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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
/* Script decoding templates for processing byte data as UTF-8 or UTF-16. */
#ifndef mozilla_dom_ScriptDecoding_h
#define mozilla_dom_ScriptDecoding_h
#include "mozilla/Assertions.h" // MOZ_ASSERT
#include "mozilla/CheckedInt.h" // mozilla::CheckedInt
#include "mozilla/Encoding.h" // mozilla::Decoder
#include "mozilla/Span.h" // mozilla::Span
#include "mozilla/UniquePtr.h" // mozilla::UniquePtr
#include <stddef.h> // size_t
#include <stdint.h> // uint8_t, uint32_t
#include <type_traits> // std::is_same
namespace mozilla::dom {
template <typename Unit>
struct ScriptDecoding {
static_assert(std::is_same<Unit, char16_t>::value ||
std::is_same<Unit, Utf8Unit>::value,
"must be either UTF-8 or UTF-16");
};
template <>
struct ScriptDecoding<char16_t> {
static CheckedInt<size_t> MaxBufferLength(const UniquePtr<Decoder>& aDecoder,
uint32_t aByteLength) {
return aDecoder->MaxUTF16BufferLength(aByteLength);
}
static size_t DecodeInto(const UniquePtr<Decoder>& aDecoder,
const Span<const uint8_t>& aSrc,
Span<char16_t> aDest, bool aEndOfSource) {
uint32_t result;
size_t read;
size_t written;
std::tie(result, read, written, std::ignore) =
aDecoder->DecodeToUTF16(aSrc, aDest, aEndOfSource);
MOZ_ASSERT(result == kInputEmpty);
MOZ_ASSERT(read == aSrc.Length());
MOZ_ASSERT(written <= aDest.Length());
return written;
}
};
template <>
struct ScriptDecoding<Utf8Unit> {
static CheckedInt<size_t> MaxBufferLength(const UniquePtr<Decoder>& aDecoder,
uint32_t aByteLength) {
return aDecoder->MaxUTF8BufferLength(aByteLength);
}
static size_t DecodeInto(const UniquePtr<Decoder>& aDecoder,
const Span<const uint8_t>& aSrc,
Span<Utf8Unit> aDest, bool aEndOfSource) {
uint32_t result;
size_t read;
size_t written;
// Until C++ char8_t happens, our decoder APIs deal in |uint8_t| while
// |Utf8Unit| internally deals with |char|, so there's inevitable impedance
// mismatch between |aDest| as |Utf8Unit| and |AsWritableBytes(aDest)| as
// |Span<uint8_t>|. :-( The written memory will be interpreted through
// |char Utf8Unit::mValue| which is *permissible* because any object's
// memory can be interpreted as |char|. Unfortunately, until
// twos-complement is mandated, we have to play fast and loose and *hope*
// interpreting memory storing |uint8_t| as |char| will pick up the desired
// wrapped-around value. ¯\_(ツ)_/¯
std::tie(result, read, written, std::ignore) =
aDecoder->DecodeToUTF8(aSrc, AsWritableBytes(aDest), aEndOfSource);
MOZ_ASSERT(result == kInputEmpty);
MOZ_ASSERT(read == aSrc.Length());
MOZ_ASSERT(written <= aDest.Length());
return written;
}
};
} // namespace mozilla::dom
#endif // mozilla_dom_ScriptDecoding_h