Replace substrings in C

main.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char* string_replace(char* source, size_t sourceSize, char* substring, char* with) {
    char* substring_source = strstr(source, substring);
    if (substring_source == NULL) {
        return NULL;
    }
    
    if (sourceSize < strlen(source) + (strlen(with) - strlen(substring))) {
        printf("Buffer size is too small\n");
        return NULL;
    }
    
    memmove(
        substring_source + strlen(with),
        substring_source + strlen(substring),
        strlen(substring_source) - strlen(substring) + 1
    );
    
    memcpy(substring_source, with, strlen(with));
    return substring_source + strlen(with);
}

int main(int argc, char* argv[]) {
    char str[100] = "The apples are delicious apples";
    printf("%s\n", str);
    while(string_replace(str, 100, "apples", "hamburgers"));
    printf("%s\n", str);
    return 0;
}