1/* $NetBSD: ftruncate.c,v 1.1.1.2 2012/09/09 16:07:42 christos Exp $ */ 2 3#ifndef LINT 4static const char rcsid[] = "Id: ftruncate.c,v 1.3 2005/04/27 18:16:45 sra Exp "; 5#endif 6 7/*! \file 8 * \brief 9 * ftruncate - set file size, BSD Style 10 * 11 * shortens or enlarges the file as neeeded 12 * uses some undocumented locking call. It is known to work on SCO unix, 13 * other vendors should try. 14 * The #error directive prevents unsupported OSes 15 */ 16 17#include "port_before.h" 18 19#if defined(M_UNIX) 20#define OWN_FTRUNCATE 21#include <stdio.h> 22#ifdef _XOPEN_SOURCE 23#undef _XOPEN_SOURCE 24#endif 25#ifdef _POSIX_SOURCE 26#undef _POSIX_SOURCE 27#endif 28 29#include <fcntl.h> 30 31#include "port_after.h" 32 33int 34__ftruncate(int fd, long wantsize) { 35 long cursize; 36 37 /* determine current file size */ 38 if ((cursize = lseek(fd, 0L, 2)) == -1) 39 return (-1); 40 41 /* maybe lengthen... */ 42 if (cursize < wantsize) { 43 if (lseek(fd, wantsize - 1, 0) == -1 || 44 write(fd, "", 1) == -1) { 45 return (-1); 46 } 47 return (0); 48 } 49 50 /* maybe shorten... */ 51 if (wantsize < cursize) { 52 struct flock fl; 53 54 fl.l_whence = 0; 55 fl.l_len = 0; 56 fl.l_start = wantsize; 57 fl.l_type = F_WRLCK; 58 return (fcntl(fd, F_FREESP, &fl)); 59 } 60 return (0); 61} 62#endif 63 64#ifndef OWN_FTRUNCATE 65int __bindcompat_ftruncate; 66#endif 67