[C] 16進制字串與 byte 陣列戶轉

 Convert between hex string and byte array.

以空間換取時間, 盡量減少計算跟比較.

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static uint8_t HEX_VALUE[256] = { // x0 x1 x2 x3 x4 x5 x6 x7 x8 x9 xA xB xC xD xE xF 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0x 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 1x 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 2x 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 0, 0, 0, 0, 0, // 3x 0,10,11,12,13,14,15, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 4x 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 5x 0,10,11,12,13,14,15, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 6x 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 7x 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 8x 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 9x 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // Ax 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // Bx 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // Cx 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // Dx 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // Ex 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 // Fx }; static uint8_t HEX_CHAR[16] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' }; void bytes2hex(uint8_t* src, char* dest, uint8_t srcsize) { uint8_t flag; uint8_t pos; flag = 0; pos = 0; while (srcsize--) { if (flag || src[srcsize]) { dest[pos++] = HEX_CHAR[src[srcsize]>>4]; dest[pos++] = HEX_CHAR[src[srcsize]&0xf]; } } } void hex2bytes(char *src, uint8_t* dest, uint8_t destsize) { uint8_t len; uint8_t pos; uint8_t hilo; uint8_t byte; uint8_t lohi[2]; char *cptr; len = strlen(src); if (len > (destsize* 2)) { return; } cptr = src + len; pos = 0; ++len; while (len) { memset(lohi, 0, 2); hilo = 2; while (hilo-- && --len) { lohi[hilo] = HEX_VALUE[*--cptr]; } dest[pos++] = lohi[1] | (lohi[0] << 4); } return; }