| Geant4 Cross Reference |
1 // -*- C++ -*-
2 //
3 // -----------------------------------------------------------------------
4 // HEP Random
5 // --- engineIDulong ---
6 // function implementation file
7 // -----------------------------------------------------------------------
8 //
9 // =======================================================================
10 // Mark Fischler - Created: Mar. 8, 2005
11 // =======================================================================
12
13 #include <string>
14 #include <vector>
15
16 namespace CLHEP {
17
18 static std::vector<unsigned long> gen_crc_table() {
19 /* generate the table of CRC remainders for all possible bytes */
20 static const unsigned long POLYNOMIAL = 0x04c11db7UL;
21 std::vector<unsigned long> crc_table;
22 for ( unsigned long i = 0; i < 256; ++i ) {
23 unsigned long crc = i << 24;
24 for ( int j = 0; j < 8; j++ ) {
25 if ( crc & 0x80000000UL ) {
26 crc = ( ( crc << 1 ) ^ POLYNOMIAL ) & 0xffffffffUL;
27 } else {
28 crc = ( crc << 1 ) & 0xffffffffUL;
29 }
30 }
31 crc_table.push_back(crc);
32 }
33 return crc_table;
34 }
35
36 unsigned long crc32ul(const std::string & s) {
37 static const std::vector<unsigned long> crc_table = gen_crc_table();
38 unsigned long crc = 0;
39 unsigned long end = s.length();
40 for (unsigned long j = 0; j != end; ++j) {
41 int i = ( (int) ( crc >> 24) ^ s[j] ) & 0xff;
42 crc = ( ( crc << 8 ) ^ crc_table[i] ) & 0xffffffffUL;
43 }
44 return crc;
45 }
46
47 } // namespace CLHEP
48
49