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/logging.h"
+
+namespace {
+static const size_t kHeaderLength = sizeof(uint32);
+COMPILE_ASSERT(sizeof(size_t) >= kHeaderLength,
+               ChunkedByteBufferNotSupportedOnThisArchitecture);
+}
+
+namespace speech {
+
+ChunkedByteBuffer::ChunkedByteBuffer()
+  : partial_chunk_(new Chunk()),
+    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 Chunk());
+    }
+  }
+  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());
+}
+
+size_t ChunkedByteBuffer::GetNextChunkLength() const {
+  return GetNextChunk(NULL);
+}
+
+size_t ChunkedByteBuffer::GetNextChunk(const uint8** start_ptr) const {
+  if (chunks_.empty())
+    return static_cast<size_t>(0U);
+  const Chunk& first_chunk = *(*chunks_.begin());
+  DCHECK_EQ(first_chunk.header.size(), kHeaderLength);
+  DCHECK_EQ(first_chunk.content.size(), first_chunk.ExpectedContentLength());
+  if (start_ptr != NULL)
+    *start_ptr = &first_chunk.content[0];
+  return first_chunk.content.size();
+}
+
+void ChunkedByteBuffer::RemoveNextChunk() {
+  DCHECK(!chunks_.empty());
+  total_bytes_stored_ -= GetNextChunkLength();
+  total_bytes_stored_ -= kHeaderLength;
+  chunks_.erase(chunks_.begin());
+}
+
+void ChunkedByteBuffer::Clear() {
+  chunks_.reset();
+  partial_chunk_.reset(new Chunk());
+  total_bytes_stored_ = 0;
+}
+
+size_t ChunkedByteBuffer::Chunk::ExpectedContentLength() const {
+  DCHECK_EQ(header.size(), kHeaderLength);
+  return static_cast<size_t>(ChunkedByteBuffer::ReadBigEndian32(&header[0]));
+}
+
+uint32 ChunkedByteBuffer::ReadBigEndian32(const uint8* buffer) {

[Satish, 2012/04/24 09:10:14]

Move this out to the anonymous namespace at the top of this file as it doesn't
depend on this class and is used only by 'struct Chunk'

+  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 speech