OpenE2K
/
gcc
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

re PR libstdc++/11722 ([3.4 only] Unbuffered filebuf::sgetn is slow) 

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.

From-SVN: r87453
This commit is contained in:
Paolo Carlini 2004-09-13 22:21:34 +00:00
parent 90c609e51a
commit c56e3d82fc
4 changed files with 166 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
libstdc++-v3/ChangeLog
View File

@ -1,4 +1,16 @@
2004-09-14 Hans-Peter Nilsson <hp@bitrange.com>
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.
2004-09-13 Hans-Peter Nilsson <hp@bitrange.com>
* testsuite/lib/libstdc++.exp: Use gcc wrapper.exp and call
libstdc++_maybe_build_wrapper instead of using local code.

69
libstdc++-v3/include/bits/fstream.tcc
View File

@ -494,6 +494,71 @@ namespace std
return __elen == __plen;
}
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>::
@ -504,8 +569,8 @@ namespace std
// 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;

19
libstdc++-v3/include/std/std_fstream.h
View File

@ -419,24 +419,7 @@ namespace std
// [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

85
libstdc++-v3/testsuite/performance/27_io/filebuf_sgetn_unbuf.cc Normal file
View File

@ -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;
}