mediaview: Implement ArcDocumentsProviderBackendDelegate.

chrome/browser/chromeos/arc/fileapi/arc_documents_provider_file_stream_reader.h

+// 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.
+
+#ifndef CHROME_BROWSER_CHROMEOS_ARC_FILEAPI_ARC_DOCUMENTS_PROVIDER_FILE_STREAM_READER_H_
+#define CHROME_BROWSER_CHROMEOS_ARC_FILEAPI_ARC_DOCUMENTS_PROVIDER_FILE_STREAM_READER_H_
+
+#include <memory>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "storage/browser/fileapi/file_stream_reader.h"
+
+class GURL;
+
+namespace storage {
+
+class FileSystemURL;
+
+}  // namespace storage
+
+namespace arc {
+
+class ArcDocumentsProviderRootMap;
+
+// FileStreamReader implementation for ARC documents provider file system.
+// It actually delegates operations to ArcContentFileSystemFileStreamReader.
+// TODO(crbug.com/678886): Write unit tests.
+class ArcDocumentsProviderFileStreamReader : public storage::FileStreamReader {
+ public:
+  // |roots| can be released soon after the constructor returns.
+  ArcDocumentsProviderFileStreamReader(const storage::FileSystemURL& url,
+                                       int64_t offset,
+                                       ArcDocumentsProviderRootMap* roots);
+  ~ArcDocumentsProviderFileStreamReader() override;
+
+  // storage::FileStreamReader override:
+  int Read(net::IOBuffer* buffer,
+           int buffer_length,
+           const net::CompletionCallback& callback) override;
+  int64_t GetLength(const net::Int64CompletionCallback& callback) override;
+
+ private:
+  void OnResolveToContentUrl(const GURL& content_url);
+  void RunPendingRead(scoped_refptr<net::IOBuffer> buffer,
+                      int buffer_length,
+                      const net::CompletionCallback& callback);
+  void RunPendingGetLength(const net::Int64CompletionCallback& callback);
+
+  const int64_t offset_;
+  bool content_url_resolved_;
+  std::unique_ptr<storage::FileStreamReader> underlying_reader_;
+  std::vector<base::Closure> pending_operations_;
+
+  base::WeakPtrFactory<ArcDocumentsProviderFileStreamReader> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ArcDocumentsProviderFileStreamReader);
+};
+
+}  // namespace arc
+
+#endif  // CHROME_BROWSER_CHROMEOS_ARC_FILEAPI_ARC_DOCUMENTS_PROVIDER_FILE_STREAM_READER_H_