Avoid excess lseek etc.

* src/buffer.c, src/delete.c: Do not include system-ioctl.h.
* src/buffer.c (guess_seekable_archive): Remove.  This is now done
by get_archive_status, in a different way.
(get_archive_status): New function that gets archive_stat
unless remote, and sets seekable_archive etc.
(_open_archive): Prefer bool for boolean.
(_open_archive, new_volume): Get archive status consistently
by calling get_archive_status in both places.
* src/buffer.c (backspace_output):
* src/compare.c (verify_volume):
* src/delete.c (move_archive):
Let mtioseek worry about mtio.
* src/common.h (archive_stat): New global, replacing ar_dev and
ar_ino.  All uses changed.
* src/delete.c (move_archive): Check for integer overflow.
Also report overflow if the archive position would go negative.
* src/system.c: Include system-ioctl.h, for MTIOCTOP etc.
(mtioseek): New function, which also checks for integer overflow.
(sys_save_archive_dev_ino): Remove.
(archive_stat): Now
(sys_get_archive_stat): Also initialize mtioseekable_archive.
(sys_file_is_archive): Don’t return true if the archive is /dev/null
since it’s not a problem in that case.
(sys_detect_dev_null_output): Cache dev_null_stat.

doc: omit MS-DOS mentions in doc
It’s really FAT32 we’re worried about now, not MS-DOS.
And doschk is no longer a GNU program.

1 files changed, 6 insertions, 4 deletions

diff --git a/src/common.h b/src/common.h
index 62149113..58c1b6c1 100644
--- a/src/common.h
+++ b/src/common.h
@@ -392,9 +392,8 @@ struct name
     char *caname;               /* canonical name */
   };
 
-/* Obnoxious test to see if dimwit is trying to dump the archive.  */
-GLOBAL dev_t ar_dev;
-GLOBAL ino_t ar_ino;
+/* Status of archive file, or all zeros if remote.  */
+GLOBAL struct stat archive_stat;
 
 /* Flags for reading, searching, and fstatatting files.  */
 GLOBAL int open_read_flags;
@@ -402,6 +401,9 @@ GLOBAL int open_searchdir_flags;
 GLOBAL int fstatat_flags;
 
 GLOBAL int seek_option;
+
+/* true if archive if lseek should be used on the archive, 0 if it
+   should not be used.  */
 GLOBAL bool seekable_archive;
 
 GLOBAL dev_t root_device;
@@ -896,7 +898,6 @@ void xattr_map_free (struct xattr_map *xattr_map);
 /* Module system.c */
 
 void sys_detect_dev_null_output (void);
-void sys_save_archive_dev_ino (void);
 void sys_wait_for_child (pid_t, bool);
 void sys_spawn_shell (void);
 bool sys_compare_uid (struct stat *a, struct stat *b);
@@ -914,6 +915,7 @@ int sys_exec_info_script (const char **archive_name, int volume_number);
 void sys_exec_checkpoint_script (const char *script_name,
 				 const char *archive_name,
 				 int checkpoint_number);
+bool mtioseek (bool count_files, off_t count);
 
 /* Module compare.c */
 void report_difference (struct tar_stat_info *st, const char *message, ...)