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Date: Fri, 07 Mar 2003 21:26:00 -0000
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To: paolo@gcc.gnu.org
Cc: gcc-prs@gcc.gnu.org,
From: Paolo Carlini <pcarlini@unitus.it>
Subject: Re: libstdc++/9424: i/ostream::operator>>/<<(streambuf*) drops characters
Reply-To: Paolo Carlini <pcarlini@unitus.it>
X-SW-Source: 2003-03/txt/msg00370.txt.bz2
List-Id: <gcc-prs.sourceware.org>

The following reply was made to PR libstdc++/9424; it has been noted by GNATS.

From: Paolo Carlini <pcarlini@unitus.it>
To: Nathan Myers <ncm@cantrip.org>
Cc: libstdc++@gcc.gnu.org,  gcc-gnats@gcc.gnu.org
Subject: Re: libstdc++/9424: i/ostream::operator>>/<<(streambuf*) drops characters
Date: Fri, 07 Mar 2003 22:25:52 +0100

 Nathan Myers wrote:
 
 >>int_type c;
 >>while ((c = sbin->sbumpc()) != traits_type::eof() &&
 >>       (sbout->sputc(c) != traits_type::eof())
 >>  {}
 >>
 >I seem to recall that sbumpc() can be implemented more efficiently
 >than snextc, although it's just possible I was smoking crack.
 >
 Hi Nathan. Thanks for your feedback.
 Indeed (*), the basic loop is much more elegant in terms of sbumpc, and more
 efficient too, I guess, since our snextc is implemented in terms of  sbumpc:
 
     int_type
     snextc()
       {
         int_type __eof = traits_type::eof();
         return (traits_type::eq_int_type(this->sbumpc(), __eof)
                 ? __eof : this->sgetc());
       }
 
 However, in the application I want to count separately the number of 
 succesful
 reads (__charsread) and writes (__xtrct) like this:
 
     __xtrct = __charsread = 0;
     int_type __c = __sbin->sgetc();
     while (!_Traits::eq_int_type(__c, _Traits::eof()))
       {
         ++__charsread;
         if (_Traits::eq_int_type(__sbout->sputc(_Traits::to_char_type(__c)),
                                  _Traits::eof()))
           break;
         ++__xtrct;
         ++__ret;
         __c = __sbin->snextc();
       }
 
 and can't see a straightforward way to use your suggestion. Can you?
 
 Otherwise, as indicated by Benjamin, for the time being I would check in
 this correctness fix with the promise of returning to this function to
 streamline it in the _near_ future.
 
 Thanks,
 Paolo.
 
 (*) I want to buy crack from your pusher: seems excellent!