encapsulation of strlen(), strcpy(), strncpy(), strcat(), strncat(), strcmp(), strncmp() functions

size_t strlen(char* str){assert(str != NULL);int len ​​= 0;while(*str != '\0'){str++;len++;}return len;}char* strcpy(char* dest, const char* src){assert(dest != NULL && src != NULL);char* tmp = dest;while(*src != '\0'){*tmp++ = *src++;}*tmp = '\0';return dest;}char* strncpy(char* dest, const char* src, size_t n){assert(dest != NULL && src != NULL);char* tmp = dest;int len ​​= strlen(tmp);int m = n;while(n--> 0 && *src != '\0'){*tmp++ = *src++;}if(m > len) //Do not add '\0' when the number of characters to be copied is less than the length of the original string*tmp = '\0';return dest;}char* strcat(char* dest, const char* src){assert(dest != NULL && src != NULL);char* tmp = dest;while(*tmp != '\0'){tmp++;}while(*src != '\0'){*tmp++ = *src++;}*tmp = '\0';return dest;}char* strncat(char* dest, const char* src, size_t n){assert(dest != NULL && src != NULL);char* tmp = dest;while(*tmp != '\0'){tmp++;}while(n--> 0 && *src != '\0'){*tmp++ = *src++;}*tmp = '\0';return dest;}int strcmp(const char* s1, const char* s2){assert(s1 != NULL && s2 != NULL);while(*s1 != '\0' && *s2 != '\0' && *s1 == *s2){s1++;s2++;}if(*s1 < *s2)return -1;if(*s1 > *s2)return 1;return 0;}int strncmp(const char* s1, const char* s2, size_t n){assert(s1 != NULL && s2 != NULL);while(--n > 0 && *s1 != '\0' && *s2 != '\0' && *s1 == *s2)//Before using -- will not cause an extra last digit{s1++;s2++;}if(*s1 < *s2)return -1;if(*s1 > *s2)return 1;return 0;}