1/* This is part of libio/iostream, providing -*- C++ -*- input/output.
2Copyright (C) 1993 Free Software Foundation
3
4This file is part of the GNU IO Library.  This library is free
5software; you can redistribute it and/or modify it under the
6terms of the GNU General Public License as published by the
7Free Software Foundation; either version 2, or (at your option)
8any later version.
9
10This library is distributed in the hope that it will be useful,
11but WITHOUT ANY WARRANTY; without even the implied warranty of
12MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13GNU General Public License for more details.
14
15You should have received a copy of the GNU General Public License
16along with this library; see the file COPYING.  If not, write to the Free
17Software Foundation, 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
18
19As a special exception, if you link this library with files
20compiled with a GNU compiler to produce an executable, this does not cause
21the resulting executable to be covered by the GNU General Public License.
22This exception does not however invalidate any other reasons why
23the executable file might be covered by the GNU General Public License.
24
25Written by Per Bothner (bothner@cygnus.com). */
26
27#ifndef _INDSTREAM_H
28#define _INDSTREAM_H
29
30#ifdef __GNUG__
31#pragma interface
32#endif
33
34#include <iostream.h>
35
36extern "C++" {
37// An indirectbuf is one that forwards all of its I/O requests
38// to another streambuf.
39// All get-related requests are sent to get_stream().
40// All put-related requests are sent to put_stream().
41
42// An indirectbuf can be used to implement Common Lisp
43// synonym-streams and two-way-streams.
44//
45// class synonymbuf : public indirectbuf {
46//    Symbol *sym;
47//    synonymbuf(Symbol *s) { sym = s; }
48//    virtual streambuf *lookup_stream(int mode) {
49//        return coerce_to_streambuf(lookup_value(sym)); }
50// };
51
52class indirectbuf : public streambuf {
53  protected:
54    streambuf *_get_stream;  // Optional cache for get_stream().
55    streambuf *_put_stream;  // Optional cache for put_stream().
56    int _delete_flags;
57  public:
58    streambuf *get_stream()
59	{ return _get_stream ? _get_stream : lookup_stream(ios::in); }
60    streambuf *put_stream()
61	{ return _put_stream ? _put_stream : lookup_stream(ios::out); }
62    virtual streambuf *lookup_stream(int/*mode*/) { return NULL; } // ERROR!
63    indirectbuf(streambuf *get=NULL, streambuf *put=NULL, int delete_mode=0);
64    virtual ~indirectbuf();
65    virtual streamsize xsputn(const char* s, streamsize n);
66    virtual streamsize xsgetn(char* s, streamsize n);
67    virtual int underflow();
68    virtual int uflow();
69    virtual int overflow(int c = EOF);
70    virtual streampos seekoff(streamoff, _seek_dir, int mode=ios::in|ios::out);
71    virtual streampos seekpos(streampos pos, int mode = ios::in|ios::out);
72    virtual int sync();
73    virtual int pbackfail(int c);
74};
75} // extern "C++"
76
77#endif /* !_INDSTREAM_H */
78