C++ 中strcpy标准写法实例详解

strcpy标准写法

实例代码：

// CppReference.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
using namespace std;


char *strcpy_v1(char *dest , const char *src)
{
  //调试时，使用断言，入口检测
  assert( (dest!=NULL) && (src!=NULL) );
  
  //注意这里的内存指向参数dest所在的内存，不是栈内存，因而可以在函数中返回
  char *to = dest;
  
  //主要操作在while条件中完成
  while( (*dest++ = *src++)!='')
  {
    NULL;  
  }
  
  //返回拷贝字符串首地址，方便连缀，比如strlen(strcpy(dest,"hello"))
  return to;
}


char *strcpy_v2(char *dest , const char *src)
{
  char *d = dest;
  char c;
  
  while((c=*src++) != '')
  {
    *(dest++)=c;
  }
  
  *dest='';
  
  return d;
}


char *strcpy_v2_error(char *dest , const char *src)
{
  char *d = dest;
  char c;
  
  while((c=*src++) != '')
  {
    *(d++)=c;
  }
  
  *d='';
  
  return d;
}



char *strcpy_v3(char *dest , const char *src)
{
  char *d = dest;
  char c;
  
  while(*src)
    *dest++ = *src++;
    
  *dest='';
  
  return d;
}


char *strcpy_v4(char *dest , const char *src)
{
  char *d = dest;
  char c;
  
  while( (*dest = *src)!='')
  {
    src++;
    dest++; 
  }
    
  *dest='';
  
  return d;
}


char *strcpy_v5(char* _restrict dest , const char* _restrict src)
{
  char *d = dest;
  char c;
  
  while( (*dest = *src)!='')
  {
    src++;
    dest++; 
  }
    
  *dest='';
  
  return d;
}


char *strcpy_v6(char* _restrict dest , const char* _restrict src)
{
  char *d = dest;
  char c;
  
  while(*dest++=*src++); 
  return d;
}



int _tmain(int argc, _TCHAR* argv[])
{
  char buf[512];
  
  char *buf2 = (char *)calloc(50,sizeof(char));
  
  char *buf3 = (char *)malloc(50*sizeof(char));
  
  char *buf5 = (char *)malloc(50*sizeof(char));
  
  char *buf6 = (char *)malloc(50*sizeof(char));
  
  printf("using strcpy_v1,the string 'Hello,World''s length is : %dn",strlen(strcpy_v1(buf,"Hello,World")));
  
  printf("using strcpy_v2,the string 'This is the best age''s length is : %dn",strlen(strcpy_v2(buf2,"This is the best age")));
  
  printf("using strcpy_v2,the string 'This is the best age''s length is : %dn",strlen(strcpy_v2_error(buf2,"This is the best age")));
  
  printf("using strcpy_v3,the string 'This is the best age''s length is : %dn",strlen(strcpy_v3(buf3,"This is the best age")));
  
  printf("using strcpy_v5,the string 'This is the best age''s length is : %dn",strlen(strcpy_v5(buf5,"This is the best age")));
  
  printf("using strcpy_v6,the string 'This is the best age''s length is : %dn",strlen(strcpy_v6(buf6,"This is the best age")));
 
  system("pause");
  
  return 0;
}

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