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/*
* Copyright (C) 2010, Robert Eisele <robert@xarg.org> All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "CyclicRedundancyCheck.h"
#include <wtf/Vector.h>
static void makeCrcTable(unsigned crcTable[256])
{
for (unsigned i = 0; i < 256; i++) {
unsigned c = i;
for (int k = 0; k < 8; k++) {
if (c & 1)
c = -306674912 ^ ((c >> 1) & 0x7fffffff);
else
c = c >> 1;
}
crcTable[i] = c;
}
}
unsigned computeCrc(const Vector<unsigned char>& buffer)
{
static unsigned crcTable[256];
static bool crcTableComputed = false;
if (!crcTableComputed) {
makeCrcTable(crcTable);
crcTableComputed = true;
}
unsigned crc = 0xffffffffL;
for (size_t i = 0; i < buffer.size(); ++i)
crc = crcTable[(crc ^ buffer[i]) & 0xff] ^ ((crc >> 8) & 0x00ffffffL);
return crc ^ 0xffffffffL;
}
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