/* vi: set sw=4 ts=4: */
/*
 * tac implementation for busybox
 *
 * Copyright (C) 2003  Yang Xiaopeng  <yxp at hanwang.com.cn>
 * Copyright (C) 2007  Natanael Copa  <natanael.copa@gmail.com>
 * Copyright (C) 2007  Tito Ragusa    <farmatito@tiscali.it>
 *
 * Licensed under GPLv2, see file License in this tarball for details.
 *
 */

/* tac - concatenate and print files in reverse */

/* Based on Yang Xiaopeng's (yxp at hanwang.com.cn) patch
 * http://www.uclibc.org/lists/busybox/2003-July/008813.html
 */

#include "libbb.h"

/* This is a NOEXEC applet. Be very careful! */

struct lstring {
	int size;
	char buf[1];
};

int tac_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int tac_main(int argc ATTRIBUTE_UNUSED, char **argv)
{
	char **name;
	FILE *f;
	struct lstring *line = NULL;
	llist_t *list = NULL;
	int retval = EXIT_SUCCESS;

#if ENABLE_DESKTOP
/* tac from coreutils 6.9 supports:
       -b, --before
              attach the separator before instead of after
       -r, --regex
              interpret the separator as a regular expression
       -s, --separator=STRING
              use STRING as the separator instead of newline
We support none, but at least we will complain or handle "--":
*/
	getopt32(argv, "");
	argv += optind;
#else
	argv++;
#endif
	if (!*argv)
		*--argv = (char *)"-";
	/* We will read from last file to first */
	name = argv;
	while (*name)
		name++;

	do {
		int ch, i;

		name--;
		f = fopen_or_warn_stdin(*name);
		if (f == NULL) {
			/* error message is printed by fopen_or_warn_stdin */
			retval = EXIT_FAILURE;
			continue;
		}

		errno = i = 0;
		do {
			ch = fgetc(f);
			if (ch != EOF) {
				if (!(i & 0x7f))
					/* Grow on every 128th char */
					line = xrealloc(line, i + 0x7f + sizeof(int) + 1);
				line->buf[i++] = ch;
			}
			if (ch == '\n' || (ch == EOF && i != 0)) {
				line = xrealloc(line, i + sizeof(int));
				line->size = i;
				llist_add_to(&list, line);
				line = NULL;
				i = 0;
			}
		} while (ch != EOF);
		/* fgetc sets errno to ENOENT on EOF, we don't want
		 * to warn on this non-error! */
		if (errno && errno != ENOENT) {
			bb_simple_perror_msg(*name);
			retval = EXIT_FAILURE;
		}
	} while (name != argv);

	while (list) {
		line = (struct lstring *)list->data;
		xwrite(STDOUT_FILENO, line->buf, line->size);
		if (ENABLE_FEATURE_CLEAN_UP) {
			free(llist_pop(&list));
		} else {
			list = list->link;
		}
	}

	return retval;
}