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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+/**
+ * Conversions from jsval to primitive values
+ */
+
+#ifndef mozilla_dom_PrimitiveConversions_h
+#define mozilla_dom_PrimitiveConversions_h
+
+#include <limits>
+#include <math.h>
+#include <stdint.h>
+
+#include "jsapi.h"
+#include "js/Conversions.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/ErrorResult.h"
+#include "mozilla/FloatingPoint.h"
+
+namespace mozilla {
+namespace dom {
+
+template<typename T>
+struct TypeName {
+};
+
+template<>
+struct TypeName<int8_t> {
+ static const char* value() {
+ return "byte";
+ }
+};
+template<>
+struct TypeName<uint8_t> {
+ static const char* value() {
+ return "octet";
+ }
+};
+template<>
+struct TypeName<int16_t> {
+ static const char* value() {
+ return "short";
+ }
+};
+template<>
+struct TypeName<uint16_t> {
+ static const char* value() {
+ return "unsigned short";
+ }
+};
+template<>
+struct TypeName<int32_t> {
+ static const char* value() {
+ return "long";
+ }
+};
+template<>
+struct TypeName<uint32_t> {
+ static const char* value() {
+ return "unsigned long";
+ }
+};
+template<>
+struct TypeName<int64_t> {
+ static const char* value() {
+ return "long long";
+ }
+};
+template<>
+struct TypeName<uint64_t> {
+ static const char* value() {
+ return "unsigned long long";
+ }
+};
+
+
+enum ConversionBehavior {
+ eDefault,
+ eEnforceRange,
+ eClamp
+};
+
+template<typename T, ConversionBehavior B>
+struct PrimitiveConversionTraits {
+};
+
+template<typename T>
+struct DisallowedConversion {
+ typedef int jstype;
+ typedef int intermediateType;
+
+private:
+ static inline bool converter(JSContext* cx, JS::Handle<JS::Value> v,
+ jstype* retval) {
+ MOZ_CRASH("This should never be instantiated!");
+ }
+};
+
+struct PrimitiveConversionTraits_smallInt {
+ // The output of JS::ToInt32 is determined as follows:
+ // 1) The value is converted to a double
+ // 2) Anything that's not a finite double returns 0
+ // 3) The double is rounded towards zero to the nearest integer
+ // 4) The resulting integer is reduced mod 2^32. The output of this
+ // operation is an integer in the range [0, 2^32).
+ // 5) If the resulting number is >= 2^31, 2^32 is subtracted from it.
+ //
+ // The result of all this is a number in the range [-2^31, 2^31)
+ //
+ // WebIDL conversions for the 8-bit, 16-bit, and 32-bit integer types
+ // are defined in the same way, except that step 4 uses reduction mod
+ // 2^8 and 2^16 for the 8-bit and 16-bit types respectively, and step 5
+ // is only done for the signed types.
+ //
+ // C/C++ define integer conversion semantics to unsigned types as taking
+ // your input integer mod (1 + largest value representable in the
+ // unsigned type). Since 2^32 is zero mod 2^8, 2^16, and 2^32,
+ // converting to the unsigned int of the relevant width will correctly
+ // perform step 4; in particular, the 2^32 possibly subtracted in step 5
+ // will become 0.
+ //
+ // Once we have step 4 done, we're just going to assume 2s-complement
+ // representation and cast directly to the type we really want.
+ //
+ // So we can cast directly for all unsigned types and for int32_t; for
+ // the smaller-width signed types we need to cast through the
+ // corresponding unsigned type.
+ typedef int32_t jstype;
+ typedef int32_t intermediateType;
+ static inline bool converter(JSContext* cx, JS::Handle<JS::Value> v,
+ jstype* retval) {
+ return JS::ToInt32(cx, v, retval);
+ }
+};
+template<>
+struct PrimitiveConversionTraits<int8_t, eDefault> : PrimitiveConversionTraits_smallInt {
+ typedef uint8_t intermediateType;
+};
+template<>
+struct PrimitiveConversionTraits<uint8_t, eDefault> : PrimitiveConversionTraits_smallInt {
+};
+template<>
+struct PrimitiveConversionTraits<int16_t, eDefault> : PrimitiveConversionTraits_smallInt {
+ typedef uint16_t intermediateType;
+};
+template<>
+struct PrimitiveConversionTraits<uint16_t, eDefault> : PrimitiveConversionTraits_smallInt {
+};
+template<>
+struct PrimitiveConversionTraits<int32_t, eDefault> : PrimitiveConversionTraits_smallInt {
+};
+template<>
+struct PrimitiveConversionTraits<uint32_t, eDefault> : PrimitiveConversionTraits_smallInt {
+};
+
+template<>
+struct PrimitiveConversionTraits<int64_t, eDefault> {
+ typedef int64_t jstype;
+ typedef int64_t intermediateType;
+ static inline bool converter(JSContext* cx, JS::Handle<JS::Value> v,
+ jstype* retval) {
+ return JS::ToInt64(cx, v, retval);
+ }
+};
+
+template<>
+struct PrimitiveConversionTraits<uint64_t, eDefault> {
+ typedef uint64_t jstype;
+ typedef uint64_t intermediateType;
+ static inline bool converter(JSContext* cx, JS::Handle<JS::Value> v,
+ jstype* retval) {
+ return JS::ToUint64(cx, v, retval);
+ }
+};
+
+template<typename T>
+struct PrimitiveConversionTraits_Limits {
+ static inline T min() {
+ return std::numeric_limits<T>::min();
+ }
+ static inline T max() {
+ return std::numeric_limits<T>::max();
+ }
+};
+
+template<>
+struct PrimitiveConversionTraits_Limits<int64_t> {
+ static inline int64_t min() {
+ return -(1LL << 53) + 1;
+ }
+ static inline int64_t max() {
+ return (1LL << 53) - 1;
+ }
+};
+
+template<>
+struct PrimitiveConversionTraits_Limits<uint64_t> {
+ static inline uint64_t min() {
+ return 0;
+ }
+ static inline uint64_t max() {
+ return (1LL << 53) - 1;
+ }
+};
+
+template<typename T, bool (*Enforce)(JSContext* cx, const double& d, T* retval)>
+struct PrimitiveConversionTraits_ToCheckedIntHelper {
+ typedef T jstype;
+ typedef T intermediateType;
+
+ static inline bool converter(JSContext* cx, JS::Handle<JS::Value> v,
+ jstype* retval) {
+ double intermediate;
+ if (!JS::ToNumber(cx, v, &intermediate)) {
+ return false;
+ }
+
+ return Enforce(cx, intermediate, retval);
+ }
+};
+
+template<typename T>
+inline bool
+PrimitiveConversionTraits_EnforceRange(JSContext* cx, const double& d, T* retval)
+{
+ static_assert(std::numeric_limits<T>::is_integer,
+ "This can only be applied to integers!");
+
+ if (!mozilla::IsFinite(d)) {
+ return ThrowErrorMessage(cx, MSG_ENFORCE_RANGE_NON_FINITE, TypeName<T>::value());
+ }
+
+ bool neg = (d < 0);
+ double rounded = floor(neg ? -d : d);
+ rounded = neg ? -rounded : rounded;
+ if (rounded < PrimitiveConversionTraits_Limits<T>::min() ||
+ rounded > PrimitiveConversionTraits_Limits<T>::max()) {
+ return ThrowErrorMessage(cx, MSG_ENFORCE_RANGE_OUT_OF_RANGE, TypeName<T>::value());
+ }
+
+ *retval = static_cast<T>(rounded);
+ return true;
+}
+
+template<typename T>
+struct PrimitiveConversionTraits<T, eEnforceRange> :
+ public PrimitiveConversionTraits_ToCheckedIntHelper<T, PrimitiveConversionTraits_EnforceRange<T> > {
+};
+
+template<typename T>
+inline bool
+PrimitiveConversionTraits_Clamp(JSContext* cx, const double& d, T* retval)
+{
+ static_assert(std::numeric_limits<T>::is_integer,
+ "This can only be applied to integers!");
+
+ if (mozilla::IsNaN(d)) {
+ *retval = 0;
+ return true;
+ }
+ if (d >= PrimitiveConversionTraits_Limits<T>::max()) {
+ *retval = PrimitiveConversionTraits_Limits<T>::max();
+ return true;
+ }
+ if (d <= PrimitiveConversionTraits_Limits<T>::min()) {
+ *retval = PrimitiveConversionTraits_Limits<T>::min();
+ return true;
+ }
+
+ MOZ_ASSERT(mozilla::IsFinite(d));
+
+ // Banker's rounding (round ties towards even).
+ // We move away from 0 by 0.5f and then truncate. That gets us the right
+ // answer for any starting value except plus or minus N.5. With a starting
+ // value of that form, we now have plus or minus N+1. If N is odd, this is
+ // the correct result. If N is even, plus or minus N is the correct result.
+ double toTruncate = (d < 0) ? d - 0.5 : d + 0.5;
+
+ T truncated = static_cast<T>(toTruncate);
+
+ if (truncated == toTruncate) {
+ /*
+ * It was a tie (since moving away from 0 by 0.5 gave us the exact integer
+ * we want). Since we rounded away from 0, we either already have an even
+ * number or we have an odd number but the number we want is one closer to
+ * 0. So just unconditionally masking out the ones bit should do the trick
+ * to get us the value we want.
+ */
+ truncated &= ~1;
+ }
+
+ *retval = truncated;
+ return true;
+}
+
+template<typename T>
+struct PrimitiveConversionTraits<T, eClamp> :
+ public PrimitiveConversionTraits_ToCheckedIntHelper<T, PrimitiveConversionTraits_Clamp<T> > {
+};
+
+
+template<ConversionBehavior B>
+struct PrimitiveConversionTraits<bool, B> : public DisallowedConversion<bool> {};
+
+template<>
+struct PrimitiveConversionTraits<bool, eDefault> {
+ typedef bool jstype;
+ typedef bool intermediateType;
+ static inline bool converter(JSContext* /* unused */, JS::Handle<JS::Value> v,
+ jstype* retval) {
+ *retval = JS::ToBoolean(v);
+ return true;
+ }
+};
+
+
+template<ConversionBehavior B>
+struct PrimitiveConversionTraits<float, B> : public DisallowedConversion<float> {};
+
+template<ConversionBehavior B>
+struct PrimitiveConversionTraits<double, B> : public DisallowedConversion<double> {};
+
+struct PrimitiveConversionTraits_float {
+ typedef double jstype;
+ typedef double intermediateType;
+ static inline bool converter(JSContext* cx, JS::Handle<JS::Value> v,
+ jstype* retval) {
+ return JS::ToNumber(cx, v, retval);
+ }
+};
+
+template<>
+struct PrimitiveConversionTraits<float, eDefault> : PrimitiveConversionTraits_float {
+};
+template<>
+struct PrimitiveConversionTraits<double, eDefault> : PrimitiveConversionTraits_float {
+};
+
+
+template<typename T, ConversionBehavior B>
+bool ValueToPrimitive(JSContext* cx, JS::Handle<JS::Value> v, T* retval)
+{
+ typename PrimitiveConversionTraits<T, B>::jstype t;
+ if (!PrimitiveConversionTraits<T, B>::converter(cx, v, &t))
+ return false;
+
+ *retval = static_cast<T>(
+ static_cast<typename PrimitiveConversionTraits<T, B>::intermediateType>(t));
+ return true;
+}
+
+} // namespace dom
+} // namespace mozilla
+
+#endif /* mozilla_dom_PrimitiveConversions_h */