зеркало из https://github.com/mozilla/gecko-dev.git
136 строки
4.4 KiB
C++
136 строки
4.4 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
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/* vim: set ts=2 sw=2 et tw=79: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this file,
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* You can obtain one at http://mozilla.org/MPL/2.0/. */
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/**
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* Conversions from jsval to primitive values
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*/
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#ifndef mozilla_dom_PrimitiveConversions_h
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#define mozilla_dom_PrimitiveConversions_h
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#include "xpcpublic.h"
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namespace mozilla {
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namespace dom {
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template<typename T>
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struct PrimitiveConversionTraits {
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};
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struct PrimitiveConversionTraits_smallInt {
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// The output of JS::ToInt32 is determined as follows:
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// 1) The value is converted to a double
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// 2) Anything that's not a finite double returns 0
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// 3) The double is rounded towards zero to the nearest integer
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// 4) The resulting integer is reduced mod 2^32. The output of this
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// operation is an integer in the range [0, 2^32).
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// 5) If the resulting number is >= 2^31, 2^32 is subtracted from it.
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//
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// The result of all this is a number in the range [-2^31, 2^31)
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//
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// WebIDL conversions for the 8-bit, 16-bit, and 32-bit integer types
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// are defined in the same way, except that step 4 uses reduction mod
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// 2^8 and 2^16 for the 8-bit and 16-bit types respectively, and step 5
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// is only done for the signed types.
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//
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// C/C++ define integer conversion semantics to unsigned types as taking
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// your input integer mod (1 + largest value representable in the
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// unsigned type). Since 2^32 is zero mod 2^8, 2^16, and 2^32,
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// converting to the unsigned int of the relevant width will correctly
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// perform step 4; in particular, the 2^32 possibly subtracted in step 5
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// will become 0.
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//
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// Once we have step 4 done, we're just going to assume 2s-complement
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// representation and cast directly to the type we really want.
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//
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// So we can cast directly for all unsigned types and for int32_t; for
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// the smaller-width signed types we need to cast through the
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// corresponding unsigned type.
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typedef int32_t jstype;
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typedef int32_t intermediateType;
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static inline bool converter(JSContext* cx, JS::Value v, jstype* retval) {
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return JS::ToInt32(cx, v, retval);
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}
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};
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template<>
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struct PrimitiveConversionTraits<int8_t> : PrimitiveConversionTraits_smallInt {
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typedef uint8_t intermediateType;
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};
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template<>
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struct PrimitiveConversionTraits<uint8_t> : PrimitiveConversionTraits_smallInt {
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};
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template<>
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struct PrimitiveConversionTraits<int16_t> : PrimitiveConversionTraits_smallInt {
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typedef uint16_t intermediateType;
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};
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template<>
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struct PrimitiveConversionTraits<uint16_t> : PrimitiveConversionTraits_smallInt {
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};
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template<>
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struct PrimitiveConversionTraits<int32_t> : PrimitiveConversionTraits_smallInt {
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};
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template<>
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struct PrimitiveConversionTraits<uint32_t> : PrimitiveConversionTraits_smallInt {
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};
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template<>
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struct PrimitiveConversionTraits<bool> {
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typedef JSBool jstype;
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typedef bool intermediateType;
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static inline bool converter(JSContext* cx, JS::Value v, jstype* retval) {
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return JS_ValueToBoolean(cx, v, retval);
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}
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};
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template<>
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struct PrimitiveConversionTraits<int64_t> {
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typedef int64_t jstype;
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typedef int64_t intermediateType;
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static inline bool converter(JSContext* cx, JS::Value v, jstype* retval) {
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return xpc::ValueToInt64(cx, v, retval);
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}
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};
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template<>
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struct PrimitiveConversionTraits<uint64_t> {
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typedef uint64_t jstype;
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typedef uint64_t intermediateType;
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static inline bool converter(JSContext* cx, JS::Value v, jstype* retval) {
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return xpc::ValueToUint64(cx, v, retval);
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}
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};
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struct PrimitiveConversionTraits_float {
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typedef double jstype;
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typedef double intermediateType;
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static inline bool converter(JSContext* cx, JS::Value v, jstype* retval) {
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return JS::ToNumber(cx, v, retval);
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}
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};
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template<>
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struct PrimitiveConversionTraits<float> : PrimitiveConversionTraits_float {
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};
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template<>
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struct PrimitiveConversionTraits<double> : PrimitiveConversionTraits_float {
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};
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template<typename T>
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bool ValueToPrimitive(JSContext* cx, JS::Value v, T* retval)
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{
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typename PrimitiveConversionTraits<T>::jstype t;
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if (!PrimitiveConversionTraits<T>::converter(cx, v, &t))
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return false;
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*retval =
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static_cast<typename PrimitiveConversionTraits<T>::intermediateType>(t);
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return true;
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}
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} // namespace dom
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} // namespace mozilla
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#endif /* mozilla_dom_PrimitiveConversions_h */
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