字符串和十六进制互相转换

#include <stdio.h>
#include <string.h>

int strToHex(char *ch, char *hex);
int hexToStr(char *hex, char *ch);
int hexCharToValue(const char ch);
char valueToHexCh(const int value);

int main(int argc, char *argv[])
{
    char ch[1024];
    char hex[1024];
    char result[1024];
    char *p_ch = ch;
    char *p_hex = hex;
    char *p_result = result;

    printf("please input the string:");
    scanf("%s",p_ch);

    strToHex(p_ch,p_hex);

    printf("the hex is:%s\n",p_hex);
    hexToStr(p_hex, p_result);
    printf("the string is:%s\n", p_result);
    return 0;
}

int strToHex(char *ch, char *hex)
{
    int high,low;
    int tmp = 0;
    if(ch == NULL || hex == NULL)
    {
        return -1;
    }

    if(strlen(ch) == 0)
    {
        return -2;
    }

    while(*ch)
    {
        tmp = (int)*ch;
        high = tmp >> 4;
        low = tmp & 15;
        *hex++ = valueToHexCh(high); //先写高字节
        *hex++ = valueToHexCh(low); //其次写低字节
        ch++;
    }

    *hex = '\0';
    return 0;
}

int hexToStr(char *hex, char *ch)
{
    int high,low;
    int tmp = 0;

    if(hex == NULL || ch == NULL)
    {
        return -1;
    }

    if(strlen(hex) %2 == 1)
    {
        return -2;
    }

    while(*hex)
    {
        high = hexCharToValue(*hex);
        if(high < 0)
        {
            *ch = '\0';
            return -3;
        }

        hex++; //指针移动到下一个字符上

        low = hexCharToValue(*hex);

        if(low < 0)
        {
            *ch = '\0';
            return -3;
        }

        tmp = (high << 4) + low;
        *ch++ = (char)tmp;
        hex++;
    }
    *ch = '\0';
    return 0;
}



int hexCharToValue(const char ch)
{
    int result = 0;

    //获取16进制的高字节位数据
    if(ch >= '0' && ch <= '9')
    {
        result = (int)(ch - '0');
    }
    else if(ch >= 'a' && ch <= 'z')
    {
        result = (int)(ch - 'a') + 10;
    }
    else if(ch >= 'A' && ch <= 'Z')
    {
        result = (int)(ch - 'A') + 10;
    }
    else
    {
        result = -1;
    }

    return result;
}

char valueToHexCh(const int value)
{
    char result = '\0';
    if(value >= 0 && value <= 9)
    {
        result = (char)(value + 48); //48为ascii编码的‘0’字符编码值
    }
    else if(value >= 10 && value <= 15)
    {
        result = (char)(value - 10 + 65); //减去10则找出其在16进制的偏移量，65为ascii的'A'的字符编码值
    }
    else
    {
        ;
    }

    return result;
}