1 files changed, 77 insertions, 0 deletions
diff --git a/libio/indstream.h b/libio/indstream.h
new file mode 100644
index 00000000000..c4558623d07
--- /dev/null
+++ b/libio/indstream.h
@@ -0,0 +1,77 @@
+/* This is part of libio/iostream, providing -*- C++ -*- input/output.
+Copyright (C) 1993 Free Software Foundation
+
+This file is part of the GNU IO Library.  This library is free
+software; you can redistribute it and/or modify it under the
+terms of the GNU General Public License as published by the
+Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+This library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this library; see the file COPYING.  If not, write to the Free
+Software Foundation, 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+
+As a special exception, if you link this library with files
+compiled with a GNU compiler to produce an executable, this does not cause
+the resulting executable to be covered by the GNU General Public License.
+This exception does not however invalidate any other reasons why
+the executable file might be covered by the GNU General Public License.
+
+Written by Per Bothner (bothner@cygnus.com). */
+
+#ifndef _INDSTREAM_H
+#define _INDSTREAM_H
+
+#ifdef __GNUG__
+#pragma interface
+#endif
+
+#include <iostream.h>
+
+extern "C++" {
+// An indirectbuf is one that forwards all of its I/O requests
+// to another streambuf.
+// All get-related requests are sent to get_stream().
+// All put-related requests are sent to put_stream().
+
+// An indirectbuf can be used to implement Common Lisp
+// synonym-streams and two-way-streams.
+//
+// class synonymbuf : public indirectbuf {
+//    Symbol *sym;
+//    synonymbuf(Symbol *s) { sym = s; }
+//    virtual streambuf *lookup_stream(int mode) {
+//        return coerce_to_streambuf(lookup_value(sym)); }
+// };
+
+class indirectbuf : public streambuf {
+  protected:
+    streambuf *_get_stream;  // Optional cache for get_stream().
+    streambuf *_put_stream;  // Optional cache for put_stream().
+    int _delete_flags;
+  public:
+    streambuf *get_stream()
+	{ return _get_stream ? _get_stream : lookup_stream(ios::in); }
+    streambuf *put_stream()
+	{ return _put_stream ? _put_stream : lookup_stream(ios::out); }
+    virtual streambuf *lookup_stream(int/*mode*/) { return NULL; } // ERROR!
+    indirectbuf(streambuf *get=NULL, streambuf *put=NULL, int delete_mode=0);
+    virtual ~indirectbuf();
+    virtual streamsize xsputn(const char* s, streamsize n);
+    virtual streamsize xsgetn(char* s, streamsize n);
+    virtual int underflow();
+    virtual int uflow();
+    virtual int overflow(int c = EOF);
+    virtual streampos seekoff(streamoff, _seek_dir, int mode=ios::in|ios::out);
+    virtual streampos seekpos(streampos pos, int mode = ios::in|ios::out);
+    virtual int sync();
+    virtual int pbackfail(int c);
+};
+} // extern "C++"
+
+#endif /* !_INDSTREAM_H */