Linux实现 memcpy和memmove

内存复制详解

最新推荐文章于 2025-09-11 22:56:57 发布

转载最新推荐文章于 2025-09-11 22:56:57 发布 · 999 阅读

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#linux #function #access #io

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本文详细介绍了内存复制函数 memcpy 和 memmove 的实现原理与使用场景。memcpy 用于非重叠内存区域的复制，而 memmove 能够处理源目标重叠的情况。通过对两种函数内部实现过程的分析，帮助读者理解如何高效地进行内存操作。

/**
* 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 = dest;
   const char *s = src;

   while (count--)
       *tmp++ = *s++;
   return dest;
}

/**
* memmove - Copy one area of memory to another
* @dest: Where to copy to
* @src: Where to copy from
* @count: The size of the area.
*
* Unlike memcpy(), memmove() copes with overlapping areas.
*/
void *memmove(void *dest, const void *src, size_t count)
{
   char *tmp;
   const char *s;

   if (dest <= src) {
       tmp = dest;
       s = src;
       while (count--)
           *tmp++ = *s++;
   } else {
       tmp = dest;
       tmp += count;
       s = src;
       s += count;
       while (count--)
           *--tmp = *--s;
   }
   return dest;
}