WG21/N0930
                                                               X3J16/96-0112
                                                               Thomas Plum
Four IOstreams recommendations
 
 
Four IOstreams recommendations are proposed below, interspersed amid the
minutes of the IOstreams ad-hoc group.
 
>Date: Thu, 23 May 1996 10:17:21 -0700
>From: clamage@pacific-88.Eng.Sun.COM (Steve Clamage)
>Message-Id: <199605231717.KAA14983@taumet.eng.sun.com>
>Subject: IOStreams working group recommendations
>X-Sun-Charset: ISO-8859-1
>
>To: C++ libraries mailing list
>Message c++std-lib-4709
>
>The following is a paper that will appear in the next mailing.
>
>	Doc No:	X3J16/96-0096
>		WG21/N0914
>	Date:	May 23, 1996
>	Project:	Programming Language C++
>	Reply-To:	Stephen D. Clamage
>			stephen.clamage@eng.sun.com
>
>
>IOstreams WG recommendations
>
>	Re: IOstream issues list X3J16/96-0079 WG21/N0897 of May 15, 1996.
>
>	Members of the IOstream library working group met informally on 21-22 May to review
>all the outstanding Chapter 27 issues. Recommendations of this group are given below.
>Each issue, except for those left open, was assigned to a person who will present a com-
>plete recommendation with WP language to the full IOstream working group at Stock-
>holm.
 ...
>27-005 not_eof specification (TP)
>Recommend: Yields a value which is not equal to eof. The value is unspecified. (The WP
>requires that (not_eof(e)==e) if (e!=eof), and forces a change from existing practice. The
>recommendation allows existing implementions to remain unchanged.)
 
Revise description of char_traits::not_eof to specify ...
 
Yields a value which is not equal to eof. The value is otherwise unspecified.
 
>27-806 filebuf::seekoff description (TP)
>Recommend: Accept in principle the recommendations in the public comment. Eight-bit
>streams behave like stdio FILEs. For wide streams, seeks are allowed provided the exter-
>nal file meets certain criteria to be worked out by TP.
 
Effects: If the stream is opened as a text file or has state-dependent conversions,
the only permissible seeks are with zero offset relative to the beginning or
current position of the file.  Otherwise ... [copy text from basic_stringstream].
 
Note: I don't find any special criteria for wide streams; binary streams are
seekable just as for narrow streams.  The catch is, there are no implied
relationships between number of widechars read and seek position; the implementation
can (and in many implementations does) use the same widechar<->multibyte
encodings on a binary stream as on a text stream.  But I'm not sure that this
requires any WP wording.
 
>27-811 missing filebuf::sync (TP)
>Recommend: For output, perhaps adapt wording from C standard. (Intent is clear.) For >in/out, flush output then really seek to current file position. For input files, >implementation-defined.
 
[Rather than copying C wording, I'm pointing to it; something like this ...]
 
Effects: If pbase() is non-null, the characters between pbase() and pptr() are
written to the stream; then the associated file is flushed (as if by calling
std::fflush(file) ).
 
>27-910 streampos type (TP)
>Recommend: Resolve as in issues list, and add streampos to <iosfwd>.
 
I.e.: Add back streampos, as being the pos_type used on streams instantiated on
tiny characters.  Replace all references to streampos by references to pos_type
throughout the iostreams chapter.  (When streams are instantiated on char,
pos_type == streampos.)  Add streampos to <iosfwd>.