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Cygwin: lseek: implement SEEK_DATA and SEEK_HOLE for files 

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen 2023-08-09 17:18:14 +02:00
parent b6fbe0fc2e
commit edfa581d3c
1 changed files with 84 additions and 1 deletions
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85
winsup/cygwin/fhandler/base.cc
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@ -1109,7 +1109,7 @@ fhandler_base::lseek (off_t offset, int whence)
}
fpi.CurrentByteOffset.QuadPart += offset;
break;
default: /* SEEK_END */
case SEEK_END:
status = NtQueryInformationFile (get_handle (), &io, &fsi, sizeof fsi,
FileStandardInformation);
if (!NT_SUCCESS (status))
@ -1119,6 +1119,89 @@ fhandler_base::lseek (off_t offset, int whence)
}
fpi.CurrentByteOffset.QuadPart = fsi.EndOfFile.QuadPart + offset;
break;
case SEEK_DATA:
case SEEK_HOLE:
{
FILE_ALLOCATED_RANGE_BUFFER inp, out;
status = NtQueryInformationFile (get_handle (), &io, &fsi, sizeof fsi,
FileStandardInformation);
if (!NT_SUCCESS (status))
{
__seterrno_from_nt_status (status);
return -1;
}
/* Per Linux man page, ENXIO if offset is beyond EOF */
if (offset > fsi.EndOfFile.QuadPart)
{
set_errno (ENXIO);
return -1;
}
if (!pc.support_sparse ())
{
/* Default behaviour if sparse files are not supported:
SEEK_DATA: seek to offset
SEEK_HOLE: seek to EOF */
fpi.CurrentByteOffset.QuadPart = (whence == SEEK_DATA)
? offset
: fsi.EndOfFile.QuadPart;
break;
}
inp.FileOffset.QuadPart = offset;
inp.Length.QuadPart = fsi.EndOfFile.QuadPart - offset;
/* Note that we only fetch a single region, so we expect the
function to fail with STATUS_BUFFER_OVERFLOW. It still
returns the data region containing offset, or the next
region after offset, if offset is within a hole. */
status = NtFsControlFile (get_output_handle (), NULL, NULL, NULL,
&io, FSCTL_QUERY_ALLOCATED_RANGES,
&inp, sizeof inp,
&out, sizeof out);
if (!NT_SUCCESS (status) && status != STATUS_BUFFER_OVERFLOW)
{
/* On error, fall back to default behaviour, see above. */
fpi.CurrentByteOffset.QuadPart = (whence == SEEK_DATA)
? offset
: fsi.EndOfFile.QuadPart;
break;
}
if (io.Information == 0)
{
/* No valid region, so offset is within a hole at EOF.
SEEK_DATA: ENXIO
SEEK_HOLE: seek to offset */
if (whence == SEEK_DATA)
{
set_errno (ENXIO);
return -1;
}
fpi.CurrentByteOffset.QuadPart = offset;
}
else if (out.FileOffset.QuadPart == offset)
{
/* offset within valid data range? In that case, that region
supposedly starts at offset, and the region length is corrected
accordingly. That's quite helpful.
SEEK_DATA: seek to offset
SEEK_HOLE: seek to end of range */
fpi.CurrentByteOffset.QuadPart = offset;
if (whence == SEEK_HOLE)
fpi.CurrentByteOffset.QuadPart += out.Length.QuadPart;
}
else
{
/* Is range beyond offset?
SEEK_DATA: seek to start of range
SEEK_HOLE: seek to offset */
fpi.CurrentByteOffset.QuadPart = (whence == SEEK_DATA)
? out.FileOffset.QuadPart
: offset;
}
}
break;
default: /* Should never be reached */
set_errno (EINVAL);
return -1;
}
debug_printf ("setting file pointer to %U", fpi.CurrentByteOffset.QuadPart);