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 "base/logging.h"
+#include "net/base/io_buffer.h"
+#include "third_party/zlib/zlib.h"
+
+namespace net {
+
+WebSocketDeflater::WebSocketDeflater(int window_bits,
+                                     ContextTakeOverMode mode)
+    : stream_(new z_stream),
+      mode_(mode),
+      are_bytes_added_(false) {
+  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,
+                            8,  // default mem level
+                            Z_DEFAULT_STRATEGY);
+  DCHECK_EQ(Z_OK, result);
+}
+
+WebSocketDeflater::~WebSocketDeflater() {
+  DCHECK(stream_);
+  deflateEnd(stream_.get());
+  stream_.reset(NULL);
+}
+
+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;
+
+  // The estimation by deflateBound is not accurate if the zlib has some
+  // remaining input of the last compression.
+  size_t estimation = deflateBound(stream_.get(), size);
+  DCHECK_GT(estimation, 0u);
+  do {
+    if (Deflate(estimation, Z_NO_FLUSH) != Z_OK)
+      return false;
+    estimation *= 2;
+  } while (stream_->avail_in > 0);
+  return true;
+}
+
+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.
+    DCHECK(buffer_.empty());
+    buffer_.push_back('\x02');
+    buffer_.push_back('\x00');
+    Reset();
+    return true;
+  }
+  stream_->next_in = NULL;
+  stream_->avail_in = 0;
+
+  const size_t kFinishAvailableSize = 4096;
+  do {
+    int result = Deflate(kFinishAvailableSize, Z_SYNC_FLUSH);
+    if (result != Z_OK && result != Z_BUF_ERROR) {
+      Reset();
+      return false;
+    }
+  } while (!stream_->avail_out);

[tyoshino (SeeGerritForStatus), 2013/09/06 07:09:24]

don't we have to continue until we see Z_BUF_ERROR?

[yhirano, 2013/09/06 10:07:26]

Done.

+  // Remove 4 octets from the tail as the specification requires.
+  if (CurrentOutputSize() < 4) {
+    Reset();
+    return false;
+  }
+  buffer_.resize(buffer_.size() - 4);
+  Reset();
+  return true;
+}
+
+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::Reset() {

[tyoshino (SeeGerritForStatus), 2013/09/06 07:09:24]

Reset clears only the state of Deflate. buffer_ is kept. Could you give this
method more descriptive name?

[yhirano, 2013/09/06 10:07:26]

Done.

+  if (mode_ == DO_NOT_TAKE_OVER_CONTEXT)
+    deflateReset(stream_.get());
+  are_bytes_added_ = false;
+}
+
+int WebSocketDeflater::Deflate(size_t avail_out, int flush) {
+  DCHECK_GT(avail_out, 0u);
+  size_t current = buffer_.size();
+  // TODO(yhirano): std::deque initializes the expanded area,
+  // but the initialization is actually not necessary.
+  buffer_.resize(buffer_.size() + avail_out);
+  stream_->next_out = reinterpret_cast<Bytef*>(&buffer_[current]);

[tyoshino (SeeGerritForStatus), 2013/09/06 07:09:24]

is buffer for deque guaranteed to be contiguous?

deque< scoped_refptr<IOBufferWithSize> > is used in socket_stream for similar
purpose.

[yhirano, 2013/09/06 10:07:26]

Thanks, you are right.
I introduced fixed_buffer_ as a member variable and used it to call deflate().

+  stream_->avail_out = avail_out;
+
+  int result = deflate(stream_.get(), flush);
+  buffer_.resize(buffer_.size() - stream_->avail_out);
+  return result;
+}
+
+}  // namespace net