =
+ * - 63: ?
+ * - 64: @
+ */
+static const bool js_isUriReservedPlusPound[] = {
+/*       0     1     2     3     4     5     6     7     8     9  */
+/*  0 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  1 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  2 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  3 */ ____, ____, ____, ____, ____, true, true, ____, true, ____,
+/*  4 */ ____, ____, ____, true, true, ____, ____, true, ____, ____,
+/*  5 */ ____, ____, ____, ____, ____, ____, ____, ____, true, true,
+/*  6 */ ____, true, ____, true, true, ____, ____, ____, ____, ____,
+/*  7 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  8 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  9 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/* 10 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/* 11 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/* 12 */ ____, ____, ____, ____, ____, ____, ____, ____
+};
+
+/*
+ * Uri unescaped chars:
+ * -      33: !
+ * -      39: '
+ * -      40: (
+ * -      41: )
+ * -      42: *
+ * -      45: -
+ * -      46: .
+ * -  48..57: 0-9
+ * -  65..90: A-Z
+ * -      95: _
+ * - 97..122: a-z
+ * -     126: ~
+ */
+static const bool js_isUriUnescaped[] = {
+/*       0     1     2     3     4     5     6     7     8     9  */
+/*  0 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  1 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  2 */ ____, ____, ____, ____, ____, ____, ____, ____, ____, ____,
+/*  3 */ ____, ____, ____, true, ____, ____, ____, ____, ____, true,
+/*  4 */ true, true, true, ____, ____, true, true, ____, true, true,
+/*  5 */ true, true, true, true, true, true, true, true, ____, ____,
+/*  6 */ ____, ____, ____, ____, ____, true, true, true, true, true,
+/*  7 */ true, true, true, true, true, true, true, true, true, true,
+/*  8 */ true, true, true, true, true, true, true, true, true, true,
+/*  9 */ true, ____, ____, ____, ____, true, ____, true, true, true,
+/* 10 */ true, true, true, true, true, true, true, true, true, true,
+/* 11 */ true, true, true, true, true, true, true, true, true, true,
+/* 12 */ true, true, true, ____, ____, ____, true, ____
+};
+
+#undef ____
+
+#define URI_CHUNK 64U
+
+static inline bool
+TransferBufferToString(StringBuffer& sb, MutableHandleValue rval)
+{
+    JSString* str = sb.finishString();
+    if (!str)
+        return false;
+    rval.setString(str);
+    return true;
+}
+
+/*
+ * ECMA 3, 15.1.3 URI Handling Function Properties
+ *
+ * The following are implementations of the algorithms
+ * given in the ECMA specification for the hidden functions
+ * 'Encode' and 'Decode'.
+ */
+enum EncodeResult { Encode_Failure, Encode_BadUri, Encode_Success };
+
+template <typename CharT>
+static EncodeResult
+Encode(StringBuffer& sb, const CharT* chars, size_t length,
+       const bool* unescapedSet, const bool* unescapedSet2)
+{
+    static const char HexDigits[] = "0123456789ABCDEF"; /* NB: uppercase */
+
+    char16_t hexBuf[4];
+    hexBuf[0] = '%';
+    hexBuf[3] = 0;
+
+    for (size_t k = 0; k < length; k++) {
+        char16_t c = chars[k];
+        if (c < 128 && (unescapedSet[c] || (unescapedSet2 && unescapedSet2[c]))) {
+            if (!sb.append(c))
+                return Encode_Failure;
+        } else {
+            if (unicode::IsTrailSurrogate(c))
+                return Encode_BadUri;
+
+            uint32_t v;
+            if (!unicode::IsLeadSurrogate(c)) {
+                v = c;
+            } else {
+                k++;
+                if (k == length)
+                    return Encode_BadUri;
+
+                char16_t c2 = chars[k];
+                if (!unicode::IsTrailSurrogate(c2))
+                    return Encode_BadUri;
+
+                v = unicode::UTF16Decode(c, c2);
+            }
+            uint8_t utf8buf[4];
+            size_t L = OneUcs4ToUtf8Char(utf8buf, v);
+            for (size_t j = 0; j < L; j++) {
+                hexBuf[1] = HexDigits[utf8buf[j] >> 4];
+                hexBuf[2] = HexDigits[utf8buf[j] & 0xf];
+                if (!sb.append(hexBuf, 3))
+                    return Encode_Failure;
+            }
+        }
+    }
+
+    return Encode_Success;
+}
+
+static bool
+Encode(JSContext* cx, HandleLinearString str, const bool* unescapedSet,
+       const bool* unescapedSet2, MutableHandleValue rval)
+{
+    size_t length = str->length();
+    if (length == 0) {
+        rval.setString(cx->runtime()->emptyString);
+        return true;
+    }
+
+    StringBuffer sb(cx);
+    if (!sb.reserve(length))
+        return false;
+
+    EncodeResult res;
+    if (str->hasLatin1Chars()) {
+        AutoCheckCannotGC nogc;
+        res = Encode(sb, str->latin1Chars(nogc), str->length(), unescapedSet, unescapedSet2);
+    } else {
+        AutoCheckCannotGC nogc;
+        res = Encode(sb, str->twoByteChars(nogc), str->length(), unescapedSet, unescapedSet2);
+    }
+
+    if (res == Encode_Failure)
+        return false;
+
+    if (res == Encode_BadUri) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_BAD_URI);
+        return false;
+    }
+
+    MOZ_ASSERT(res == Encode_Success);
+    return TransferBufferToString(sb, rval);
+}
+
+enum DecodeResult { Decode_Failure, Decode_BadUri, Decode_Success };
+
+template <typename CharT>
+static DecodeResult
+Decode(StringBuffer& sb, const CharT* chars, size_t length, const bool* reservedSet)
+{
+    for (size_t k = 0; k < length; k++) {
+        char16_t c = chars[k];
+        if (c == '%') {
+            size_t start = k;
+            if ((k + 2) >= length)
+                return Decode_BadUri;
+
+            if (!JS7_ISHEX(chars[k+1]) || !JS7_ISHEX(chars[k+2]))
+                return Decode_BadUri;
+
+            uint32_t B = JS7_UNHEX(chars[k+1]) * 16 + JS7_UNHEX(chars[k+2]);
+            k += 2;
+            if (!(B & 0x80)) {
+                c = char16_t(B);
+            } else {
+                int n = 1;
+                while (B & (0x80 >> n))
+                    n++;
+
+                if (n == 1 || n > 4)
+                    return Decode_BadUri;
+
+                uint8_t octets[4];
+                octets[0] = (uint8_t)B;
+                if (k + 3 * (n - 1) >= length)
+                    return Decode_BadUri;
+
+                for (int j = 1; j < n; j++) {
+                    k++;
+                    if (chars[k] != '%')
+                        return Decode_BadUri;
+
+                    if (!JS7_ISHEX(chars[k+1]) || !JS7_ISHEX(chars[k+2]))
+                        return Decode_BadUri;
+
+                    B = JS7_UNHEX(chars[k+1]) * 16 + JS7_UNHEX(chars[k+2]);
+                    if ((B & 0xC0) != 0x80)
+                        return Decode_BadUri;
+
+                    k += 2;
+                    octets[j] = char(B);
+                }
+                uint32_t v = JS::Utf8ToOneUcs4Char(octets, n);
+                if (v >= unicode::NonBMPMin) {
+                    if (v > unicode::NonBMPMax)
+                        return Decode_BadUri;
+
+                    char16_t H = unicode::LeadSurrogate(v);
+                    if (!sb.append(H))
+                        return Decode_Failure;
+                    c = unicode::TrailSurrogate(v);
+                } else {
+                    c = char16_t(v);
+                }
+            }
+            if (c < 128 && reservedSet && reservedSet[c]) {
+                if (!sb.append(chars + start, k - start + 1))
+                    return Decode_Failure;
+            } else {
+                if (!sb.append(c))
+                    return Decode_Failure;
+            }
+        } else {
+            if (!sb.append(c))
+                return Decode_Failure;
+        }
+    }
+
+    return Decode_Success;
+}
+
+static bool
+Decode(JSContext* cx, HandleLinearString str, const bool* reservedSet, MutableHandleValue rval)
+{
+    size_t length = str->length();
+    if (length == 0) {
+        rval.setString(cx->runtime()->emptyString);
+        return true;
+    }
+
+    StringBuffer sb(cx);
+
+    DecodeResult res;
+    if (str->hasLatin1Chars()) {
+        AutoCheckCannotGC nogc;
+        res = Decode(sb, str->latin1Chars(nogc), str->length(), reservedSet);
+    } else {
+        AutoCheckCannotGC nogc;
+        res = Decode(sb, str->twoByteChars(nogc), str->length(), reservedSet);
+    }
+
+    if (res == Decode_Failure)
+        return false;
+
+    if (res == Decode_BadUri) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_BAD_URI);
+        return false;
+    }
+
+    MOZ_ASSERT(res == Decode_Success);
+    return TransferBufferToString(sb, rval);
+}
+
+static bool
+str_decodeURI(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    RootedLinearString str(cx, ArgToRootedString(cx, args, 0));
+    if (!str)
+        return false;
+
+    return Decode(cx, str, js_isUriReservedPlusPound, args.rval());
+}
+
+static bool
+str_decodeURI_Component(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    RootedLinearString str(cx, ArgToRootedString(cx, args, 0));
+    if (!str)
+        return false;
+
+    return Decode(cx, str, nullptr, args.rval());
+}
+
+static bool
+str_encodeURI(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    RootedLinearString str(cx, ArgToRootedString(cx, args, 0));
+    if (!str)
+        return false;
+
+    return Encode(cx, str, js_isUriUnescaped, js_isUriReservedPlusPound, args.rval());
+}
+
+static bool
+str_encodeURI_Component(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    RootedLinearString str(cx, ArgToRootedString(cx, args, 0));
+    if (!str)
+        return false;
+
+    return Encode(cx, str, js_isUriUnescaped, nullptr, args.rval());
+}
+
+/*
+ * Convert one UCS-4 char and write it into a UTF-8 buffer, which must be at
+ * least 4 bytes long.  Return the number of UTF-8 bytes of data written.
+ */
+uint32_t
+js::OneUcs4ToUtf8Char(uint8_t* utf8Buffer, uint32_t ucs4Char)
+{
+    MOZ_ASSERT(ucs4Char <= unicode::NonBMPMax);
+
+    if (ucs4Char < 0x80) {
+        utf8Buffer[0] = uint8_t(ucs4Char);
+        return 1;
+    }
+
+    uint32_t a = ucs4Char >> 11;
+    uint32_t utf8Length = 2;
+    while (a) {
+        a >>= 5;
+        utf8Length++;
+    }
+
+    MOZ_ASSERT(utf8Length <= 4);
+
+    uint32_t i = utf8Length;
+    while (--i) {
+        utf8Buffer[i] = uint8_t((ucs4Char & 0x3F) | 0x80);
+        ucs4Char >>= 6;
+    }
+
+    utf8Buffer[0] = uint8_t(0x100 - (1 << (8 - utf8Length)) + ucs4Char);
+    return utf8Length;
+}
+
+size_t
+js::PutEscapedStringImpl(char* buffer, size_t bufferSize, GenericPrinter* out, JSLinearString* str,
+                         uint32_t quote)
+{
+    size_t len = str->length();
+    AutoCheckCannotGC nogc;
+    return str->hasLatin1Chars()
+           ? PutEscapedStringImpl(buffer, bufferSize, out, str->latin1Chars(nogc), len, quote)
+           : PutEscapedStringImpl(buffer, bufferSize, out, str->twoByteChars(nogc), len, quote);
+}
+
+template <typename CharT>
+size_t
+js::PutEscapedStringImpl(char* buffer, size_t bufferSize, GenericPrinter* out, const CharT* chars,
+                         size_t length, uint32_t quote)
+{
+    enum {
+        STOP, FIRST_QUOTE, LAST_QUOTE, CHARS, ESCAPE_START, ESCAPE_MORE
+    } state;
+
+    MOZ_ASSERT(quote == 0 || quote == '\'' || quote == '"');
+    MOZ_ASSERT_IF(!buffer, bufferSize == 0);
+    MOZ_ASSERT_IF(out, !buffer);
+
+    if (bufferSize == 0)
+        buffer = nullptr;
+    else
+        bufferSize--;
+
+    const CharT* charsEnd = chars + length;
+    size_t n = 0;
+    state = FIRST_QUOTE;
+    unsigned shift = 0;
+    unsigned hex = 0;
+    unsigned u = 0;
+    char c = 0;  /* to quell GCC warnings */
+
+    for (;;) {
+        switch (state) {
+          case STOP:
+            goto stop;
+          case FIRST_QUOTE:
+            state = CHARS;
+            goto do_quote;
+          case LAST_QUOTE:
+            state = STOP;
+          do_quote:
+            if (quote == 0)
+                continue;
+            c = (char)quote;
+            break;
+          case CHARS:
+            if (chars == charsEnd) {
+                state = LAST_QUOTE;
+                continue;
+            }
+            u = *chars++;
+            if (u < ' ') {
+                if (u != 0) {
+                    const char* escape = strchr(js_EscapeMap, (int)u);
+                    if (escape) {
+                        u = escape[1];
+                        goto do_escape;
+                    }
+                }
+                goto do_hex_escape;
+            }
+            if (u < 127) {
+                if (u == quote || u == '\\')
+                    goto do_escape;
+                c = (char)u;
+            } else if (u < 0x100) {
+                goto do_hex_escape;
+            } else {
+                shift = 16;
+                hex = u;
+                u = 'u';
+                goto do_escape;
+            }
+            break;
+          do_hex_escape:
+            shift = 8;
+            hex = u;
+            u = 'x';
+          do_escape:
+            c = '\\';
+            state = ESCAPE_START;
+            break;
+          case ESCAPE_START:
+            MOZ_ASSERT(' ' <= u && u < 127);
+            c = (char)u;
+            state = ESCAPE_MORE;
+            break;
+          case ESCAPE_MORE:
+            if (shift == 0) {
+                state = CHARS;
+                continue;
+            }
+            shift -= 4;
+            u = 0xF & (hex >> shift);
+            c = (char)(u + (u < 10 ? '0' : 'A' - 10));
+            break;
+        }
+        if (buffer) {
+            MOZ_ASSERT(n <= bufferSize);
+            if (n != bufferSize) {
+                buffer[n] = c;
+            } else {
+                buffer[n] = '\0';
+                buffer = nullptr;
+            }
+        } else if (out) {
+            if (out->put(&c, 1) < 0)
+                return size_t(-1);
+        }
+        n++;
+    }
+  stop:
+    if (buffer)
+        buffer[n] = '\0';
+    return n;
+}
+
+template size_t
+js::PutEscapedStringImpl(char* buffer, size_t bufferSize, GenericPrinter* out, const Latin1Char* chars,
+                         size_t length, uint32_t quote);
+
+template size_t
+js::PutEscapedStringImpl(char* buffer, size_t bufferSize, GenericPrinter* out, const char* chars,
+                         size_t length, uint32_t quote);
+
+template size_t
+js::PutEscapedStringImpl(char* buffer, size_t bufferSize, GenericPrinter* out, const char16_t* chars,
+                         size_t length, uint32_t quote);
+
+template size_t
+js::PutEscapedString(char* buffer, size_t bufferSize, const Latin1Char* chars, size_t length,
+                     uint32_t quote);
+
+template size_t
+js::PutEscapedString(char* buffer, size_t bufferSize, const char16_t* chars, size_t length,
+                     uint32_t quote);
+
+static bool
+FlatStringMatchHelper(JSContext* cx, HandleString str, HandleString pattern, bool* isFlat, int32_t* match)
+{
+    RootedLinearString linearPattern(cx, pattern->ensureLinear(cx));
+    if (!linearPattern)
+        return false;
+
+    static const size_t MAX_FLAT_PAT_LEN = 256;
+    if (linearPattern->length() > MAX_FLAT_PAT_LEN || StringHasRegExpMetaChars(linearPattern)) {
+        *isFlat = false;
+        return true;
+    }
+
+    *isFlat = true;
+    if (str->isRope()) {
+        if (!RopeMatch(cx, &str->asRope(), linearPattern, match))
+            return false;
+    } else {
+        *match = StringMatch(&str->asLinear(), linearPattern);
+    }
+
+    return true;
+}
+
+static bool
+BuildFlatMatchArray(JSContext* cx, HandleString str, HandleString pattern, int32_t match,
+                    MutableHandleValue rval)
+{
+    if (match < 0) {
+        rval.setNull();
+        return true;
+    }
+
+    /* Get the templateObject that defines the shape and type of the output object */
+    JSObject* templateObject = cx->compartment()->regExps.getOrCreateMatchResultTemplateObject(cx);
+    if (!templateObject)
+        return false;
+
+    RootedArrayObject arr(cx, NewDenseFullyAllocatedArrayWithTemplate(cx, 1, templateObject));
+    if (!arr)
+        return false;
+
+    /* Store a Value for each pair. */
+    arr->setDenseInitializedLength(1);
+    arr->initDenseElement(0, StringValue(pattern));
+
+    /* Set the |index| property. (TemplateObject positions it in slot 0) */
+    arr->setSlot(0, Int32Value(match));
+
+    /* Set the |input| property. (TemplateObject positions it in slot 1) */
+    arr->setSlot(1, StringValue(str));
+
+#ifdef DEBUG
+    RootedValue test(cx);
+    RootedId id(cx, NameToId(cx->names().index));
+    if (!NativeGetProperty(cx, arr, id, &test))
+        return false;
+    MOZ_ASSERT(test == arr->getSlot(0));
+    id = NameToId(cx->names().input);
+    if (!NativeGetProperty(cx, arr, id, &test))
+        return false;
+    MOZ_ASSERT(test == arr->getSlot(1));
+#endif
+
+    rval.setObject(*arr);
+    return true;
+}
+
+#ifdef DEBUG
+static bool
+CallIsStringOptimizable(JSContext* cx, const char* name, bool* result)
+{
+    JSAtom* atom = Atomize(cx, name, strlen(name));
+    if (!atom)
+        return false;
+    RootedPropertyName propName(cx, atom->asPropertyName());
+
+    RootedValue funcVal(cx);
+    if (!GlobalObject::getSelfHostedFunction(cx, cx->global(), propName, propName, 0, &funcVal))
+        return false;
+
+    FixedInvokeArgs<0> args(cx);
+
+    RootedValue rval(cx);
+    if (!Call(cx, funcVal, UndefinedHandleValue, args, &rval))
+        return false;
+
+    *result = rval.toBoolean();
+    return true;
+}
+#endif
+
+bool
+js::FlatStringMatch(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    MOZ_ASSERT(args.length() == 2);
+    MOZ_ASSERT(args[0].isString());
+    MOZ_ASSERT(args[1].isString());
+#ifdef DEBUG
+    bool isOptimizable = false;
+    if (!CallIsStringOptimizable(cx, "IsStringMatchOptimizable", &isOptimizable))
+        return false;
+    MOZ_ASSERT(isOptimizable);
+#endif
+
+    RootedString str(cx,args[0].toString());
+    RootedString pattern(cx, args[1].toString());
+
+    bool isFlat = false;
+    int32_t match = 0;
+    if (!FlatStringMatchHelper(cx, str, pattern, &isFlat, &match))
+        return false;
+
+    if (!isFlat) {
+        args.rval().setUndefined();
+        return true;
+    }
+
+    return BuildFlatMatchArray(cx, str, pattern, match, args.rval());
+}
+
+bool
+js::FlatStringSearch(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    MOZ_ASSERT(args.length() == 2);
+    MOZ_ASSERT(args[0].isString());
+    MOZ_ASSERT(args[1].isString());
+#ifdef DEBUG
+    bool isOptimizable = false;
+    if (!CallIsStringOptimizable(cx, "IsStringSearchOptimizable", &isOptimizable))
+        return false;
+    MOZ_ASSERT(isOptimizable);
+#endif
+
+    RootedString str(cx,args[0].toString());
+    RootedString pattern(cx, args[1].toString());
+
+    bool isFlat = false;
+    int32_t match = 0;
+    if (!FlatStringMatchHelper(cx, str, pattern, &isFlat, &match))
+        return false;
+
+    if (!isFlat) {
+        args.rval().setInt32(-2);
+        return true;
+    }
+
+    args.rval().setInt32(match);
+    return true;
+}