Creation of ByteStream class.

content/browser/download/byte_stream.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/download/byte_stream.h"
+
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/memory/weak_ptr.h"
+#include "base/memory/ref_counted.h"
+#include "base/sequenced_task_runner.h"
+
+namespace {
+
+typedef std::deque<std::pair<scoped_refptr<net::IOBuffer>, size_t> >
+ContentVector;
+
+// The fraction of the buffer that must be ready to send on the input
+// before we ship data to the output.
+static const int kFractionBufferBeforeSending = 3;
+
+// The fraction of the buffer that must have been consumed on the output
+// before we update the input window.
+static const int kFractionReadBeforeWindowUpdate = 3;
+
+class ByteStreamOutputImpl;
+
+// A poor man's weak pointer; a RefCountedThreadSafe boolean that can be
+// cleared in an object destructor and accessed to check for object
+// existence.  We can't use weak pointers because they're tightly tied to
+// threads rather than task runners.
+// TODO(rdsmith): A better solution would be extending weak pointers
+// to support SequencedTaskRunners.
+struct LifetimeFlag : public base::RefCountedThreadSafe<LifetimeFlag> {
+ public:
+  LifetimeFlag() : is_alive_(true) { }
+  bool is_alive_;
+
+ protected:
+  friend class base::RefCountedThreadSafe<LifetimeFlag>;
+  virtual ~LifetimeFlag() { }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(LifetimeFlag);
+};
+
+// For both ByteStreamInputImpl and ByteStreamOutputImpl, Construction and
+// SetPeer may happen anywhere; all other operations on each class must
+// happen in the context of their SequencedTaskRunner.

[benjhayden, 2012/05/18 14:21:06]

Is there any way to DCHECK this? I find that kind of DCHECK to be very helpful
when reading the code.

[Randy Smith (Not in Mondays), 2012/05/18 21:55:15]

Agreed.  Done.

+class ByteStreamInputImpl : public content::ByteStreamInput {
+ public:
+  ByteStreamInputImpl(scoped_refptr<base::SequencedTaskRunner> task_runner,
+                      scoped_refptr<LifetimeFlag> lifetime_flag,
+                      size_t buffer_size);
+  virtual ~ByteStreamInputImpl();
+
+  // Must be called before any operations are performed.
+  void SetPeer(ByteStreamOutputImpl* peer,
+               scoped_refptr<base::SequencedTaskRunner> peer_task_runner,
+               scoped_refptr<LifetimeFlag> peer_lifetime_flag);
+
+  // Overridden from ByteStreamInput.
+  virtual bool Write(scoped_refptr<net::IOBuffer> buffer,
+                     size_t byte_count) OVERRIDE;
+  virtual void Close(content::DownloadInterruptReason status) OVERRIDE;
+  virtual void RegisterCallback(const base::Closure& source_callback) OVERRIDE;
+
+  // PostTask target from |ByteStreamOutputImpl::MaybeUpdateInput|.
+  static void UpdateWindow(scoped_refptr<LifetimeFlag> lifetime_flag,
+                           ByteStreamInputImpl* target,
+                           size_t bytes_consumed);
+
+ private:
+  // Called from UpdateWindow when object existence has been validated.
+  void UpdateWindowInternal(size_t bytes_consumed);
+
+  void PostToPeer(bool complete, content::DownloadInterruptReason status);
+
+  const size_t total_buffer_size_;
+
+  // All data objects in this class are only valid to access on
+  // this task runner except as otherwise noted.
+  scoped_refptr<base::SequencedTaskRunner> my_task_runner_;
+
+  // True while this object is alive.
+  scoped_refptr<LifetimeFlag> my_lifetime_flag_;
+
+  base::Closure space_available_callback_;
+  ContentVector input_contents_;
+  size_t input_contents_size_;
+
+  // ** Peer information.
+
+  scoped_refptr<base::SequencedTaskRunner> peer_task_runner_;
+
+  // How much we've sent to the output that for flow control purposes we
+  // must assume hasn't been read yet.
+  size_t output_size_used_;
+
+  // Only valid to access on peer_task_runner_.
+  scoped_refptr<LifetimeFlag> peer_lifetime_flag_;
+
+  // Only valid to access on peer_task_runner_ if
+  // |*peer_lifetime_flag_ == true|
+  ByteStreamOutputImpl* peer_;
+};
+
+class ByteStreamOutputImpl : public content::ByteStreamOutput {
+ public:
+  ByteStreamOutputImpl(scoped_refptr<base::SequencedTaskRunner> task_runner,
+                       scoped_refptr<LifetimeFlag> lifetime_flag,
+                       size_t buffer_size);
+  virtual ~ByteStreamOutputImpl();
+
+  // Must be called before any operations are performed.
+  void SetPeer(ByteStreamInputImpl* peer,
+               scoped_refptr<base::SequencedTaskRunner> peer_task_runner,
+               scoped_refptr<LifetimeFlag> peer_lifetime_flag);
+
+  // Overridden from ByteStreamOutput.
+  virtual StreamState Read(scoped_refptr<net::IOBuffer>* data,
+                           size_t* length) OVERRIDE;
+  virtual content::DownloadInterruptReason GetStatus() const OVERRIDE;
+  virtual void RegisterCallback(const base::Closure& sink_callback) OVERRIDE;
+
+  // PostTask target from |ByteStreamInputImpl::MaybePostToPeer| and
+  // |ByteStreamInputImpl::Close|.
+  // Receive data from our peer.
+  // static because it may be called after the object it is targeting
+  // has been destroyed.  It may not access |*target|
+  // if |*object_lifetime_flag| is false.
+  static void TransferData(
+      scoped_refptr<LifetimeFlag> object_lifetime_flag,
+      ByteStreamOutputImpl* target,
+      scoped_ptr<ContentVector> transfer_buffer,
+      size_t transfer_buffer_bytes,
+      bool source_complete,
+      content::DownloadInterruptReason status);
+
+ private:
+  // Called from TransferData once object existence has been validated.
+  void TransferDataInternal(
+      scoped_ptr<ContentVector> transfer_buffer,
+      size_t transfer_buffer_bytes,
+      bool source_complete,
+      content::DownloadInterruptReason status);
+
+  void MaybeUpdateInput();
+
+  const size_t total_buffer_size_;
+
+  scoped_refptr<base::SequencedTaskRunner> my_task_runner_;
+
+  // True while this object is alive.
+  scoped_refptr<LifetimeFlag> my_lifetime_flag_;
+
+  ContentVector available_contents_;
+  size_t available_contents_size_;
+
+  bool received_status_;
+  content::DownloadInterruptReason status_;
+
+  base::Closure data_available_callback_;
+
+  // Time of last point at which data in stream transitioned from full
+  // to non-full.  Nulled when a callback is sent.
+  base::Time last_non_full_time_;
+
+  // ** Peer information
+
+  scoped_refptr<base::SequencedTaskRunner> peer_task_runner_;
+
+  // How much has been removed from this class that we haven't told
+  // the input about yet.
+  size_t unreported_consumed_bytes_;
+
+  // Only valid to access on peer_task_runner_.
+  scoped_refptr<LifetimeFlag> peer_lifetime_flag_;
+
+  // Only valid to access on peer_task_runner_ if
+  // |*peer_lifetime_flag_ == true|
+  ByteStreamInputImpl* peer_;
+};
+
+ByteStreamInputImpl::ByteStreamInputImpl(
+    scoped_refptr<base::SequencedTaskRunner> task_runner,
+    scoped_refptr<LifetimeFlag> lifetime_flag,
+    size_t buffer_size)
+    : total_buffer_size_(buffer_size),
+      my_task_runner_(task_runner),
+      my_lifetime_flag_(lifetime_flag),
+      input_contents_size_(0),
+      output_size_used_(0),
+      peer_(NULL) {
+  DCHECK(my_lifetime_flag_.get());
+  my_lifetime_flag_->is_alive_ = true;
+}
+
+ByteStreamInputImpl::~ByteStreamInputImpl() {
+  my_lifetime_flag_->is_alive_ = false;
+}
+
+void ByteStreamInputImpl::SetPeer(
+    ByteStreamOutputImpl* peer,
+    scoped_refptr<base::SequencedTaskRunner> peer_task_runner,
+    scoped_refptr<LifetimeFlag> peer_lifetime_flag) {
+  peer_ = peer;
+  peer_task_runner_ = peer_task_runner;
+  peer_lifetime_flag_ = peer_lifetime_flag;
+}
+
+bool ByteStreamInputImpl::Write(
+    scoped_refptr<net::IOBuffer> buffer, size_t byte_count) {
+  input_contents_.push_back(std::make_pair(buffer, byte_count));
+  input_contents_size_ += byte_count;
+
+  // Arbitrarily, we buffer to a third of the total size before sending.
+  if (input_contents_size_ > total_buffer_size_ / kFractionBufferBeforeSending)
+    PostToPeer(false, content::DOWNLOAD_INTERRUPT_REASON_NONE);
+
+  return (input_contents_size_ + output_size_used_ <= total_buffer_size_);
+}
+
+void ByteStreamInputImpl::Close(
+    content::DownloadInterruptReason status) {
+  PostToPeer(true, status);
+}
+
+void ByteStreamInputImpl::RegisterCallback(
+    const base::Closure& source_callback) {
+  space_available_callback_ = source_callback;
+}
+
+// static
+void ByteStreamInputImpl::UpdateWindow(
+    scoped_refptr<LifetimeFlag> lifetime_flag, ByteStreamInputImpl* target,
+    size_t bytes_consumed) {
+  // If the target object isn't alive anymore, we do nothing.
+  if (!lifetime_flag->is_alive_) return;
+
+  target->UpdateWindowInternal(bytes_consumed);
+}
+
+void ByteStreamInputImpl::UpdateWindowInternal(size_t bytes_consumed) {
+  DCHECK_GE(output_size_used_, bytes_consumed);
+  output_size_used_ -= bytes_consumed;
+
+  // Callback if we were above the limit and we're now <= to it.
+  size_t total_known_size_used =
+      input_contents_size_ + output_size_used_;
+
+  if (total_known_size_used <= total_buffer_size_ &&
+      (total_known_size_used + bytes_consumed > total_buffer_size_) &&
+      !space_available_callback_.is_null())
+    space_available_callback_.Run();
+}
+
+void ByteStreamInputImpl::PostToPeer(
+    bool complete, content::DownloadInterruptReason status) {
+  // Valid contexts in which to call.
+  DCHECK(complete || 0 != input_contents_size_);
+
+  scoped_ptr<ContentVector> transfer_buffer(new ContentVector);
+  size_t buffer_size = 0;
+  if (0 != input_contents_size_) {
+    transfer_buffer.reset(new ContentVector);
+    transfer_buffer->swap(input_contents_);
+    buffer_size = input_contents_size_;
+    output_size_used_ += input_contents_size_;
+    input_contents_size_ = 0;
+  }
+  peer_task_runner_->PostTask(
+      FROM_HERE, base::Bind(
+          &ByteStreamOutputImpl::TransferData,
+          peer_lifetime_flag_,
+          peer_,
+          base::Passed(transfer_buffer.Pass()),
+          buffer_size,
+          complete,
+          status));
+}
+
+ByteStreamOutputImpl::ByteStreamOutputImpl(
+    scoped_refptr<base::SequencedTaskRunner> task_runner,
+    scoped_refptr<LifetimeFlag> lifetime_flag,
+    size_t buffer_size)
+    : total_buffer_size_(buffer_size),
+      my_task_runner_(task_runner),
+      my_lifetime_flag_(lifetime_flag),
+      available_contents_size_(0),
+      received_status_(false),
+      status_(content::DOWNLOAD_INTERRUPT_REASON_NONE),
+      unreported_consumed_bytes_(0),
+      peer_(NULL) {
+  DCHECK(my_lifetime_flag_.get());
+  my_lifetime_flag_->is_alive_ = true;
+}
+
+ByteStreamOutputImpl::~ByteStreamOutputImpl() {
+  my_lifetime_flag_->is_alive_ = false;
+}
+
+void ByteStreamOutputImpl::SetPeer(
+    ByteStreamInputImpl* peer,
+    scoped_refptr<base::SequencedTaskRunner> peer_task_runner,
+    scoped_refptr<LifetimeFlag> peer_lifetime_flag) {
+  peer_ = peer;
+  peer_task_runner_ = peer_task_runner;
+  peer_lifetime_flag_ = peer_lifetime_flag;
+}
+
+ByteStreamOutputImpl::StreamState
+ByteStreamOutputImpl::Read(scoped_refptr<net::IOBuffer>* data,
+                           size_t* length) {
+  if (available_contents_.size()) {
+    *data = available_contents_.front().first;
+    *length = available_contents_.front().second;
+    available_contents_.pop_front();
+    DCHECK_GE(available_contents_size_, *length);

[benjhayden, 2012/05/18 14:21:06]

Did you mean to delete |available_contents_size_|, or is this DCHECK alone
necessary enough to be worth keeping the member variable?

[Randy Smith (Not in Mondays), 2012/05/18 21:55:15]

Good point--deleted.

+    available_contents_size_ -= *length;
+    unreported_consumed_bytes_ += *length;
+
+    MaybeUpdateInput();
+    return STREAM_HAS_DATA;
+  }
+  if (received_status_) {
+    return STREAM_COMPLETE;
+  }
+  return STREAM_EMPTY;
+}
+
+content::DownloadInterruptReason
+ByteStreamOutputImpl::GetStatus() const {
+  DCHECK(received_status_);
+  return status_;
+}
+
+void ByteStreamOutputImpl::RegisterCallback(
+    const base::Closure& sink_callback) {
+  data_available_callback_ = sink_callback;
+}
+
+// static
+void ByteStreamOutputImpl::TransferData(
+    scoped_refptr<LifetimeFlag> object_lifetime_flag,
+    ByteStreamOutputImpl* target,
+    scoped_ptr<ContentVector> transfer_buffer,
+    size_t buffer_size,
+    bool source_complete,
+    content::DownloadInterruptReason status) {
+  // If our target is no longer alive, do nothing.
+  if (!object_lifetime_flag->is_alive_) return;
+
+  target->TransferDataInternal(
+      transfer_buffer.Pass(), buffer_size, source_complete, status);
+}
+
+void ByteStreamOutputImpl::TransferDataInternal(
+    scoped_ptr<ContentVector> transfer_buffer,
+    size_t buffer_size,
+    bool source_complete,
+    content::DownloadInterruptReason status) {
+  bool was_empty = available_contents_.empty();
+
+  if (transfer_buffer.get()) {
+    available_contents_.insert(available_contents_.end(),
+                                        transfer_buffer->begin(),
+                                        transfer_buffer->end());
+    available_contents_size_ += buffer_size;
+  }
+
+  if (source_complete) {
+    received_status_ = true;
+    status_ = status;
+  }
+
+  // Callback on transition from empty to non-empty, or
+  // source complete.
+  if (((was_empty && !available_contents_.empty()) ||
+       source_complete) &&
+      !data_available_callback_.is_null())
+    data_available_callback_.Run();
+}
+
+// Decide whether or not to send the input a window update.
+// Currently we do that whenever we've got unreported consumption
+// greater than 1/3 of total size.
+void ByteStreamOutputImpl::MaybeUpdateInput() {
+  if (unreported_consumed_bytes_ <=
+      total_buffer_size_ / kFractionReadBeforeWindowUpdate)
+    return;
+
+  peer_task_runner_->PostTask(
+      FROM_HERE, base::Bind(
+          &ByteStreamInputImpl::UpdateWindow,
+          peer_lifetime_flag_,
+          peer_,
+          unreported_consumed_bytes_));
+  unreported_consumed_bytes_ = 0;
+}
+
+}  // namespace
+
+namespace content {
+
+ByteStreamOutput::~ByteStreamOutput() { }
+
+ByteStreamInput::~ByteStreamInput() { }
+
+void CreateByteStream(
+    scoped_refptr<base::SequencedTaskRunner> input_task_runner,
+    scoped_refptr<base::SequencedTaskRunner> output_task_runner,
+    size_t buffer_size,
+    scoped_ptr<ByteStreamInput>* input,
+    scoped_ptr<ByteStreamOutput>* output) {
+  scoped_refptr<LifetimeFlag> input_flag(new LifetimeFlag());
+  scoped_refptr<LifetimeFlag> output_flag(new LifetimeFlag());
+
+  ByteStreamInputImpl* in = new ByteStreamInputImpl(
+      input_task_runner, input_flag, buffer_size);
+  ByteStreamOutputImpl* out = new ByteStreamOutputImpl(
+      output_task_runner, output_flag, buffer_size);
+
+  in->SetPeer(out, output_task_runner, output_flag);
+  out->SetPeer(in, input_task_runner, input_flag);
+  input->reset(in);
+  output->reset(out);
+}
+
+}  // namespace content