wireshark/wiretap/file_wrappers.c

/* file_wrappers.c
 *
 * $Id: file_wrappers.c,v 1.12 2002/08/28 20:30:44 jmayer Exp $
 *
 * Wiretap Library
 * Copyright (c) 1998 by Gilbert Ramirez <gram@alumni.rice.edu>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

/*
 * OK, now this is tricky.
 *
 * At least on FreeBSD 3.2, "/usr/include/zlib.h" includes
 * "/usr/include/zconf.h", which, if HAVE_UNISTD_H is defined,
 * #defines "z_off_t" to be "off_t", and if HAVE_UNISTD_H is
 * not defines, #defines "z_off_t" to be "long" if it's not
 * already #defined.
 *
 * In 4.4-Lite-derived systems such as FreeBSD, "off_t" is
 * "long long int", not "long int", so the definition of "z_off_t" -
 * and therefore the types of the arguments to routines such as
 * "gzseek()", as declared, with prototypes, in "zlib.h" - depends
 * on whether HAVE_UNISTD_H is defined prior to including "zlib.h"!
 *
 * It's not defined in the FreeBSD 3.2 "zlib", so if we include "zlib.h"
 * after defining HAVE_UNISTD_H, we get a misdeclaration of "gzseek()",
 * and, if we're building with "zlib" support, anything that seeks
 * on a file may not work.
 *
 * Other BSDs may have the same problem, if they haven't done something
 * such as defining HAVE_UNISTD_H in "zconf.h".
 *
 * "config.h" defines HAVE_UNISTD_H, on all systems that have it, and all
 * 4.4-Lite-derived BSDs have it.  Therefore, given that "zlib.h" is included
 * by "file_wrappers.h", that means that unless we include "zlib.h" before
 * we include "config.h", we get a misdeclaration of "gzseek()".
 *
 * Unfortunately, it's "config.h" that tells us whether we have "zlib"
 * in the first place, so we don't know whether to include "zlib.h"
 * until we include "config.h"....
 *
 * A similar problem appears to occur with "gztell()", at least on
 * NetBSD.
 *
 * To add further complication, on recent versions, at least, of OpenBSD,
 * the Makefile for zlib defines HAVE_UNISTD_H.
 *
 * So what we do is, on all OSes other than OpenBSD, *undefine* HAVE_UNISTD_H
 * before including "wtap.h" (we need "wtap.h" to get the WTAP_ERR_ZLIB
 * values, and it also includes "zlib.h" if HAVE_ZLIB" is defined), and,
 * if we have zlib, make "file_seek()" and "file_tell()" subroutines, so
 * that the only calls to "gzseek()" and "gztell()" are in this file, which,
 * by dint of the hackery described above, manages to correctly declare
 * "gzseek()" and "gztell()".
 *
 * On OpenBSD, we forcibly *define* HAVE_UNISTD_H if it's not defined.
 *
 * Hopefully, the BSDs will, over time, remove the test for HAVE_UNISTD_H
 * from "zconf.h", so that "gzseek()" and "gztell()" will be declared
 * with the correct signature regardless of whether HAVE_UNISTD_H is
 * defined, so that if they change the signature we don't have to worry
 * about making sure it's defined or not defined.
 *
 * DO NOT, UNDER ANY CIRCUMSTANCES, REMOVE THE FOLLOWING LINES, OR MOVE
 * THEM AFTER THE INCLUDE OF "wtap.h"!  Doing so will cause any program
 * using Wiretap to read capture files to fail miserably on a FreeBSD
 * 3.2 or 3.3 system - and possibly some other BSD systems - if zlib is
 * installed.  If you *must* include <unistd.h> here, do so *before*
 * including "wtap.h", and before undefining HAVE_UNISTD_H.  If you
 * *must* have HAVE_UNISTD_H defined before including "wtap.h", put
 * "file_error()" into a file by itself, which can cheerfully include
 * "wtap.h" and get "gzseek()" misdeclared, and include just "zlib.h"
 * in this file - *after* undefining HAVE_UNISTD_H.
 */
#ifdef __OpenBSD__
#ifndef HAVE_UNISTD_H
#define HAVE_UNISTD_H
#endif /* HAVE_UNISTD_H */
#else /* __OpenBSD__ */
#undef HAVE_UNISTD_H
#endif /* __OpenBSD__ */

#include <errno.h>
#include <stdio.h>
#include "wtap-int.h"
#include "file_wrappers.h"

#ifdef HAVE_LIBZ
long
file_seek(void *stream, long offset, int whence, int *err)
{
	long ret;

	ret = gzseek(stream, (z_off_t)offset, whence);
	if (ret == -1) {
		/*
		 * XXX - "gzseek()", as of zlib 1.1.4, doesn't set
		 * "z_err" for the stream, so "gzerror()" could return
		 * a bogus Z_OK.
		 *
		 * As this call failed, we know "gzerror()" shouldn't
		 * return Z_OK; if it does, we assume that "errno" is
		 * the real error.
		 */
		*err = file_error(stream);
		if (*err == 0)
			*err = errno;
	}
	return ret;
}

long
file_tell(void *stream)
{
	return (long)gztell(stream);
}
#else /* HAVE_LIBZ */
long
file_seek(void *stream, long offset, int whence, int *err)
{
	long ret;

	ret = fseek(stream, offset, whence);
	if (ret == -1)
		*err = file_error(stream);
	return ret;
}
#endif /* HAVE_LIBZ */

/*
 * Routine to return a Wiretap error code (0 for no error, an errno
 * for a file error, or a WTAP_ERR_ code for other errors) for an
 * I/O stream.
 */
#ifdef HAVE_LIBZ
int
file_error(void *fh)
{
	int errnum;

	gzerror(fh, &errnum);
	switch (errnum) {

	case Z_OK:		/* no error */
		return 0;

	case Z_STREAM_END:	/* EOF - not an error */
		return 0;

	case Z_ERRNO:		/* file I/O error */
		return errno;

	default:
		return WTAP_ERR_ZLIB + errnum;
	}
}
#else /* HAVE_LIBZ */
int
file_error(FILE *fh)
{
	if (ferror(fh))
		return errno;
	else
		return 0;
}
#endif /* HAVE_LIBZ */