text: #include "libmx.h"
  
  char *mx_strstr(const char *haystack, const char *needle) {
      const char *p = haystack;
  
      if (mx_strlen(needle) == 0)
          return (char *) p;
      for ( ; (p = mx_strchr(p, *needle)) != 0; p++) {
          if (mx_strncmp(p, needle, mx_strlen(needle)) == 0)
              return (char *) p;
      }
      return 0;
  }
  