सी/सी ++

Question

में 32-बिट सीआरसी लुकअप टेबल की गणना करें मैं 32-बिट सीआरसी लुकअप टेबल की गणना करना चाहता हूं। एक तरह से मैंने कोशिश की this website से निम्नलिखित कोड का उपयोग करना है:

#include <iostream> 
#include <stdint.h> 

void make_crc_table() 
{ 
    unsigned long POLYNOMIAL = 0x04c11db7; 
    unsigned long WIDTH = 8 * sizeof(unsigned long); 
    unsigned long TOPBIT = 1 << (WIDTH - 1); 
    unsigned long crcTable[256]; 
    unsigned long remainder; 
    // Compute the remainder of each possible dividend 
    for (int dividend = 0; dividend < 256; ++dividend) 
    { 
     // Start with the dividend followed by zeros 
     remainder = dividend << (WIDTH - 8); 

     // Perform modulo-2 division, a bit at a time 
     for (unsigned long bit = 8; bit > 0; --bit) 
     { 
      // Try to divide the current data bit 
      if (remainder & TOPBIT) 
      { 
       remainder = (remainder << 1)^POLYNOMIAL; 
      } 
      else 
      { 
       remainder = (remainder << 1); 
      } 
     } 
     crcTable[dividend] = remainder; 
    } 

    // Print the CRC table 
    for (int i = 0; i < 256; i++) 
    { 
     if (i % 4 == 0) 
     { 
      std::cout <<"\n"; 
     } 
     std::cout << std::hex << crcTable[i]; 
     std::cout << ", "; 
    } 
} 

int main() 
{ 
    make_crc_table(); 
    return 0; 
} 

एक और तरीका है मैंने कोशिश की निम्नलिखित कोड है कि मैं this StackOverflow question से पाया का उपयोग करना है, और कोड from here in a file called CRC Calculator.zip

#include <iostream> 
#include <stdint.h> 

#define POLYNOMIAL  0x04C11DB7 
uint32_t A_crcLookupTable[256] = {0}; 
#define WIDTH (8 * sizeof(uint32_t)) 
#define TOPBIT (((uint32_t)1) << (WIDTH - 1)) 

#define FP_reflect_DATA(_DATO)      (_DATO) 
#define FP_reflect_CRCTableValue(_CRCTableValue) (_CRCTableValue) 

uint32_t F_CRC_ObtenValorDeTabla(uint8_t VP_Pos_Tabla) 
{ 
    uint32_t VP_CRCTableValue = 0; 
    uint8_t VP_Pos_bit = 0; 

    VP_CRCTableValue = ((uint32_t) FP_reflect_DATA(VP_Pos_Tabla)) << (WIDTH - 8); 

    for (VP_Pos_bit = 0; VP_Pos_bit < 8; VP_Pos_bit++) 
    { 
     if (VP_CRCTableValue & TOPBIT) 
     { 
      VP_CRCTableValue = (VP_CRCTableValue << 1)^POLYNOMIAL; 
     } 
     else 
     { 
      VP_CRCTableValue = (VP_CRCTableValue << 1); 
     } 
    } 
    return (FP_reflect_CRCTableValue(VP_CRCTableValue)); 
} 

void F_CRC_InicializaTabla(void) 
{ 
    uint16_t VP_Pos_Array = 0; 

    for (VP_Pos_Array = 0; VP_Pos_Array < 256; VP_Pos_Array++) 
    { 
     A_crcLookupTable[VP_Pos_Array] = F_CRC_ObtenValorDeTabla((uint8_t)(VP_Pos_Array &0xFF)); 

    } 

} 


void make_crc_table() 
{ 
    F_CRC_InicializaTabla(); 

    // Print the CRC table 
    for (int i = 0; i < 256; i++) 
    { 
     if (i % 4 == 0) 
     { 
      std::cout <<"\n"; 
     } 
     std::cout << std::hex << A_crcLookupTable[i]; 
     std::cout << ", "; 
    } 
} 

int main() 
{ 
    make_crc_table(); 
    return 0; 
} 

डाउनलोड किया जा सकता यहां बताया गया है सही अंतिम मेज, होना चाहिए पर this link आधारित है:

// The constants here are for the CRC-32 generator 
// polynomial, as defined in the Microsoft 
// Systems Journal, March 1995, pp. 107-108 
CONST 
    table: ARRAY[0..255] OF DWORD = 
($00000000, $77073096, $EE0E612C, $990951BA, 
    $076DC419, $706AF48F, $E963A535, $9E6495A3, 
    $0EDB8832, $79DCB8A4, $E0D5E91E, $97D2D988, 
    $09B64C2B, $7EB17CBD, $E7B82D07, $90BF1D91, 
    $1DB71064, $6AB020F2, $F3B97148, $84BE41DE, 
    $1ADAD47D, $6DDDE4EB, $F4D4B551, $83D385C7, 
    $136C9856, $646BA8C0, $FD62F97A, $8A65C9EC, 
    $14015C4F, $63066CD9, $FA0F3D63, $8D080DF5, 
    $3B6E20C8, $4C69105E, $D56041E4, $A2677172, 
    $3C03E4D1, $4B04D447, $D20D85FD, $A50AB56B, 
    $35B5A8FA, $42B2986C, $DBBBC9D6, $ACBCF940, 
    $32D86CE3, $45DF5C75, $DCD60DCF, $ABD13D59, 
    $26D930AC, $51DE003A, $C8D75180, $BFD06116, 
    $21B4F4B5, $56B3C423, $CFBA9599, $B8BDA50F, 
    $2802B89E, $5F058808, $C60CD9B2, $B10BE924, 
    $2F6F7C87, $58684C11, $C1611DAB, $B6662D3D, 

    $76DC4190, $01DB7106, $98D220BC, $EFD5102A, 
    $71B18589, $06B6B51F, $9FBFE4A5, $E8B8D433, 
    $7807C9A2, $0F00F934, $9609A88E, $E10E9818, 
    $7F6A0DBB, $086D3D2D, $91646C97, $E6635C01, 
    $6B6B51F4, $1C6C6162, $856530D8, $F262004E, 
    $6C0695ED, $1B01A57B, $8208F4C1, $F50FC457, 
    $65B0D9C6, $12B7E950, $8BBEB8EA, $FCB9887C, 
    $62DD1DDF, $15DA2D49, $8CD37CF3, $FBD44C65, 
    $4DB26158, $3AB551CE, $A3BC0074, $D4BB30E2, 
    $4ADFA541, $3DD895D7, $A4D1C46D, $D3D6F4FB, 
    $4369E96A, $346ED9FC, $AD678846, $DA60B8D0, 
    $44042D73, $33031DE5, $AA0A4C5F, $DD0D7CC9, 
    $5005713C, $270241AA, $BE0B1010, $C90C2086, 
    $5768B525, $206F85B3, $B966D409, $CE61E49F, 
    $5EDEF90E, $29D9C998, $B0D09822, $C7D7A8B4, 
    $59B33D17, $2EB40D81, $B7BD5C3B, $C0BA6CAD, 

    $EDB88320, $9ABFB3B6, $03B6E20C, $74B1D29A, 
    $EAD54739, $9DD277AF, $04DB2615, $73DC1683, 
    $E3630B12, $94643B84, $0D6D6A3E, $7A6A5AA8, 
    $E40ECF0B, $9309FF9D, $0A00AE27, $7D079EB1, 
    $F00F9344, $8708A3D2, $1E01F268, $6906C2FE, 
    $F762575D, $806567CB, $196C3671, $6E6B06E7, 
    $FED41B76, $89D32BE0, $10DA7A5A, $67DD4ACC, 
    $F9B9DF6F, $8EBEEFF9, $17B7BE43, $60B08ED5, 
    $D6D6A3E8, $A1D1937E, $38D8C2C4, $4FDFF252, 
    $D1BB67F1, $A6BC5767, $3FB506DD, $48B2364B, 
    $D80D2BDA, $AF0A1B4C, $36034AF6, $41047A60, 
    $DF60EFC3, $A867DF55, $316E8EEF, $4669BE79, 
    $CB61B38C, $BC66831A, $256FD2A0, $5268E236, 
    $CC0C7795, $BB0B4703, $220216B9, $5505262F, 
    $C5BA3BBE, $B2BD0B28, $2BB45A92, $5CB36A04, 
    $C2D7FFA7, $B5D0CF31, $2CD99E8B, $5BDEAE1D, 

    $9B64C2B0, $EC63F226, $756AA39C, $026D930A, 
    $9C0906A9, $EB0E363F, $72076785, $05005713, 
    $95BF4A82, $E2B87A14, $7BB12BAE, $0CB61B38, 
    $92D28E9B, $E5D5BE0D, $7CDCEFB7, $0BDBDF21, 
    $86D3D2D4, $F1D4E242, $68DDB3F8, $1FDA836E, 
    $81BE16CD, $F6B9265B, $6FB077E1, $18B74777, 
    $88085AE6, $FF0F6A70, $66063BCA, $11010B5C, 
    $8F659EFF, $F862AE69, $616BFFD3, $166CCF45, 
    $A00AE278, $D70DD2EE, $4E048354, $3903B3C2, 
    $A7672661, $D06016F7, $4969474D, $3E6E77DB, 
    $AED16A4A, $D9D65ADC, $40DF0B66, $37D83BF0, 
    $A9BCAE53, $DEBB9EC5, $47B2CF7F, $30B5FFE9, 
    $BDBDF21C, $CABAC28A, $53B39330, $24B4A3A6, 
    $BAD03605, $CDD70693, $54DE5729, $23D967BF, 
    $B3667A2E, $C4614AB8, $5D681B02, $2A6F2B94, 
    $B40BBE37, $C30C8EA1, $5A05DF1B, $2D02EF8D); 

बहरहाल, यह क्या मेरी उत्पादन दोनों कार्यक्रमों (मैं उत्पादन diffed किये जाने वाले, और यह उन दोनों के लिए ही है) से है, और यह गलत है:

0, 4c11db7, 9823b6e, d4326d9, 
130476dc, 17c56b6b, 1a864db2, 1e475005, 
2608edb8, 22c9f00f, 2f8ad6d6, 2b4bcb61, 
350c9b64, 31cd86d3, 3c8ea00a, 384fbdbd, 
4c11db70, 48d0c6c7, 4593e01e, 4152fda9, 
5f15adac, 5bd4b01b, 569796c2, 52568b75, 
6a1936c8, 6ed82b7f, 639b0da6, 675a1011, 
791d4014, 7ddc5da3, 709f7b7a, 745e66cd, 
9823b6e0, 9ce2ab57, 91a18d8e, 95609039, 
8b27c03c, 8fe6dd8b, 82a5fb52, 8664e6e5, 
be2b5b58, baea46ef, b7a96036, b3687d81, 
ad2f2d84, a9ee3033, a4ad16ea, a06c0b5d, 
d4326d90, d0f37027, ddb056fe, d9714b49, 
c7361b4c, c3f706fb, ceb42022, ca753d95, 
f23a8028, f6fb9d9f, fbb8bb46, ff79a6f1, 
e13ef6f4, e5ffeb43, e8bccd9a, ec7dd02d, 
34867077, 30476dc0, 3d044b19, 39c556ae, 
278206ab, 23431b1c, 2e003dc5, 2ac12072, 
128e9dcf, 164f8078, 1b0ca6a1, 1fcdbb16, 
18aeb13, 54bf6a4, 808d07d, cc9cdca, 
7897ab07, 7c56b6b0, 71159069, 75d48dde, 
6b93dddb, 6f52c06c, 6211e6b5, 66d0fb02, 
5e9f46bf, 5a5e5b08, 571d7dd1, 53dc6066, 
4d9b3063, 495a2dd4, 44190b0d, 40d816ba, 
aca5c697, a864db20, a527fdf9, a1e6e04e, 
bfa1b04b, bb60adfc, b6238b25, b2e29692, 
8aad2b2f, 8e6c3698, 832f1041, 87ee0df6, 
99a95df3, 9d684044, 902b669d, 94ea7b2a, 
e0b41de7, e4750050, e9362689, edf73b3e, 
f3b06b3b, f771768c, fa325055, fef34de2, 
c6bcf05f, c27dede8, cf3ecb31, cbffd686, 
d5b88683, d1799b34, dc3abded, d8fba05a, 
690ce0ee, 6dcdfd59, 608edb80, 644fc637, 
7a089632, 7ec98b85, 738aad5c, 774bb0eb, 
4f040d56, 4bc510e1, 46863638, 42472b8f, 
5c007b8a, 58c1663d, 558240e4, 51435d53, 
251d3b9e, 21dc2629, 2c9f00f0, 285e1d47, 
36194d42, 32d850f5, 3f9b762c, 3b5a6b9b, 
315d626, 7d4cb91, a97ed48, e56f0ff, 
1011a0fa, 14d0bd4d, 19939b94, 1d528623, 
f12f560e, f5ee4bb9, f8ad6d60, fc6c70d7, 
e22b20d2, e6ea3d65, eba91bbc, ef68060b, 
d727bbb6, d3e6a601, dea580d8, da649d6f, 
c423cd6a, c0e2d0dd, cda1f604, c960ebb3, 
bd3e8d7e, b9ff90c9, b4bcb610, b07daba7, 
ae3afba2, aafbe615, a7b8c0cc, a379dd7b, 
9b3660c6, 9ff77d71, 92b45ba8, 9675461f, 
8832161a, 8cf30bad, 81b02d74, 857130c3, 
5d8a9099, 594b8d2e, 5408abf7, 50c9b640, 
4e8ee645, 4a4ffbf2, 470cdd2b, 43cdc09c, 
7b827d21, 7f436096, 7200464f, 76c15bf8, 
68860bfd, 6c47164a, 61043093, 65c52d24, 
119b4be9, 155a565e, 18197087, 1cd86d30, 
29f3d35, 65e2082, b1d065b, fdc1bec, 
3793a651, 3352bbe6, 3e119d3f, 3ad08088, 
2497d08d, 2056cd3a, 2d15ebe3, 29d4f654, 
c5a92679, c1683bce, cc2b1d17, c8ea00a0, 
d6ad50a5, d26c4d12, df2f6bcb, dbee767c, 
e3a1cbc1, e760d676, ea23f0af, eee2ed18, 
f0a5bd1d, f464a0aa, f9278673, fde69bc4, 
89b8fd09, 8d79e0be, 803ac667, 84fbdbd0, 
9abc8bd5, 9e7d9662, 933eb0bb, 97ffad0c, 
afb010b1, ab710d06, a6322bdf, a2f33668, 
bcb4666d, b8757bda, b5365d03, b1f740b4, 

Answer 1

बिट्स उलट कर रहे हैं। ध्यान दें कि array[0x80] के लिए तालिका प्रविष्टि (0x80 0x01 उलटा हुआ है) = 0xEDB88320, जो 0x04C11DB7 उलट है।

उदाहरण कोड:

#include <iostream> 
#include <iomanip> 

void make_crc_table(unsigned long crcTable[]) { 
    unsigned long POLYNOMIAL = 0xEDB88320; 
    unsigned long remainder; 
    unsigned char b = 0; 
    do { 
     // Start with the data byte 
     remainder = b; 
     for (unsigned long bit = 8; bit > 0; --bit) { 
      if (remainder & 1) 
       remainder = (remainder >> 1)^POLYNOMIAL; 
      else 
       remainder = (remainder >> 1); 
     } 
     crcTable[(size_t)b] = remainder; 
    } while(0 != ++b); 
} 

unsigned long gen_crc(unsigned char *p, size_t n, unsigned long crcTable[]) { 
    unsigned long crc = 0xfffffffful; 
    size_t i; 
    for(i = 0; i < n; i++) 
     crc = crcTable[*p++^(crc&0xff)]^(crc>>8); 
    return(~crc); 
} 

int main() { 
    unsigned long crcTable[256]; 
    make_crc_table(crcTable); 
    // Print the CRC table 
    for (size_t i = 0; i < 256; i++) { 
     std::cout << std::setfill('0') << std::setw(8) << std::hex << crcTable[i]; 
     if (i % 4 == 3) 
      std::cout << std::endl; 
     else 
      std::cout << ", "; 
    } 
    return 0; 
} 

Answer 2

अगर पर्याप्त फ्लैश और रैम (एम्बेडेड सॉफ्टवेयर) नहीं है, आप इस सुविधा का उपयोग कर सकते हैं:

uint32_t CRC32_function(uint8_t *buf, uint32_t len){ 

    uint32_t val, crc; 
    uint8_t i; 

    crc = 0xFFFFFFFF; 
    while(len--){ 
     val=(crc^*buf++)&0xFF; 
     for(i=0; i<8; i++){ 
      val = val & 1 ? (val>>1)^0xEDB88320 : val>>1; 
     } 
     crc = val^crc>>8; 
    } 
    return crc^0xFFFFFFFF; 
} 

लेकिन सीआरसी गणना अधिक समय लगता है।