import newlib-2000-02-17 snapshot

newlib/libc/stdio/freopen.c

@@ -0,0 +1,151 @@
+/*
+ * Copyright (c) 1990 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms are permitted
+ * provided that the above copyright notice and this paragraph are
+ * duplicated in all such forms and that any documentation,
+ * advertising materials, and other materials related to such
+ * distribution and use acknowledge that the software was developed
+ * by the University of California, Berkeley.  The name of the
+ * University may not be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+ */
+
+/*
+FUNCTION
+<<freopen>>---open a file using an existing file descriptor
+
+INDEX
+	freopen
+
+ANSI_SYNOPSIS
+	#include <stdio.h>
+	FILE *freopen(const char *<[file]>, const char *<[mode]>,
+		      FILE *<[fp]>);
+
+TRAD_SYNOPSIS
+	#include <stdio.h>
+	FILE *freopen(<[file]>, <[mode]>, <[fp]>)
+	char *<[file]>;
+	char *<[mode]>;
+	FILE *<[fp]>;
+
+DESCRIPTION
+Use this variant of <<fopen>> if you wish to specify a particular file
+descriptor <[fp]> (notably <<stdin>>, <<stdout>>, or <<stderr>>) for
+the file.
+
+If <[fp]> was associated with another file or stream, <<freopen>>
+closes that other file or stream (but ignores any errors while closing
+it).
+
+<[file]> and <[mode]> are used just as in <<fopen>>.
+
+RETURNS
+If successful, the result is the same as the argument <[fp]>.  If the
+file cannot be opened as specified, the result is <<NULL>>.
+
+PORTABILITY
+ANSI C requires <<freopen>>.
+
+Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,
+<<lseek>>, <<open>>, <<read>>, <<sbrk>>, <<write>>.
+*/
+
+#include <time.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include "local.h"
+
+/*
+ * Re-direct an existing, open (probably) file to some other file.
+ */
+
+FILE *
+_DEFUN (freopen, (file, mode, fp),
+	_CONST char *file _AND
+	_CONST char *mode _AND
+	register FILE *fp)
+{
+  register int f;
+  int flags, oflags, e;
+  struct _reent *ptr;
+
+  CHECK_INIT (fp);
+  ptr = fp->_data;
+
+  if ((flags = __sflags (ptr, mode, &oflags)) == 0)
+    {
+      (void) fclose (fp);
+      return NULL;
+    }
+
+  /*
+   * Remember whether the stream was open to begin with, and
+   * which file descriptor (if any) was associated with it.
+   * If it was attached to a descriptor, defer closing it,
+   * so that, e.g., freopen("/dev/stdin", "r", stdin) works.
+   * This is unnecessary if it was not a Unix file.
+   */
+
+  if (fp->_flags == 0)
+    fp->_flags = __SEOF;	/* hold on to it */
+  else
+    {
+      if (fp->_flags & __SWR)
+	(void) fflush (fp);
+      /* if close is NULL, closing is a no-op, hence pointless */
+      if (fp->_close != NULL)
+	(void) (*fp->_close) (fp->_cookie);
+    }
+
+  /*
+   * Now get a new descriptor to refer to the new file.
+   */
+
+  f = _open_r (ptr, (char *) file, oflags, 0666);
+  e = ptr->_errno;
+
+  /*
+   * Finish closing fp.  Even if the open succeeded above,
+   * we cannot keep fp->_base: it may be the wrong size.
+   * This loses the effect of any setbuffer calls,
+   * but stdio has always done this before.
+   */
+
+  if (fp->_flags & __SMBF)
+    _free_r (ptr, (char *) fp->_bf._base);
+  fp->_w = 0;
+  fp->_r = 0;
+  fp->_p = NULL;
+  fp->_bf._base = NULL;
+  fp->_bf._size = 0;
+  fp->_lbfsize = 0;
+  if (HASUB (fp))
+    FREEUB (fp);
+  fp->_ub._size = 0;
+  if (HASLB (fp))
+    FREELB (fp);
+  fp->_lb._size = 0;
+
+  if (f < 0)
+    {				/* did not get it after all */
+      fp->_flags = 0;		/* set it free */
+      ptr->_errno = e;		/* restore in case _close clobbered */
+      return NULL;
+    }
+
+  fp->_flags = flags;
+  fp->_file = f;
+  fp->_cookie = (_PTR) fp;
+  fp->_read = __sread;
+  fp->_write = __swrite;
+  fp->_seek = __sseek;
+  fp->_close = __sclose;
+  return fp;
+}