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changeset 25657:db326f3aacf4

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Improve fread speed by a further 2.5X when SKIP parameter used (bug #54100). * oct-stream.cc (stream::fread): Use C++ seekg and tellg versus C seek and tell for a 2.5X speedup.
author Rik <rik@octave.org>
date Sun, 22 Jul 2018 20:40:02 -0700
parents fbc2730a653b
children 0812413a0bb7
files libinterp/corefcn/oct-stream.cc
diffstat 1 files changed, 7 insertions(+), 7 deletions(-) [+]
line wrap: on
line diff
--- a/libinterp/corefcn/oct-stream.cc	Sun Jul 22 15:37:57 2018 -0700
+++ b/libinterp/corefcn/oct-stream.cc	Sun Jul 22 20:40:02 2018 -0700
@@ -6609,10 +6609,10 @@
         off_t eof_pos = 0;
         if (skip != 0 && is && ! is.eof ())
           {
-            off_t orig_pos = tell ();
-            seek (0, SEEK_END);
-            eof_pos = tell ();
-            seek (orig_pos, SEEK_SET);
+            off_t orig_pos = is.tellg ();
+            is.seekg (0, is.end);
+            eof_pos = is.tellg ();
+            is.seekg (orig_pos, is.beg);
           }
 
         std::list <void *> input_buf_list;
@@ -6646,13 +6646,13 @@
               {
                 // Attempt to skip.
                 // If skip would move past EOF, position at EOF.
-                off_t orig_pos = tell ();
+                off_t orig_pos = is.tellg ();
                 off_t remaining = eof_pos - orig_pos;
 
                 if (remaining < skip)
-                  seek (0, SEEK_END);
+                  is.seekg (0, is.end);
                 else
-                  seek (skip, SEEK_CUR);
+                  is.seekg (skip, is.cur);
 
                 if (! is)
                   break;