From owner-freebsd-hackers@FreeBSD.ORG  Wed Feb 17 22:20:15 2010
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Delivered-To: freebsd-hackers@FreeBSD.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 87DB41065697;
	Wed, 17 Feb 2010 22:20:15 +0000 (UTC)
	(envelope-from nox@jelal.kn-bremen.de)
Received: from smtp.kn-bremen.de (gelbbaer.kn-bremen.de [78.46.108.116])
	by mx1.freebsd.org (Postfix) with ESMTP id 49C3C8FC13;
	Wed, 17 Feb 2010 22:20:15 +0000 (UTC)
Received: by smtp.kn-bremen.de (Postfix, from userid 10)
	id A2EB11E00771; Wed, 17 Feb 2010 23:01:38 +0100 (CET)
Received: from triton8.kn-bremen.de (noident@localhost [127.0.0.1])
	by triton8.kn-bremen.de (8.14.3/8.14.3) with ESMTP id o1HLxfZQ019932;
	Wed, 17 Feb 2010 22:59:41 +0100 (CET)
	(envelope-from nox@triton8.kn-bremen.de)
Received: (from nox@localhost)
	by triton8.kn-bremen.de (8.14.3/8.14.3/Submit) id o1HLxfZx019931;
	Wed, 17 Feb 2010 22:59:41 +0100 (CET) (envelope-from nox)
From: Juergen Lock <nox@jelal.kn-bremen.de>
Date: Wed, 17 Feb 2010 22:59:40 +0100
To: freebsd-hackers@FreeBSD.org
Message-ID: <20100217215940.GA19713@triton8.kn-bremen.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
User-Agent: Mutt/1.5.20 (2009-06-14)
X-Mailman-Approved-At: Wed, 17 Feb 2010 22:47:25 +0000
Cc: kientzle@FreeBSD.org
Subject: "tar tfv /dev/cd0" speedup patch
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>, 
	<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 17 Feb 2010 22:20:15 -0000

Hi!

 I recently wanted to quickly look at an optical disc without mounting it
and since bsdtar/libarchive know iso9660 I just did the command in the
Subject.  It worked, but it was sloow... :(  Apparently it read all of
the disc without seeking.  The following patch fixes this, is something
like this desired?  If yes I could look how to do the same for Linux,
I _think_ there you could just check for S_ISBLK and try to lseek to
the end and back, at least that seems to be how you find out the size
of a block device there...

 Cheers,
	Juergen

Index: lib/libarchive/archive_read_open_filename.c
@@ -44,6 +44,10 @@
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>
 #endif
+#ifdef __FreeBSD__
+#include <sys/ioctl.h>
+#include <sys/disk.h>
+#endif
 
 #include "archive.h"
 
@@ -83,6 +87,9 @@
 	struct read_file_data *mine;
 	void *b;
 	int fd;
+#ifdef __FreeBSD__
+	off_t mediasize = 0;
+#endif
 
 	archive_clear_error(a);
 	if (filename == NULL || filename[0] == '\0') {
@@ -143,6 +150,17 @@
 		 */
 		mine->can_skip = 1;
 	}
+#ifdef __FreeBSD__
+	/*
+	 * on FreeBSD if a device supports the DIOCGMEDIASIZE ioctl
+	 * it is a disk-like device and should be seekable.
+	 */
+	else if (S_ISCHR(st.st_mode) &&
+	    !ioctl(fd, DIOCGMEDIASIZE, &mediasize) && mediasize) {
+		archive_read_extract_set_skip_file(a, st.st_dev, st.st_ino);
+		mine->can_skip = 1;
+	}
+#endif
 	return (archive_read_open2(a, mine,
 		NULL, file_read, file_skip, file_close));
 }