char *chstohex ( char* chs ){    char hex[16] = { ‘0‘, ‘1‘, ‘2‘, ‘3‘, ‘4‘, ‘5‘, ‘6‘,         ‘7‘, ‘8‘,‘9‘, ‘A‘, ‘B‘, ‘C‘, ‘D‘, ‘E‘, ‘F‘    };    int len = strlen ( chs );    char* ascii = NULL ;    ascii = (char*)calloc ( len * 3 + 1, sizeof(char) );            // calloc ascii        int i = 0;    while( i < len )    {        ascii[i*2] = hex[(int)( (char)chs[i] / 16 )] ;        ascii[i*2 + 1] = hex[(int)( (char)chs[i] % 16 )] ;        ++i;    }    return ascii;                    // ascii 返回之前未释放}// 函数输入16进制字符串，输出对应的字符串char *hextochs ( char* ascii ){    int len = strlen ( ascii ) ;    if( len%2 != 0 )        return NULL ;    char *chs = NULL ;    chs = (char*)calloc( len / 2 + 1, sizeof(char) );                // calloc chs    int  i = 0 ;    char ch[2] = {0};    while( i < len )    {        ch[0] = ( (int)ascii[i] > 64 ) ? ( ascii[i]%16 + 9 ) : ascii[i]%16 ;        ch[1] = ( (int)ascii[i + 1] > 64 ) ? ( ascii[i + 1]%16 + 9 ) : ascii[i + 1]%16 ;                chs[i/2] = (char)( ch[0]*16 + ch[1] );        i += 2;    }    return chs ;            // chs 返回前未释放}