mirrors/tar
1
0
Fork 0
mirror of https://git.savannah.gnu.org/git/tar.git synced 2026-04-28 12:17:07 +00:00
Code Issues Packages Projects Releases Wiki Activity

tar: optimize -c --sparse when file is entirely sparse

Browse Source 
* src/sparse.c (sparse_scan_file): If the file is entirely sparse,
that is, if ST_NBLOCKS is zero, don't bother scanning for nonzero
blocks.  Idea by Kit Westneat, communicated by Bernd Schubert in
<http://lists.gnu.org/archive/html/bug-tar/2010-08/msg00038.html>.
Also, omit unnecessary lseek at start of file.
This commit is contained in:
Paul Eggert
2010-08-24 17:28:11 -07:00
parent a59c819beb
commit a9895fd20c
1 changed files with 28 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

54
src/sparse.c
View File

@@ -217,43 +217,45 @@ sparse_scan_file (struct tar_sparse_file *file)
struct tar_stat_info *st = file->stat_info;
int fd = file->fd;
char buffer[BLOCKSIZE];
size_t count;
size_t count = 0;
off_t offset = 0;
struct sp_array sp = {0, 0};
if (!lseek_or_error (file, 0))
return false;
st->archive_file_size = 0;
if (!tar_sparse_scan (file, scan_begin, NULL))
return false;
while ((count = safe_read (fd, buffer, sizeof buffer)) != 0
&& count != SAFE_READ_ERROR)
if (ST_NBLOCKS (st->stat) == 0)
offset = st->stat.st_size;
else
{
/* Analyze the block. */
if (zero_block_p (buffer, count))
if (!tar_sparse_scan (file, scan_begin, NULL))
return false;
while ((count = safe_read (fd, buffer, sizeof buffer)) != 0
&& count != SAFE_READ_ERROR)
{
if (sp.numbytes)
/* Analyze the block. */
if (zero_block_p (buffer, count))
{
sparse_add_map (st, &sp);
sp.numbytes = 0;
if (!tar_sparse_scan (file, scan_block, NULL))
if (sp.numbytes)
{
sparse_add_map (st, &sp);
sp.numbytes = 0;
if (!tar_sparse_scan (file, scan_block, NULL))
return false;
}
}
else
{
if (sp.numbytes == 0)
sp.offset = offset;
sp.numbytes += count;
st->archive_file_size += count;
if (!tar_sparse_scan (file, scan_block, buffer))
return false;
}
}
else
{
if (sp.numbytes == 0)
sp.offset = offset;
sp.numbytes += count;
st->archive_file_size += count;
if (!tar_sparse_scan (file, scan_block, buffer))
return false;
}
offset += count;
offset += count;
}
}
if (sp.numbytes == 0)