经典的memcpy、strncpy的实现代码

最新推荐文章于 2024-03-16 21:07:27 发布

转载最新推荐文章于 2024-03-16 21:07:27 发布 · 1.2k 阅读

文章标签：

#string #function #access #io

本文介绍了内存复制函数memcpy以及字符串复制函数strcpy和strncpy的实现原理。这些函数用于在C语言中高效地处理内存和字符串数据，是程序员必须掌握的基础知识。

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/**
* memcpy - Copy one area of memory to another
* @dest: Where to copy to
* @src: Where to copy from
* @count: The size of the area.
*
* You should not use this function to access IO space, use memcpy_toio()
* or memcpy_fromio() instead.
*/
void * memcpy(void * dest,const void *src,size_t count)
{
char *tmp = (char *) dest, *s = (char *) src;

while (count--)
*tmp++ = *s++;

return dest;
}

/**
* strncpy - Copy a length-limited, %NUL-terminated string
* @dest: Where to copy the string to
* @src: Where to copy the string from
* @count: The maximum number of bytes to copy
*
* Note that unlike userspace strncpy, this does not %NUL-pad the buffer.
* However, the result is not %NUL-terminated if the source exceeds
* @count bytes.
*/
char * strncpy(char * dest,const char *src,size_t count)
{
char *tmp = dest;

while (count-- && (*dest++ = *src++) != '/0')
/* nothing */;

return tmp;
}

/**
* strcpy - Copy a %NUL terminated string
* @dest: Where to copy the string to
* @src: Where to copy the string from
*/
char * strcpy(char * dest,const char *src)
{
char *tmp = dest;

while ((*dest++ = *src++) != '/0')
/* nothing */;
return tmp;
}