C库函数之memcpy的实现

C库函数之memcpy的实现

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memcpy的实现方式是当满足四字节对齐时，进行四字节的拷贝，不满足时进行单字节的拷贝。例如拷贝10个字节，循环两次拷贝四字节，在循环两次拷贝一字节。

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void mem_memcpy(void* dst, const void* src, unsigned int cnt)
{
  char *d = (char*)(void *)dst;
  const char *s = src;

  while (cnt >= sizeof (int)) {
    *(int*)d = *(int*)s;
    d += sizeof (int);
    s += sizeof (int);
    cnt -= sizeof (int);
  }
  while ((cnt) > 0U){
    *d = *s;
    d += 1U;
    s += 1U;
    cnt -= 1U;
  }
}

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end