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