Introduce SharedMemoryDataConsumerHandle.

content/child/shared_memory_data_consumer_handle.cc

Index: content/child/shared_memory_data_consumer_handle.cc
diff --git a/content/child/shared_memory_data_consumer_handle.cc b/content/child/shared_memory_data_consumer_handle.cc
new file mode 100644
index 0000000000000000000000000000000000000000..2dc61df1058643a82c5d3c2c39f6695c0b783fe3
--- /dev/null
+++ b/content/child/shared_memory_data_consumer_handle.cc
@@ -0,0 +1,192 @@
+// Copyright 2015 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/child/shared_memory_data_consumer_handle.h"
+
+#include <algorithm>
+#include <deque>
+#include <vector>
+
+#include "content/public/child/fixed_received_data.h"
+
+namespace content {
+
+using Result = blink::WebDataConsumerHandle::Result;
+
+class SharedMemoryDataConsumerHandle::Context final
+    : public base::RefCountedThreadSafe<Context> {
+ public:
+  Context()
+      : result_(Ok),
+        first_offset_(0),
+        client_(nullptr),
+        is_reader_active_(true) {}
+
+  bool IsEmpty() const { return queue_.empty(); }
+  void Clear() {
+    for (RequestPeer::ReceivedData* data : queue_) {
+      delete data;
+    }
+    queue_.clear();
+    first_offset_ = 0;
+    client_ = nullptr;
+  }
+  RequestPeer::ReceivedData* Top() { return queue_.front(); }
+  void Push(scoped_ptr<RequestPeer::ReceivedData> data) {
+    queue_.push_back(data.release());
+  }
+  size_t first_offset() const { return first_offset_; }
+  Result result() const { return result_; }
+  void set_result(Result r) { result_ = r; }
+  Client* client() { return client_; }
+  void set_client(Client* client) { client_ = client; }
+  bool is_reader_active() const { return is_reader_active_; }
+  void set_is_reader_active(bool b) { is_reader_active_ = b; }
+  void Consume(size_t s) {
+    first_offset_ += s;
+    RequestPeer::ReceivedData* top = Top();
+    if (static_cast<size_t>(top->length()) <= first_offset_) {
+      delete top;
+      queue_.pop_front();
+      first_offset_ = 0;
+    }
+  }
+
+ private:
+  friend class base::RefCountedThreadSafe<Context>;
+  ~Context() {
+    // This is necessary because the queue stores raw pointers.
+    Clear();
+  }
+
+  // |result_| stores the ultimate state of this handle if it has. Otherwise,
+  // |Ok| is set.
+  Result result_;
+  // TODO(yhirano): Use std::deque<scoped_ptr<ReceivedData>> once it is allowed.
+  std::deque<RequestPeer::ReceivedData*> queue_;
+  size_t first_offset_;
+  Client* client_;
+  bool is_reader_active_;
+
+  DISALLOW_COPY_AND_ASSIGN(Context);
+};
+
+SharedMemoryDataConsumerHandle::Writer::Writer(
+    const scoped_refptr<Context>& context,
+    BackpressureMode mode)
+    : context_(context), mode_(mode) {
+}
+
+SharedMemoryDataConsumerHandle::Writer::~Writer() {
+  Close();
+}
+
+void SharedMemoryDataConsumerHandle::Writer::AddData(
+    scoped_ptr<RequestPeer::ReceivedData> data) {
+  if (!data->length()) {
+    // We omit empty data.
+    return;
+  }
+
+  if (!context_->is_reader_active()) {
+    // No one is interested in the data.
+    return;
+  }
+
+  bool needs_notification = context_->client() && context_->IsEmpty();
+  scoped_ptr<RequestPeer::ReceivedData> data_to_pass;
+  if (mode_ == kApplyBackpressure) {
+    data_to_pass = data.Pass();
+  } else {
+    data_to_pass = make_scoped_ptr(new FixedReceivedData(data.get()));
+  }
+  context_->Push(data_to_pass.Pass());
+
+  if (needs_notification)
+    context_->client()->didGetReadable();
+}
+
+void SharedMemoryDataConsumerHandle::Writer::Close() {
+  if (context_->result() == Ok) {
+    context_->set_result(Done);
+    if (context_->client() && context_->IsEmpty())
+      context_->client()->didGetReadable();
+  }
+}
+
+SharedMemoryDataConsumerHandle::SharedMemoryDataConsumerHandle(
+    BackpressureMode mode,
+    scoped_ptr<Writer>* writer)
+    : context_(new Context) {
+  writer->reset(new Writer(context_, mode));
+}
+
+SharedMemoryDataConsumerHandle::~SharedMemoryDataConsumerHandle() {
+  context_->set_is_reader_active(false);
+  context_->Clear();
+}
+
+Result SharedMemoryDataConsumerHandle::read(void* data,
+                                            size_t size,
+                                            Flags flags,
+                                            size_t* read_size_to_return) {
+  size_t total_read_size = 0;
+  *read_size_to_return = 0;
+  if (context_->result() != Ok && context_->result() != Done)
+    return context_->result();
+
+  while (!context_->IsEmpty() && total_read_size < size) {
+    const auto& top = context_->Top();
+    size_t readable = top->length() - context_->first_offset();
+    size_t writable = size - total_read_size;
+    size_t read_size = std::min(readable, writable);
+    const char* begin = top->payload() + context_->first_offset();
+    std::copy(begin, begin + read_size,
+              static_cast<char*>(data) + total_read_size);
+    total_read_size += read_size;
+    context_->Consume(read_size);
+  }
+  *read_size_to_return = total_read_size;
+  return total_read_size ? Ok : context_->result() == Done ? Done : ShouldWait;
+}
+
+Result SharedMemoryDataConsumerHandle::beginRead(const void** buffer,
+                                                 Flags flags,
+                                                 size_t* available) {
+  *buffer = nullptr;
+  *available = 0;
+
+  if (context_->result() != Ok && context_->result() != Done)
+    return context_->result();
+
+  if (context_->IsEmpty())
+    return context_->result() == Done ? Done : ShouldWait;
+
+  const auto& top = context_->Top();
+  *buffer = top->payload() + context_->first_offset();
+  *available = top->length() - context_->first_offset();
+
+  return Ok;
+}
+
+Result SharedMemoryDataConsumerHandle::endRead(size_t read_size) {
+  if (context_->IsEmpty())
+    return UnexpectedError;
+
+  context_->Consume(read_size);
+  return Ok;
+}
+
+void SharedMemoryDataConsumerHandle::registerClient(Client* client) {
+  context_->set_client(client);
+
+  if (!context_->IsEmpty())
+    client->didGetReadable();
+}
+
+void SharedMemoryDataConsumerHandle::unregisterClient() {
+  context_->set_client(nullptr);
+}
+
+}  // namespace content