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+/* Copyright (C) 1991, 1992 Free Software Foundation, Inc.
+This file is part of the GNU C Library.
+
+The GNU C Library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Library General Public License as
+published by the Free Software Foundation; either version 2 of the
+License, or (at your option) any later version.
+
+The GNU C 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
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with the GNU C Library; see the file COPYING.LIB. If
+not, write to the Free Software Foundation, Inc., 675 Mass Ave,
+Cambridge, MA 02139, USA. */
+
+/* This file provides glue between Unix stdio and GNU stdio.
+ It supports use of Unix stdio `getc' and `putc' (and, by extension,
+ `getchar' and `putchar') macros on GNU stdio streams (they are slow, but
+ they work). It also supports all stdio operations (including Unix
+ `getc' and `putc') on Unix's stdin, stdout, and stderr (the elements of
+ `_iob').
+
+ The reasoning behind this is to allow programs (and especially
+ libraries) compiled with Unix header files to work with the GNU C
+ library. */
+
+#include <ansidecl.h>
+#include <stdio.h>
+#include <errno.h>
+
+typedef union
+ {
+ struct
+ {
+ int magic;
+ FILE **streamp; /* Overlaps GNU stdio `bufp' member. */
+ /* These two overlap the GNU stdio `get_limit' and `put_limit'
+ members. They must be <= `streamp'/`bufp' for GNU getc and putc
+ to do the right thing. */
+ FILE **streamp2, **streamp3;
+ } glue;
+ struct _iobuf
+ {
+ int _cnt;
+ unsigned char *_ptr;
+ unsigned char *_base;
+ int _bufsiz;
+ short int _flag;
+ char _file;
+ } unix_iobuf;
+ FILE gnu_stream;
+ } unix_FILE;
+
+/* These are the Unix stdio's stdin, stdout, and stderr.
+ In Unix stdin is (&_iob[0]), stdout is (&_iob[1]), and stderr is
+ (&_iob[2]). The magic number marks these as glued streams. The
+ __validfp macro in stdio.h is used by every stdio function. It checks
+ for glued streams, and replaces them with the GNU stdio stream. */
+unix_FILE _iob[] =
+ {
+#define S(name) { { _GLUEMAGIC, &name, &name, &name } }
+ S (stdin),
+ S (stdout),
+ S (stderr),
+#undef S
+ };
+
+/* Called by the Unix stdio `getc' macro.
+ The macro is assumed to look something like:
+ (--file->_cnt < 0 ? _filbuf (file) ...)
+ In a Unix stdio FILE `_cnt' is the first element.
+ In a GNU stdio or glued FILE, the first element is the magic number. */
+int
+DEFUN(_filbuf, (file), unix_FILE *file)
+{
+ switch (++file->glue.magic) /* Compensate for Unix getc's decrement. */
+ {
+ case _GLUEMAGIC:
+ /* This is a glued stream. */
+ return getc (*file->glue.streamp);
+
+ case _IOMAGIC:
+ /* This is a normal GNU stdio stream. */
+ return getc ((FILE *) file);
+
+ default:
+ /* Bogus stream. */
+ errno = EINVAL;
+ return EOF;
+ }
+}
+
+/* Called by the Unix stdio `putc' macro. Much like getc, above. */
+int
+DEFUN(_flsbuf, (c, file),
+ int c AND unix_FILE *file)
+{
+ /* Compensate for putc's decrement. */
+ switch (++file->glue.magic)
+ {
+ case _GLUEMAGIC:
+ return putc (c, *file->glue.streamp);
+
+ case _IOMAGIC:
+ return putc (c, (FILE *) file);
+
+ default:
+ errno = EINVAL;
+ return EOF;
+ }
+}