[Blob] BlobReader class & tests, and removal of all redundant reading.

storage/browser/blob/blob_url_request_job_factory.cc

 // Copyright (c) 2011 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 "storage/browser/blob/blob_url_request_job_factory.h"
 
 #include "base/basictypes.h"
 #include "base/strings/string_util.h"
 #include "net/base/request_priority.h"
 #include "net/url_request/url_request_context.h"
 #include "storage/browser/blob/blob_data_handle.h"
 #include "storage/browser/blob/blob_storage_context.h"
 #include "storage/browser/blob/blob_url_request_job.h"
 #include "storage/browser/fileapi/file_system_context.h"
 
 namespace storage {
 
 namespace {
 
 int kUserDataKey;  // The value is not important, the addr is a key.
 
-BlobDataHandle* GetRequestedBlobDataHandle(net::URLRequest* request) {
-  return static_cast<BlobDataHandle*>(request->GetUserData(&kUserDataKey));
-}
-
 }  // namespace
 
 // static
 scoped_ptr<net::URLRequest> BlobProtocolHandler::CreateBlobRequest(
     scoped_ptr<BlobDataHandle> blob_data_handle,
     const net::URLRequestContext* request_context,
     net::URLRequest::Delegate* request_delegate) {
   const GURL kBlobUrl("blob://see_user_data/");
   scoped_ptr<net::URLRequest> request = request_context->CreateRequest(
       kBlobUrl, net::DEFAULT_PRIORITY, request_delegate);
   SetRequestedBlobDataHandle(request.get(), blob_data_handle.Pass());
   return request.Pass();
 }
 
 // static
 void BlobProtocolHandler::SetRequestedBlobDataHandle(
     net::URLRequest* request,
     scoped_ptr<BlobDataHandle> blob_data_handle) {
   request->SetUserData(&kUserDataKey, blob_data_handle.release());
 }
 
+// static
+BlobDataHandle* BlobProtocolHandler::GetRequestBlobDataHandle(
+    net::URLRequest* request) {
+  return static_cast<BlobDataHandle*>(request->GetUserData(&kUserDataKey));
+}
+
 BlobProtocolHandler::BlobProtocolHandler(
     BlobStorageContext* context,
     storage::FileSystemContext* file_system_context,
     const scoped_refptr<base::SingleThreadTaskRunner>& task_runner)
     : file_system_context_(file_system_context),
       file_task_runner_(task_runner) {
   if (context)
     context_ = context->AsWeakPtr();
 }
 
 BlobProtocolHandler::~BlobProtocolHandler() {
 }
 
 net::URLRequestJob* BlobProtocolHandler::MaybeCreateJob(
     net::URLRequest* request, net::NetworkDelegate* network_delegate) const {
-  return new storage::BlobURLRequestJob(request,
-                                        network_delegate,
-                                        LookupBlobData(request),
-                                        file_system_context_.get(),
-                                        file_task_runner_.get());
+  return new storage::BlobURLRequestJob(
+      request, network_delegate, LookupBlobHandle(request),
+      file_system_context_.get(), file_task_runner_.get());
 }
 
-scoped_ptr<BlobDataSnapshot> BlobProtocolHandler::LookupBlobData(
+BlobDataHandle* BlobProtocolHandler::LookupBlobHandle(
     net::URLRequest* request) const {
-  BlobDataHandle* blob_data_handle = GetRequestedBlobDataHandle(request);
+  BlobDataHandle* blob_data_handle = GetRequestBlobDataHandle(request);
   if (blob_data_handle)
-    return blob_data_handle->CreateSnapshot().Pass();
+    return blob_data_handle;
   if (!context_.get())
     return NULL;
 
   // Support looking up based on uuid, the FeedbackExtensionAPI relies on this.
   // TODO(michaeln): Replace this use case and others like it with a BlobReader
   // impl that does not depend on urlfetching to perform this function.
   const std::string kPrefix("blob:uuid/");
   if (!base::StartsWith(request->url().spec(), kPrefix,
                         base::CompareCase::SENSITIVE))
     return NULL;
   std::string uuid = request->url().spec().substr(kPrefix.length());
   scoped_ptr<BlobDataHandle> handle = context_->GetBlobDataFromUUID(uuid);
-  scoped_ptr<BlobDataSnapshot> snapshot;
+  BlobDataHandle* handle_ptr = handle.get();
   if (handle) {
-    snapshot = handle->CreateSnapshot().Pass();
     SetRequestedBlobDataHandle(request, handle.Pass());
   }
-  return snapshot.Pass();
+  return handle_ptr;
 }
 
 }  // namespace storage