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Count short read slop when seeking

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* src/buffer.c (short_read_slop): New static var.
(get_archive_status): Treat anything other than fifos and sockets
as potentially seekable; they’ll tell us if they aren’t, whereas
fifos and sockets cannot be seekable.  Check named files for
initial offset too, to deal with names like /dev/stdin.
Do not worry about start_offset’s value if !seekable_archive,
as it won’t be used.  Use short_read_slop.
(short_read, try_new_volume, simple_flush_read, _gnu_flush_read):
Set short_read_slop.
This commit is contained in:
Paul Eggert
2024-11-02 09:54:10 -07:00
parent 04b4f491a8
commit 15d35a0f61
1 changed files with 20 additions and 14 deletions
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34
src/buffer.c
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@@ -47,6 +47,7 @@ static tarlong prev_written; /* bytes written on previous volumes */
static tarlong bytes_written; /* bytes written on this volume */
static void *record_buffer[2]; /* allocated memory */
static bool record_index;
static idx_t short_read_slop; /* excess bytes at end of short read */
/* FIXME: The following variables should ideally be static to this
module. However, this cannot be done yet. The cleanup continues! */
@@ -703,22 +704,20 @@ get_archive_status (enum access_mode wanted_access, bool backed_up_flag)
= (! (multi_volume_option || use_compress_program_option)
&& (seek_option < 0
? (_isrmt (archive)
|| S_ISREG (archive_stat.st_mode)
|| S_ISBLK (archive_stat.st_mode))
: seek_option));
|| ! (S_ISFIFO (archive_stat.st_mode)
|| S_ISSOCK (archive_stat.st_mode)))
: seek_option != 0));
if (wanted_access == ACCESS_READ)
{
if (archive == STDIN_FILENO && seekable_archive)
if (seekable_archive)
{
start_offset = lseek (archive, 0, SEEK_CUR);
if (start_offset == -1)
start_offset = (lseek (archive, 0, SEEK_CUR)
- (record_end - record_start) * BLOCKSIZE
- short_read_slop);
if (start_offset < 0)
seekable_archive = false;
else
start_offset -= (record_end - record_start) * BLOCKSIZE;
}
else
start_offset = 0;
}
else
sys_detect_dev_null_output ();
@@ -999,7 +998,7 @@ short_read (idx_t status)
paxfatal (0, ngettext ("Unaligned block (%td byte) in archive",
"Unaligned block (%td bytes) in archive",
rest),
rest),
rest);
}
@@ -1008,6 +1007,7 @@ short_read (idx_t status)
}
record_end = record_start + (record_size - left) / BLOCKSIZE;
short_read_slop = (record_size - left) % BLOCKSIZE;
records_read++;
}
@@ -1451,6 +1451,7 @@ try_new_volume (void)
< 0)
archive_read_error ();
short_read_slop = 0;
if (status != record_size)
short_read (status);
@@ -1813,6 +1814,7 @@ simple_flush_read (void)
ptrdiff_t nread;
while ((nread = rmtread (archive, record_start->buffer, record_size)) < 0)
archive_read_error ();
short_read_slop = 0;
if (nread == record_size)
records_read++;
else
@@ -1873,10 +1875,14 @@ _gnu_flush_read (void)
/* Necessary for blocking_factor == 1 */
flush_archive ();
}
else if (nread == record_size)
records_read++;
else
short_read (nread);
{
short_read_slop = 0;
if (nread == record_size)
records_read++;
else
short_read (nread);
}
}
static void