Date: Wed, 17 Feb 2010 22:59:40 +0100 From: Juergen Lock <nox@jelal.kn-bremen.de> To: freebsd-hackers@FreeBSD.org Cc: kientzle@FreeBSD.org Subject: "tar tfv /dev/cd0" speedup patch Message-ID: <20100217215940.GA19713@triton8.kn-bremen.de>
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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));
}
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