C语言 str2bin 和 bin2str 实现

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 = '';
}

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

    printf("source char =%c ", 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! ");
        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 ", byte_total);

        byte_total += byte_post;

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

    byte buff[4] = {0};

    byte buff2[4] = {0};

    memset(buff, -1, 4);

    bin2str(binstr, buff, 4);

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

    str2bin(binstr, buff2, 4);

    bin2str(binstr2, buff2, 4);

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

    printf("bbbb ");
}

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。