usr/src/lib/libc/port/gen/truncate.c

   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 }