forked from KolibriOS/kolibrios
172 lines
6.3 KiB
C
172 lines
6.3 KiB
C
/****************************************************************************
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*
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* Open Watcom Project
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*
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* Portions Copyright (c) 1983-2002 Sybase, Inc. All Rights Reserved.
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*
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* ========================================================================
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*
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* This file contains Original Code and/or Modifications of Original
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* Code as defined in and that are subject to the Sybase Open Watcom
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* Public License version 1.0 (the 'License'). You may not use this file
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* except in compliance with the License. BY USING THIS FILE YOU AGREE TO
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* ALL TERMS AND CONDITIONS OF THE LICENSE. A copy of the License is
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* provided with the Original Code and Modifications, and is also
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* available at www.sybase.com/developer/opensource.
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*
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* The Original Code and all software distributed under the License are
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* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
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* EXPRESS OR IMPLIED, AND SYBASE AND ALL CONTRIBUTORS HEREBY DISCLAIM
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* ALL SUCH WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR
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* NON-INFRINGEMENT. Please see the License for the specific language
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* governing rights and limitations under the License.
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*
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* ========================================================================
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*
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* Description: Platform independent tmpfile() implementation.
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*
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****************************************************************************/
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#include "variety.h"
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#include "rtinit.h"
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#include <stdio.h>
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#include <stdlib.h>
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#include <stddef.h>
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#include <fcntl.h>
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#include <direct.h>
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#include <string.h>
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#include <process.h>
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#include <unistd.h>
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#include <errno.h>
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#include "rtdata.h"
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#include "tmpfname.h"
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#include "seterrno.h"
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#include "openmode.h"
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#define OPEN_MODE (O_RDWR | O_CREAT | O_BINARY)
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#define PMODE (S_IREAD | S_IWRITE)
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/* Netware doesn't define these */
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/* Symbolic constants for the access() function */
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#if !defined( F_OK )
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#define R_OK 4 /* Test for read permission */
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#define W_OK 2 /* Test for write permission */
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#define X_OK 1 /* Test for execute permission */
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#define F_OK 0 /* Test for existence of file */
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#endif
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extern void __MkTmpFile( char *buf, int num );
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extern void __RmTmpFile( FILE *fp );
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extern void (*__RmTmpFileFn)( FILE *fp );
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char __tmpfnext = _TMP_INIT_CHAR;
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_WCRTLINK FILE *tmpfile( void ) /* create a temporary file */
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{
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int hdl;
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int old_errno;
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int our_errno;
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char suffix1;
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char suffix2;
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FILE *fp;
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char name1[PATH_MAX + _TMPFNAME_LENGTH + 1];
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char name2[PATH_MAX + _TMPFNAME_LENGTH + 1];
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old_errno = _RWD_errno;
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suffix1 = 0;
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for( ;; ) {
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// Part I
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for( ;; ) {
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__MkTmpFile( name1, suffix1 );
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// if a file by this name does not exist
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if( access( name1, F_OK ) != 0 ) {
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// then let's try to create it
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hdl = sopen( name1, OPEN_MODE, OPENMODE_DENY_COMPAT, PMODE );
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// if we created it then continue with part II
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if( hdl != -1 ) break;
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__set_errno( EAGAIN );
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}
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suffix1++;
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// give up after _TMP_INIT_CHAR tries JBS 99/10/26
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if( suffix1 >= _TMP_INIT_CHAR ) return NULL;
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}
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close( hdl );
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// Part II
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/* we now have a empty file. Let's try to rename it
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rename should be an atomic operation in the operating system
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so if it succeeds we can be sure no one else has this file.
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Consider the following sequence:
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task1: access x.y => file does not exist
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task2: access x.y => file does not exist
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task1: fopen x.y => succeeds
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task2: fopen x.y => succeeds (now have both tasks with x.y open)
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task1: rename x.y to y.y => succeeds, can use this file
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task2: rename x.y to y.y => fails (because x.y no longer exists)
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task2: start over again to get a new file name
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task2: succeeds second time around since no more race condition
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with task1.
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*/
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suffix2 = _RWD_tmpfnext; // only one of these per process
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for( ;; ) {
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if( suffix2 == suffix1 ) {
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suffix2++;
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}
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__MkTmpFile( name2, suffix2 );
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if( rename( name1, name2 ) == 0 ) { // if rename worked
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// The file is now ours. Let's try to open it.
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fp = fopen( name2, "wb+" );
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if( fp != NULL ) {
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fp->_flag |= _TMPFIL;
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_FP_TMPFCHAR(fp) = suffix2;
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__set_errno( old_errno );
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return( fp );
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}
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// We couldn't open it, probably because we have run out of handles.
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// Remove the renamed file.
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our_errno = errno;
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remove( name2 );
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__set_errno( our_errno );
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return( NULL );
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}
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// The rename didn't work or we couldn't open the renamed file.
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// One of two possibilities:
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// (1) The "to" name already exists.
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// (2) Another process renamed it away from us.
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// Check for case (2).
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// Quit if "from" file is gone and start over.
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if( access( name1, F_OK ) != 0 ) break;
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// Must be case (1). Try another "to" name.
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++suffix2;
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if( suffix2 == 0 ) {
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suffix2 = _TMP_INIT_CHAR;
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}
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_RWD_tmpfnext = suffix2; // update for all processes
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}
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}
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}
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/* tmpfil() pulls in a lot of overhead that many programs do not need. But */
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/* since temp files are removed on program shutdown, the code to remove */
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/* them would always get linked in even if the program never heard of temp */
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/* files. Since we know that temporary files can _only_ be created through */
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/* tmpfile(), we can have a dummy __RmTmpFile() by default and use the */
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/* real thing only if tmpfil() was called. */
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void __Init_Tmpfl( void )
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{
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// Just assign the function address
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__RmTmpFileFn = __RmTmpFile;
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}
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AXI( __Init_Tmpfl, INIT_PRIORITY_RUNTIME )
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