C和指针之动态内存分配之编程练习3

   

    

     

      

     
     

      

       #include <stdio.h>
      
     
    

     

      

     
     

      

       #include <stdlib.h>
      
     
    

     

      

     
     

      
 
      
     
    

     

      

     
     

      

       #define OFFSET 5
      
     
    

     

      

     
     

      
 
      
     
    

     

      

     
     

      

       char *my_strcpy()
      
     
    

     

      

     
     

      

       {
      
     
    

     

      

     
     

      
 
      
     
    

     

      

     
     

      

        char *buffer = NULL;
      
     
    

     

      

     
     

      

        //缓冲区的长度
      
     
    

     

      

     
     

      

        int buffer_len = 0;
      
     
    

     

      

     
     

      

        //屏幕字符总长度
      
     
    

     

      

     
     

      

        int all_len = 0;
      
     
    

     

      

     
     

      

        char *p = buffer;
      
     
    

     

      

     
     

      

        int ch;
      
     
    

     

      

     
     

      

        while ((ch = getchar()) != '\n' && ch != EOF)
      
     
    

     

      

     
     

      

        {
      
     
    

     

      

     
     

      

        if (all_len >= buffer_len)
      
     
    

     

      

     
     

      

        {
      
     
    

     

      

     
     

      

        //再次申请的长度
      
     
    

     

      

     
     

      

        buffer_len += OFFSET;
      
     
    

     

      

     
     

      

        //扩充内存空间
      
     
    

     

      

     
     

      

        buffer = realloc(buffer, buffer_len);
      
     
    

     

      

     
     

      

        //指向刚申请内存空间的空闲地方
      
     
    

     

      

     
     

      

        p = buffer + all_len;
      
     
    

     

      

     
     

      

        }
      
     
    

     

      

     
     

      

        all_len++;
      
     
    

     

      

     
     

      

        *p++ = ch;
      
     
    

     

      

     
     

      

        }