Add FileReader interface and implement FileSystemFileReader

webkit/blob/file_reader.h

Index: webkit/blob/file_reader.h
diff --git a/webkit/blob/file_reader.h b/webkit/blob/file_reader.h
new file mode 100644
index 0000000000000000000000000000000000000000..3232c8759c83de884503ac594cd2cb9719b39e3e
--- /dev/null
+++ b/webkit/blob/file_reader.h
@@ -0,0 +1,36 @@
+// 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.
+
+#ifndef WEBKIT_BLOB_FILE_READER_H_
+#define WEBKIT_BLOB_FILE_READER_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "net/base/completion_callback.h"
+#include "webkit/blob/blob_export.h"
+
+namespace net {
+class FileStream;
+class IOBuffer;
+}
+
+namespace webkit_blob {
+
+// A generic interface for reading a file-like object.
+class BLOB_EXPORT FileReader {
+ public:
+  virtual ~FileReader() {}
+
+  // Reads from the current cursor position asynchronously.
+  // This works mostly same as how net::FileStream::Read() works except that
+  // it internally opens (and seeks) the file if it is not opened yet.

[michaeln, 2012/04/13 20:24:51]

The middle two lines in this doc comment seem out of place on this abstract
interface. Consider moving them to the overriden methods on LocalFileReader and
FileSystemFileReader.

[kinuko, 2012/04/16 10:24:21]

Done.

+  // It is invalid to call Read while there is an in-flight Read operation.
+  virtual int Read(net::IOBuffer* buf, int buf_len,
+                   const net::CompletionCallback& callback) = 0;
+};
+
+}  // namespace webkit_blob
+
+#endif  // WEBKIT_BLOB_FILE_READER_H_