memcpy, strncpy, strcpy

最新推荐文章于 2025-08-17 10:20:22 发布

原创最新推荐文章于 2025-08-17 10:20:22 发布 · 195 阅读

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#FreeBSD #C #C++ #C# #Access

本文详细介绍了几种常用的字符串操作函数，包括memcpy、strncpy、strcpy等，并提供了不同操作系统下的实现示例。通过这些示例，读者可以了解到如何在C语言中进行字符串的复制，并注意到不同函数在处理边界情况时的行为差异。

收集的一些基本函数实现手法，备忘~~

memcpy


/**
* 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


/**
* 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


/**
* 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;
}

FreeBSD中strcpy


char *strcpy(char * __restrict to, const char * __restrict from)
{
    char *save = to;

    for (; (*to = *from); ++from, ++to);
    return(save);
}

OpenBSD 3.9中strcpy


char *strcpy(char *to, const char *from)
{
    char *save = to;

    for (; (*to = *from) != ''; ++from, ++to);
    return(save);
}

:-)