1/* Part of SWI-Prolog 2 3 Author: Jan Wielemaker 4 E-mail: J.Wielemaker@vu.nl 5 WWW: http://www.swi-prolog.org 6 Copyright (c) 2015, VU University Amsterdam 7 All rights reserved. 8 9 Redistribution and use in source and binary forms, with or without 10 modification, are permitted provided that the following conditions 11 are met: 12 13 1. Redistributions of source code must retain the above copyright 14 notice, this list of conditions and the following disclaimer. 15 16 2. Redistributions in binary form must reproduce the above copyright 17 notice, this list of conditions and the following disclaimer in 18 the documentation and/or other materials provided with the 19 distribution. 20 21 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 24 FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 25 COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 27 BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 28 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 29 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 31 ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 32 POSSIBILITY OF SUCH DAMAGE. 33*/ 34 35:- module(prolog_stream, 36 [ open_prolog_stream/4 % +Module, +Mode, -Stream, +Data 37 ]). 38:- use_foreign_library(foreign(prolog_stream)). 39 40/** <module> A stream with Prolog callbacks 41 42This library defines a Prolog stream that realises its low-level I/O 43with callbacks to Prolog. The library was developed to bind normal 44Prolog I/O to Pengines I/O. This type of I/O redirection is probably the 45primary use case. 46*/ 47 48%! open_prolog_stream(+Module, +Mode, -Stream, +Options) 49% 50% Create a new stream that implements its I/O by calling 51% predicates in Module. The called predicates are: 52% 53% - Module:stream_write(+Stream, +String) 54% Called for a `Mode = write` stream if data is available. 55% String contains the (textual) data that is written 56% to Stream. The callback is called if the buffer of 57% Stream overflows, the user calls flush_output(Stream) 58% or Stream is closed and there is buffered data. 59% - Module:stream_read(+Stream, -Term) 60% Called for a `Mode == read` stream to get new data. On 61% success the stream extracts text from the provided Term. 62% Term is typically a string, atom, code or character list. 63% If term is not one of the above, it is handed to writeq/1. 64% To signal end-of-file, unify stream with an empty text, 65% e.g., `stream_read(Stream, "")`. 66% - Module:stream_close(+Stream) 67% Called when the stream is closed. This predicate must 68% succeed. The callback can be used to cleanup associated 69% resources. 70% 71% The current implementation only deals with text streams. The 72% stream uses the =wchar_t= encoding. The buffer size must be a 73% multiple of =wchar_t=, i.e., a multiple of four for portability. 74% The _newline_ mode of the stream is =posix= on all platforms, 75% disabling the translation `"\n" --> "\r\n"`. 76% 77% @arg Options is currently ignored. 78% @bug Futher versions might require additional callbacks. As we 79% demand all callbacks to be defined, existing code needs 80% to implement the new callbacks.