* fhandler_floppy.cc (fhandler_dev_floppy::lseek): Don't invalidate

	devbuf if new position is within buffered range.

1 files changed, 15 insertions, 1 deletions

diff --git a/winsup/cygwin/fhandler_floppy.cc b/winsup/cygwin/fhandler_floppy.cc
index ee8d56b57..bcd0c7df6 100644
--- a/winsup/cygwin/fhandler_floppy.cc
+++ b/winsup/cygwin/fhandler_floppy.cc
@@ -410,6 +410,7 @@ fhandler_dev_floppy::lseek (_off64_t offset, int whence)
 {
   char buf[bytes_per_sector];
   _off64_t lloffset = offset;
+  _off64_t current_pos = (_off64_t) -1;
   LARGE_INTEGER sector_aligned_offset;
   size_t bytes_left;
 
@@ -420,7 +421,8 @@ fhandler_dev_floppy::lseek (_off64_t offset, int whence)
     }
   else if (whence == SEEK_CUR)
     {
-      lloffset += get_current_position () - (devbufend - devbufstart);
+      current_pos = get_current_position ();
+      lloffset += current_pos - (devbufend - devbufstart);
       whence = SEEK_SET;
     }
 
@@ -430,6 +432,18 @@ fhandler_dev_floppy::lseek (_off64_t offset, int whence)
       return -1;
     }
 
+  /* If new position is in buffered range, adjust buffer and return */
+  if (devbufstart < devbufend)
+    {
+      if (current_pos == (_off64_t) -1)
+	current_pos = get_current_position ();
+      if (current_pos - devbufend <= lloffset && lloffset <= current_pos)
+	{
+	  devbufstart = devbufend - (current_pos - lloffset);
+	  return lloffset;
+	}
+    }
+
   sector_aligned_offset.QuadPart = (lloffset / bytes_per_sector)
 				   * bytes_per_sector;
   bytes_left = lloffset - sector_aligned_offset.QuadPart;