Make WebURLLoader capable of retaining received buffers.

content/child/shared_memory_received_data_factory.cc

Index: content/child/shared_memory_received_data_factory.cc
diff --git a/content/child/shared_memory_received_data_factory.cc b/content/child/shared_memory_received_data_factory.cc
new file mode 100644
index 0000000000000000000000000000000000000000..7e9f9d9ee8256f4e7959b5a08c65220148d6bb43
--- /dev/null
+++ b/content/child/shared_memory_received_data_factory.cc
@@ -0,0 +1,131 @@
+// 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_received_data_factory.h"
+
+#include <algorithm>
+
+#include "content/common/resource_messages.h"
+#include "ipc/ipc_sender.h"
+
+namespace content {
+
+class SharedMemoryReceivedDataFactory::SharedMemoryReceivedData final
+    : public RequestPeer::ReceivedData {
+ public:
+  SharedMemoryReceivedData(
+      const char* payload,
+      int length,
+      int encoded_length,
+      scoped_refptr<SharedMemoryReceivedDataFactory> factory,
+      SharedMemoryReceivedDataFactory::TicketId id)
+      : payload_(payload),
+        length_(length),
+        encoded_length_(encoded_length),
+        factory_(factory),
+        id_(id) {}
+
+  ~SharedMemoryReceivedData() override { factory_->Reclaim(id_); }
+
+  const char* payload() const override { return payload_; }
+  int length() const override { return length_; }
+  int encoded_length() const override { return encoded_length_; }
+
+ private:
+  const char* const payload_;
+  const int length_;
+  const int encoded_length_;
+
+  scoped_refptr<SharedMemoryReceivedDataFactory> factory_;
+  SharedMemoryReceivedDataFactory::TicketId id_;
+
+  DISALLOW_COPY_AND_ASSIGN(SharedMemoryReceivedData);
+};
+
+SharedMemoryReceivedDataFactory::SharedMemoryReceivedDataFactory(
+    IPC::Sender* message_sender,
+    int request_id,
+    linked_ptr<base::SharedMemory> memory)
+    : id_(0),
+      oldest_(0),
+      message_sender_(message_sender),
+      request_id_(request_id),
+      is_stopped_(false),
+      memory_(memory) {
+}
+
+SharedMemoryReceivedDataFactory::~SharedMemoryReceivedDataFactory() {
+  if (!is_stopped_)
+    SendAck(released_tickets_.size());
+}
+
+scoped_ptr<RequestPeer::ReceivedData> SharedMemoryReceivedDataFactory::Create(
+    int offset,
+    int length,
+    int encoded_length) {
+  const char* start = static_cast<char*>(memory_->memory());
+  const char* payload = start + offset;
+  TicketId id = id_++;
+
+  return make_scoped_ptr(
+      new SharedMemoryReceivedData(payload, length, encoded_length, this, id));
+}
+
+void SharedMemoryReceivedDataFactory::Stop() {
+  is_stopped_ = true;
+  released_tickets_.clear();
+  message_sender_ = nullptr;
+}
+
+class SharedMemoryReceivedDataFactory::TicketComparator final {
+ public:
+  explicit TicketComparator(TicketId oldest) : oldest_(oldest) {}
+  bool operator()(TicketId x, TicketId y) const {
+    if ((oldest_ <= x) == (oldest_ <= y))
+      return x <= y;
+
+    return (oldest_ <= x);
+  }
+
+ private:
+  TicketId oldest_;
+};
+
+void SharedMemoryReceivedDataFactory::Reclaim(TicketId id) {
+  if (is_stopped_)
+    return;
+  if (oldest_ != id) {
+    released_tickets_.push_back(id);
+    return;
+  }
+
+  ++oldest_;
+  SendAck(1);
+  if (released_tickets_.empty()) {
+    // Fast path: (hopefully) the most typical case.
+    return;
+  }
+  std::sort(released_tickets_.begin(), released_tickets_.end(),
+            TicketComparator(oldest_));
+  size_t count = 0;
+  for (size_t i = 0;; ++i) {
+    if (i == released_tickets_.size() ||
+        released_tickets_[i] != static_cast<TicketId>(id + i + 1)) {
+      count = i;
+      break;
+    }
+  }
+  released_tickets_.erase(released_tickets_.begin(),
+                          released_tickets_.begin() + count);
+  oldest_ += count;
+  SendAck(count);
+}
+
+void SharedMemoryReceivedDataFactory::SendAck(size_t count) {
+  for (size_t i = 0; i < count; ++i) {
+    message_sender_->Send(new ResourceHostMsg_DataReceived_ACK(request_id_));
+  }
+}
+
+}  // namespace content