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// 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_STREAM_READER_H_
#define WEBKIT_BLOB_FILE_STREAM_READER_H_
#include "base/basictypes.h"
#include "base/compiler_specific.h"
#include "net/base/completion_callback.h"
#include "webkit/storage/webkit_storage_export.h"
namespace net {
class IOBuffer;
}
namespace webkit_blob {
// A generic interface for reading a file-like object.
class WEBKIT_STORAGE_EXPORT FileStreamReader {
public:
// It is valid to delete the reader at any time. If the stream is deleted
// while it has a pending read, its callback will not be called.
virtual ~FileStreamReader() {}
// Reads from the current cursor position asynchronously.
//
// Up to buf_len bytes will be copied into buf. (In other words, partial
// reads are allowed.) Returns the number of bytes copied, 0 if at
// end-of-file, or an error code if the operation could not be performed.
// If the read could not complete synchronously, then ERR_IO_PENDING is
// returned, and the callback will be run on the thread where Read()
// was called, when the read has completed.
//
// It is invalid to call Read while there is an in-flight Read operation.
//
// If the stream is deleted while it has an in-flight Read operation
// |callback| will not be called.
virtual int Read(net::IOBuffer* buf, int buf_len,
const net::CompletionCallback& callback) = 0;
// Returns the length of the file if it could successfully retrieve the
// file info *and* its last modification time equals to
// expected_modification_time_ (rv >= 0 cases).
// Otherwise, a negative error code is returned (rv < 0 cases).
// If the stream is deleted while it has an in-flight GetLength operation
// |callback| will not be called.
virtual int GetLength(const net::Int64CompletionCallback& callback) = 0;
};
} // namespace webkit_blob
#endif // WEBKIT_BLOB_FILE_STREAM_READER_H_
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