模拟实现memcpy 与 memmove

 1 #include<stdio.h>
 2 #include<assert.h>
 3 void Memcpy(void* destanation, const void* source, size_t num)
 4 {
 5  assert(destanation != 0);
 6  assert(source != 0);
 7  char* dest = (char*)destanation;
 8  char* sour = (char*)source;
 9  for (size_t i = 0; i < num; i++)
10  {
11   dest[i] = sour[i];
12  }
13  return destanation;
14 }
15 void Memmove(void* destanation, const char* source, size_t num)
16 {
17  assert(destanation != 0);
18  assert(source != 0);
19  char* dest = (char*)destanation;
20  char* sour = (char*)source;
21  //两种情况：
22  if (sour<dest&&sour + num>dest)
23  {
24   //1.缓冲区重合就从后往前拷贝
25   for (int i = num - 1; i >= 0; --i)
26   {
27    dest[i] = source[i];
28   }
29  }
30  else
31  {
32   //2.缓冲区没重合，代码和memcpy一样
33   Memcpy(destanation, source, num);
34  }
35 }
36 int main()
37 {
38  int arr1[4] = { 1,2,3,4 };
39  int arr2[4] = { 0 };
40  Memcpy(arr1, arr2, sizeof(arr1));
41  for (int i = 0; i < sizeof(arr1) / sizeof(int); i++)
42  {
43   printf("%d",arr2[i]);
44  }
45  return 0;
46 }