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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "third_party/blink/renderer/modules/encoding/text_encoder_stream.h"
#include <stdint.h>
#include <string.h>
#include <memory>
#include <optional>
#include <utility>
#include "third_party/blink/renderer/bindings/core/v8/script_promise.h"
#include "third_party/blink/renderer/bindings/core/v8/to_v8_traits.h"
#include "third_party/blink/renderer/bindings/core/v8/v8_string_resource.h"
#include "third_party/blink/renderer/core/streams/transform_stream_default_controller.h"
#include "third_party/blink/renderer/core/streams/transform_stream_transformer.h"
#include "third_party/blink/renderer/core/typed_arrays/dom_typed_array.h"
#include "third_party/blink/renderer/platform/bindings/exception_state.h"
#include "third_party/blink/renderer/platform/bindings/script_state.h"
#include "third_party/blink/renderer/platform/wtf/text/text_codec.h"
#include "third_party/blink/renderer/platform/wtf/text/text_encoding.h"
#include "third_party/blink/renderer/platform/wtf/text/text_encoding_registry.h"
#include "v8/include/v8.h"
namespace blink {
class TextEncoderStream::Transformer final : public TransformStreamTransformer {
public:
explicit Transformer(ScriptState* script_state)
: encoder_(NewTextCodec(WTF::UTF8Encoding())),
script_state_(script_state) {}
Transformer(const Transformer&) = delete;
Transformer& operator=(const Transformer&) = delete;
// Implements the "encode and enqueue a chunk" algorithm. For efficiency, only
// the characters at the end of chunks are special-cased.
ScriptPromise<IDLUndefined> Transform(
v8::Local<v8::Value> chunk,
TransformStreamDefaultController* controller,
ExceptionState& exception_state) override {
V8StringResource<> input_resource{script_state_->GetIsolate(), chunk};
if (!input_resource.Prepare(exception_state)) {
return EmptyPromise();
}
const String input = input_resource;
if (input.empty())
return ToResolvedUndefinedPromise(script_state_.Get());
const std::optional<UChar> high_surrogate = pending_high_surrogate_;
pending_high_surrogate_ = std::nullopt;
std::string prefix;
std::string result;
if (input.Is8Bit()) {
if (high_surrogate.has_value()) {
// An 8-bit code unit can never be part of an astral character, so no
// check is needed.
prefix = ReplacementCharacterInUtf8();
}
result = encoder_->Encode(input.Span8(), WTF::kNoUnencodables);
} else {
bool have_output =
Encode16BitString(input, high_surrogate, &prefix, &result);
if (!have_output)
return ToResolvedUndefinedPromise(script_state_.Get());
}
DOMUint8Array* array =
CreateDOMUint8ArrayFromTwoStdStringsConcatenated(prefix, result);
controller->enqueue(script_state_, ScriptValue::From(script_state_, array),
exception_state);
return ToResolvedUndefinedPromise(script_state_.Get());
}
// Implements the "encode and flush" algorithm.
ScriptPromise<IDLUndefined> Flush(
TransformStreamDefaultController* controller,
ExceptionState& exception_state) override {
if (!pending_high_surrogate_.has_value())
return ToResolvedUndefinedPromise(script_state_.Get());
const std::string replacement_character = ReplacementCharacterInUtf8();
controller->enqueue(
script_state_,
ScriptValue::From(
script_state_,
DOMUint8Array::Create(base::as_byte_span(replacement_character))),
exception_state);
return ToResolvedUndefinedPromise(script_state_.Get());
}
ScriptState* GetScriptState() override { return script_state_.Get(); }
void Trace(Visitor* visitor) const override {
visitor->Trace(script_state_);
TransformStreamTransformer::Trace(visitor);
}
private:
static std::string ReplacementCharacterInUtf8() { return "\ufffd"; }
static DOMUint8Array* CreateDOMUint8ArrayFromTwoStdStringsConcatenated(
const std::string& string1,
const std::string& string2) {
const wtf_size_t length1 = static_cast<wtf_size_t>(string1.length());
const wtf_size_t length2 = static_cast<wtf_size_t>(string2.length());
DOMUint8Array* const array = DOMUint8Array::Create(length1 + length2);
auto [string1_span, string2_span] = array->ByteSpan().split_at(length1);
string1_span.copy_from(base::as_byte_span(string1));
string2_span.copy_from(base::as_byte_span(string2));
return array;
}
// Returns true if either |*prefix| or |*result| have been set to a non-empty
// value.
bool Encode16BitString(const String& input,
std::optional<UChar> high_surrogate,
std::string* prefix,
std::string* result) {
base::span<const UChar> input_span = input.Span16();
DCHECK(!input_span.empty());
if (high_surrogate.has_value()) {
const UChar code_unit = input_span.front();
if (code_unit >= 0xDC00 && code_unit <= 0xDFFF) {
const UChar astral_character[2] = {high_surrogate.value(), code_unit};
// Third argument is ignored, as above.
*prefix = encoder_->Encode(base::span(astral_character),
WTF::kNoUnencodables);
input_span = input_span.subspan<1u>();
if (input_span.empty()) {
return true;
}
} else {
*prefix = ReplacementCharacterInUtf8();
}
}
const UChar final_token = input_span.back();
if (final_token >= 0xD800 && final_token <= 0xDBFF) {
pending_high_surrogate_ = final_token;
input_span = input_span.first(input_span.size() - 1u);
if (input_span.empty()) {
return prefix->length() != 0;
}
}
// Third argument is ignored, as above.
*result = encoder_->Encode(input_span, WTF::kEntitiesForUnencodables);
DCHECK_NE(result->length(), 0u);
return true;
}
std::unique_ptr<WTF::TextCodec> encoder_;
// There is no danger of ScriptState leaking across worlds because a
// TextEncoderStream can only be accessed from the world that created it.
Member<ScriptState> script_state_;
std::optional<UChar> pending_high_surrogate_;
};
TextEncoderStream* TextEncoderStream::Create(ScriptState* script_state,
ExceptionState& exception_state) {
return MakeGarbageCollected<TextEncoderStream>(script_state, exception_state);
}
TextEncoderStream::~TextEncoderStream() = default;
String TextEncoderStream::encoding() const {
return "utf-8";
}
ReadableStream* TextEncoderStream::readable() const {
return transform_->Readable();
}
WritableStream* TextEncoderStream::writable() const {
return transform_->Writable();
}
void TextEncoderStream::Trace(Visitor* visitor) const {
visitor->Trace(transform_);
ScriptWrappable::Trace(visitor);
}
TextEncoderStream::TextEncoderStream(ScriptState* script_state,
ExceptionState& exception_state)
: transform_(TransformStream::Create(
script_state,
MakeGarbageCollected<Transformer>(script_state),
exception_state)) {}
} // namespace blink
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