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      1 /*
      2  * CDDL HEADER START
      3  *
      4  * The contents of this file are subject to the terms of the
      5  * Common Development and Distribution License (the "License").
      6  * You may not use this file except in compliance with the License.
      7  *
      8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
      9  * or http://www.opensolaris.org/os/licensing.
     10  * See the License for the specific language governing permissions
     11  * and limitations under the License.
     12  *
     13  * When distributing Covered Code, include this CDDL HEADER in each
     14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     15  * If applicable, add the following below this CDDL HEADER, with the
     16  * fields enclosed by brackets "[]" replaced with your own identifying
     17  * information: Portions Copyright [yyyy] [name of copyright owner]
     18  *
     19  * CDDL HEADER END
     20  */
     21 
     22 /*
     23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
     24  * Use is subject to license terms.
     25  */
     26 
     27 /*	Copyright (c) 1988 AT&T	*/
     28 /*	  All Rights Reserved  	*/
     29 
     30 #pragma ident	"%Z%%M%	%I%	%E% SMI"
     31 
     32 /*
     33  * ftruncate() and truncate() set a file to a specified
     34  * length using fcntl(F_FREESP) system call. If the file
     35  * was previously longer than length, the bytes past the
     36  * length will no longer be accessible. If it was shorter,
     37  * bytes not written will be zero filled.
     38  */
     39 
     40 #include <sys/feature_tests.h>
     41 
     42 #if !defined(_LP64) && _FILE_OFFSET_BITS == 64
     43 #pragma weak _ftruncate64 = ftruncate64
     44 #pragma weak _truncate64 = truncate64
     45 #define	ftruncate	ftruncate64
     46 #define	truncate	truncate64
     47 #endif /* !_LP64 && _FILE_OFFSET_BITS == 64 */
     48 
     49 #include "lint.h"
     50 #include <unistd.h>
     51 #include <stdio.h>
     52 #include <fcntl.h>
     53 #include <pthread.h>
     54 #include <sys/types.h>
     55 
     56 int
     57 ftruncate(int fildes, off_t len)
     58 {
     59 	struct flock lck;
     60 
     61 	lck.l_whence = 0;	/* offset l_start from beginning of file */
     62 	lck.l_start = len;
     63 	lck.l_type = F_WRLCK;	/* setting a write lock */
     64 	lck.l_len = (off_t)0;	/* until the end of the file address space */
     65 
     66 	if (fcntl(fildes, F_FREESP, &lck) == -1) {
     67 		return (-1);
     68 	}
     69 	return (0);
     70 }
     71 
     72 int
     73 truncate(const char *path, off_t len)
     74 {
     75 
     76 	int rval = 0;
     77 	int cancel_state;
     78 	int fd;
     79 
     80 	/*
     81 	 * truncate() is not a cancellation point,
     82 	 * even though it calls open() and close().
     83 	 */
     84 	(void) pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cancel_state);
     85 	if ((fd = open(path, O_WRONLY)) == -1 || ftruncate(fd, len) == -1)
     86 		rval = -1;
     87 	if (fd >= 0)
     88 		(void) close(fd);
     89 	(void) pthread_setcancelstate(cancel_state, NULL);
     90 	return (rval);
     91 }
     92