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// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/351564777): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif
#include "third_party/blink/renderer/platform/image-decoders/fast_shared_buffer_reader.h"
namespace blink {
FastSharedBufferReader::FastSharedBufferReader(
scoped_refptr<SegmentReader> data)
: data_(std::move(data)),
segment_(nullptr),
segment_length_(0),
data_position_(0) {}
FastSharedBufferReader::~FastSharedBufferReader() = default;
void FastSharedBufferReader::SetData(scoped_refptr<SegmentReader> data) {
if (data == data_) {
return;
}
data_ = std::move(data);
ClearCache();
}
void FastSharedBufferReader::ClearCache() {
segment_ = nullptr;
segment_length_ = 0;
data_position_ = 0;
}
const char* FastSharedBufferReader::GetConsecutiveData(size_t data_position,
size_t length,
char* buffer) const {
CHECK_LE(data_position + length, data_->size());
// Use the cached segment if it can serve the request.
if (data_position >= data_position_ &&
data_position + length <= data_position_ + segment_length_) {
return segment_ + data_position - data_position_;
}
// Return a pointer into |data_| if the request doesn't span segments.
GetSomeDataInternal(data_position);
if (length <= segment_length_) {
return segment_;
}
for (char* dest = buffer;;) {
size_t copy = std::min(length, segment_length_);
memcpy(dest, segment_, copy);
length -= copy;
if (!length) {
return buffer;
}
// Continue reading the next segment.
dest += copy;
GetSomeDataInternal(data_position_ + copy);
}
}
size_t FastSharedBufferReader::GetSomeData(const char*& some_data,
size_t data_position) const {
GetSomeDataInternal(data_position);
some_data = segment_;
return segment_length_;
}
void FastSharedBufferReader::GetSomeDataInternal(size_t data_position) const {
data_position_ = data_position;
base::span<const char> segment =
base::as_chars(data_->GetSomeData(data_position));
segment_ = segment.data();
segment_length_ = segment.size();
DCHECK(segment_length_);
}
} // namespace blink
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