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convert fgetln to getline. this improves portability and sets a good
better example for other code to follow. in the common case, grep uses
mmap anyway (so no functional change). despite fgetln doing sneaky things
with stdio internals, preliminary analysis by lauri suggests this may
actually reduce the number of allocations.
from Lauri Tirkkonen.

/*	$OpenBSD: file.c,v 1.15 2019/01/31 01:30:46 tedu Exp $	*/

/*-
 * Copyright (c) 1999 James Howard and Dag-Erling Coïdan Smørgrav
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/stat.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <zlib.h>

#include "grep.h"

static char	 fname[PATH_MAX];
static char	*lnbuf;
static size_t	 lnbufsize;

#define FILE_STDIO	0
#define FILE_MMAP	1
#define FILE_GZIP	2

struct file {
	int	 type;
	int	 noseek;
	FILE	*f;
	mmf_t	*mmf;
	gzFile	*gzf;
};

#ifndef NOZ
static char *
gzfgetln(gzFile *f, size_t *len)
{
	size_t		n;
	int		c;

	for (n = 0; ; ++n) {
		c = gzgetc(f);
		if (c == -1) {
			const char *gzerrstr;
			int gzerr;

			if (gzeof(f))
				break;

			gzerrstr = gzerror(f, &gzerr);
			if (gzerr == Z_ERRNO)
				err(2, "%s", fname);
			else
				errx(2, "%s: %s", fname, gzerrstr);
		}
		if (n >= lnbufsize) {
			lnbufsize *= 2;
			lnbuf = grep_realloc(lnbuf, ++lnbufsize);
		}
		if (c == '\n')
			break;
		lnbuf[n] = c;
	}

	if (gzeof(f) && n == 0)
		return NULL;
	*len = n;
	return lnbuf;
}
#endif

file_t *
grep_fdopen(int fd)
{
	file_t *f;
	struct stat sb;

	if (fd == STDIN_FILENO)
		snprintf(fname, sizeof fname, "(standard input)");
	else if (fname[0] == '\0')
		snprintf(fname, sizeof fname, "(fd %d)", fd);

	if (fstat(fd, &sb) == -1)
		return NULL;
	if (S_ISDIR(sb.st_mode)) {
		errno = EISDIR;
		return NULL;
	}

	f = grep_malloc(sizeof *f);

#ifndef NOZ
	if (Zflag) {
		f->type = FILE_GZIP;
		f->noseek = lseek(fd, 0L, SEEK_SET) == -1;
		if ((f->gzf = gzdopen(fd, "r")) != NULL)
			return f;
	}
#endif
	f->noseek = isatty(fd);
#ifndef SMALL
	/* try mmap first; if it fails, try stdio */
	if (!f->noseek && (f->mmf = mmopen(fd, &sb)) != NULL) {
		f->type = FILE_MMAP;
		return f;
	}
#endif
	f->type = FILE_STDIO;
	if ((f->f = fdopen(fd, "r")) != NULL)
		return f;

	free(f);
	return NULL;
}

file_t *
grep_open(char *path)
{
	file_t *f;
	int fd;

	snprintf(fname, sizeof fname, "%s", path);

	if ((fd = open(fname, O_RDONLY)) == -1)
		return NULL;

	f = grep_fdopen(fd);
	if (f == NULL)
		close(fd);
	return f;
}

int
grep_bin_file(file_t *f)
{
	if (f->noseek)
		return 0;

	switch (f->type) {
	case FILE_STDIO:
		return bin_file(f->f);
#ifndef SMALL
	case FILE_MMAP:
		return mmbin_file(f->mmf);
#endif
#ifndef NOZ
	case FILE_GZIP:
		return gzbin_file(f->gzf);
#endif
	default:
		/* can't happen */
		errx(2, "invalid file type");
	}
}

char *
grep_fgetln(file_t *f, size_t *l)
{
	switch (f->type) {
	case FILE_STDIO:
		if ((*l = getline(&lnbuf, &lnbufsize, f->f)) == -1) {
			if (ferror(f->f))
				err(2, "%s: getline", fname);
			else
				return NULL;
		}
		return lnbuf;
#ifndef SMALL
	case FILE_MMAP:
		return mmfgetln(f->mmf, l);
#endif
#ifndef NOZ
	case FILE_GZIP:
		return gzfgetln(f->gzf, l);
#endif
	default:
		/* can't happen */
		errx(2, "invalid file type");
	}
}

void
grep_close(file_t *f)
{
	switch (f->type) {
	case FILE_STDIO:
		fclose(f->f);
		break;
#ifndef SMALL
	case FILE_MMAP:
		mmclose(f->mmf);
		break;
#endif
#ifndef NOZ
	case FILE_GZIP:
		gzclose(f->gzf);
		break;
#endif
	default:
		/* can't happen */
		errx(2, "invalid file type");
	}
	free(f);
}