showMem.c setMem.c 及其改进

#ifndef MEMUTIL_H_INCLUDED

#define MEMUTIL_H_INCLUDED

// Show memory

void showMem(void *, unsigned);

// Setup memory

int setMem(void *, const char *);

#endif // MEMUTIL_H_INCLUDED

　　

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

// Display memory

void showMem(void *p, unsigned size)

{

    char *buf = 0;

    int prs = 0;

    unsigned i;

	buf = (char *)malloc(size * 9);

    printf("Show %p, count %u bits.\n", p, size * 8);

    for (i = 0; i < size; i++)

    {

        char ch = ((char *)p)[i]; // Get char p[i]

        int j;

        for (j = 0; j < 8; j++) // p[i] to 8 bit unsigned int

        {

            unsigned tmp = 0;

            tmp = ch >> (8 - j - 1) & 1;

            sprintf(&buf[prs], "%u", tmp % 2);

            prs = strlen(buf);

        }

        sprintf(&buf[prs], " ");

        prs++;

    }

    buf[prs - 1] = '\0';

    puts(buf);

}

　　

#include <stdio.h>

#include <string.h>

#include <stdlib.h>

#include "MemUtil.h"

// Setup memory

// Return:

// 0  -Setting succeed

// !0 -Setting failed

int setMem(void *p, const char *c)

{

    int le;

    char *str = 0; // 去除空格的副本

    int i;

    int j;

    char ch;

    le = strlen(c);

    i = le - 1;

    str = (char *)malloc(le * 8 / 9 + 2);

    str[0] = '\0';

    // 去除空格

    i = 0;

    while ((ch = *(char *)c++) != '\0')

    {

        if (ch == ' ')

            continue;

        if (ch == '1' || ch == '0')

        {

            str[i++] = ch;

            str[i] = '\0';

        } else {

            printf("错误, 未知的字符: %c.", ch);

            return !0;

        }

    }

    if ((le = strlen(str)) % 8 != 0)

    {

        printf("拒绝执行, 长度错误: %d.\n", le % 8);

        return !0;

    }

    i = 0;

    j = le / 8;

    for (; i < j; i++)

    {

        char tmp = 0;

        int k = 0;

        for (; k < 8; k++)

        {

            tmp |= (str[i * 8 + k] ^ 0x30) << (7 - k);

        }

        ((char *)p)[i] = tmp;

    }

    return 0;

}

　　上面这些代码看似可以工作, 然而!!!!!!!!!!!

　　就在某一天我准备使用它打造一个二进制文件工具的时候, 发生了爆炸!!!!!!! showMem 处理 200 KB居然耗时 80 s !!!!!!!!!!!!!!!!!!!! 当然其中 puts 占用了绝大部分"功劳", 试着优化一下

 #include <stdio.h>

 #include <stdlib.h>

 #include <string.h>

 char *showMem(void *p, unsigned size)

 {

     char *buf = ;

     int prs = ;

     unsigned i = ;

     unsigned j = ;

     char ch = '\0';

     unsigned tmp = ;

     if ((buf = (char *)malloc(size * )) == )

     {

         fprintf(stderr, "Execute failed, PC have not memory.\n");

         return ;

     }

     printf("Show %p, count %u bits.\n", p, size * );

     for (i = ; i < size; i++)

     {

         ch = ((char *)p)[i]; // Get char p[i]

         for (j = ; j < ; j++) // p[i] to 8 bit unsigned int

         {

             tmp = ch >> ( - j) & ;

             buf[prs++] = (tmp ==  ? 0x30 : 0x31);

         }

         buf[prs++] = ' ';

     }

     buf[prs - ] = '\0';

     puts(buf);

     return buf;

 }

showMem.c 性能40+倍提升( -_-! )

 #include <stdio.h>

 #include <string.h>

 #include <stdlib.h>

 #include "MemUtil.h"

 // Setting memory

 // Return:

 //      设置完成的字节数

 //      -1 代表错误

 int setMem(void *p, const char *c)

 {

     int le = ;

     char *str = ; // 去除空格的副本

     int i = ;

     int j = ;

     char ch = ;

     le = strlen(c);

     str = (char *)malloc(le);

     // 去除空格和换行

     while ((ch = *(char *)c++) != '\0')

     {

         if (ch == ' ' || ch == '\n')

             continue;

         if (ch == 0x31 || ch == 0x30)

         {

             str[i++] = ch;

         } else {

             printf("Oops, dead character %c.", ch);

             return -;

         }

     }

     str[i] = '\0';

     if ((le = strlen(str)) %  != )

     {

         printf("You setting data is fucking, 错误的余数 %d.\n", le % );

         return -;

     }

     i = ;

     j = le / ;

     for (; i < j; i++)

     {

         char tmp = ;

         int k = ;

         for (; k < ; k++)

         {

             tmp |= (str[i *  + k] ^ 0x30) << ( - k);

         }

         ((char *)p)[i] = tmp;

     }

     return j;

 }

setMem.c 优化调整