Initial Contribution

libc/stdio/freopen.c

@@ -0,0 +1,158 @@
+/*	$OpenBSD: freopen.c,v 1.9 2005/08/08 08:05:36 espie Exp $ */
+/*-
+ * Copyright (c) 1990, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Chris Torek.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include "local.h"
+
+/* 
+ * Re-direct an existing, open (probably) file to some other file. 
+ * ANSI is written such that the original file gets closed if at
+ * all possible, no matter what.
+ */
+FILE *
+freopen(const char *file, const char *mode, FILE *fp)
+{
+	int f;
+	int flags, isopen, oflags, sverrno, wantfd;
+
+	if ((flags = __sflags(mode, &oflags)) == 0) {
+		(void) fclose(fp);
+		return (NULL);
+	}
+
+	if (!__sdidinit)
+		__sinit();
+
+	/*
+	 * There are actually programs that depend on being able to "freopen"
+	 * descriptors that weren't originally open.  Keep this from breaking.
+	 * 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; freopen("/dev/stdin", "r", stdin)
+	 * should work.  This is unnecessary if it was not a Unix file.
+	 */
+	if (fp->_flags == 0) {
+		fp->_flags = __SEOF;	/* hold on to it */
+		isopen = 0;
+		wantfd = -1;
+	} else {
+		/* flush the stream; ANSI doesn't require this. */
+		if (fp->_flags & __SWR)
+			(void) __sflush(fp);
+		/* if close is NULL, closing is a no-op, hence pointless */
+		isopen = fp->_close != NULL;
+		if ((wantfd = fp->_file) < 0 && isopen) {
+			(void) (*fp->_close)(fp->_cookie);
+			isopen = 0;
+		}
+	}
+
+	/* Get a new descriptor to refer to the new file. */
+	f = open(file, oflags, DEFFILEMODE);
+	if (f < 0 && isopen) {
+		/* If out of fd's close the old one and try again. */
+		if (errno == ENFILE || errno == EMFILE) {
+			(void) (*fp->_close)(fp->_cookie);
+			isopen = 0;
+			f = open(file, oflags, DEFFILEMODE);
+		}
+	}
+	sverrno = 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 (isopen && f != wantfd)
+		(void) (*fp->_close)(fp->_cookie);
+	if (fp->_flags & __SMBF)
+		free((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);
+	_UB(fp)._size = 0;
+	WCIO_FREE(fp);
+	if (HASLB(fp))
+		FREELB(fp);
+	fp->_lb._size = 0;
+
+	if (f < 0) {			/* did not get it after all */
+		fp->_flags = 0;		/* set it free */
+		errno = sverrno;	/* restore in case _close clobbered */
+		return (NULL);
+	}
+
+	/*
+	 * If reopening something that was open before on a real file, try
+	 * to maintain the descriptor.  Various C library routines (perror)
+	 * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
+	 */
+	if (wantfd >= 0 && f != wantfd) {
+		if (dup2(f, wantfd) >= 0) {
+			(void) close(f);
+			f = wantfd;
+		}
+	}
+
+	fp->_flags = flags;
+	fp->_file = f;
+	fp->_cookie = fp;
+	fp->_read = __sread;
+	fp->_write = __swrite;
+	fp->_seek = __sseek;
+	fp->_close = __sclose;
+
+	/*
+	 * When opening in append mode, even though we use O_APPEND,
+	 * we need to seek to the end so that ftell() gets the right
+	 * answer.  If the user then alters the seek pointer, or
+	 * the file extends, this will fail, but there is not much
+	 * we can do about this.  (We could set __SAPP and check in
+	 * fseek and ftell.)
+	 */
+	if (oflags & O_APPEND)
+		(void) __sseek((void *)fp, (fpos_t)0, SEEK_END);
+	return (fp);
+}