Initialize the simple cache backend at runtime.

net/disk_cache/cache_creator.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 "base/file_util.h"
+#include "base/metrics/field_trial.h"
+#include "base/stringprintf.h"
+#include "net/base/net_errors.h"
+#include "net/disk_cache/backend_impl.h"
+#include "net/disk_cache/cache_util.h"
+#include "net/disk_cache/mem_backend_impl.h"
+#include "net/disk_cache/simple/simple_backend_impl.h"
+
+namespace disk_cache {
+
+CacheCreator::CacheCreator(
+    const base::FilePath& path, bool force, int max_bytes,
+    net::CacheType type, uint32 flags,
+    base::MessageLoopProxy* thread, net::NetLog* net_log,
+    disk_cache::Backend** backend,
+    const net::CompletionCallback& callback)
+    : path_(path),
+      force_(force),
+      retry_(false),
+      max_bytes_(max_bytes),
+      type_(type),
+      flags_(flags),
+      thread_(thread),
+      backend_(backend),
+      callback_(callback),
+      created_cache_(NULL),
+      net_log_(net_log) {
+  }
+
+CacheCreator::~CacheCreator() {
+}
+
+int CacheCreator::Run() {
+  if (type_ == net::MEMORY_CACHE) {
+    *backend_ = disk_cache::MemBackendImpl::CreateBackend(max_bytes_, net_log_);
+    return *backend_ ? net::OK : net::ERR_FAILED;
+  }
+  // TODO(pasko): The two caches should never coexist. Set up cache cleanup in
+  // two cases: (1) the other version of the cache exists, (2) we are in the
+  // "Control" group of the experiment.
+  if (base::FieldTrialList::FindFullName("SimpleCacheTrial") == "Yes") {
+    // TODO(gavinp,pasko): While simple backend development proceeds, we're only
+    // testing it against net::DISK_CACHE. Turn it on for more cache types as
+    // appropriate.
+    if (type_ == net::DISK_CACHE) {
+      VLOG(1) << "Using the Simple Cache Backend.";
+      return disk_cache::SimpleBackendImpl::CreateBackend(path_, max_bytes_,
+          type_, disk_cache::kNone, thread_, net_log_, backend_,
+          base::Bind(&CacheCreator::OnIOComplete, base::Unretained(this)));
+    }
+  }
+  disk_cache::BackendImpl* new_cache = new disk_cache::BackendImpl(
+      path_, thread_, net_log_);
+  created_cache_ = new_cache;
+  new_cache->SetMaxSize(max_bytes_);
+  new_cache->SetType(type_);
+  new_cache->SetFlags(flags_);
+  int rv = new_cache->Init(
+      base::Bind(&CacheCreator::OnIOComplete, base::Unretained(this)));
+  DCHECK_EQ(net::ERR_IO_PENDING, rv);
+  return rv;
+}
+
+void CacheCreator::DoCallback(int result) {
+  DCHECK_NE(net::ERR_IO_PENDING, result);
+  if (result == net::OK) {
+    *backend_ = created_cache_;
+  } else {
+    LOG(ERROR) << "Unable to create cache";
+    *backend_ = NULL;
+    delete created_cache_;
+  }
+  callback_.Run(result);
+  delete this;
+}
+
+// If the initialization of the cache fails, and |force| is true, we will
+// discard the whole cache and create a new one.
+void CacheCreator::OnIOComplete(int result) {
+  if (result == net::OK || !force_ || retry_)
+    return DoCallback(result);
+
+  // This is a failure and we are supposed to try again, so delete the object,
+  // delete all the files, and try again.
+  retry_ = true;
+  delete created_cache_;
+  created_cache_ = NULL;
+  if (!disk_cache::DelayedCacheCleanup(path_))
+    return DoCallback(result);
+
+  // The worker thread will start deleting files soon, but the original folder
+  // is not there anymore... let's create a new set of files.
+  int rv = Run();
+  DCHECK_EQ(net::ERR_IO_PENDING, rv);
+}
+
+int CreateCacheBackend(net::CacheType type, const base::FilePath& path,
+    int max_bytes, bool force, base::MessageLoopProxy* thread,
+    net::NetLog* net_log, Backend** backend,
+    const net::CompletionCallback& callback) {
+  DCHECK(!callback.is_null());
+  DCHECK(thread || type == net::MEMORY_CACHE);
+  CacheCreator* creator = new CacheCreator(path, force, max_bytes, type, kNone,
+                                           thread, net_log, backend, callback);
+  return creator->Run();
+}
+
+
+}  // namespace disk_cache