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- // Copyright 2013 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #include "net/websockets/websocket_deflater.h"
- #include <string.h>
- #include <algorithm>
- #include <vector>
- #include "base/check_op.h"
- #include "base/containers/circular_deque.h"
- #include "net/base/io_buffer.h"
- #include "third_party/zlib/zlib.h"
- namespace net {
- WebSocketDeflater::WebSocketDeflater(ContextTakeOverMode mode) : mode_(mode) {}
- WebSocketDeflater::~WebSocketDeflater() {
- if (stream_) {
- deflateEnd(stream_.get());
- stream_.reset(nullptr);
- }
- }
- bool WebSocketDeflater::Initialize(int window_bits) {
- DCHECK(!stream_);
- stream_ = std::make_unique<z_stream>();
- DCHECK_LE(8, window_bits);
- DCHECK_GE(15, window_bits);
- // Use a negative value to compress a raw deflate stream.
- //
- // Upgrade window_bits = 8 to 9 because zlib is unable to compress at
- // window_bits = 8. Historically, zlib has silently increased the window size
- // during compression in this case, although this is no longer done for raw
- // deflate streams since zlib 1.2.9.
- //
- // Because of a zlib deflate quirk, back-references will not use the entire
- // range of 1 << window_bits, but will instead use a restricted range of (1 <<
- // window_bits) - 262. With an increased window_bits = 9, back-references will
- // be within a range of 250. These can still be decompressed with window_bits
- // = 8 and the 256-byte window used there.
- //
- // Both the requirement to do this upgrade and the ability to compress with
- // window_bits = 9 while expecting a decompressor to function with window_bits
- // = 8 are quite specific to zlib's particular deflate implementation, but not
- // specific to any particular inflate implementation.
- //
- // See https://crbug.com/691074
- window_bits = -std::max(window_bits, 9);
- memset(stream_.get(), 0, sizeof(*stream_));
- int result = deflateInit2(stream_.get(),
- Z_DEFAULT_COMPRESSION,
- Z_DEFLATED,
- window_bits,
- 8, // default mem level
- Z_DEFAULT_STRATEGY);
- if (result != Z_OK) {
- deflateEnd(stream_.get());
- stream_.reset();
- return false;
- }
- const size_t kFixedBufferSize = 4096;
- fixed_buffer_.resize(kFixedBufferSize);
- return true;
- }
- bool WebSocketDeflater::AddBytes(const char* data, size_t size) {
- if (!size)
- return true;
- are_bytes_added_ = true;
- stream_->next_in = reinterpret_cast<Bytef*>(const_cast<char*>(data));
- stream_->avail_in = size;
- int result = Deflate(Z_NO_FLUSH);
- DCHECK(result != Z_BUF_ERROR || !stream_->avail_in);
- return result == Z_BUF_ERROR;
- }
- bool WebSocketDeflater::Finish() {
- if (!are_bytes_added_) {
- // Since consecutive calls of deflate with Z_SYNC_FLUSH and no input
- // lead to an error, we create and return the output for the empty input
- // manually.
- buffer_.push_back('\x00');
- ResetContext();
- return true;
- }
- stream_->next_in = nullptr;
- stream_->avail_in = 0;
- int result = Deflate(Z_SYNC_FLUSH);
- // Deflate returning Z_BUF_ERROR means that it's successfully flushed and
- // blocked for input data.
- if (result != Z_BUF_ERROR) {
- ResetContext();
- return false;
- }
- // Remove 4 octets from the tail as the specification requires.
- if (CurrentOutputSize() < 4) {
- ResetContext();
- return false;
- }
- buffer_.resize(buffer_.size() - 4);
- ResetContext();
- return true;
- }
- void WebSocketDeflater::PushSyncMark() {
- DCHECK(!are_bytes_added_);
- const char data[] = {'\x00', '\x00', '\xff', '\xff'};
- buffer_.insert(buffer_.end(), &data[0], &data[sizeof(data)]);
- }
- scoped_refptr<IOBufferWithSize> WebSocketDeflater::GetOutput(size_t size) {
- size_t length_to_copy = std::min(size, buffer_.size());
- base::circular_deque<char>::iterator begin = buffer_.begin();
- base::circular_deque<char>::iterator end = begin + length_to_copy;
- auto result = base::MakeRefCounted<IOBufferWithSize>(length_to_copy);
- std::copy(begin, end, result->data());
- buffer_.erase(begin, end);
- return result;
- }
- void WebSocketDeflater::ResetContext() {
- if (mode_ == DO_NOT_TAKE_OVER_CONTEXT)
- deflateReset(stream_.get());
- are_bytes_added_ = false;
- }
- int WebSocketDeflater::Deflate(int flush) {
- int result = Z_OK;
- do {
- stream_->next_out = reinterpret_cast<Bytef*>(fixed_buffer_.data());
- stream_->avail_out = fixed_buffer_.size();
- result = deflate(stream_.get(), flush);
- size_t size = fixed_buffer_.size() - stream_->avail_out;
- buffer_.insert(buffer_.end(), fixed_buffer_.data(),
- fixed_buffer_.data() + size);
- } while (result == Z_OK);
- return result;
- }
- } // namespace net
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