/*
 * tilde.c: Expand ~/ and ~user/ style pathnames
 *
 * $Id: tilde.c,v 1.1 1996/09/26 20:21:51 mb Exp mb $
 *
 * Copyright (c) 1996 Martin Buck  <martin-2.buck@student.uni-ulm.de>
 * Read COPYING for more information
 *
 */

#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <pwd.h>
#include <sys/types.h>
#include "safe_malloc.h"
#include "tilde.h"



/* Expand filenames with leading ~/ or ~user/. Returns NULL, if user doesn't exist. Returned
 * string points to statically allocated storage and may be overwritten by subsequent calls.
 */
char *
tilde_expand(const char *dir) {
  static char *ret = NULL;
  char *home, *user;
  int userlen;
  struct passwd *pw;
  
  if (ret) {
    free(ret);
    ret = NULL;
  }
  if (*dir == '~') {
    userlen = strcspn(dir + 1, "/");

    /* Expand ~/ */
    if (!userlen) {
      if (!(home = getenv("HOME")) && (pw = getpwuid(getuid()))) {
        home = pw->pw_dir;
      }
      if (home) {
        ret = sstrdup(home);
        ret = sstrapp(ret, &dir[1]);
      }

    /* Expand ~user/ */
    } else {
      user = smalloc(userlen);
      memcpy(user, dir + 1, userlen);
      if ((pw = getpwnam(user)) && pw->pw_dir) {
        ret = sstrdup(pw->pw_dir);
        ret = sstrapp(ret, &dir[userlen + 1]);
      }
      free(user);
    }
  } else {
    ret = sstrdup(dir);
  }
  return ret;
}


/* Like tilde_expand(), but uses srealloc() to resize original string instead of using
 * static storage.
 */
int
tilde_expand_realloc(char **dir) {
  char *str;
  
  if ((str = tilde_expand(*dir))) {
    *dir = srealloc(*dir, strlen(str) + 1);
    strcpy(*dir, str);
    return 0;
  } else {
    return -1;
  }
}