mediaview: Implement ArcDocumentsProviderBackendDelegate.

chrome/browser/chromeos/arc/fileapi/arc_documents_provider_backend_delegate.cc

 // Copyright 2016 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 "chrome/browser/chromeos/arc/fileapi/arc_documents_provider_backend_delegate.h"
 
 #include <utility>
 
 #include "base/logging.h"
+#include "base/memory/ptr_util.h"
+#include "chrome/browser/chromeos/arc/fileapi/arc_content_file_system_url_util.h"
+#include "chrome/browser/chromeos/arc/fileapi/arc_documents_provider_file_stream_reader.h"
+#include "chrome/browser/chromeos/arc/fileapi/arc_documents_provider_root.h"
 #include "content/public/browser/browser_thread.h"
 #include "storage/browser/fileapi/file_stream_reader.h"
 #include "storage/browser/fileapi/file_stream_writer.h"
 #include "url/gurl.h"
 
 using content::BrowserThread;
 
 namespace arc {
 
 ArcDocumentsProviderBackendDelegate::ArcDocumentsProviderBackendDelegate()
-    : async_file_util_(&roots_) {}
+    : async_file_util_(&roots_), weak_ptr_factory_(this) {}
 
 ArcDocumentsProviderBackendDelegate::~ArcDocumentsProviderBackendDelegate() {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
 }
 
 storage::AsyncFileUtil* ArcDocumentsProviderBackendDelegate::GetAsyncFileUtil(
     storage::FileSystemType type) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   return &async_file_util_;
 }
 
 std::unique_ptr<storage::FileStreamReader>
 ArcDocumentsProviderBackendDelegate::CreateFileStreamReader(
     const storage::FileSystemURL& url,
     int64_t offset,
     int64_t max_bytes_to_read,
     const base::Time& expected_modification_time,
     storage::FileSystemContext* context) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  NOTIMPLEMENTED();  // TODO(crbug.com/671511): Implement this function.
-  return nullptr;
+
+  std::unique_ptr<ArcDocumentsProviderFileStreamReader> reader =

[hidehiko, 2016/12/18 14:29:18]

Optional: I'd recommend to use "auto", because of
- consistency that auto + MakeUnique is used in many places in ARC code, and
- simplicity that the type appears only once.

[Shuhei Takahashi, 2016/12/19 03:05:56]

Sure, changed to use auto.

+      base::MakeUnique<ArcDocumentsProviderFileStreamReader>(offset);
+
+  base::FilePath path;
+  ArcDocumentsProviderRoot* root = roots_.ParseAndLookup(url, &path);
+  if (!root) {
+    reader->SetContentUrl(GURL());
+    return std::move(reader);

[Luis Héctor Chávez, 2016/12/17 00:05:26]

Huh, why did the pessimizing move warning not trigger? Anyways, remove the
std::move on return statements.

[Shuhei Takahashi, 2016/12/17 00:23:09]

I'm not sure why, but returning std::unique_ptr<Derived> in a function with
return value type std::unique<Base> gives a compile error on g++ 4.x, but not on
g++ 5.x.

http://melpon.org/wandbox/permlink/B2S4qXDpmznhtNR9
http://melpon.org/wandbox/permlink/fLZveKGpfiwgSJcU

[hidehiko, 2016/12/18 14:29:18]

IIUC, it's C++11 spec about copy elision. 
cf)
http://stackoverflow.com/questions/22018115/converting-stdunique-ptrderived-t...

[Shuhei Takahashi, 2016/12/19 03:05:55]

I know that spec but I was wondering why gcc 5.x allows it even with
-std=c++11... Anyway, I think we need std::move() here.

+  }
+
+  root->ResolveToContentUrl(
+      path, base::Bind(&ArcDocumentsProviderFileStreamReader::SetContentUrl,
+                       reader->GetWeakPtr()));
+  return std::move(reader);
 }
 
 std::unique_ptr<storage::FileStreamWriter>
 ArcDocumentsProviderBackendDelegate::CreateFileStreamWriter(
     const storage::FileSystemURL& url,
     int64_t offset,
     storage::FileSystemContext* context) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   NOTREACHED();  // Read-only file system.
   return nullptr;
 }
 
 storage::WatcherManager* ArcDocumentsProviderBackendDelegate::GetWatcherManager(
     storage::FileSystemType type) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   NOTREACHED();  // Non-watchable file system.
   return nullptr;
 }
 
 void ArcDocumentsProviderBackendDelegate::GetRedirectURLForContents(
     const storage::FileSystemURL& url,
     const storage::URLCallback& callback) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  NOTIMPLEMENTED();  // TODO(crbug.com/671511): Implement this function.
-  callback.Run(GURL());
+
+  base::FilePath path;
+  ArcDocumentsProviderRoot* root = roots_.ParseAndLookup(url, &path);
+  if (!root) {
+    callback.Run(GURL());
+    return;
+  }
+
+  root->ResolveToContentUrl(
+      path, base::Bind(&ArcDocumentsProviderBackendDelegate::
+                           GetRedirectURLForContentsWithContentUrl,
+                       weak_ptr_factory_.GetWeakPtr(), callback));
+}
+
+void ArcDocumentsProviderBackendDelegate::
+    GetRedirectURLForContentsWithContentUrl(
+        const storage::URLCallback& callback,
+        const GURL& content_url) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  callback.Run(ArcUrlToExternalFileUrl(content_url));
 }
 
 }  // namespace arc