Gabriele Cosmo
50 lines
1.4 KiB
C++
50 lines
1.4 KiB
C++
// $Id:$
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// -*- C++ -*-
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//
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// -----------------------------------------------------------------------
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// HEP Random
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// --- engineIDulong ---
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// function implementation file
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// -----------------------------------------------------------------------
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//
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// =======================================================================
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// Mark Fischler - Created: Mar. 8, 2005
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// =======================================================================
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#include <string>
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#include <vector>
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namespace CLHEP {
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static std::vector<unsigned long> gen_crc_table() {
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/* generate the table of CRC remainders for all possible bytes */
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static const unsigned long POLYNOMIAL = 0x04c11db7UL;
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std::vector<unsigned long> crc_table;
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for ( unsigned long i = 0; i < 256; ++i ) {
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unsigned long crc = i << 24;
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for ( int j = 0; j < 8; j++ ) {
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if ( crc & 0x80000000UL ) {
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crc = ( ( crc << 1 ) ^ POLYNOMIAL ) & 0xffffffffUL;
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} else {
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crc = ( crc << 1 ) & 0xffffffffUL;
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}
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}
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crc_table.push_back(crc);
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}
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return crc_table;
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}
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unsigned long crc32ul(const std::string & s) {
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static const std::vector<unsigned long> crc_table = gen_crc_table();
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unsigned long crc = 0;
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int end = s.length();
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for (int j = 0; j != end; ++j) {
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int i = ( (int) ( crc >> 24) ^ s[j] ) & 0xff;
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crc = ( ( crc << 8 ) ^ crc_table[i] ) & 0xffffffffUL;
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}
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return crc;
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}
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} // namespace CLHEP
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