Use file's mtime as mtime for its extended header.

This makes two pax archives binary equivalent if they
have the same contents and care is taken to make extended
headers otherwise reproducible, e.g. by using:

  --pax-option=exthdr.name=%d/PaxHeaders/%f,atime:=0

Proposed by Michael D. Adams <mdmkolbe@gmail.com>.

* src/common.h (start_private_header): Take time_t as 3rd param.
(xheader_write): Likewise.
* src/create.c (start_private_header): Take time_t as 3rd param.
All callers updated.
(write_extended): Use file's mtime as mtime for its extended header,
Use current time stamp as mtime for global headers.
(xheader_write): Take time_t as 3rd param.

diff --git a/src/common.h b/src/common.h
index c2a92d228dd497a2089353ca9919d1f920307b01..0020f08964a0983e2435d34df9bfb8cbe17900c9 100644 (file)
--- a/src/common.h
+++ b/src/common.h
@@ -452,7 +452,7 @@ void finish_header (struct tar_stat_info *st, union block *header,
 void simple_finish_header (union block *header);
 union block * write_extended (bool global, struct tar_stat_info *st,
                              union block *old_header);
-union block *start_private_header (const char *name, size_t size);
+union block *start_private_header (const char *name, size_t size, time_t t);
 void write_eot (void);
 void check_links (void);
 void exclusion_tag_warning (const char *dirname, const char *tagname,
@@ -717,7 +717,7 @@ void xheader_decode_global (struct xheader *xhdr);
 void xheader_store (char const *keyword, struct tar_stat_info *st,
                    void const *data);
 void xheader_read (struct xheader *xhdr, union block *header, size_t size);
-void xheader_write (char type, char *name, struct xheader *xhdr);
+void xheader_write (char type, char *name, time_t t, struct xheader *xhdr);
 void xheader_write_global (struct xheader *xhdr);
 void xheader_finish (struct xheader *hdr);
 void xheader_destroy (struct xheader *hdr);

diff --git a/src/create.c b/src/create.c
index d4b9ae7e4738bb0909d7c7905f24a6f4325c1443..a964bc2824a416a118e69fa0c31fa334904a76c6 100644 (file)
--- a/src/create.c
+++ b/src/create.c
@@ -515,9 +515,8 @@ write_eot (void)
 
 /* Write a "private" header */
 union block *
-start_private_header (const char *name, size_t size)
+start_private_header (const char *name, size_t size, time_t t)
 {
-  time_t t;
   union block *header = find_next_block ();
 
   memset (header->buffer, 0, sizeof (union block));
@@ -525,7 +524,6 @@ start_private_header (const char *name, size_t size)
   tar_name_copy_str (header->header.name, name, NAME_FIELD_SIZE);
   OFF_TO_CHARS (size, header->header.size);
 
-  time (&t);
   TIME_TO_CHARS (t, header->header.mtime);
   MODE_TO_CHARS (S_IFREG|S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH, header->header.mode);
   UID_TO_CHARS (getuid (), header->header.uid);
@@ -563,13 +561,13 @@ write_gnu_long_link (struct tar_stat_info *st, const char *p, char type)
   union block *header;
   char *tmpname;
 
-  header = start_private_header ("././@LongLink", size);
-  FILL(header->header.mtime, '0');
-  FILL(header->header.mode, '0');
-  FILL(header->header.uid, '0');
-  FILL(header->header.gid, '0');
-  FILL(header->header.devmajor, 0);
-  FILL(header->header.devminor, 0);
+  header = start_private_header ("././@LongLink", size, time (NULL));
+  FILL (header->header.mtime, '0');
+  FILL (header->header.mode, '0');
+  FILL (header->header.uid, '0');
+  FILL (header->header.gid, '0');
+  FILL (header->header.devmajor, 0);
+  FILL (header->header.devminor, 0);
   uid_to_uname (0, &tmpname);
   UNAME_TO_CHARS (tmpname, header->header.uname);
   free (tmpname);
@@ -712,7 +710,8 @@ write_extended (bool global, struct tar_stat_info *st, union block *old_header)
   union block *header, hp;
   char *p;
   int type;
-
+  time_t t;
+  
   if (st->xhdr.buffer || st->xhdr.stk == NULL)
     return old_header;
 
@@ -722,13 +721,15 @@ write_extended (bool global, struct tar_stat_info *st, union block *old_header)
     {
       type = XGLTYPE;
       p = xheader_ghdr_name ();
+      time (&t);
     }
   else
     {
       type = XHDTYPE;
       p = xheader_xhdr_name (st);
+      t = st->stat.st_mtime;
     }
-  xheader_write (type, p, &st->xhdr);
+  xheader_write (type, p, t, &st->xhdr);
   free (p);
   header = find_next_block ();
   memcpy (header, &hp.buffer, sizeof (hp.buffer));

diff --git a/src/xheader.c b/src/xheader.c
index c779c0ad47c6aad23b4011e4a007879bb4e2a5e3..e8fd6a207171bf7111c9f19821aa745c3c7849fa 100644 (file)
--- a/src/xheader.c
+++ b/src/xheader.c
@@ -364,14 +364,14 @@ xheader_ghdr_name (void)
 }
 
 void
-xheader_write (char type, char *name, struct xheader *xhdr)
+xheader_write (char type, char *name, time_t t, struct xheader *xhdr)
 {
   union block *header;
   size_t size;
   char *p;
 
   size = xhdr->size;
-  header = start_private_header (name, size);
+  header = start_private_header (name, size, t);
   header->header.typeflag = type;
 
   simple_finish_header (header);
@@ -413,7 +413,7 @@ xheader_write_global (struct xheader *xhdr)
   for (kp = keyword_global_override_list; kp; kp = kp->next)
     code_string (kp->value, kp->pattern, xhdr);
   xheader_finish (xhdr);
-  xheader_write (XGLTYPE, name = xheader_ghdr_name (), xhdr);
+  xheader_write (XGLTYPE, name = xheader_ghdr_name (), time (NULL), xhdr);
   free (name);
 }