ServiceWorkerWriteToCacheJob: refactor

content/browser/service_worker/service_worker_cache_writer.cc

Index: content/browser/service_worker/service_worker_cache_writer.cc
diff --git a/content/browser/service_worker/service_worker_cache_writer.cc b/content/browser/service_worker/service_worker_cache_writer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e7df07ab81afd07992c78b2b2aadcda77bc42bb8
--- /dev/null
+++ b/content/browser/service_worker/service_worker_cache_writer.cc
@@ -0,0 +1,596 @@
+// 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/browser/service_worker/service_worker_cache_writer.h"
+
+#include <string>
+
+#include "content/browser/appcache/appcache_response.h"
+#include "content/browser/service_worker/service_worker_disk_cache.h"
+#include "content/browser/service_worker/service_worker_storage.h"
+
+namespace {
+
+const size_t kCopyBufferSize = 16 * 1024;
+
+enum {
+  STATE_READ_HEADERS_FOR_COMPARE,
+  STATE_READ_HEADERS_FOR_COMPARE_DONE,
+  STATE_READ_DATA_FOR_COMPARE,
+  STATE_READ_DATA_FOR_COMPARE_DONE,
+  STATE_READ_HEADERS_FOR_COPY,
+  STATE_READ_HEADERS_FOR_COPY_DONE,
+  STATE_READ_DATA_FOR_COPY,
+  STATE_READ_DATA_FOR_COPY_DONE,
+  STATE_WRITE_HEADERS_FOR_PASSTHROUGH,
+  STATE_WRITE_HEADERS_FOR_PASSTHROUGH_DONE,
+  STATE_WRITE_DATA_FOR_PASSTHROUGH,
+  STATE_WRITE_DATA_FOR_PASSTHROUGH_DONE,
+  STATE_WRITE_HEADERS_FOR_COPY,
+  STATE_WRITE_HEADERS_FOR_COPY_DONE,
+  STATE_WRITE_DATA_FOR_COPY,
+  STATE_WRITE_DATA_FOR_COPY_DONE,
+};
+
+// Shim class used to turn always-async functions into async-or-result
+// functions. See the comments below near ReadInfoHelper.
+class AsyncOnlyCompletionCallbackAdaptor
+    : public base::RefCounted<AsyncOnlyCompletionCallbackAdaptor> {
+ public:
+  AsyncOnlyCompletionCallbackAdaptor(const net::CompletionCallback& callback)
+      : done_(false),
+        async_(false),
+        result_(net::ERR_IO_PENDING),
+        callback_(callback) {}
+
+  void set_async(bool async) { async_ = async; }
+  bool async() { return async_; }
+  bool done() { return done_; }
+  int result() { return result_; }
+
+  void WrappedCallback(int result) {
+    result_ = result;
+    if (async_)
+      callback_.Run(result);
+    else
+      done_ = true;
+  }
+
+ private:
+  friend class base::RefCounted<AsyncOnlyCompletionCallbackAdaptor>;
+  virtual ~AsyncOnlyCompletionCallbackAdaptor() {}
+
+  bool done_;
+  bool async_;
+  int result_;
+  net::CompletionCallback callback_;
+};
+
+}  // namespace
+
+namespace content {
+
+ServiceWorkerCacheWriter::StateMachine::State::State() {}
+
+ServiceWorkerCacheWriter::StateMachine::State::State(
+    int id,
+    const std::string& name,
+    const StateMachine::Handler& handler)
+    : id(id), name(name), handler(handler) {}
+
+ServiceWorkerCacheWriter::StateMachine::State::~State() {}
+
+ServiceWorkerCacheWriter::StateMachine::StateMachine() : state_(STATE_START) {}
+ServiceWorkerCacheWriter::StateMachine::~StateMachine() {}
+
+void ServiceWorkerCacheWriter::StateMachine::AddState(
+    int id,
+    const std::string& name,
+    const StateMachine::Handler& handler) {
+  State state(id, name, handler);
+  states_[id] = state;
+}
+
+void ServiceWorkerCacheWriter::StateMachine::AddTransition(int from_id,
+                                                           int to_id) {
+  DCHECK_EQ(1U, states_.count(from_id));
+  DCHECK_EQ(1U, states_.count(to_id));
+  DCHECK_NE(to_id, STATE_START);
+  DCHECK_NE(from_id, STATE_DONE);
+  states_[from_id].allowed_to.insert(to_id);
+}
+
+void ServiceWorkerCacheWriter::StateMachine::CheckValidTransition(int from_id,
+                                                                  int to_id) {
+  DCHECK_EQ(1U, states_.count(from_id)) << " State " << from_id
+                                        << " does not exist.";
+  DCHECK_EQ(1U, states_.count(to_id)) << " State " << to_id << " (from "
+                                      << states_[from_id].name
+                                      << ") does not exist.";
+  if (to_id == STATE_DONE)
+    return;
+  DCHECK_EQ(1U, states_[from_id].allowed_to.count(to_id))
+      << " Transition from " << states_[from_id].name << " to "
+      << states_[to_id].name << " is not allowed.";
+}
+
+int ServiceWorkerCacheWriter::StateMachine::Run(int status) {
+  DCHECK_EQ(1U, states_.count(state_));
+  bool pause = false;
+  VLOG(1) << "Run: initial " << states_[state_].name;
+  do {
+    int next_state = -1;
+    VLOG(1) << "  running " << states_[state_].name;
+    status = states_[state_].handler.Run(&next_state, &pause, status);
+    VLOG(1) << "    -> " << states_[next_state].name << " " << pause << " "
+            << status;
+    CheckValidTransition(state_, next_state);
+    state_ = next_state;
+  } while (status >= net::OK && state_ != STATE_DONE && !pause);
+  return status;
+}
+
+ServiceWorkerCacheWriter::ServiceWorkerCacheWriter(
+    const ResponseReaderCreator& reader_creator,
+    const ResponseWriterCreator& writer_creator)
+    : reader_creator_(reader_creator),
+      writer_creator_(writer_creator),
+      weak_factory_(this) {
+// This macro defines the state |id| to be named "name" and be bound to this
+// object's method called name, so:
+//   DEFINE_STATE(STATE_FOO, Foo)
+// Defines a state STATE_FOO, named "Foo", that is bound to this->Foo().
+#define DEFINE_STATE(id, name) \
+  state_machine_.AddState(     \
+      id, #name,               \
+      base::Bind(&ServiceWorkerCacheWriter::name, base::Unretained(this)))
+
+  DEFINE_STATE(StateMachine::STATE_START, Start);
+  DEFINE_STATE(StateMachine::STATE_DONE, Done);
+
+  DEFINE_STATE(STATE_WRITE_HEADERS_FOR_PASSTHROUGH, WriteHeadersForPassthrough);
+  DEFINE_STATE(STATE_WRITE_HEADERS_FOR_PASSTHROUGH_DONE,
+               WriteHeadersForPassthroughDone);
+  DEFINE_STATE(STATE_WRITE_DATA_FOR_PASSTHROUGH, WriteDataForPassthrough);
+  DEFINE_STATE(STATE_WRITE_DATA_FOR_PASSTHROUGH_DONE,
+               WriteDataForPassthroughDone);
+
+  DEFINE_STATE(STATE_READ_HEADERS_FOR_COMPARE, ReadHeadersForCompare);
+  DEFINE_STATE(STATE_READ_HEADERS_FOR_COMPARE_DONE, ReadHeadersForCompareDone);
+  DEFINE_STATE(STATE_READ_DATA_FOR_COMPARE, ReadDataForCompare);
+  DEFINE_STATE(STATE_READ_DATA_FOR_COMPARE_DONE, ReadDataForCompareDone);
+
+  DEFINE_STATE(STATE_READ_HEADERS_FOR_COPY, ReadHeadersForCopy);
+  DEFINE_STATE(STATE_READ_HEADERS_FOR_COPY_DONE, ReadHeadersForCopyDone);
+  DEFINE_STATE(STATE_WRITE_HEADERS_FOR_COPY, WriteHeadersForCopy);
+  DEFINE_STATE(STATE_WRITE_HEADERS_FOR_COPY_DONE, WriteHeadersForCopyDone);
+
+  DEFINE_STATE(STATE_READ_DATA_FOR_COPY, ReadDataForCopy);
+  DEFINE_STATE(STATE_READ_DATA_FOR_COPY_DONE, ReadDataForCopyDone);
+  DEFINE_STATE(STATE_WRITE_DATA_FOR_COPY, WriteDataForCopy);
+  DEFINE_STATE(STATE_WRITE_DATA_FOR_COPY_DONE, WriteDataForCopyDone);
+
+#undef DEFINE_STATE
+
+  state_machine_.AddTransition(StateMachine::STATE_START,
+                               STATE_WRITE_HEADERS_FOR_PASSTHROUGH);
+  state_machine_.AddTransition(StateMachine::STATE_START,
+                               STATE_READ_HEADERS_FOR_COMPARE);
+  // The passthrough write loop:
+  //   WriteHeaders -> WriteHeadersDone -> WriteData -> WriteDataDone
+  //   -> WriteData
+  state_machine_.AddTransition(STATE_WRITE_HEADERS_FOR_PASSTHROUGH,
+                               STATE_WRITE_HEADERS_FOR_PASSTHROUGH_DONE);
+  state_machine_.AddTransition(STATE_WRITE_HEADERS_FOR_PASSTHROUGH_DONE,
+                               STATE_WRITE_DATA_FOR_PASSTHROUGH);
+  state_machine_.AddTransition(STATE_WRITE_DATA_FOR_PASSTHROUGH,
+                               STATE_WRITE_DATA_FOR_PASSTHROUGH_DONE);
+  state_machine_.AddTransition(STATE_WRITE_DATA_FOR_PASSTHROUGH_DONE,
+                               STATE_WRITE_DATA_FOR_PASSTHROUGH);
+
+  // The comparator loop:
+  //   ReadHeaders -> ReadHeadersDone -> ReadData -> ReadDataDone -> ReadData
+  // Exits via ReadHeadersForCopy.
+  // ReadDataForCompareDone has a self-edge, see the comments in the
+  // function for details.
+  state_machine_.AddTransition(STATE_READ_HEADERS_FOR_COMPARE,
+                               STATE_READ_HEADERS_FOR_COMPARE_DONE);
+  state_machine_.AddTransition(STATE_READ_HEADERS_FOR_COMPARE_DONE,
+                               STATE_READ_DATA_FOR_COMPARE);
+  state_machine_.AddTransition(STATE_READ_DATA_FOR_COMPARE,
+                               STATE_READ_DATA_FOR_COMPARE_DONE);
+  state_machine_.AddTransition(STATE_READ_DATA_FOR_COMPARE_DONE,
+                               STATE_READ_DATA_FOR_COMPARE);
+  state_machine_.AddTransition(STATE_READ_DATA_FOR_COMPARE_DONE,
+                               STATE_READ_DATA_FOR_COMPARE_DONE);
+  state_machine_.AddTransition(STATE_READ_DATA_FOR_COMPARE_DONE,
+                               STATE_READ_HEADERS_FOR_COPY);
+
+  // ReadHeaders -> ReadHeadersDone -> WriteHeaders -> WriteHeadersDone
+  // -> ReadData
+  state_machine_.AddTransition(STATE_READ_HEADERS_FOR_COPY,
+                               STATE_READ_HEADERS_FOR_COPY_DONE);
+  state_machine_.AddTransition(STATE_READ_HEADERS_FOR_COPY_DONE,
+                               STATE_WRITE_HEADERS_FOR_COPY);
+  state_machine_.AddTransition(STATE_WRITE_HEADERS_FOR_COPY,
+                               STATE_WRITE_HEADERS_FOR_COPY_DONE);
+  state_machine_.AddTransition(STATE_WRITE_HEADERS_FOR_COPY_DONE,
+                               STATE_READ_DATA_FOR_COPY);
+
+  // The ReadDataForCopy loop:
+  //   ReadData -> ReadDataDone -> WriteData -> WriteDataDone -> ReadData
+  // This can bail out via:
+  //   ReadData -> WriteDataForPassthrough
+  state_machine_.AddTransition(STATE_READ_DATA_FOR_COPY,
+                               STATE_READ_DATA_FOR_COPY_DONE);
+  state_machine_.AddTransition(STATE_READ_DATA_FOR_COPY_DONE,
+                               STATE_WRITE_DATA_FOR_COPY);
+  state_machine_.AddTransition(STATE_WRITE_DATA_FOR_COPY,
+                               STATE_WRITE_DATA_FOR_COPY_DONE);
+  state_machine_.AddTransition(STATE_WRITE_DATA_FOR_COPY_DONE,
+                               STATE_READ_DATA_FOR_COPY);
+  state_machine_.AddTransition(STATE_READ_DATA_FOR_COPY,
+                               STATE_WRITE_DATA_FOR_PASSTHROUGH);
+}
+
+ServiceWorkerCacheWriter::~ServiceWorkerCacheWriter() {}
+
+net::Error ServiceWorkerCacheWriter::WriteHeaders(
+    HttpResponseInfoIOBuffer* headers,
+    const OnWriteCompleteCallback& callback) {
+  headers_to_write_ = headers;
+  pending_callback_ = callback;
+  int result = state_machine_.Run(net::OK);

[falken, 2015/08/28 05:45:24]

When trying to trace through this code I found it's a bit inconvenient to figure
out what would actually be called here. Maybe it'd be convenient to comment or
DCHECK saying we're in STATE_WRITE_HEADERS_FOR_PASSTHROUGH or
STATE_WRITE_HEADERS_FOR_COPY or that WriteHeadersForPassthrough or
WriteHeadersForCopy would be called? Or is that overkill... just an idea.

[Elly Fong-Jones, 2015/08/31 15:03:45]

We're actually in STATE_START here. I've added a DCHECK_EQ to that effect. From
STATE_START we move to either WRITE_HEADERS_FOR_PASSTHROUGH or
READ_HEADERS_FOR_COMPARE depending whether we have an existing reader to compare
against.

+  return result >= 0 ? net::OK : static_cast<net::Error>(result);
+}
+
+net::Error ServiceWorkerCacheWriter::WriteData(
+    net::IOBuffer* buf,
+    size_t buf_size,
+    const OnWriteCompleteCallback& callback) {
+  data_to_write_ = buf;
+  len_to_write_ = buf_size;
+  pending_callback_ = callback;
+  int result = state_machine_.Run(net::OK);
+  return result >= 0 ? net::OK : static_cast<net::Error>(result);
+}
+
+size_t ServiceWorkerCacheWriter::BytesWritten() const {
+  return bytes_written_;
+}
+
+int ServiceWorkerCacheWriter::Start(int* next_state, bool* pause, int result) {
+  bytes_written_ = 0;
+  compare_reader_ = reader_creator_.Run();
+  if (compare_reader_.get())
+    *next_state = STATE_READ_HEADERS_FOR_COMPARE;
+  else
+    // No existing reader, just write the headers back directly.
+    *next_state = STATE_WRITE_HEADERS_FOR_PASSTHROUGH;
+  return net::OK;
+}
+
+int ServiceWorkerCacheWriter::ReadHeadersForCompare(int* next_state,
+                                                    bool* pause,
+                                                    int result) {
+  DCHECK(headers_to_write_);
+
+  headers_to_read_ = new HttpResponseInfoIOBuffer;
+  *next_state = STATE_READ_HEADERS_FOR_COMPARE_DONE;
+  return ReadInfoHelper(compare_reader_, headers_to_read_.get());
+}
+
+int ServiceWorkerCacheWriter::ReadHeadersForCompareDone(int* next_state,
+                                                        bool* pause,
+                                                        int result) {
+  if (result < 0) {
+    *next_state = StateMachine::STATE_DONE;
+    return static_cast<int>(result);
+  }
+  cached_length_ = headers_to_read_->response_data_size;
+  net_length_ = headers_to_write_->response_data_size;
+  bytes_compared_ = 0;
+  *pause = true;
+  *next_state = STATE_READ_DATA_FOR_COMPARE;
+  return net::OK;
+}
+
+int ServiceWorkerCacheWriter::ReadDataForCompare(int* next_state,
+                                                 bool* pause,
+                                                 int result) {
+  DCHECK(data_to_write_);
+
+  data_to_read_ = new net::IOBuffer(len_to_write_);
+  len_to_read_ = len_to_write_;
+  *next_state = STATE_READ_DATA_FOR_COMPARE_DONE;
+  compare_offset_ = 0;
+  return ReadDataHelper(compare_reader_, data_to_read_.get(), len_to_read_);
+}
+
+int ServiceWorkerCacheWriter::ReadDataForCompareDone(int* next_state,
+                                                     bool* pause,
+                                                     int result) {
+  DCHECK(data_to_read_);
+  DCHECK(data_to_write_);
+  DCHECK_EQ(len_to_read_, len_to_write_);
+  DCHECK_LE(result + compare_offset_, static_cast<size_t>(len_to_write_));
+
+  if (result < 0) {
+    *next_state = StateMachine::STATE_DONE;
+    return result;
+  }
+
+  // Premature EOF while reading the AppCache data to compare. Fail the

[falken, 2015/08/28 05:45:24]

I wouldn't call it AppCache data. Service worker happens to reuse the AppCache
implementation code for storing http responses but they are better thought as
two separate things. Service worker scripts are stored in the "service worker
script cache" (incidentally, AppCache uses blockfile disk cache backend for this
and service worker uses SimpleCache). Maybe just saying "data from disk" is
best.

[Elly Fong-Jones, 2015/08/31 15:03:45]

Done.

+  // comparison.
+  if (result == 0) {
+    *next_state = STATE_READ_HEADERS_FOR_COPY;
+    return net::OK;
+  }
+
+  // Compare the data from AppCache to the data from the network.
+  if (memcmp(data_to_read_->data(), data_to_write_->data() + compare_offset_,
+             result)) {
+    // Data mismatched. This method already validated that all the bytes through
+    // |bytes_compared_| were identical, so copy the first |bytes_compared_|
+    // over, then start writing network data back after the changed point.
+    //
+    // Note that the state machine does NOT get paused here, since there is
+    // still further work to do before this object is ready to handle another
+    // WriteData call.
+    *next_state = STATE_READ_HEADERS_FOR_COPY;
+    return net::OK;
+  }
+
+  compare_offset_ += result;
+
+  // This is a little bit tricky. It is possible that not enough data was read
+  // to finish comparing the entire block of data from the network (which is
+  // kept in len_to_write_), so this method may need to issue another read and
+  // return to this state.
+  //
+  // Compare isn't complete yet. Issue another read for the remaining data. Note
+  // that this reuses the same IOBuffer.
+  if (compare_offset_ < static_cast<size_t>(len_to_read_)) {
+    *next_state = STATE_READ_DATA_FOR_COMPARE_DONE;
+    return ReadDataHelper(compare_reader_, data_to_read_.get(),
+                          len_to_read_ - compare_offset_);
+  }
+
+  // Cached entry is longer than the network entry but the prefix matches. Copy
+  // just the prefix.
+  if (bytes_compared_ + compare_offset_ >= net_length_ &&
+      net_length_ < cached_length_) {
+    *next_state = STATE_READ_HEADERS_FOR_COPY;
+    return net::OK;
+  }
+
+  // bytes_compared_ only gets incremented when a full block is compared, to
+  // avoid having to use only parts of the buffered network data.
+  bytes_compared_ += result;
+  *next_state = STATE_READ_DATA_FOR_COMPARE;
+  *pause = true;
+  return net::OK;
+}
+
+int ServiceWorkerCacheWriter::WriteHeadersForPassthrough(int* next_state,
+                                                         bool* pause,
+                                                         int result) {
+  writer_ = writer_creator_.Run();
+  *next_state = STATE_WRITE_HEADERS_FOR_PASSTHROUGH_DONE;
+  return WriteInfoHelper(writer_, headers_to_write_.get());
+}
+
+int ServiceWorkerCacheWriter::WriteHeadersForPassthroughDone(int* next_state,
+                                                             bool* pause,
+                                                             int result) {
+  *next_state = STATE_WRITE_DATA_FOR_PASSTHROUGH;
+  *pause = true;
+  return net::OK;
+}
+
+int ServiceWorkerCacheWriter::WriteDataForPassthrough(int* next_state,
+                                                      bool* pause,
+                                                      int result) {
+  *next_state = STATE_WRITE_DATA_FOR_PASSTHROUGH_DONE;
+  return WriteDataHelper(writer_, data_to_write_.get(), len_to_write_);
+}
+
+int ServiceWorkerCacheWriter::WriteDataForPassthroughDone(int* next_state,
+                                                          bool* pause,
+                                                          int result) {
+  if (result < 0) {
+    *next_state = StateMachine::STATE_DONE;
+    return static_cast<int>(result);
+  }
+  bytes_written_ += result;
+  *next_state = STATE_WRITE_DATA_FOR_PASSTHROUGH;
+  *pause = true;
+  return net::OK;
+}
+
+int ServiceWorkerCacheWriter::ReadHeadersForCopy(int* next_state,
+                                                 bool* pause,
+                                                 int result) {
+  bytes_copied_ = 0;
+  copy_reader_ = reader_creator_.Run();
+  headers_to_read_ = new HttpResponseInfoIOBuffer;
+  data_to_copy_ = new net::IOBuffer(kCopyBufferSize);
+  *next_state = STATE_READ_HEADERS_FOR_COPY_DONE;
+  return ReadInfoHelper(copy_reader_, headers_to_read_.get());
+}
+
+int ServiceWorkerCacheWriter::ReadHeadersForCopyDone(int* next_state,
+                                                     bool* pause,
+                                                     int result) {
+  if (result < 0) {
+    *next_state = StateMachine::STATE_DONE;
+    return static_cast<int>(result);
+  }
+  *next_state = STATE_WRITE_HEADERS_FOR_COPY;
+  return net::OK;
+}
+
+// Write the just-read headers back to the cache.
+// Note that this method must create |writer_|, since the only paths to this
+// state never create a writer.
+// Also note that this *discards* the read headers and replaces them with the
+// net headers.
+int ServiceWorkerCacheWriter::WriteHeadersForCopy(int* next_state,
+                                                  bool* pause,
+                                                  int result) {
+  DCHECK(!writer_);
+  writer_ = writer_creator_.Run();
+  *next_state = STATE_WRITE_HEADERS_FOR_COPY_DONE;
+  return WriteInfoHelper(writer_, headers_to_write_.get());
+}
+
+int ServiceWorkerCacheWriter::WriteHeadersForCopyDone(int* next_state,
+                                                      bool* pause,
+                                                      int result) {
+  if (result < 0) {
+    *next_state = StateMachine::STATE_DONE;
+    return static_cast<int>(result);
+  }
+  *next_state = STATE_READ_DATA_FOR_COPY;
+  return net::OK;
+}
+
+int ServiceWorkerCacheWriter::ReadDataForCopy(int* next_state,
+                                              bool* pause,
+                                              int result) {
+  size_t to_read = std::min(kCopyBufferSize, bytes_compared_ - bytes_copied_);
+  // At this point, all compared bytes have been read. Currently
+  // |data_to_write_| and |len_to_write_| hold the chunk of network input that
+  // caused the comparison failure, so those need to be written back and this
+  // object needs to go into passthrough mode.
+  if (to_read == 0) {
+    *next_state = STATE_WRITE_DATA_FOR_PASSTHROUGH;
+    return net::OK;
+  }
+  *next_state = STATE_READ_DATA_FOR_COPY_DONE;
+  return ReadDataHelper(copy_reader_, data_to_copy_.get(), to_read);
+}
+
+int ServiceWorkerCacheWriter::ReadDataForCopyDone(int* next_state,
+                                                  bool* pause,
+                                                  int result) {
+  if (result < 0) {
+    *next_state = StateMachine::STATE_DONE;
+    return result;
+  }
+  *next_state = STATE_WRITE_DATA_FOR_COPY;
+  return result;
+}
+
+int ServiceWorkerCacheWriter::WriteDataForCopy(int* next_state,
+                                               bool* pause,
+                                               int result) {
+  *next_state = STATE_WRITE_DATA_FOR_COPY_DONE;
+  DCHECK_GT(result, 0);
+  return WriteDataHelper(writer_, data_to_copy_.get(), result);
+}
+
+int ServiceWorkerCacheWriter::WriteDataForCopyDone(int* next_state,
+                                                   bool* pause,
+                                                   int result) {
+  if (result < 0) {
+    *next_state = StateMachine::STATE_DONE;
+    return result;
+  }
+  bytes_written_ += result;
+  bytes_copied_ += result;
+  *next_state = STATE_READ_DATA_FOR_COPY;
+  return result;
+}
+
+int ServiceWorkerCacheWriter::Done(int* next_state, bool* pause, int result) {
+  *next_state = StateMachine::STATE_DONE;
+  return net::OK;
+}
+
+// These helpers adapt the AppCache "always use the callback" pattern to the
+// //net "only use the callback for async" pattern using
+// AsyncCompletionCallbackAdaptor.
+//
+// Specifically, these methods return result codes directly for synchronous
+// completions, and only run their callback (which is AsyncRunStateMachine) for
+// asynchronous completions.
+
+int ServiceWorkerCacheWriter::ReadInfoHelper(
+    const scoped_ptr<ServiceWorkerResponseReader>& reader,
+    HttpResponseInfoIOBuffer* buf) {
+  net::CompletionCallback run_callback =
+      base::Bind(&ServiceWorkerCacheWriter::AsyncRunStateMachine,
+                 weak_factory_.GetWeakPtr());
+  scoped_refptr<AsyncOnlyCompletionCallbackAdaptor> adaptor(
+      new AsyncOnlyCompletionCallbackAdaptor(run_callback));
+  reader->ReadInfo(
+      buf, base::Bind(&AsyncOnlyCompletionCallbackAdaptor::WrappedCallback,
+                      adaptor));
+  adaptor->set_async(true);
+  return adaptor->result();
+}
+
+int ServiceWorkerCacheWriter::ReadDataHelper(
+    const scoped_ptr<ServiceWorkerResponseReader>& reader,
+    net::IOBuffer* buf,
+    int buf_len) {
+  net::CompletionCallback run_callback =
+      base::Bind(&ServiceWorkerCacheWriter::AsyncRunStateMachine,
+                 weak_factory_.GetWeakPtr());
+  scoped_refptr<AsyncOnlyCompletionCallbackAdaptor> adaptor(
+      new AsyncOnlyCompletionCallbackAdaptor(run_callback));
+  reader->ReadData(
+      buf, buf_len,
+      base::Bind(&AsyncOnlyCompletionCallbackAdaptor::WrappedCallback,
+                 adaptor));
+  adaptor->set_async(true);
+  return adaptor->result();
+}
+
+int ServiceWorkerCacheWriter::WriteInfoHelper(
+    const scoped_ptr<ServiceWorkerResponseWriter>& writer,
+    HttpResponseInfoIOBuffer* buf) {
+  net::CompletionCallback run_callback =
+      base::Bind(&ServiceWorkerCacheWriter::AsyncRunStateMachine,
+                 weak_factory_.GetWeakPtr());
+  scoped_refptr<AsyncOnlyCompletionCallbackAdaptor> adaptor(
+      new AsyncOnlyCompletionCallbackAdaptor(run_callback));
+  writer->WriteInfo(
+      buf, base::Bind(&AsyncOnlyCompletionCallbackAdaptor::WrappedCallback,
+                      adaptor));
+  adaptor->set_async(true);
+  return adaptor->result();
+}
+
+int ServiceWorkerCacheWriter::WriteDataHelper(
+    const scoped_ptr<ServiceWorkerResponseWriter>& writer,
+    net::IOBuffer* buf,
+    int buf_len) {
+  net::CompletionCallback run_callback =
+      base::Bind(&ServiceWorkerCacheWriter::AsyncRunStateMachine,
+                 weak_factory_.GetWeakPtr());
+  scoped_refptr<AsyncOnlyCompletionCallbackAdaptor> adaptor(
+      new AsyncOnlyCompletionCallbackAdaptor(run_callback));
+  writer->WriteData(
+      buf, buf_len,
+      base::Bind(&AsyncOnlyCompletionCallbackAdaptor::WrappedCallback,
+                 adaptor));
+  adaptor->set_async(true);
+  return adaptor->result();
+}
+
+void ServiceWorkerCacheWriter::AsyncRunStateMachine(int result) {
+  result = state_machine_.Run(result);
+  // If the result is ERR_IO_PENDING, the pending callback will be run by a
+  // later invocation of AsyncRunStateMachine.
+  if (result != net::ERR_IO_PENDING) {
+    OnWriteCompleteCallback callback = pending_callback_;
+    pending_callback_.Reset();
+    net::Error error = result >= 0 ? net::OK : static_cast<net::Error>(result);
+    callback.Run(error);
+  }
+}
+
+}  // namespace content