path: root/js/src/vm/String-inl.h

/* -*- 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/. */

#ifndef vm_String_inl_h
#define vm_String_inl_h

#include "vm/String.h"

#include "mozilla/PodOperations.h"
#include "mozilla/Range.h"

#include "jscntxt.h"
#include "jscompartment.h"

#include "gc/Allocator.h"
#include "gc/Marking.h"

namespace js {

// Allocate a thin inline string if possible, and a fat inline string if not.
template <AllowGC allowGC, typename CharT>
static MOZ_ALWAYS_INLINE JSInlineString*
AllocateInlineString(ExclusiveContext* cx, size_t len, CharT** chars)
{
    MOZ_ASSERT(JSInlineString::lengthFits<CharT>(len));

    if (JSThinInlineString::lengthFits<CharT>(len)) {
        JSThinInlineString* str = JSThinInlineString::new_<allowGC>(cx);
        if (!str)
            return nullptr;
        *chars = str->init<CharT>(len);
        return str;
    }

    JSFatInlineString* str = JSFatInlineString::new_<allowGC>(cx);
    if (!str)
        return nullptr;
    *chars = str->init<CharT>(len);
    return str;
}

// Create a thin inline string if possible, and a fat inline string if not.
template <AllowGC allowGC, typename CharT>
static MOZ_ALWAYS_INLINE JSInlineString*
NewInlineString(ExclusiveContext* cx, mozilla::Range<const CharT> chars)
{
    /*
     * Don't bother trying to find a static atom; measurement shows that not
     * many get here (for one, Atomize is catching them).
     */

    size_t len = chars.length();
    CharT* storage;
    JSInlineString* str = AllocateInlineString<allowGC>(cx, len, &storage);
    if (!str)
        return nullptr;

    mozilla::PodCopy(storage, chars.begin().get(), len);
    storage[len] = 0;
    return str;
}

// Create a thin inline string if possible, and a fat inline string if not.
template <typename CharT>
static MOZ_ALWAYS_INLINE JSInlineString*
NewInlineString(ExclusiveContext* cx, HandleLinearString base, size_t start, size_t length)
{
    MOZ_ASSERT(JSInlineString::lengthFits<CharT>(length));

    CharT* chars;
    JSInlineString* s = AllocateInlineString<CanGC>(cx, length, &chars);
    if (!s)
        return nullptr;

    JS::AutoCheckCannotGC nogc;
    mozilla::PodCopy(chars, base->chars<CharT>(nogc) + start, length);
    chars[length] = 0;
    return s;
}

static inline void
StringWriteBarrierPost(js::ExclusiveContext* maybecx, JSString** strp)
{
}

static inline void
StringWriteBarrierPostRemove(js::ExclusiveContext* maybecx, JSString** strp)
{
}

} /* namespace js */

MOZ_ALWAYS_INLINE bool
JSString::validateLength(js::ExclusiveContext* maybecx, size_t length)
{
    if (MOZ_UNLIKELY(length > JSString::MAX_LENGTH)) {
        js::ReportAllocationOverflow(maybecx);
        return false;
    }

    return true;
}

MOZ_ALWAYS_INLINE void
JSRope::init(js::ExclusiveContext* cx, JSString* left, JSString* right, size_t length)
{
    d.u1.length = length;
    d.u1.flags = ROPE_FLAGS;
    if (left->hasLatin1Chars() && right->hasLatin1Chars())
        d.u1.flags |= LATIN1_CHARS_BIT;
    d.s.u2.left = left;
    d.s.u3.right = right;
    js::StringWriteBarrierPost(cx, &d.s.u2.left);
    js::StringWriteBarrierPost(cx, &d.s.u3.right);
}

template <js::AllowGC allowGC>
MOZ_ALWAYS_INLINE JSRope*
JSRope::new_(js::ExclusiveContext* cx,
             typename js::MaybeRooted<JSString*, allowGC>::HandleType left,
             typename js::MaybeRooted<JSString*, allowGC>::HandleType right,
             size_t length)
{
    if (!validateLength(cx, length))
        return nullptr;
    JSRope* str = static_cast<JSRope*>(js::Allocate<JSString, allowGC>(cx));
    if (!str)
        return nullptr;
    str->init(cx, left, right, length);
    return str;
}

MOZ_ALWAYS_INLINE void
JSDependentString::init(js::ExclusiveContext* cx, JSLinearString* base, size_t start,
                        size_t length)
{
    MOZ_ASSERT(start + length <= base->length());
    d.u1.length = length;
    JS::AutoCheckCannotGC nogc;
    if (base->hasLatin1Chars()) {
        d.u1.flags = DEPENDENT_FLAGS | LATIN1_CHARS_BIT;
        d.s.u2.nonInlineCharsLatin1 = base->latin1Chars(nogc) + start;
    } else {
        d.u1.flags = DEPENDENT_FLAGS;
        d.s.u2.nonInlineCharsTwoByte = base->twoByteChars(nogc) + start;
    }
    d.s.u3.base = base;
    js::StringWriteBarrierPost(cx, reinterpret_cast<JSString**>(&d.s.u3.base));
}

MOZ_ALWAYS_INLINE JSLinearString*
JSDependentString::new_(js::ExclusiveContext* cx, JSLinearString* baseArg, size_t start,
                        size_t length)
{
    /*
     * Try to avoid long chains of dependent strings. We can't avoid these
     * entirely, however, due to how ropes are flattened.
     */
    if (baseArg->isDependent()) {
        if (mozilla::Maybe<size_t> offset = baseArg->asDependent().baseOffset()) {
            start += *offset;
            baseArg = baseArg->asDependent().base();
        }
    }

    MOZ_ASSERT(start + length <= baseArg->length());

    /*
     * Do not create a string dependent on inline chars from another string,
     * both to avoid the awkward moving-GC hazard this introduces and because it
     * is more efficient to immediately undepend here.
     */
    bool useInline = baseArg->hasTwoByteChars()
                     ? JSInlineString::lengthFits<char16_t>(length)
                     : JSInlineString::lengthFits<JS::Latin1Char>(length);
    if (useInline) {
        js::RootedLinearString base(cx, baseArg);
        return baseArg->hasLatin1Chars()
               ? js::NewInlineString<JS::Latin1Char>(cx, base, start, length)
               : js::NewInlineString<char16_t>(cx, base, start, length);
    }

    if (baseArg->isExternal() && !baseArg->ensureFlat(cx->asJSContext()))
        return nullptr;

    JSDependentString* str = static_cast<JSDependentString*>(js::Allocate<JSString, js::NoGC>(cx));
    if (str) {
        str->init(cx, baseArg, start, length);
        return str;
    }

    js::RootedLinearString base(cx, baseArg);

    str = static_cast<JSDependentString*>(js::Allocate<JSString>(cx));
    if (!str)
        return nullptr;
    str->init(cx, base, start, length);
    return str;
}

MOZ_ALWAYS_INLINE void
JSFlatString::init(const char16_t* chars, size_t length)
{
    d.u1.length = length;
    d.u1.flags = FLAT_BIT;
    d.s.u2.nonInlineCharsTwoByte = chars;
}

MOZ_ALWAYS_INLINE void
JSFlatString::init(const JS::Latin1Char* chars, size_t length)
{
    d.u1.length = length;
    d.u1.flags = FLAT_BIT | LATIN1_CHARS_BIT;
    d.s.u2.nonInlineCharsLatin1 = chars;
}

template <js::AllowGC allowGC, typename CharT>
MOZ_ALWAYS_INLINE JSFlatString*
JSFlatString::new_(js::ExclusiveContext* cx, const CharT* chars, size_t length)
{
    MOZ_ASSERT(chars[length] == CharT(0));

    if (!validateLength(cx, length))
        return nullptr;

    JSFlatString* str;
    if (cx->compartment()->isAtomsCompartment())
        str = js::Allocate<js::NormalAtom, allowGC>(cx);
    else
        str = static_cast<JSFlatString*>(js::Allocate<JSString, allowGC>(cx));
    if (!str)
        return nullptr;

    str->init(chars, length);
    return str;
}

inline js::PropertyName*
JSFlatString::toPropertyName(JSContext* cx)
{
#ifdef DEBUG
    uint32_t dummy;
    MOZ_ASSERT(!isIndex(&dummy));
#endif
    if (isAtom())
        return asAtom().asPropertyName();
    JSAtom* atom = js::AtomizeString(cx, this);
    if (!atom)
        return nullptr;
    return atom->asPropertyName();
}

template <js::AllowGC allowGC>
MOZ_ALWAYS_INLINE JSThinInlineString*
JSThinInlineString::new_(js::ExclusiveContext* cx)
{
    if (cx->compartment()->isAtomsCompartment())
        return (JSThinInlineString*)(js::Allocate<js::NormalAtom, allowGC>(cx));

    return static_cast<JSThinInlineString*>(js::Allocate<JSString, allowGC>(cx));
}

template <js::AllowGC allowGC>
MOZ_ALWAYS_INLINE JSFatInlineString*
JSFatInlineString::new_(js::ExclusiveContext* cx)
{
    if (cx->compartment()->isAtomsCompartment())
        return (JSFatInlineString*)(js::Allocate<js::FatInlineAtom, allowGC>(cx));

    return js::Allocate<JSFatInlineString, allowGC>(cx);
}

template<>
MOZ_ALWAYS_INLINE JS::Latin1Char*
JSThinInlineString::init<JS::Latin1Char>(size_t length)
{
    MOZ_ASSERT(lengthFits<JS::Latin1Char>(length));
    d.u1.length = length;
    d.u1.flags = INIT_THIN_INLINE_FLAGS | LATIN1_CHARS_BIT;
    return d.inlineStorageLatin1;
}

template<>
MOZ_ALWAYS_INLINE char16_t*
JSThinInlineString::init<char16_t>(size_t length)
{
    MOZ_ASSERT(lengthFits<char16_t>(length));
    d.u1.length = length;
    d.u1.flags = INIT_THIN_INLINE_FLAGS;
    return d.inlineStorageTwoByte;
}

template<>
MOZ_ALWAYS_INLINE JS::Latin1Char*
JSFatInlineString::init<JS::Latin1Char>(size_t length)
{
    MOZ_ASSERT(lengthFits<JS::Latin1Char>(length));
    d.u1.length = length;
    d.u1.flags = INIT_FAT_INLINE_FLAGS | LATIN1_CHARS_BIT;
    return d.inlineStorageLatin1;
}

template<>
MOZ_ALWAYS_INLINE char16_t*
JSFatInlineString::init<char16_t>(size_t length)
{
    MOZ_ASSERT(lengthFits<char16_t>(length));
    d.u1.length = length;
    d.u1.flags = INIT_FAT_INLINE_FLAGS;
    return d.inlineStorageTwoByte;
}

MOZ_ALWAYS_INLINE void
JSExternalString::init(const char16_t* chars, size_t length, const JSStringFinalizer* fin)
{
    MOZ_ASSERT(fin);
    MOZ_ASSERT(fin->finalize);
    d.u1.length = length;
    d.u1.flags = EXTERNAL_FLAGS;
    d.s.u2.nonInlineCharsTwoByte = chars;
    d.s.u3.externalFinalizer = fin;
}

MOZ_ALWAYS_INLINE JSExternalString*
JSExternalString::new_(JSContext* cx, const char16_t* chars, size_t length,
                       const JSStringFinalizer* fin)
{
    if (!validateLength(cx, length))
        return nullptr;
    JSExternalString* str = js::Allocate<JSExternalString>(cx);
    if (!str)
        return nullptr;
    str->init(chars, length, fin);
    cx->updateMallocCounter((length + 1) * sizeof(char16_t));
    return str;
}

inline JSLinearString*
js::StaticStrings::getUnitStringForElement(JSContext* cx, JSString* str, size_t index)
{
    MOZ_ASSERT(index < str->length());

    char16_t c;
    if (!str->getChar(cx, index, &c))
        return nullptr;
    if (c < UNIT_STATIC_LIMIT)
        return getUnit(c);
    return NewDependentString(cx, str, index, 1);
}

inline JSAtom*
js::StaticStrings::getLength2(char16_t c1, char16_t c2)
{
    MOZ_ASSERT(fitsInSmallChar(c1));
    MOZ_ASSERT(fitsInSmallChar(c2));
    size_t index = (((size_t)toSmallChar[c1]) << 6) + toSmallChar[c2];
    return length2StaticTable[index];
}

MOZ_ALWAYS_INLINE void
JSString::finalize(js::FreeOp* fop)
{
    /* FatInline strings are in a different arena. */
    MOZ_ASSERT(getAllocKind() != js::gc::AllocKind::FAT_INLINE_STRING);
    MOZ_ASSERT(getAllocKind() != js::gc::AllocKind::FAT_INLINE_ATOM);

    if (isFlat())
        asFlat().finalize(fop);
    else
        MOZ_ASSERT(isDependent() || isRope());
}

inline void
JSFlatString::finalize(js::FreeOp* fop)
{
    MOZ_ASSERT(getAllocKind() != js::gc::AllocKind::FAT_INLINE_STRING);
    MOZ_ASSERT(getAllocKind() != js::gc::AllocKind::FAT_INLINE_ATOM);

    if (!isInline())
        fop->free_(nonInlineCharsRaw());
}

inline void
JSFatInlineString::finalize(js::FreeOp* fop)
{
    MOZ_ASSERT(getAllocKind() == js::gc::AllocKind::FAT_INLINE_STRING);

    if (!isInline())
        fop->free_(nonInlineCharsRaw());
}

inline void
JSAtom::finalize(js::FreeOp* fop)
{
    MOZ_ASSERT(JSString::isAtom());
    MOZ_ASSERT(JSString::isFlat());
    MOZ_ASSERT(getAllocKind() == js::gc::AllocKind::ATOM ||
               getAllocKind() == js::gc::AllocKind::FAT_INLINE_ATOM);

    if (!isInline())
        fop->free_(nonInlineCharsRaw());
}

inline void
JSExternalString::finalize(js::FreeOp* fop)
{
    if (!JSString::isExternal()) {
        // This started out as an external string, but was turned into a
        // non-external string by JSExternalString::ensureFlat.
        MOZ_ASSERT(isFlat());
        fop->free_(nonInlineCharsRaw());
        return;
    }

    const JSStringFinalizer* fin = externalFinalizer();
    fin->finalize(zone(), fin, const_cast<char16_t*>(rawTwoByteChars()));
}

#endif /* vm_String_inl_h */