Introduced ChunkedByteBuffer class which will be needed by next speech recognition CLs.

content/browser/speech/chunked_byte_buffer.cc

+// Copyright (c) 2012 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 "content/browser/speech/chunked_byte_buffer.h"
+
+#include <algorithm>
+
+#include "base/basictypes.h"
+#include "base/lazy_instance.h"
+#include "base/logging.h"
+
+namespace {
+
+static const size_t kHeaderLength = sizeof(uint32);
+
+COMPILE_ASSERT(sizeof(size_t) >= kHeaderLength,
+               ChunkedByteBufferNotSupportedOnThisArchitecture);
+
+uint32 ReadBigEndian32(const uint8* buffer) {
+  return (static_cast<uint32>(buffer[3])) |
+         (static_cast<uint32>(buffer[2]) <<  8) |
+         (static_cast<uint32>(buffer[1]) << 16) |
+         (static_cast<uint32>(buffer[0]) << 24);
+}
+
+}  // namespace
+
+namespace speech {
+
+ChunkedByteBuffer::ChunkedByteBuffer()
+  : partial_chunk_(new ByteBufferChunk()),
+    total_bytes_stored_(0) {
+}
+
+ChunkedByteBuffer::~ChunkedByteBuffer() {
+  Clear();
+}
+
+void ChunkedByteBuffer::Append(const uint8* start, size_t length) {
+  DCHECK(length > 0);
+  size_t remaining_bytes = length;
+  const uint8* next_data = start;
+
+  while (remaining_bytes > 0) {
+    DCHECK(partial_chunk_ != NULL);
+    size_t insert_length = 0;
+    bool header_completed = false;
+    bool content_completed = false;
+    std::vector<uint8>* insert_target;
+
+    if (partial_chunk_->header.size() < kHeaderLength) {
+      const size_t bytes_to_complete_header =
+          kHeaderLength - partial_chunk_->header.size();
+      insert_length = std::min(bytes_to_complete_header, remaining_bytes);
+      insert_target = &partial_chunk_->header;
+      header_completed = (remaining_bytes >= bytes_to_complete_header);
+    } else {
+      DCHECK_LT(partial_chunk_->content.size(),
+                partial_chunk_->ExpectedContentLength());
+      const size_t bytes_to_complete_chunk =
+          partial_chunk_->ExpectedContentLength() -
+          partial_chunk_->content.size();
+      insert_length = std::min(bytes_to_complete_chunk, remaining_bytes);
+      insert_target = &partial_chunk_->content;
+      content_completed = (remaining_bytes >= bytes_to_complete_chunk);
+    }
+
+    DCHECK_GT(insert_length, 0U);
+    DCHECK_LE(insert_length, remaining_bytes);
+    DCHECK_LE(next_data + insert_length, start + length);
+    insert_target->insert(insert_target->end(),
+                          next_data,
+                          next_data + insert_length);
+    next_data += insert_length;
+    remaining_bytes -= insert_length;
+
+    if (header_completed) {
+      DCHECK_EQ(partial_chunk_->header.size(), kHeaderLength);
+      DCHECK_NE(partial_chunk_->ExpectedContentLength(), 0U);
+      partial_chunk_->content.reserve(partial_chunk_->ExpectedContentLength());
+    } else if (content_completed) {
+      DCHECK_EQ(partial_chunk_->content.size(),
+                partial_chunk_->ExpectedContentLength());
+      chunks_.push_back(partial_chunk_.release());
+      partial_chunk_.reset(new ByteBufferChunk());
+    }
+  }
+  DCHECK_EQ(next_data, start + length);
+  total_bytes_stored_ += length;
+}
+
+void ChunkedByteBuffer::Append(const std::string& string) {
+  Append(reinterpret_cast<const uint8*>(string.data()), string.size());
+}
+
+bool ChunkedByteBuffer::HasChunks() const {
+  return !chunks_.empty();
+}
+
+const ByteBufferChunk& ChunkedByteBuffer::GetFirstChunk() const {
+  CR_DEFINE_STATIC_LOCAL(ByteBufferChunk, kEmptyChunk, ());
+  if (chunks_.empty())
+    return kEmptyChunk;
+  return **chunks_.begin();
+}
+
+scoped_ptr<ByteBufferChunk> ChunkedByteBuffer::PopChunk() {
+  if (chunks_.empty())
+    return scoped_ptr<ByteBufferChunk>();
+  scoped_ptr<ByteBufferChunk> chunk(*chunks_.begin());
+  chunks_.weak_erase(chunks_.begin());
+  DCHECK_EQ(chunk->header.size(), kHeaderLength);
+  DCHECK_EQ(chunk->content.size(), chunk->ExpectedContentLength());
+  total_bytes_stored_ -= chunk->GetLength();
+  total_bytes_stored_ -= kHeaderLength;
+  return chunk.Pass();
+}
+
+void ChunkedByteBuffer::Clear() {
+  chunks_.reset();
+  partial_chunk_.reset(new ByteBufferChunk());
+  total_bytes_stored_ = 0;
+}
+
+ByteBufferChunk::ByteBufferChunk() {
+}
+
+ByteBufferChunk::~ByteBufferChunk() {
+}
+
+const uint8* ByteBufferChunk::GetData() const {
+  return &content[0];
+}
+
+size_t ByteBufferChunk::GetLength() const {
+  return content.size();
+}
+
+size_t ByteBufferChunk::ExpectedContentLength() const {
+  DCHECK_EQ(header.size(), kHeaderLength);
+  return static_cast<size_t>(ReadBigEndian32(&header[0]));
+}
+
+}  // namespace speech