Use C language to simulate strcpy, strcat, strcat, memcpy, memmove

Use C language to simulate strcpy, strcat, strcat, memcpy, memmove

1. simulate Implementation of strcpy # include <stdio. h> # include <stdlib. h> # include <string. h> # include <assert. h> char * my_strcpy (char * dst, const char * src) {assert (dst! = NULL); assert (src! = NULL); char * ret = dst; while (* dst ++ = * src ++ )! = '\ 0'); return ret;} int main () {char arr1 [] = "hello world !!! "; Char arr2 [20]; my_strcpy (arr2, arr1); printf (" % s \ n ", arr2); system (" pause "); return 0;} 2. simulate Implementation of strcat # include <stdio. h> # include <assert. h> # include <stdlib. h> char * strcat (char * dest, char const * src) {assert (dest); assert (src); char * temp = dest; while (* dest) {dest ++;} while (* src) {* dest ++ = * src ++;} * dest = '\ 0'; return temp;} int main () {char arr [50] = "I come from china !! "; Char * p =" me too !! "; Strcat (arr, p); printf (" % s ", arr); system (" pause "); return 0 ;}3. simulate Implementation of strcat # include <stdio. h> # include <assert. h> # include <stdlib. h> int my_strcmp (const char * arr1, const char * arr2) {assert (arr1); assert (arr2); while (* arr1 = * arr2) {if (* arr1 = '\ 0') {return 1;} arr1 ++; arr2 ++;} return * arr1-* arr2;} int main () {char * s1 = "I am a student! "; Char * s2 =" I am a student! "; Int ret = my_strcmp (s1, s2); if (ret = 1) {printf (" the two strings are the same! \ N ");} else {printf (" the difference between the two strings is % d \ n ", ret);} system (" pause "); return 0;} 4. simulate the implementation of memcpy # include <stdio. h> # include <string. h> # include <assert. h> # include <stdlib. h> void * my_memcpy (void * dest, const void * src, size_t n) {assert (dest); assert (src); char * p = (char *) dest; const char * q = (char *) src; while (n --) {* p = * q; p ++; q ++;} return dest;} int main () {int arr1 [100] = {100, 11}; int arr2 [] = {0}; int I = 0; int num; printf ("Enter the number of copies:"); scanf ("% d", & num); my_memcpy (arr2, arr1, 4 * num ); for (I = 0; I <num; I ++) {printf ("% d", arr2 [I]);} printf ("\ n "); system ("pause"); return 0;} 5. simulate the implementation of memmove # include <stdio. h> # include <string. h> # include <assert. h> # include <stdlib. h> void * my_memcpy (void * dest, const void * src, size_t n) {assert (dest); assert (src); char * p = (char *) dest; const char * q = (char *) src; if (p> q & p <q + n) {while (n --) {* (p + n) = * (q + n) ;}} else {while (n --) {* p = * q; p ++; q ++ ;}} return dest ;} int main () {int arr [] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; int I = 0; my_memcpy (arr + 4, arr + 2, 20); for (I = 0; I <10; I ++) {printf ("% d ", arr [I]);} printf ("\ n"); system ("pause"); return 0 ;}