Implement WebSocketDeflater.

net/websockets/websocket_deflater.cc

+// Copyright (c) 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 <deque>
+#include <vector>
+
+#include "base/logging.h"
+#include "net/base/io_buffer.h"
+#include "third_party/zlib/zlib.h"
+
+namespace net {
+
+WebSocketDeflater::WebSocketDeflater(ContextTakeOverMode mode)
+    : mode_(mode), are_bytes_added_(false) {}
+
+WebSocketDeflater::~WebSocketDeflater() {
+  if (stream_) {
+    deflateEnd(stream_.get());
+    stream_.reset(NULL);
+  }
+}
+
+bool WebSocketDeflater::Initialize(int window_bits) {
+  DCHECK(!stream_);
+  stream_.reset(new z_stream);
+
+  DCHECK_LE(8, window_bits);
+  DCHECK_GE(15, window_bits);
+  memset(stream_.get(), 0, sizeof(*stream_));
+  int result = deflateInit2(stream_.get(),
+                            Z_DEFAULT_COMPRESSION,
+                            Z_DEFLATED,
+                            -window_bits,  // Negative value for raw deflate
+                            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('\x02');
+    buffer_.push_back('\x00');
+    ResetContext();
+    return true;
+  }
+  stream_->next_in = NULL;
+  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) {
+  std::deque<char>::iterator begin = buffer_.begin();
+  std::deque<char>::iterator end = begin + std::min(size, buffer_.size());
+
+  scoped_refptr<IOBufferWithSize> result = new IOBufferWithSize(end - begin);
+  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_[0]);
+    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_[0], &fixed_buffer_[size]);
+  } while (result == Z_OK);
+  return result;
+}
+
+}  // namespace net