Linux C 快速的八进制转二进制实现

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一种快速的 八进制 转 二进制 C语言 实现。

code

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chunli@blog:~/source/oct$ cat main.c
#include <ctype.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

char isoctal[]={
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0
};

const char*
octal2binary(const char *str, int len, char *buff, int size)
{
    int offset = 0;
    int index = 0;
    while(offset < len && index < size)
    {
        //至少剩余4字符, 以\开头, 3位数字结尾, 尾部检测
        unsigned char char0 = str[offset+0];
        unsigned char char1 = str[offset+1];
        unsigned char char2 = str[offset+2];
        unsigned char char3 = str[offset+3];
        unsigned char char4 = str[offset+4];
        if(len - offset >= 4 && '\\' == char0 && isoctal[char1] && isoctal[char2] && isoctal[char3] && !isdigit(char4))
        {
            buff[index++] = strtoul(str + offset + 1, NULL, 8);
            offset +=4;
        }
        else
        {
            buff[index++] = str[offset++];
        }
    }
    return buff;
}

int main()
{
    char buff[64];
    const char *p = "Hello World! \\344\\270\\255\\346\\226\\207ABC\\346\\265\\213\\350\\257\\225\\345\\255\\227\\347\\254\\246\\344\\270\\262\\056";
    printf("%s\n",p);

    octal2binary(p, strlen(p), buff, sizeof(buff));
    printf("%s\n", buff);
}
chunli@blog:~/source/oct$

编译运行

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chunli@blog:~/source/oct$ gcc -Wall   main.c  && ./a.out
Hello World! \344\270\255\346\226\207ABC\346\265\213\350\257\225\345\255\227\347\254\246\344\270\262\056
Hello World! 中文ABC测试字符串.
chunli@blog:~/source/oct$