需求介绍

在编码或者调试过程中经常需要进行 字节码转换为 十六进制的字符串， 或者将 十六进制字符串 转换为 字节码的需求。

即：  字节码 （内存中存储的 01 串）：    11111111

<------>

FF

Code

linux上调试通过。

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

// Stringify binary data. Output buffer must be twice as big as input,
// because each byte takes 2 bytes in string representation
static void bin2str(char *to, const unsigned char *p, size_t len) {
  static const char *hex = "0123456789abcdef";

for (; len--; p++) {
    *to++ = hex[p[0] >> 4];
    *to++ = hex[p[0] & 0x0f];
  }
  *to = ‘\0‘;
}

unsigned char char2val(const char source)
{
    static const char * hex = "0123456789abcdef";
    size_t index = 0;
    int bLegalChar = 0;

printf("source char =%c\n", source);

for ( index=0 ; index < 16; index++ )
    {
        if ( source == *(hex+index)  )
        {
            bLegalChar = 1;
            break;
        }
    }

if ( !bLegalChar )
    {
        return -1;   
    }

if ( ‘0‘ <= source && source <=‘9‘  )
    {
        return (unsigned char) (source - ‘0‘);
    }
    else if ( ‘a‘ <= source && source <= ‘f‘ )
    {
        return (unsigned char) (source - ‘a‘) + 10 ;
    }
    else
    {
        return -1;
    }
}

// translate hex string to dest bin buff, which is len in length
static void str2bin(const char* source, unsigned char * dest, size_t len)
{
    unsigned char byte_total = 0;
    unsigned char byte_pre = 0;
    unsigned char byte_post = 0;
    const char *  hex = 0;
    size_t destIndex = 0;

if ( strlen(source) % 2 == 1 )
    {
        printf("!! hex string len error!\n");
        return;
    }

hex = source;
    while ( *(hex) )
    {
        byte_pre = char2val(*hex);
        hex++;

byte_post = char2val(*hex);
        hex++;

byte_total = byte_pre << 4 ;
        printf("byte_total pre << 4 = %d\n", byte_total);

byte_total += byte_post;

printf("byte_pre=%d\n", byte_pre);
        printf("byte_post=%d\n", byte_post);
        printf("byte_total=%d\n", byte_total);

if ( destIndex < len )
        {
            *(dest + destIndex) = byte_total;
            destIndex++;
        }
        else
        {
            break;
        }
    }
}

#define byte unsigned char

#define default_val (unsigned long)-1

void main()
{

char binstr[1024] = {0};
    char binstr2[1024] = {0};

printf("aaaa\n");

byte buff[4] = {0};

byte buff2[4] = {0};

memset(buff, -1, 4);

bin2str(binstr, buff, 4);

printf("buff binstr =%s\n", binstr );

str2bin(binstr, buff2, 4);

bin2str(binstr2, buff2, 4);

printf("buff2 binstr2 =%s\n", binstr2);

printf("bbbb\n");
}

效果

代码演示了， 将一个 4 byte的空间， 初始化为 –1 ， 即全部bit位置设置为 1， 然后将此空间转换为 hex字符串，

然后再将此hex字符串转换为 byte字节码空间。