Added CompoundBuffer that will be used to store data in the encoding/decoding

remoting/base/compound_buffer.cc

+// Copyright (c) 2010 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 <functional>
+
+#include "base/logging.h"
+#include "net/base/io_buffer.h"
+#include "remoting/base/compound_buffer.h"
+
+namespace remoting {
+
+CompoundBuffer::DataChunk::DataChunk(
+    net::IOBuffer* buffer, const char* data_start, int data_size)
+    : buffer(buffer),
+      data_start(data_start),
+      data_size(data_size) {
+}
+
+CompoundBuffer::CompoundBuffer()
+    : total_bytes_(0),
+      current_buffer_(0),
+      current_buffer_position_(0),
+      position_(0),
+      last_returned_size_(0) {
+}
+
+CompoundBuffer::~CompoundBuffer() {
+}
+
+void CompoundBuffer::Clear() {
+  buffers_.clear();
+  total_bytes_ = 0;
+  position_ = 0;
+  last_returned_size_ = 0;
+  current_buffer_ = 0;
+  current_buffer_position_ = 0;
+}
+
+

[awong, 2010/11/12 02:40:06]

remove extra newline

[Sergey Ulanov, 2010/11/13 04:43:39]

Done.

+void CompoundBuffer::Append(net::IOBuffer* buffer,
+                            const char* data, int data_size) {
+  // A weak check that the |data| is within |buffer|.
+  DCHECK_GE(data, buffer->data());
+  DCHECK_GT(data_size, 0);
+
+  DCHECK_EQ(position_, 0); // Haven't started reading.

[awong, 2010/11/12 02:40:06]

So the API contract is that once you start reading, you aren't supposed to
append anymore?

This should be in the class documentation.  Also, should any of these actually
be CHECKs?

[Sergey Ulanov, 2010/11/13 04:43:39]

Done.

+
+  buffers_.push_back(DataChunk(buffer, data, data_size));
+  total_bytes_ += data_size;
+}
+
+void CompoundBuffer::Append(net::IOBuffer* buffer, int data_size) {
+  Append(buffer, buffer->data(), data_size);
+}
+
+void CompoundBuffer::Prepend(net::IOBuffer* buffer,
+                             const char* data, int data_size) {
+  // A weak check that the |data| is within |buffer|.
+  DCHECK_GE(data, buffer->data());

[awong, 2010/11/12 02:40:06]

Same comments as earlier.

Also, should there be a CanAddBuffers() method or something?

[Sergey Ulanov, 2010/11/13 04:43:39]

Added locked() returns true if content is locked.

+  DCHECK_GT(data_size, 0);
+
+  DCHECK_EQ(position_, 0); // Haven't started reading.
+
+  buffers_.push_front(DataChunk(buffer, data, data_size));
+  total_bytes_ += data_size;
+}
+
+void CompoundBuffer::Prepend(net::IOBuffer* buffer, int data_size) {
+  Prepend(buffer, buffer->data(), data_size);
+}
+
+void CompoundBuffer::CopyAndAppend(const char* data, int data_size) {
+  net::IOBuffer* buffer = new net::IOBuffer(data_size);
+  memcpy(buffer->data(), data, data_size);
+  Append(buffer, buffer->data(), data_size);
+}
+
+void CompoundBuffer::CopyAndPrepend(const char* data, int data_size) {
+  net::IOBuffer* buffer = new net::IOBuffer(data_size);
+  memcpy(buffer->data(), data, data_size);
+  Prepend(buffer, buffer->data(), data_size);
+}
+
+net::IOBufferWithSize* CompoundBuffer::Assemble() const {
+  net::IOBufferWithSize* result = new net::IOBufferWithSize(total_bytes_);

[awong, 2010/11/12 02:40:06]

Are these things refcounted?

[Sergey Ulanov, 2010/11/13 04:43:39]

Yes, but we just create it, and then the caller will add references for it.
Should be safe, no?

+  Assemble(result->data(), total_bytes_);
+  return result;
+}
+
+void CompoundBuffer::Assemble(char* data, int data_size) const {
+  char* pos = data;
+  for (DataChunkList::const_iterator it = buffers_.begin();
+       it != buffers_.end(); ++it) {
+    CHECK_LE(pos + it->data_size, data + data_size);
+    memcpy(pos, it->data_start, it->data_size);
+    pos += it->data_size;
+  }
+}
+
+void CompoundBuffer::CopyFrom(const CompoundBuffer& source,
+                              int start, int end) {
+  // Check that 0 <= |start| <= |end| <= |total_bytes_|.
+  DCHECK_LE(0, start);
+  DCHECK_LE(start, end);
+  DCHECK_LE(end, source.total_bytes());
+
+  Clear();
+
+  if (end == start) {
+    return;
+  }
+
+  // Iterate over chunks in the |source| and add those that we need.
+  int pos = 0;
+  for (DataChunkList::const_iterator it = source.buffers_.begin();
+       it != source.buffers_.end(); ++it) {
+
+    // Add data from the current chunk only if it is in the specified interval.
+    if (pos + it->data_size > start && pos < end) {
+      int relative_start = std::max(0, start - pos);
+      int relative_end = std::min(it->data_size, end - pos);
+      DCHECK_LE(0, relative_start);
+      DCHECK_LT(relative_start, relative_end);
+      DCHECK_LE(relative_end, it->data_size);
+      Append(it->buffer.get(), it->data_start + relative_start,
+             relative_end - relative_start);
+    }
+
+    pos += it->data_size;
+    if (pos >= end) {
+      // We've got all the data we need.
+      break;
+    }
+  }
+
+  DCHECK_EQ(total_bytes_, end - start);
+}
+
+bool CompoundBuffer::Next(const void** data, int* size) {
+  if (current_buffer_ < buffers_.size()) {
+    // Reply with the number of bytes remaining in the current buffer.
+    const DataChunk& buffer = buffers_[current_buffer_];
+    int read_size = buffer.data_size - current_buffer_position_;
+    *data = buffer.data_start + current_buffer_position_;
+    *size = read_size;
+
+    // Adjust position.
+    ++current_buffer_;
+    current_buffer_position_ = 0;
+    position_ += read_size;
+
+    last_returned_size_ = read_size;
+    return true;
+  }
+
+  DCHECK_EQ(position_, total_bytes_);
+
+  // We've reached the end of the stream. So reset |last_returned_size_|
+  // to zero to prevent any backup request.
+  // This is the same as in ArrayInputStream.
+  // See google/protobuf/io/zero_copy_stream_impl_lite.cc.
+  last_returned_size_ = 0;
+  return false;
+}
+
+void CompoundBuffer::BackUp(int count) {
+  DCHECK_LE(count, last_returned_size_);
+  DCHECK_GT(current_buffer_, 0u);
+
+  // Rewind one buffer and rewind data offset by |count| bytes.
+  --current_buffer_;
+  const DataChunk& buffer = buffers_[current_buffer_];
+  current_buffer_position_ = buffer.data_size - count;
+  position_ -= count;
+  DCHECK_GE(position_, 0);
+
+  // Prevent additional backups.
+  last_returned_size_ = 0;
+}
+
+bool CompoundBuffer::Skip(int count) {
+  DCHECK_GE(count, 0);
+  last_returned_size_ = 0;
+
+  while (count > 0 && current_buffer_ < buffers_.size()) {
+    const DataChunk& buffer = buffers_[current_buffer_];
+    int read = std::min(count, buffer.data_size - current_buffer_position_);
+
+    // Advance the current buffer offset and position.
+    current_buffer_position_ += read;
+    position_ += read;
+    count -= read;
+
+    // If the current buffer is fully read, then advance to the next buffer.
+    if (current_buffer_position_ == buffer.data_size) {
+      ++current_buffer_;
+      current_buffer_position_ = 0;
+    }
+  }
+
+  return count == 0;
+}
+
+int64 CompoundBuffer::ByteCount() const {
+  return position_;
+}
+
+}  // namespace remoting