[ON HOLD] Implement pull-based design for content decoding

net/filter/brotli_stream_source.cc

+// Copyright 2016 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/filter/brotli_stream_source.h"
+
+#include "base/bind.h"
+#include "base/bit_cast.h"
+#include "base/metrics/histogram_macros.h"
+#include "net/filter/block_buffer.h"
+
+namespace net {
+
+BrotliStreamSource::BrotliStreamSource(scoped_ptr<StreamSource> previous)
+    : StreamSource(StreamSource::SOURCE_BROTLI, std::move(previous)),
+      decoding_status_(DecodingStatus::DECODING_IN_PROGRESS),
+      used_memory_(0),
+      used_memory_maximum_(0),
+      produced_bytes_(0),
+      consumed_bytes_(0) {
+  brotli_state_ = BrotliCreateState(AllocateMemory, FreeMemory, this);
+  CHECK(brotli_state_);
+}
+
+BrotliStreamSource::~BrotliStreamSource() {
+  BrotliDestroyState(brotli_state_);
+  brotli_state_ = nullptr;
+  DCHECK(used_memory_ == 0);
+
+  UMA_HISTOGRAM_ENUMERATION(
+      "BrotliStreamSource.Status", static_cast<int>(decoding_status_),
+      static_cast<int>(DecodingStatus::DECODING_STATUS_COUNT));
+  if (decoding_status_ == DecodingStatus::DECODING_DONE) {
+    // CompressionPercent is undefined when there is no output produced.
+    if (produced_bytes_ != 0) {
+      UMA_HISTOGRAM_PERCENTAGE(
+          "BrotliStreamSource.CompressionPercent",
+          static_cast<int>((consumed_bytes_ * 100) / produced_bytes_));
+    }
+  }
+  // All code here is for gathering stats, and can be removed when
+  // BrotliStreamSource is considered stable.
+  static const int kBuckets = 48;
+  static const int64_t kMaxKb = 1 << (kBuckets / 3);  // 64MiB in KiB
+  UMA_HISTOGRAM_CUSTOM_COUNTS("BrotliStreamSource.UsedMemoryKB",
+                              used_memory_maximum_ / 1024, 1, kMaxKb, kBuckets);
+}
+
+Error BrotliStreamSource::ReadInternal(IOBuffer* dest_buffer,
+                                       size_t dest_buffer_size,
+                                       size_t* bytes_read) {
+  const uint8_t* next_in = bit_cast<uint8_t*>(buffer_->bytes());
+  size_t available_in = buffer_->bytes_left();
+  uint8_t* next_out = bit_cast<uint8_t*>(dest_buffer->data());
+  size_t available_out = dest_buffer_size;
+  size_t total_out = 0;
+  BrotliResult result =
+      BrotliDecompressStream(&available_in, &next_in, &available_out, &next_out,
+                             &total_out, brotli_state_);
+
+  size_t bytes_used = buffer_->bytes_left() - available_in;
+  size_t bytes_written = dest_buffer_size - available_out;
+  CHECK_GE(bytes_used, 0u);
+  CHECK_GE(bytes_written, 0u);
+  *bytes_read = bytes_written;
+  produced_bytes_ += bytes_written;
+  consumed_bytes_ += bytes_used;
+
+  buffer_->WasDrained(bytes_used);
+
+  switch (result) {
+    case BROTLI_RESULT_NEEDS_MORE_OUTPUT:
+    // Fall through.
+    case BROTLI_RESULT_SUCCESS:
+      decoding_status_ = DecodingStatus::DECODING_DONE;
+      return OK;
+    case BROTLI_RESULT_NEEDS_MORE_INPUT:
+      decoding_status_ = DecodingStatus::DECODING_IN_PROGRESS;
+      if (bytes_written > 0) {
+        return OK;
+      }
+      break;
+    // If the decompressor threw an error, fail synchronously.
+    default:
+      decoding_status_ = DecodingStatus::DECODING_ERROR;
+      return ERR_CONTENT_DECODING_FAILED;
+  }
+
+  DCHECK_EQ(BROTLI_RESULT_NEEDS_MORE_INPUT, result);
+
+  // Since Decompress needs more input, it has consumed all existing input.
+  DCHECK(!buffer_->HasMoreBytes());
+
+  return OK;
+}
+
+void* BrotliStreamSource::AllocateMemory(void* opaque, size_t size) {
+  BrotliStreamSource* filter = reinterpret_cast<BrotliStreamSource*>(opaque);
+  return filter->AllocateMemoryInternal(size);
+}
+
+void BrotliStreamSource::FreeMemory(void* opaque, void* address) {
+  BrotliStreamSource* filter = reinterpret_cast<BrotliStreamSource*>(opaque);
+  filter->FreeMemoryInternal(address);
+}
+
+void* BrotliStreamSource::AllocateMemoryInternal(size_t size) {
+  size_t* array = reinterpret_cast<size_t*>(malloc(size + sizeof(size_t)));
+  if (!array)
+    return nullptr;
+  used_memory_ += size;
+  if (used_memory_maximum_ < used_memory_)
+    used_memory_maximum_ = used_memory_;
+  array[0] = size;
+  return &array[1];
+}
+
+void BrotliStreamSource::FreeMemoryInternal(void* address) {
+  if (!address)
+    return;
+  size_t* array = reinterpret_cast<size_t*>(address);
+  used_memory_ -= array[-1];
+  free(&array[-1]);
+}
+
+}  // namespace net