# HG changeset patch
# User John W. Eaton <jwe@octave.org>
# Date 1312987961 14400
# Node ID 8372d50de75a823392af7ce7fcf67d95faf8299e
# Parent  1be5f06d9fa77a4e6d8ab122612db915d060f27c
improve logic of octave_stream::seek funtion

* oct-stream.cc (octave_stream::seek): Find initial and EOF positions
before attempting to seek to requested position.

diff -r 1be5f06d9fa7 -r 8372d50de75a src/oct-stream.cc
--- a/src/oct-stream.cc	Tue Aug 09 23:23:59 2011 -0400
+++ b/src/oct-stream.cc	Wed Aug 10 10:52:41 2011 -0400
@@ -2860,38 +2860,60 @@
     {
       clearerr ();
 
+      // Find current position so we can return to it if needed.
+
       long orig_pos = rep->tell ();
 
-      status = rep->seek (offset, origin);
+      // Move to end of file.  If successful, find the offset of the end.
+
+      status = rep->seek (0, SEEK_END);
 
       if (status == 0)
         {
-          long save_pos = rep->tell ();
-
-          rep->seek (0, SEEK_END);
-
-          long pos_eof = rep->tell ();
-
-          // I don't think save_pos can be less than zero, but we'll
-          // check anyway...
-
-          if (save_pos > pos_eof || save_pos < 0)
+          long eof_pos = rep->tell ();
+
+          if (origin == SEEK_CUR)
+            {
+              // Move back to original position, otherwise we will be
+              // seeking from the end of file which is probably not the
+              // original location.
+
+              rep->seek (orig_pos, SEEK_SET);
+            }
+
+          // Attempt to move to desired position; may be outside bounds
+          // of existing file.
+
+          status = rep->seek (offset, origin);
+
+          if (status == 0)
             {
-              // Seek outside bounds of file.  Failure should leave
-              // position unchanged.
+              // Where are we after moving to desired position?
+
+              long desired_pos = rep->tell ();
+
+              // I don't think save_pos can be less than zero, but we'll
+              // check anyway...
+
+              if (desired_pos > eof_pos || desired_pos < 0)
+                {
+                  // Seek outside bounds of file.  Failure should leave
+                  // position unchanged.
+
+                  rep->seek (orig_pos, SEEK_SET);
+
+                  status = -1;
+                }
+            }
+          else
+            {
+              // Seeking to the desired position failed.  Move back to
+              // original position and return failure status.
 
               rep->seek (orig_pos, SEEK_SET);
 
               status = -1;
             }
-          else
-            {
-              // Is it possible for this to fail?  We are just
-              // returning to a position after the first successful
-              // seek.
-
-              rep->seek (save_pos, SEEK_SET);
-            }
         }
     }