[v3] Fix libstdc++/11722

[Paolo Carlini <pcarlini at suse dot de>]

Hi,

tested x86-linux, committed to mainline.

Paolo.

/////////////
2004-09-13  Paolo Carlini  <pcarlini@suse.de>

	PR libstdc++/11722
	* include/std/std_fstream.h (xsgetn): Declare only.
	* include/bits/fstream.tcc (xsgetn): Define, optimize for the
	always_noconv() case: when __n > __buflen, copy the available
	buffer and issue a direct read.
	* testsuite/performance/27_io/filebuf_sgetn_unbuf.cc: New.

	* include/bits/fstream.tcc (xsputn): Minor tweak, reorder a
	conditional.

diff -urN libstdc++-v3-orig/include/bits/fstream.tcc libstdc++-v3/include/bits/fstream.tcc
--- libstdc++-v3-orig/include/bits/fstream.tcc	2004-05-23 01:46:32.000000000 +0200
+++ libstdc++-v3/include/bits/fstream.tcc	2004-09-13 20:21:22.000000000 +0200
@@ -497,6 +497,71 @@
    template<typename _CharT, typename _Traits>
      streamsize
      basic_filebuf<_CharT, _Traits>::
+     xsgetn(_CharT* __s, streamsize __n)
+     {
+       // Clear out pback buffer before going on to the real deal...
+       streamsize __ret = 0;
+       if (this->_M_pback_init)
+	 {
+	   if (__n > 0 && this->gptr() == this->eback())
+	     {
+	       *__s++ = *this->gptr();
+	       this->gbump(1);
+	       __ret = 1;
+	       --__n;
+	     }
+	   _M_destroy_pback();
+	 }
+       
+       // Optimization in the always_noconv() case, to be generalized in the
+       // future: when __n > __buflen we read directly instead of using the
+       // buffer repeatedly.
+       const bool __testin = this->_M_mode & ios_base::in;
+       const streamsize __buflen = this->_M_buf_size > 1 ? this->_M_buf_size - 1
+	                                                 : 1;
+       if (__n > __buflen && __check_facet(_M_codecvt).always_noconv()
+	   && __testin && !_M_writing)
+	 {
+	   // First, copy the chars already present in the buffer.
+	   const streamsize __avail = this->egptr() - this->gptr();
+	   if (__avail == 1)
+	     *__s = *this->gptr();
+	   else if (__avail > 1)
+	     traits_type::move(__s, this->gptr(), __avail);
+	   __s += __avail;
+	   this->gbump(__avail);
+	   __ret += __avail;
+	   __n -= __avail;
+
+	   const streamsize __len = _M_file.xsgetn(reinterpret_cast<char*>(__s),
+						   __n);
+	   if (__len == -1)
+	     __throw_ios_failure(__N("basic_filebuf::xsgetn "
+				     "error reading the file"));
+	   __ret += __len;
+	   if (__len == __n)
+	     {
+	       _M_set_buffer(0);
+	       _M_reading = true;
+	     }
+	   else if (__len == 0)
+	     {
+	       // If end of file is reached, set 'uncommitted'
+	       // mode, thus allowing an immediate write without
+	       // an intervening seek.
+	       _M_set_buffer(-1);
+	       _M_reading = false;
+	     }
+	 }
+       else
+	 __ret += __streambuf_type::xsgetn(__s, __n);
+
+       return __ret;
+     }
+
+   template<typename _CharT, typename _Traits>
+     streamsize
+     basic_filebuf<_CharT, _Traits>::
      xsputn(const _CharT* __s, streamsize __n)
      {
        // Optimization in the always_noconv() case, to be generalized in the
@@ -504,8 +569,8 @@
        // using the buffer.
        streamsize __ret = 0;
        const bool __testout = this->_M_mode & ios_base::out;
-       if (__testout && !_M_reading
-	   && __check_facet(_M_codecvt).always_noconv())
+       if (__check_facet(_M_codecvt).always_noconv()
+	   && __testout && !_M_reading)
 	{
 	  // Measurement would reveal the best choice.
 	  const streamsize __chunk = 1ul << 10;
diff -urN libstdc++-v3-orig/include/std/std_fstream.h libstdc++-v3/include/std/std_fstream.h
--- libstdc++-v3-orig/include/std/std_fstream.h	2004-08-13 18:47:42.000000000 +0200
+++ libstdc++-v3/include/std/std_fstream.h	2004-09-13 12:06:50.000000000 +0200
@@ -419,24 +419,7 @@
 
       // [documentation is inherited]
       virtual streamsize
-      xsgetn(char_type* __s, streamsize __n)
-      {
-	// Clear out pback buffer before going on to the real deal...
-	streamsize __ret = 0;
-	if (this->_M_pback_init)
-	  {
-	    if (__n && this->gptr() == this->eback())
-	      {
-		*__s++ = *this->gptr();
-		this->gbump(1);
-		__ret = 1;
-	      }
-	    _M_destroy_pback();
-	  }
-	if (__ret < __n)
-	  __ret += __streambuf_type::xsgetn(__s, __n - __ret);
-	return __ret;
-      }
+      xsgetn(char_type* __s, streamsize __n);
 
       // [documentation is inherited]
       virtual streamsize
diff -urN libstdc++-v3-orig/testsuite/performance/27_io/filebuf_sgetn_unbuf.cc libstdc++-v3/testsuite/performance/27_io/filebuf_sgetn_unbuf.cc
--- libstdc++-v3-orig/testsuite/performance/27_io/filebuf_sgetn_unbuf.cc	1970-01-01 01:00:00.000000000 +0100
+++ libstdc++-v3/testsuite/performance/27_io/filebuf_sgetn_unbuf.cc	2004-09-13 12:04:44.000000000 +0200
@@ -0,0 +1,85 @@
+// Copyright (C) 2004 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library 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.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING.  If not, write to the Free
+// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+// USA.
+
+// As a special exception, you may use this file as part of a free software
+// library without restriction.  Specifically, if other files instantiate
+// templates or use macros or inline functions from this file, or you compile
+// this file and link it with other files to produce an executable, this
+// file does not by itself cause the resulting executable to be covered by
+// the GNU General Public License.  This exception does not however
+// invalidate any other reasons why the executable file might be covered by
+// the GNU General Public License.
+
+#include <cstdio>
+#include <fstream>
+#include <testsuite_performance.h>
+
+// libstdc++/11722
+int main()
+{
+  using namespace std;
+  using namespace __gnu_test;
+
+  time_counter time;
+  resource_counter resource;
+
+  const int iterations = 500000;
+  const int chunksize = 100;
+
+  char* chunk = new char[chunksize];
+  const char* name = "/usr/share/dict/linux.words";
+
+  // C
+  FILE* file = fopen(name, "r");
+  setvbuf(file, 0, _IONBF, 0);
+  start_counters(time, resource);
+  for (int i = 0; i < iterations; ++i)
+    if (fread(chunk, 1, chunksize, file) < chunksize)
+      fseek(file, 0, SEEK_SET);
+  stop_counters(time, resource);
+  fclose(file);
+  report_performance(__FILE__, "C", time, resource);
+  clear_counters(time, resource);
+
+  // C unlocked
+  file = fopen(name, "r");
+  setvbuf(file, 0, _IONBF, 0);
+  start_counters(time, resource);
+  for (int i = 0; i < iterations; ++i)
+    if (fread_unlocked(chunk, 1, chunksize, file) < chunksize)
+      fseek(file, 0, SEEK_SET);
+  stop_counters(time, resource);
+  fclose(file);
+  report_performance(__FILE__, "C unlocked", time, resource);
+  clear_counters(time, resource);
+  
+  // C++
+  filebuf buf;
+  buf.pubsetbuf(0, 0);
+  buf.open(name, ios_base::in);
+  start_counters(time, resource);
+  for (int i = 0; i < iterations; ++i)
+    if (buf.sgetn(chunk, chunksize) < chunksize)
+      buf.pubseekoff(0, ios::beg);
+  stop_counters(time, resource);
+  report_performance(__FILE__, "C++", time, resource);
+
+  delete [] chunk;
+
+  return 0;
+}