65 lines
2.4 KiB
C++
65 lines
2.4 KiB
C++
/*
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* Copyright (C) 2010, Robert Eisele <robert@xarg.org> All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met:
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*
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following disclaimer
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* in the documentation and/or other materials provided with the
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* distribution.
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* * Neither the name of Google Inc. nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "config.h"
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#include "CyclicRedundancyCheck.h"
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#include <wtf/Vector.h>
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static void makeCrcTable(unsigned crcTable[256])
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{
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for (unsigned i = 0; i < 256; i++) {
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unsigned c = i;
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for (int k = 0; k < 8; k++) {
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if (c & 1)
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c = -306674912 ^ ((c >> 1) & 0x7fffffff);
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else
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c = c >> 1;
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}
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crcTable[i] = c;
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}
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}
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unsigned computeCrc(const Vector<unsigned char>& buffer)
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{
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static unsigned crcTable[256];
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static bool crcTableComputed = false;
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if (!crcTableComputed) {
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makeCrcTable(crcTable);
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crcTableComputed = true;
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}
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unsigned crc = 0xffffffffU;
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for (size_t i = 0; i < buffer.size(); ++i)
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crc = crcTable[(crc ^ buffer[i]) & 0xff] ^ ((crc >> 8) & 0x00ffffffU);
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return crc ^ 0xffffffffU;
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}
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