library/cpp/digest/old_crc/gencrc/main.cpp


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56

#include <util/stream/output.h>

#define POLY_16 0x1021
#define POLY_32 0xEDB88320UL
#define POLY_64 ULL(0xE543279765927881)

static void crc16init() { 
    ui32 CRCTAB16[256]; 
    ui32 crc;
    int i, j;

    for (i = 0; i < 256; CRCTAB16[i++] = 0xFFFF & ((crc << 8) ^ (crc >> 8))) 
        for (crc = i, j = 8; j > 0; j--)
            if (crc & 1)
                crc = (crc >> 1) ^ POLY_16;
            else
                crc >>= 1;
 
    for (size_t k = 0; k < 256; ++k) {
        Cout << "    ULL(" << CRCTAB16[k] << ")";
 
        if (k != 255) {
            Cout << ",\n"; 
        } 
    } 
}

static void crc32init() { 
    ui32 CRCTAB32[256]; 
    ui32 crc;
    int i, j;

    for (i = 0; i < 256; CRCTAB32[i++] = crc)
        for (crc = i, j = 8; j > 0; j--)
            if (crc & 1)
                crc = (crc >> 1) ^ POLY_32;
            else
                crc >>= 1;
 
    for (size_t k = 0; k < 256; ++k) {
        Cout << "    ULL(" << CRCTAB32[k] << ")";
 
        if (k != 255) {
            Cout << ",\n"; 
        } 
    } 
}

int main() { 
    Cout << "static const ui32 CRCTAB16[] = {\n\n"; 
    crc16init(); 
    Cout << "\n};\n\n"; 
    Cout << "static const ui32 CRCTAB32[] = {\n\n"; 
    crc32init(); 
    Cout << "\n};\n\n"; 
}