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544bfe11bc
Depends on D145759 Differential Revision: https://phabricator.services.mozilla.com/D145760
88 lines
3.3 KiB
C++
88 lines
3.3 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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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
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/* Script decoding templates for processing byte data as UTF-8 or UTF-16. */
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#ifndef mozilla_dom_ScriptDecoding_h
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#define mozilla_dom_ScriptDecoding_h
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#include "mozilla/Assertions.h" // MOZ_ASSERT
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#include "mozilla/CheckedInt.h" // mozilla::CheckedInt
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#include "mozilla/Encoding.h" // mozilla::Decoder
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#include "mozilla/Span.h" // mozilla::Span
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#include "mozilla/UniquePtr.h" // mozilla::UniquePtr
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#include <stddef.h> // size_t
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#include <stdint.h> // uint8_t, uint32_t
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#include <type_traits> // std::is_same
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namespace mozilla::dom {
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template <typename Unit>
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struct ScriptDecoding {
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static_assert(std::is_same<Unit, char16_t>::value ||
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std::is_same<Unit, Utf8Unit>::value,
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"must be either UTF-8 or UTF-16");
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};
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template <>
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struct ScriptDecoding<char16_t> {
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static CheckedInt<size_t> MaxBufferLength(const UniquePtr<Decoder>& aDecoder,
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uint32_t aByteLength) {
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return aDecoder->MaxUTF16BufferLength(aByteLength);
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}
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static size_t DecodeInto(const UniquePtr<Decoder>& aDecoder,
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const Span<const uint8_t>& aSrc,
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Span<char16_t> aDest, bool aEndOfSource) {
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uint32_t result;
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size_t read;
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size_t written;
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std::tie(result, read, written, std::ignore) =
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aDecoder->DecodeToUTF16(aSrc, aDest, aEndOfSource);
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MOZ_ASSERT(result == kInputEmpty);
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MOZ_ASSERT(read == aSrc.Length());
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MOZ_ASSERT(written <= aDest.Length());
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return written;
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}
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};
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template <>
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struct ScriptDecoding<Utf8Unit> {
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static CheckedInt<size_t> MaxBufferLength(const UniquePtr<Decoder>& aDecoder,
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uint32_t aByteLength) {
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return aDecoder->MaxUTF8BufferLength(aByteLength);
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}
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static size_t DecodeInto(const UniquePtr<Decoder>& aDecoder,
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const Span<const uint8_t>& aSrc,
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Span<Utf8Unit> aDest, bool aEndOfSource) {
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uint32_t result;
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size_t read;
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size_t written;
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// Until C++ char8_t happens, our decoder APIs deal in |uint8_t| while
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// |Utf8Unit| internally deals with |char|, so there's inevitable impedance
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// mismatch between |aDest| as |Utf8Unit| and |AsWritableBytes(aDest)| as
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// |Span<uint8_t>|. :-( The written memory will be interpreted through
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// |char Utf8Unit::mValue| which is *permissible* because any object's
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// memory can be interpreted as |char|. Unfortunately, until
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// twos-complement is mandated, we have to play fast and loose and *hope*
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// interpreting memory storing |uint8_t| as |char| will pick up the desired
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// wrapped-around value. ¯\_(ツ)_/¯
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std::tie(result, read, written, std::ignore) =
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aDecoder->DecodeToUTF8(aSrc, AsWritableBytes(aDest), aEndOfSource);
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MOZ_ASSERT(result == kInputEmpty);
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MOZ_ASSERT(read == aSrc.Length());
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MOZ_ASSERT(written <= aDest.Length());
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return written;
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}
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};
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} // namespace mozilla::dom
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#endif // mozilla_dom_ScriptDecoding_h
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