memcpy和strcpy

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http://blog.csdn.net/xiaobo620/article/details/7488827

void *mymemcpy(void *dst,const void *src,size_t num)//效率优先
{
assert((dst!=NULL)&&(src!=NULL));
int wordnum = num/4;//计算有多少个32位，按4字节拷贝
int slice = num%4;//剩余的按字节拷贝
int * pintsrc = (int *)src;
int * pintdst = (int *)dst;
while(wordnum--)*pintdst++ = *pintsrc++;
while (slice--)*((char *)pintdst++) =*((char *)pintsrc++);
return dst;
}

http://blog.csdn.net/yahohi/article/details/7927806 内存重叠问题解决

void *memmove(void *dest, const void *source, size_t count)
{
assert((NULL != dest) && (NULL != source));
char *tmp_source, *tmp_dest;
tmp_source = (char *)source;
tmp_dest = (char *)dest;
if((dest + count<source) || (source + count) <dest))
{// 如果没有重叠区域
while(count--)
*tmp_dest++ = *tmp_source++;
}
else
{ //如果有重叠（反向拷贝）
tmp_source += count - 1;
tmp_dest += count - 1;
while(count--)
*--tmp_dest = *--tmp;
}
return dest;
}

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