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CRCチェックバリュー付加プログラム (サンプル)

図: コンパイル・動作確認環境
#include <STDIO.H> #include <STDLIB.H> #include <STRING.H> #include <FCNTL.H> #include <ERRNO.H> #define MAX_LEN 51200 /* ファイルサイズのMAX値 (50KB) 実状に併せて変える */ extern int errno; /*---------------------------------------------*/ /* Main */ /*---------------------------------------------*/ main(int argc,char **argv) { char file[128]; char buff[MAX_LEN]; unsigned short crc; unsigned char ch; int fd; int rc; int length; int i; unsigned short crc_tbl[256] = { 0x0000,0x1021,0x2042,0x3063,0x4084,0x50A5,0x60C6,0x70E7, 0x8108,0x9129,0xA14A,0xB16B,0xC18C,0xD1AD,0xE1CE,0xF1EF, 0x1231,0x0210,0x3273,0x2252,0x52B5,0x4294,0x72F7,0x62D6, 0x9339,0x8318,0xB37B,0xA35A,0xD3BD,0xC39C,0xF3FF,0xE3DE, 0x2462,0x3443,0x0420,0x1401,0x64E6,0x74C7,0x44A4,0x5485, 0xA56A,0xB54B,0x8528,0x9509,0xE5EE,0xF5CF,0xC5AC,0xD58D, 0x3653,0x2672,0x1611,0x0630,0x76D7,0x66F6,0x5695,0x46B4, 0xB75B,0xA77A,0x9719,0x8738,0xF7DF,0xE7FE,0xD79D,0xC7BC, 0x48C4,0x58E5,0x6886,0x78A7,0x0840,0x1861,0x2802,0x3823, 0xC9CC,0xD9ED,0xE98E,0xF9AF,0x8948,0x9969,0xA90A,0xB92B, 0x5AF5,0x4AD4,0x7AB7,0x6A96,0x1A71,0x0A50,0x3A33,0x2A12, 0xDBFD,0xCBDC,0xFBBF,0xEB9E,0x9B79,0x8B58,0xBB3B,0xAB1A, 0x6CA6,0x7C87,0x4CE4,0x5CC5,0x2C22,0x3C03,0x0C60,0x1C41, 0xEDAE,0xFD8F,0xCDEC,0xDDCD,0xAD2A,0xBD0B,0x8D68,0x9D49, 0x7E97,0x6EB6,0x5ED5,0x4EF4,0x3E13,0x2E32,0x1E51,0x0E70, 0xFF9F,0xEFBE,0xDFDD,0xCFFC,0xBF1B,0xAF3A,0x9F59,0x8F78, 0x9188,0x81A9,0xB1CA,0xA1EB,0xD10C,0xC12D,0xF14E,0xE16F, 0x1080,0x00A1,0x30C2,0x20E3,0x5004,0x4025,0x7046,0x6067, 0x83B9,0x9398,0xA3FB,0xB3DA,0xC33D,0xD31C,0xE37F,0xF35E, 0x02B1,0x1290,0x22F3,0x32D2,0x4235,0x5214,0x6277,0x7256, 0xB5EA,0xA5CB,0x95A8,0x8589,0xF56E,0xE54F,0xD52C,0xC50D, 0x34E2,0x24C3,0x14A0,0x0481,0x7466,0x6447,0x5424,0x4405, 0xA7DB,0xB7FA,0x8799,0x97B8,0xE75F,0xF77E,0xC71D,0xD73C, 0x26D3,0x36F2,0x0691,0x16B0,0x6657,0x7676,0x4615,0x5634, 0xD94C,0xC96D,0xF90E,0xE92F,0x99C8,0x89E9,0xB98A,0xA9AB, 0x5844,0x4865,0x7806,0x6827,0x18C0,0x08E1,0x3882,0x28A3, 0xCB7D,0xDB5C,0xEB3F,0xFB1E,0x8BF9,0x9BD8,0xABBB,0xBB9A, 0x4A75,0x5A54,0x6A37,0x7A16,0x0AF1,0x1AD0,0x2AB3,0x3A92, 0xFD2E,0xED0F,0xDD6C,0xCD4D,0xBDAA,0xAD8B,0x9DE8,0x8DC9, 0x7C26,0x6C07,0x5C64,0x4C45,0x3CA2,0x2C83,0x1CE0,0x0CC1, 0xEF1F,0xFF3E,0xCF5D,0xDF7C,0xAF9B,0xBFBA,0x8FD9,0x9FF8, 0x6E17,0x7E36,0x4E55,0x5E74,0x2E93,0x3EB2,0x0ED1,0x1EF0 }; if(argc !=2){ printf("Usage : xxxx file-name \n"); exit(1); } strcpy(file,argv[1]); printf(" File : %s\n",file); /* データファイル オープン */ fd = open(file,O_RDONLY); if(fd < 0){ printf(" Source File Open Error [%s]\n",file); exit(1); } length = MAX_LEN; /* データファイル リード */ rc = read(fd,buff,length); crc = 0xFFFF; length = rc; /* チェックバリュー計算 */ for(i=0;i<length;i++){ ch = buff[i]; crc = crc_tbl[(crc>>8^ch)&0xff]^(crc<<8); } /* データファイル クローズ */ close(fd); /* データファイル 再オープン */ fd = open(file,O_RDWR); if(fd < 0){ printf(" Source File Open Error [%s]\n",file); exit(1); } /* データファイル ライト */ rc = write(fd,(char *)buff,length); if(rc != length){ printf(" Source File Write Error [%s] rc = %d errno = %d \n",file,rc,errno); exit(1); } /* チェックバリュー付加 */ /* 注) 動作させるプラットフォームによってセットするバイトが逆の場合もある。*/ /* (ビッグエンディアン/リトルエンディアン) */ rc = write(fd,(char *)&crc+1,1); if(rc != 1){ printf(" Source File Write Error [%s] rc = %d errno = %d \n",file,rc,errno); exit(1); } rc = write(fd,(char *)&crc,1); if(rc != 1){ printf(" Source File Write Error [%s] rc = %d errno = %d \n",file,rc,errno); exit(1); } close(fd); exit(0); }



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