Add new simple disk cache backend.

net/disk_cache/simple/simple_entry_impl.cc

+// Copyright (c) 2013 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/disk_cache/simple/simple_entry_impl.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/callback.h"
+#include "base/location.h"
+#include "base/message_loop_proxy.h"
+#include "base/threading/worker_pool.h"
+#include "net/base/io_buffer.h"
+#include "net/base/net_errors.h"
+#include "net/disk_cache/simple/simple_synchronous_entry.h"
+
+
+namespace {
+
+typedef disk_cache::Entry::CompletionCallback CompletionCallback;
+typedef disk_cache::SimpleSynchronousEntry::SynchronousEntryCallback
+    SynchronousEntryCallback;
+
+}  // namespace
+
+namespace disk_cache {
+
+using base::FilePath;
+using base::MessageLoopProxy;
+using base::Time;
+using base::WeakPtr;
+using base::WorkerPool;
+
+// A PendingOperation represents an operation on a SynchronousEntry while it is
+// in flight. It informs the owning SimpleEntryImpl of IO completion if
+// necessary, as well as calling the IO completion callback.
+class SimpleEntryImpl::PendingOperation {

[pasko-google - do not use, 2013/02/11 13:59:25]

maybe a PendingEntryOperation would be a better name because it suggests that an
entry exists, and we are mutating it in good contrast with
PendingCreationOperation.

[gavinp, 2013/02/11 17:55:50]

Done.

+ public:
+  static SynchronousEntryCallback Create(
+      const WeakPtr<SimpleEntryImpl>& entry,
+      const CompletionCallback& completion_callback);
+
+ private:
+  PendingOperation(const WeakPtr<SimpleEntryImpl>& entry,
+                   const CompletionCallback& completion_callback);
+
+  void OnIOComplete(SimpleSynchronousEntry* sync_entry, int result);
+
+  WeakPtr<SimpleEntryImpl> entry_;
+  CompletionCallback completion_callback_;
+};
+
+// A PendingCreationOperation represents a pending operation that is creating a
+// new SimpleSynchronousEntry, such as OpenEntry() or CreateEntry(). It ensures
+// that a SimpleEntryImpl is only created after the underlying synchronous
+// operation has succeeded.
+class SimpleEntryImpl::PendingCreationOperation {
+ public:
+  static SynchronousEntryCallback Create(
+      const CompletionCallback& completion_callback,
+      Entry** out_entry);
+
+ private:
+  PendingCreationOperation(const CompletionCallback& completion_callback,
+                           Entry** out_entry);
+
+  void OnIOComplete(SimpleSynchronousEntry* sync_entry, int result);
+
+  CompletionCallback completion_callback_;
+  Entry** out_entry_;
+};
+
+// static
+SynchronousEntryCallback SimpleEntryImpl::PendingOperation::Create(
+    const WeakPtr<SimpleEntryImpl>& entry,
+    const CompletionCallback& completion_callback) {
+  PendingOperation* operation = new PendingOperation(entry,
+                                                     completion_callback);
+  DCHECK(operation);
+  return base::Bind(&PendingOperation::OnIOComplete, base::Owned(operation));
+}
+
+SimpleEntryImpl::PendingOperation::PendingOperation(
+    const WeakPtr<SimpleEntryImpl>& entry,
+    const CompletionCallback& completion_callback)
+    : entry_(entry),
+      completion_callback_(completion_callback) {
+}
+
+void SimpleEntryImpl::PendingOperation::OnIOComplete(
+    SimpleSynchronousEntry* sync_entry,
+    int result) {
+  DCHECK(sync_entry);
+  if (entry_)
+    entry_->SetSynchronousEntry(sync_entry);
+  completion_callback_.Run(result);
+}
+
+// static
+SynchronousEntryCallback SimpleEntryImpl::PendingCreationOperation::Create(
+    const CompletionCallback& completion_callback,
+    Entry** out_entry) {
+  PendingCreationOperation* operation =
+      new PendingCreationOperation(completion_callback, out_entry);
+  DCHECK(operation);
+  return base::Bind(&PendingCreationOperation::OnIOComplete,
+                    base::Owned(operation));
+}
+
+SimpleEntryImpl::PendingCreationOperation::PendingCreationOperation(
+    const CompletionCallback& completion_callback,
+    Entry** out_entry) : completion_callback_(completion_callback),
+                         out_entry_(out_entry) {
+}
+
+void SimpleEntryImpl::PendingCreationOperation::OnIOComplete(
+    SimpleSynchronousEntry* sync_entry,
+    int result) {
+  DCHECK_NE(net::ERR_IO_PENDING, result);
+
+  if (result != net::OK) {
+    DCHECK(!sync_entry) << "sync_entry = " << sync_entry;
+    completion_callback_.Run(result);
+    return;
+  }
+  DCHECK(sync_entry);
+  *out_entry_ = new SimpleEntryImpl(sync_entry);
+  DCHECK(*out_entry_);
+  completion_callback_.Run(net::OK);
+}
+
+// static
+int SimpleEntryImpl::OpenEntry(const FilePath& path,
+                               const std::string& key,
+                               Entry** entry,
+                               const CompletionCallback& callback) {
+  SynchronousEntryCallback sync_entry_callback =
+      PendingCreationOperation::Create(callback, entry);
+
+  WorkerPool::PostTask(FROM_HERE,
+                       base::Bind(&SimpleSynchronousEntry::OpenEntry, path, key,
+                                  MessageLoopProxy::current(),
+                                  sync_entry_callback),
+                       true);
+  return net::ERR_IO_PENDING;
+}
+
+// static
+int SimpleEntryImpl::CreateEntry(const FilePath& path,
+                                 const std::string& key,
+                                 Entry** entry,
+                                 const CompletionCallback& callback) {
+  SynchronousEntryCallback sync_entry_callback =
+      PendingCreationOperation::Create(callback, entry);
+  WorkerPool::PostTask(FROM_HERE,
+                       base::Bind(&SimpleSynchronousEntry::CreateEntry, path,
+                                  key, MessageLoopProxy::current(),
+                                  sync_entry_callback),
+                       true);
+  return net::ERR_IO_PENDING;
+}
+
+// static
+int SimpleEntryImpl::DoomEntry(const FilePath& path,
+                               const std::string& key,
+                               const CompletionCallback& callback) {
+  WorkerPool::PostTask(FROM_HERE,
+                       base::Bind(&SimpleSynchronousEntry::DoomEntry, path, key,
+                                  MessageLoopProxy::current(), callback),
+                       true);
+  return net::ERR_IO_PENDING;
+}
+
+void SimpleEntryImpl::Doom() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  WorkerPool::PostTask(FROM_HERE,
+                       base::Bind(&SimpleSynchronousEntry::DoomAndClose,
+                                  base::Unretained(ReleaseSynchronousEntry())),
+                       true);
+  has_been_doomed_ = true;
+}
+
+void SimpleEntryImpl::Close() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (!has_been_doomed_) {
+    WorkerPool::PostTask(FROM_HERE,
+                         base::Bind(&SimpleSynchronousEntry::Close,
+                                    base::Unretained(
+                                        ReleaseSynchronousEntry())),
+                         true);
+  }
+  // Entry::Close() is expected to release this entry. See disk_cache.h for
+  // details.
+  delete this;
+}
+
+std::string SimpleEntryImpl::GetKey() const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  return key_;
+}
+
+Time SimpleEntryImpl::GetLastUsed() const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(synchronous_entry_);
+  return synchronous_entry_->last_used();

[pasko-google - do not use, 2013/02/11 13:59:25]

is there a hidden assumption that last used cannot be requested while a write is
in flight? If there is, someone could easily break it, I believe. I assume it
will be solved by "support overlapping reads" below?

[gavinp, 2013/02/11 17:55:50]

Hopefully. The reads will change a bit once checksums are added; but I can see a
few approaches to supporting them that work.

I've made this NOTIMPLEMENTED() so it's more clear that a good answer is needed
here.

+}
+
+Time SimpleEntryImpl::GetLastModified() const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(synchronous_entry_);
+  return synchronous_entry_->last_modified();
+}
+
+int32 SimpleEntryImpl::GetDataSize(int index) const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(synchronous_entry_);
+  return synchronous_entry_->data_size(index);
+}
+
+int SimpleEntryImpl::ReadData(int index,
+                              int offset,
+                              net::IOBuffer* buf,
+                              int buf_len,
+                              const CompletionCallback& callback) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  // TODO(gavinp): Add support for overlapping reads. The net::HttpCache does
+  // make overlapping read requests when multiple transactions access the same
+  // entry as read only.

[pasko-google - do not use, 2013/02/11 13:59:25]

does it happen often? on what occasion?

[gavinp, 2013/02/11 17:55:50]

Yes, if for instance a page uses google served jQuery, and so does an iframe on
the same page.

+  DCHECK(synchronous_entry_);
+  SynchronousEntryCallback sync_entry_callback =
+      PendingOperation::Create(weak_ptr_factory_.GetWeakPtr(), callback);
+  WorkerPool::PostTask(FROM_HERE,
+                       base::Bind(&SimpleSynchronousEntry::ReadData,
+                                  base::Unretained(ReleaseSynchronousEntry()),
+                                  index, offset, scoped_refptr<IOBuffer>(buf),
+                                  buf_len, sync_entry_callback),
+                       true);
+  return net::ERR_IO_PENDING;
+}
+
+int SimpleEntryImpl::WriteData(int index,
+                               int offset,
+                               net::IOBuffer* buf,
+                               int buf_len,
+                               const CompletionCallback& callback,
+                               bool truncate) {
+  for (int i = 0; i < buf_len; ++i) {
+    char c ALLOW_UNUSED = buf->data()[i];

[pasko-google - do not use, 2013/02/11 13:59:25]

It is hard to believe that this will be optimized out, and can be expensive. Is
it data prefetching then? Hard to guess.

[gavinp, 2013/02/11 17:55:50]

That is debugging code that made it into this upload. Thanks for catching it. I
was trying to force core dumps in the posting thread: Ricardo's earlier comment
about the buf needing to be owned was absolutely correct, and I still don't
quite get why (the creator doesn't own it while waiting? I guess not!).

I'll remove it.

+  }
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(synchronous_entry_);
+  SynchronousEntryCallback sync_entry_callback =
+      PendingOperation::Create(weak_ptr_factory_.GetWeakPtr(), callback);
+  WorkerPool::PostTask(FROM_HERE,
+                       base::Bind(&SimpleSynchronousEntry::WriteData,
+                                  base::Unretained(ReleaseSynchronousEntry()),
+                                  index, offset, scoped_refptr<IOBuffer>(buf),
+                                  buf_len, sync_entry_callback, truncate),
+                       true);
+  return net::ERR_IO_PENDING;
+}
+
+int SimpleEntryImpl::ReadSparseData(int64 offset,
+                                    net::IOBuffer* buf,
+                                    int buf_len,
+                                    const CompletionCallback& callback) {
+  // TODO(gavinp): Determine if the simple backend should support sparse data.
+  DCHECK(thread_checker_.CalledOnValidThread());
+  return net::ERR_FAILED;
+}
+
+int SimpleEntryImpl::WriteSparseData(int64 offset,
+                                     net::IOBuffer* buf,
+                                     int buf_len,
+                                     const CompletionCallback& callback) {
+  // TODO(gavinp): Determine if the simple backend should support sparse data.
+  DCHECK(thread_checker_.CalledOnValidThread());
+  return net::ERR_FAILED;
+}
+
+int SimpleEntryImpl::GetAvailableRange(int64 offset,
+                                       int len,
+                                       int64* start,
+                                       const CompletionCallback& callback) {
+  // TODO(gavinp): Determine if the simple backend should support sparse data.
+  DCHECK(thread_checker_.CalledOnValidThread());
+  return net::ERR_FAILED;
+}
+
+bool SimpleEntryImpl::CouldBeSparse() const {
+  // TODO(gavinp): Determine if the simple backend should support sparse data.
+  DCHECK(thread_checker_.CalledOnValidThread());
+  return false;
+}
+
+void SimpleEntryImpl::CancelSparseIO() {
+  // TODO(gavinp): Determine if the simple backend should support sparse data.
+  DCHECK(thread_checker_.CalledOnValidThread());
+}
+
+int SimpleEntryImpl::ReadyForSparseIO(const CompletionCallback& callback) {
+  // TODO(gavinp): Determine if the simple backend should support sparse data.
+  DCHECK(thread_checker_.CalledOnValidThread());
+  return net::ERR_FAILED;
+}
+
+SimpleEntryImpl::SimpleEntryImpl(
+    SimpleSynchronousEntry* synchronous_entry)
+    : ALLOW_THIS_IN_INITIALIZER_LIST(weak_ptr_factory_(this)),
+      key_(synchronous_entry->key()),
+      synchronous_entry_(synchronous_entry),
+      has_been_doomed_(false) {
+  DCHECK(synchronous_entry);
+}
+
+SimpleEntryImpl::~SimpleEntryImpl() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(!synchronous_entry_) << "synchronous_entry_ = " << synchronous_entry_;
+}
+
+SimpleSynchronousEntry* SimpleEntryImpl::ReleaseSynchronousEntry() {
+  DCHECK(synchronous_entry_);
+  SimpleSynchronousEntry* retval = synchronous_entry_;
+  synchronous_entry_ = NULL;
+  return retval;
+}
+
+void SimpleEntryImpl::SetSynchronousEntry(
+    SimpleSynchronousEntry* synchronous_entry) {
+  DCHECK(!synchronous_entry_) << "synchronous_entry_ = " << synchronous_entry_;
+  synchronous_entry_ = synchronous_entry;
+}
+
+}  // namespace disk_cache