linux开发---10.【C】十六进制转十进制

1. 发现在u-boot中有些十六进制数，如0x30000000 0x00200000 不直观，搞个小程序直观的显示一下。

其中make_human_readable_str 是从 busybox-1.13.0/coreutils/ls.c拿过来的。

#include <stdio.h>
#include <stdlib.h>
typedef int smallint;
const char* make_human_readable_str(unsigned long long size, unsigned long block_size, unsigned long display_unit)
{
    /* The code will adjust for additional (appended) units */
    static const char unit_chars[]= { '\0', 'K', 'M', 'G', 'T', 'P', 'E' };
    static const char fmt[] = "%llu";
    static const char fmt_tenths[] = "%llu.%d%c";

    static char str[21] ; /* Sufficient for 64 bit unsigned integers */

    unsigned long long val;
    int frac;
    const char *u;
    const char *f;
    smallint no_tenths;

    if (size == 0)
        return "0";

    /* If block_size is 0 then do not print tenths */
    no_tenths = 0;
    if (block_size == 0)
    {
        no_tenths = 1;
        block_size = 1;
    }

    u = unit_chars;
    val = size * block_size;
    f = fmt;
    frac = 0;

    if (display_unit)
    {
        val += display_unit/2;    /* Deal with rounding */
        val /= display_unit;    /* Don't combine with the line */
        /* will just print it as ulonglong (below) */
    }
    else
    {
        while ((val >= 1024) && (u < unit_chars + sizeof(unit_chars) - 1))
        {
            f = fmt_tenths;
            u++;
            frac = (((int)(val % 1024)) * 10 + 1024/2) / 1024; //这句写得太牛了
            val /= 1024;
        }
        if (frac >= 10)
        {        /* We need to round up here. */
            ++val;
            frac = 0;
        }
        /* Sample code to omit decimal point and tenths digit. */
        if (no_tenths)
        {
            if (frac >= 5)
            {
                ++val;
            }
            f = "%llu%*c" /* fmt_no_tenths */;
            frac = 1;
        }
    }

    /* If f==fmt then 'frac' and 'u' are ignored. */
    snprintf(str, sizeof(str), f, val, frac, *u);

    return str;
}

int str2num(char str[])
{
    unsigned long n = 0;
    int i;
    for(i=0; str[i]!='\0'; i++)
    {
        if(str[i]>='0' && str[i]<='9')
            n = n*16 + str[i] - '0';
        if(str[i]>='a' && str[i]<='f')
            n = n*16 + str[i] - 'a' + 10;
        if(str[i]>='A' && str[i]<='F')
            n = n*16 + str[i]- 'A' + 10;
    }
    return n;
}

int main(int argc, char *argv[])
{
    unsigned long num = 0;
    if( argc < 2)
    {
        printf("usage: %s \n", argv[0]);
        return -1;
    }

    //支持输入'0x'打头的十六进制数
    if(argv[1][0]=='0' && argv[1][1]=='x' || argv[1][1]=='X')
    {
        printf("Hex:%s\n", argv[1]);
        num = str2num(&argv[1][2]);
    }
    else
    {
        printf("Hex:Ox%s\n", argv[1]);
        num = str2num(argv[1]);
    }
    printf("Dec:%ld\n", num);
    printf("readable: %s\n", make_human_readable_str(num,1,0));
    return 0;
}

实验一下：

root@ubuntu:~/test# ./test 0x30000000

Hex:0x30000000

Dec:805306368

readable: 768.0M

还不错，呵呵。