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* [newlib-cygwin/main] Cygwin: lseek: implement SEEK_DATA and SEEK_HOLE for files
@ 2023-08-09 15:25 Corinna Vinschen
0 siblings, 0 replies; only message in thread
From: Corinna Vinschen @ 2023-08-09 15:25 UTC (permalink / raw)
To: cygwin-cvs
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=edfa581d3c5a783ace9f837be1cbaccb97330c34
commit edfa581d3c5a783ace9f837be1cbaccb97330c34
Author: Corinna Vinschen <corinna@vinschen.de>
AuthorDate: Wed Aug 9 17:18:14 2023 +0200
Commit: Corinna Vinschen <corinna@vinschen.de>
CommitDate: Wed Aug 9 17:18:14 2023 +0200
Cygwin: lseek: implement SEEK_DATA and SEEK_HOLE for files
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Diff:
---
winsup/cygwin/fhandler/base.cc | 85 +++++++++++++++++++++++++++++++++++++++++-
1 file changed, 84 insertions(+), 1 deletion(-)
diff --git a/winsup/cygwin/fhandler/base.cc b/winsup/cygwin/fhandler/base.cc
index 9b49ec7b9ede..d8351d7a642e 100644
--- a/winsup/cygwin/fhandler/base.cc
+++ b/winsup/cygwin/fhandler/base.cc
@@ -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);
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2023-08-09 15:25 [newlib-cygwin/main] Cygwin: lseek: implement SEEK_DATA and SEEK_HOLE for files Corinna Vinschen
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