按所选顺序排列的任意大小字符串。可移植的数字转换，它在ASCII系统上优化得非常好。 https://godbolt.org/g/Ycah1e

#include <stdio.h>
#include <stdint.h>
#include <string.h>
int CharToDigit(const char c);
void *StringToTable(const char *str, const void *buff, const int order)
    uint8_t *ptr = (uint8_t *)buff;
    size_t len;
    int incr = order ? 1 : -1;
    if(buff && str)
        len = strlen(str);
        if(len &1) return NULL;
        ptr += order ? 0 : len / 2 - 1;
        while(*str)
            int d1 = CharToDigit(*str++);
            int d2 = CharToDigit(*str++);
            if(d1 == -1 || d2 == -1) return NULL;           
            *ptr = d1 * 16 + d2;
            ptr += incr;
    return buff;
int main(void) {
    int index = 0;
    char *str = "78deAc8912fF0f3B";
    uint8_t buff[strlen(str) / 2];
    StringToTable(str, buff, 0);
    printf("String: %s\nResult: ", str);
    for(index = 0; index < strlen(str) / 2; index++ )
        printf("[0x%02hhx]", buff[index] );
    printf("\n");
    StringToTable(str, buff, 1);
    printf("String: %s\nResult: ", str);
    for(index = 0; index < strlen(str) / 2; index++ )
        printf("[0x%02hhx]", buff[index] );
    printf("\n");
    return 0;
int CharToDigit(const char c)
    switch(c)
        case 'a':
        case 'A':
            return 10;
        case 'b':
        case 'B':
            return 11;
        case 'c':
        case 'C':
            return 12;
        case 'd':
        case 'D':
            return 13;
        case 'e':
        case 'E':
            return 14;
        case 'f':
        case 'F':
            return 15;
        case '0':
            return 0;
        case '1':
            return 1;
        case '2':
            return 2;
        case '3':
            return 3;
        case '4':
            return 4;
        case '5':
            return 5;
        case '6':
            return 6;
        case '7':
            return 7;
        case '8':
            return 8;
        case '9':
            return 9;
        default:
            return -1;
}

您可以将字符转换为int类型，如下所示

static inline int char2int(char Ch)
    return(Ch>='0'&&Ch<='9')?(Ch-'0'):(Ch-'A'+10); 
    //assuming correct input with no lowercase letters
}

两个字符，然后使用

static inline 
int chars2int(unsigned char const Chars[2])
    return (char2int(Chars[0])<<4)|(char2int(Chars[1]));
}

通过转换每对字符和几个字符：

static inline int char2int(char Ch)
    return(Ch>='0'&&Ch<='9')?(Ch-'0'):(Ch-'A'+10);
static inline 
int chars2int(unsigned char const Chars[2])
    return (char2int(Chars[0])<<4)|(char2int(Chars[1]));
#include <stdio.h>
#include <string.h>
#include <assert.h>
int main()
    char const inp[] = "DABC95C1";
    assert((sizeof(inp)-1)%2==0);
    unsigned i;
    unsigned char out[(sizeof(inp)-1)/2];