目录

memcpy(按字节的内存拷贝)

memmove(重叠内存的拷贝)

memcmp(按字节比较大小)

memset(按字节进行初始化)

memcpy(按字节的内存拷贝)

#include #include void my_memcpy(void* dest, void* str, size_t n){assert(dest && str);void* ret = dest;while (n--){*(char*)dest = *(char*)str;dest = (char*)dest + 1;str = (char*)str + 1;}return ret;}int main(){int arr1[5] = { 1,2,3,4,5 };int arr2[2] = { 0 };my_memcpy(arr2, arr1, 4);//按字节拷贝return 0;}

memmove(重叠内存的拷贝)

#include #include void* my_memmove(void* dest, const void* str, size_t count){assert(dest && str);void* ret = dest;if (dest < str){//从前往后拷贝while (count--){*(char*)dest = *(char*)str;dest = (char*)dest + 1;str = (char*)str + 1;}}else//从后往前拷贝{while (count--){*((char*)dest + count) = *((char*)str + count);}}return ret;}int main(){int arr[10] = { 0,1,2,3,4,5,6,7,8,9 };my_memmove(arr + 2, arr, 20);//从前往后my_memmove(arr, arr + 2, 20);//从后往前return 0;}

memcmp(按字节比较大小)

#include #include int my_memcmp(void* dest, const void* str, size_t count){assert(dest && str);size_t i = 0;for (i = 0; i  *((char*)str + i)){return 1;}else if (*((char*)dest + i) < *((char*)str + i)){return -1;}}return 0;}int main(){int arr1[] = { 1,2,3,4,5 };int arr2[] = { 1,2,3,4,0x11223305 };int ret = my_memcmp(arr1, arr2, 20);printf("%d\n", ret);return 0;}

memset(按字节进行初始化)

#include void* my_memset(void* dest, int n, size_t count){void* tmp = dest;while (count--){*(char*)dest = (char)n;dest = (char*)dest + 1;}return tmp;}int main(){int arr[] = { 0x11111111,0x22222222,5,6,7,8,9 };my_memset(arr, 6, 20);int i = 0;for (i = 0; i < sizeof(arr) / sizeof(arr[0]); i++){printf("%d ", arr[i]);}return 0;}