streamutil.h

C++ class libraries for network-centric, portable applications, integrated perfectly with the C++ St

//
// StreamUtil.h
//
// $Id: //poco/1.2/Foundation/include/Poco/StreamUtil.h#1 $
//
// Library: Foundation
// Package: Streams
// Module:  StreamUtil
//
// Stream implementation support.
//
// Copyright (c) 2005-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#ifndef Foundation_StreamUtil_INCLUDED
#define Foundation_StreamUtil_INCLUDED


#include "Poco/Foundation.h"


// poco_ios_init
//
// This is a workaround for a bug in the Microsoft
// implementation of iostreams.
//
// Calling basic_ios::init() multiple times for the
// same basic_ios instance results in a memory leak
// caused by the ios' locale being allocated more than
// once, each time overwriting the old pointer.
// This usually occurs in the following scenario:
//
// class MyStreamBuf: public std::streambuf
// {
//     ...
// };
//
// class MyIOS: public virtual std::ios
// {
// public:
//     MyIOS()
//     {
//         init(&_buf);
//     }
// protected:
//     MyStreamBuf _buf;
// };
//
// class MyIStream: public MyIOS, public std::istream
// {
//     ...
// };
//
// In this scenario, std::ios::init() is called twice
// (the first time by the MyIOS constructor, the second
// time by the std::istream constructor), resulting in 
// two locale objects being allocated, the pointer second 
// one overwriting the pointer to the first one and thus 
// causing a memory leak.
// 
// The workaround is to call init() only once for each
// stream object - by the istream, ostream or iostream
// constructor, and not calling init() in ios-derived
// base classes.
//
// Some stream implementations, however, require that
// init() is called in the MyIOS constructor.
// Therefore we replace each call to init() with
// the following macro:
#if defined(_MSC_VER) && (!defined(_STLP_MSVC) || defined(_STLP_NO_OWN_IOSTREAMS))
#define poco_ios_init(buf)
#else
#define poco_ios_init(buf) init(buf)
#endif


#endif // Foundation_StreamUtil_INCLUDED