From -7189995118441146576 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,7243bb67dd016622 X-Google-Attributes: gidf78e5,public From: Matt Austern Subject: Re: basic_streambuf<>::in_avail() Date: 1999/03/19 Message-ID: #1/1 X-Deja-AN: 456617953 X-NNTP-Posting-Host: isolde.engr.sgi.com Approved: stephen.clamage@sun.com (comp.std.c++) References: <%PUH2.5770$_n2.114958@carnaval.risq.qc.ca> <7crtbm$k14$1@shell7.ba.best.com> <7cttn9$s10$4@news.BelWue.DE> X-UID: 0000000001 X-Status: $$$T Organization: SGI Newsgroups: comp.std.c++ Originator: clamage@taumet kuehl@wolfurt.informatik.uni-konstanz.de (Dietmar Kuehl) writes: > : in_avail() in this example should return 1. If it fails to do so, > : you have a library bug. > > I think it is correct that 0 is returned: All standard streams maintain > only one joint position for reading and writing. After writing one character > into the stream, the write and read positions are pointing to the character > just behind the just inserted character. There is none. Thus, no character > is available for the stream and 'in_avail()' returns 0. To have 'in_avail()' > return 1 it would be necessary to seek back to the beginning of the stream. That's true for basic_filebuf, but I think Nathan is right about basic_stringbuf. There's a lot of text in 27.7.1 that only makes sense if the read and write positions are separate (see, for example, the discussion of positioning in Table 90, which explicitly says that the user can reposition one of the the read and write positions without changing the other), and I can't find any text to suggest that basic_stringbuf has a joint read/write position. My interpretation of basic_stringbuf<>::overflow() (27.7.1.3, paragraph 5) is that it should not change the position of the get pointer. In my implementation I go to some trouble to make sure of that. [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://reality.sgi.com/austern_mti/std-c++/faq.html ]