Add fpurge.

* libc/stdio/fpurge.c (fpurge, _fpurge_r): New file.
* libc/stdio/Makefile.am (ELIX_4_SOURCES, CHEWOUT_FILES, fpurge):
Build it.
* libc/stdio/Makefile.in: Regenerated.
* libc/include/stdio.h (fpurge, _fpurge_r): New declarations.
* libc/stdio/stdio.tex: Build documentation.

1 files changed, 90 insertions, 0 deletions

diff --git a/newlib/libc/stdio/fpurge.c b/newlib/libc/stdio/fpurge.c
new file mode 100644
index 000000000..41228efd7
--- /dev/null
+++ b/newlib/libc/stdio/fpurge.c
@@ -0,0 +1,90 @@
+/* Copyright (C) 2009 Eric Blake
+ * Permission to use, copy, modify, and distribute this software
+ * is freely granted, provided that this notice is preserved.
+ */
+
+/*
+FUNCTION
+<<fpurge>>---discard pending file I/O
+
+INDEX
+	fpurge
+INDEX
+	_fpurge_r
+
+ANSI_SYNOPSIS
+	#include <stdio.h>
+	int fpurge(FILE *<[fp]>);
+
+	int _fpurge_r(struct _reent *<[reent]>, FILE *<[fp]>);
+
+DESCRIPTION
+Use <<fpurge>> to clear all buffers of the given stream.  For output
+streams, this discards data not yet written to disk.  For input streams,
+this discards any data from <<ungetc>> and any data retrieved from disk
+but not yet read via <<getc>>.  This is more severe than <<fflush>>,
+and generally is only needed when manually altering the underlying file
+descriptor of a stream.
+
+The alternate function <<_fpurge_r>> is a reentrant version, where the
+extra argument <[reent]> is a pointer to a reentrancy structure, and
+<[fp]> must not be NULL.
+
+RETURNS
+<<fpurge>> returns <<0>> unless <[fp]> is not valid, in which case it
+returns <<EOF>> and sets <<errno>>.
+
+PORTABILITY
+These functions are not portable to any standard.
+
+No supporting OS subroutines are required.
+*/
+
+#include <_ansi.h>
+#include <stdio.h>
+#include <errno.h>
+#include "local.h"
+
+/* Discard I/O from a single file.  */
+
+int
+_DEFUN(_fpurge_r, (ptr, fp),
+       struct _reent *ptr _AND
+       register FILE * fp)
+{
+  int t;
+
+  CHECK_INIT (ptr, fp);
+
+  _flockfile (fp);
+
+  t = fp->_flags;
+  if (!t)
+    {
+      ptr->_errno = EBADF;
+      _funlockfile (fp);
+      return EOF;
+    }
+  fp->_p = fp->_bf._base;
+  if ((t & __SWR) == 0)
+    {
+      fp->_r = 0;
+      if (HASUB (fp))
+	FREEUB (ptr, fp);
+    }
+  else
+    fp->_w = t & (__SLBF | __SNBF) ? 0 : fp->_bf._size;
+  _funlockfile (fp);
+  return 0;
+}
+
+#ifndef _REENT_ONLY
+
+int
+_DEFUN(fpurge, (fp),
+       register FILE * fp)
+{
+  return _fpurge_r (_REENT, fp);
+}
+
+#endif /* _REENT_ONLY */