memmove实现代码

/* file: main.c */
#include <stdio.h>
#include <stdlib.h>

#define __assert(x)

static void * __memmove (void * dest, const void *src, size_t len)
{
    __assert(dest&&src);
    unsigned char* dest_p = (unsigned char*)dest;
    const unsigned char* src_p = (const unsigned char*)src;
    if (dest_p == src) return dest_p;
    if (dest_p < src_p)
        while (len--) *dest_p++ = *src_p++; /* copy from header */
    else
        while (len--) *(dest_p+len)=*(src_p+len); /* copy from tailer */
    return dest_p;
}

#define COUNT 5

int main(void)
{
    char* pnew;
    int* array;
    int i = 0;
    array = (int*)malloc(sizeof(int)*COUNT);
    __assert(array);
    memset(array, 0, sizeof(int)*COUNT);
    while (i < COUNT) {
        array[i] = i;
        i++;
    }
    for (i=0; i < COUNT; i++)
        printf("%d ", array[i]);
    printf("\n");

    __memmove(array+2, array, sizeof(int)*3);
    for(i=0; i<COUNT; i++){
        printf("%d\n",array[i]);
    }
    free (array);
}