/* Functions for dealing with sparse files
- Copyright 2003-2007, 2010, 2013-2014 Free Software Foundation, Inc.
+ Copyright 2003-2007, 2010, 2013-2016 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
st->sparse_map_avail = avail + 1;
}
-/* Scan the sparse file and create its map */
+/* Scan the sparse file byte-by-byte and create its map. */
static bool
-sparse_scan_file (struct tar_sparse_file *file)
+sparse_scan_file_raw (struct tar_sparse_file *file)
{
struct tar_stat_info *st = file->stat_info;
int fd = file->fd;
st->archive_file_size = 0;
- if (ST_NBLOCKS (st->stat) == 0)
- offset = st->stat.st_size;
- else
- {
- if (!tar_sparse_scan (file, scan_begin, NULL))
- return false;
-
- while ((count = blocking_read (fd, buffer, sizeof buffer)) != 0
- && count != SAFE_READ_ERROR)
- {
- /* Analyze the block. */
- if (zero_block_p (buffer, count))
- {
- 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;
- }
+ if (!tar_sparse_scan (file, scan_begin, NULL))
+ return false;
- offset += count;
- }
+ while ((count = blocking_read (fd, buffer, sizeof buffer)) != 0
+ && count != SAFE_READ_ERROR)
+ {
+ /* Analyze the block. */
+ if (zero_block_p (buffer, count))
+ {
+ 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;
+ }
+
+ offset += count;
}
+ /* save one more sparse segment of length 0 to indicate that
+ the file ends with a hole */
if (sp.numbytes == 0)
sp.offset = offset;
return tar_sparse_scan (file, scan_end, NULL);
}
+static bool
+sparse_scan_file_wholesparse (struct tar_sparse_file *file)
+{
+ struct tar_stat_info *st = file->stat_info;
+ struct sp_array sp = {0, 0};
+
+ /* Note that this function is called only for truly sparse files of size >= 1
+ block size (checked via ST_IS_SPARSE before). See the thread
+ http://www.mail-archive.com/bug-tar@gnu.org/msg04209.html for more info */
+ if (ST_NBLOCKS (st->stat) == 0)
+ {
+ st->archive_file_size = 0;
+ sp.offset = st->stat.st_size;
+ sparse_add_map (st, &sp);
+ return true;
+ }
+
+ return false;
+}
+
+#ifdef SEEK_HOLE
+/* Try to engage SEEK_HOLE/SEEK_DATA feature. */
+static bool
+sparse_scan_file_seek (struct tar_sparse_file *file)
+{
+ struct tar_stat_info *st = file->stat_info;
+ int fd = file->fd;
+ struct sp_array sp = {0, 0};
+ off_t offset = 0;
+ off_t data_offset;
+ off_t hole_offset;
+
+ st->archive_file_size = 0;
+
+ for (;;)
+ {
+ /* locate first chunk of data */
+ data_offset = lseek (fd, offset, SEEK_DATA);
+
+ if (data_offset == (off_t)-1)
+ /* ENXIO == EOF; error otherwise */
+ {
+ if (errno == ENXIO)
+ {
+ /* file ends with hole, add one more empty chunk of data */
+ sp.numbytes = 0;
+ sp.offset = st->stat.st_size;
+ sparse_add_map (st, &sp);
+ return true;
+ }
+ return false;
+ }
+
+ hole_offset = lseek (fd, data_offset, SEEK_HOLE);
+
+ /* according to specs, if FS does not fully support
+ SEEK_DATA/SEEK_HOLE it may just implement kind of "wrapper" around
+ classic lseek() call. We must detect it here and try to use other
+ hole-detection methods. */
+ if (offset == 0 /* first loop */
+ && data_offset == 0
+ && hole_offset == st->stat.st_size)
+ {
+ lseek (fd, 0, SEEK_SET);
+ return false;
+ }
+
+ sp.offset = data_offset;
+ sp.numbytes = hole_offset - data_offset;
+ sparse_add_map (st, &sp);
+
+ st->archive_file_size += sp.numbytes;
+ offset = hole_offset;
+ }
+
+ return true;
+}
+#endif
+
+static bool
+sparse_scan_file (struct tar_sparse_file *file)
+{
+ /* always check for completely sparse files */
+ if (sparse_scan_file_wholesparse (file))
+ return true;
+
+ switch (hole_detection)
+ {
+ case HOLE_DETECTION_DEFAULT:
+ case HOLE_DETECTION_SEEK:
+#ifdef SEEK_HOLE
+ if (sparse_scan_file_seek (file))
+ return true;
+#else
+ if (hole_detection == HOLE_DETECTION_SEEK)
+ WARN((0, 0,
+ _("\"seek\" hole detection is not supported, using \"raw\".")));
+ /* fall back to "raw" for this and all other files */
+ hole_detection = HOLE_DETECTION_RAW;
+#endif
+ case HOLE_DETECTION_RAW:
+ if (sparse_scan_file_raw (file))
+ return true;
+ }
+
+ return false;
+}
+
static struct tar_sparse_optab const oldgnu_optab;
static struct tar_sparse_optab const star_optab;
static struct tar_sparse_optab const pax_optab;
projects / debian / tar / blobdiff