//

// substr.c

//

// Copyright (c) 2013 Stephen Mathieson

// MIT licensed

//

#include <stdlib.h>

#include <string.h>

#include "strdup/strdup.h"

#include "substr.h"

/*

 * Get a substring of `str` from `start` to `end`

 */

char *

substr(const char *str, int start, int end) {

  if (0 > start) return NULL;

  int len = strlen(str);

  // -1 == length of string

  if (-1 == end) end = len;

  if (end <= start) return NULL;

  int diff = end - start;

  if (len == diff) return strdup(str);

  if (len < start) return NULL;

  if (len + 1 < end) return NULL;

  char *res = malloc(sizeof(char) * diff + 1);

  if (NULL == res) return NULL;

  memset(res, '\0', diff + 1);

  strncpy(res, str + start, diff);

  return res;

}