checksum.h

nandflash文件系统源代码

//---------------------------------------------------------- -*- Mode: C++ -*-
// $Id: Checksum.h 71 2008-07-07 15:49:14Z sriramsrao $ 
//
// Created 2006/09/12
// Author: Sriram Rao
//
// Copyright 2008 Quantcast Corp.
// Copyright 2006-2008 Kosmix Corp.
//
// This file is part of Kosmos File System (KFS).
//
// Licensed under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with
// the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied. See the License for the specific language governing
// permissions and limitations under the License.
//
// Code for computing 32-bit Adler checksums
//----------------------------------------------------------------------------

#ifndef CHUNKSERVER_CHECKSUM_H
#define CHUNKSERVER_CHECKSUM_H

#include <vector>
#include "libkfsIO/IOBuffer.h"

namespace KFS
{
/// Checksums are computed on 64KB block boundaries.  We use the
/// "rolling" 32-bit Adler checksum algorithm
const uint32_t CHECKSUM_BLOCKSIZE = 65536;

const uint32_t MOD_ADLER = 65521;

extern uint32_t OffsetToChecksumBlockNum(off_t offset);

extern uint32_t OffsetToChecksumBlockStart(off_t offset);

extern uint32_t OffsetToChecksumBlockEnd(off_t offset);

/// Call this function if you want checksum computed over CHECKSUM_BLOCKSIZE bytes
extern uint32_t ComputeBlockChecksum(IOBuffer *data, size_t len);
extern uint32_t ComputeBlockChecksum(const char *data, size_t len);

/// Call this function if you want a checksums for a sequence of CHECKSUM_BLOCKSIZE bytes
extern std::vector<uint32_t> ComputeChecksums(IOBuffer *data, size_t len);

}

#endif // CHUNKSERVER_CHECKSUM_H