X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Fclosein.c;h=20d5035eec0bcff85471d5024f4358a4baa60446;hb=c50edd6462eaaae00f8549f9bad99d4e68b94376;hp=4450d5bd8dd6be0a2fdd290942ad2773a916b001;hpb=5c323b505d3a819032d1d2ef825070faefc247e6;p=gnulib.git

diff --git a/lib/closein.c b/lib/closein.c
index 4450d5bd8..20d5035ee 100644
--- a/lib/closein.c
+++ b/lib/closein.c
@@ -1,11 +1,11 @@
 /* Close standard input, rewinding seekable stdin if necessary.
 
-   Copyright (C) 2007 Free Software Foundation, Inc.
+   Copyright (C) 2007, 2009-2013 Free Software Foundation, Inc.
 
-   This program is free software; you can redistribute it and/or modify
+   This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
-   the Free Software Foundation; either version 2, or (at your option)
-   any later version.
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
 
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ -13,8 +13,7 @@
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
-   along with this program; if not, write to the Free Software Foundation,
-   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include <config.h>
 
@@ -32,6 +31,7 @@
 #include "closeout.h"
 #include "error.h"
 #include "exitfail.h"
+#include "freadahead.h"
 #include "quotearg.h"
 
 static const char *file_name;
@@ -55,7 +55,7 @@ close_stdin_set_file_name (const char *file)
    For example, POSIX requires that these two commands behave alike:
 
      (sed -ne 1q; cat) < file
-     tail -n 1 file
+     tail -n +2 file
 
    Since close_stdin is commonly registered via 'atexit', POSIX
    and the C standard both say that it should not call 'exit',
@@ -72,7 +72,7 @@ close_stdin_set_file_name (const char *file)
    the removal of these files.
 
    It's important to detect such failures and exit nonzero because many
-   tools (most notably `make' and other build-management systems) depend
+   tools (most notably 'make' and other build-management systems) depend
    on being able to detect failure in other tools via their exit status.  */
 
 void
@@ -80,22 +80,29 @@ close_stdin (void)
 {
   bool fail = false;
 
-  /* Only attempt flush if stdin is seekable, as fflush is entitled to
-     fail on non-seekable streams.  */
-  if (fseeko (stdin, 0, SEEK_CUR) == 0 && fflush (stdin) != 0)
-    fail = true;
+  /* There is no need to flush stdin if we can determine quickly that stdin's
+     input buffer is empty; in this case we know that if stdin is seekable,
+     (fseeko (stdin, 0, SEEK_CUR), ftello (stdin))
+     == lseek (0, 0, SEEK_CUR).  */
+  if (freadahead (stdin) > 0)
+    {
+      /* Only attempt flush if stdin is seekable, as fflush is entitled to
+         fail on non-seekable streams.  */
+      if (fseeko (stdin, 0, SEEK_CUR) == 0 && fflush (stdin) != 0)
+        fail = true;
+    }
   if (close_stream (stdin) != 0)
     fail = true;
   if (fail)
     {
       /* Report failure, but defer exit until after closing stdout,
-	 since the failure report should still be flushed.  */
+         since the failure report should still be flushed.  */
       char const *close_error = _("error closing file");
       if (file_name)
-	error (0, errno, "%s: %s", quotearg_colon (file_name),
-	       close_error);
+        error (0, errno, "%s: %s", quotearg_colon (file_name),
+               close_error);
       else
-	error (0, errno, "%s", close_error);
+        error (0, errno, "%s", close_error);
     }
 
   close_stdout ();