kopia lustrzana https://gitlab.com/sane-project/backends
Initial checkin.
Gerhard Jaeger
rodzic
ada4c07892
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d498239305
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/* sane - Scanner Access Now Easy.
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Copyright (C) 2005 Gerhard Jaeger <gerhard@gjaeger.de>
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This file is part of the SANE package.
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place - Suite 330, Boston,
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MA 02111-1307, USA.
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As a special exception, the authors of SANE give permission for
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additional uses of the libraries contained in this release of SANE.
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The exception is that, if you link a SANE library with other files
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to produce an executable, this does not by itself cause the
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resulting executable to be covered by the GNU General Public
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License. Your use of that executable is in no way restricted on
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account of linking the SANE library code into it.
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This exception does not, however, invalidate any other reasons why
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the executable file might be covered by the GNU General Public
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License.
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If you submit changes to SANE to the maintainers to be included in
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a subsequent release, you agree by submitting the changes that
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those changes may be distributed with this exception intact.
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If you write modifications of your own for SANE, it is your choice
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whether to permit this exception to apply to your modifications.
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If you do not wish that, delete this exception notice.
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*/
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/** @file sanei_access.h
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* Interface file for the sanei_access functions.
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*
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* The idea is to provide some simple locking/unlocking mecanism, which
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* can be used to protect device access from more than one frontend
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* simultaneously.
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*/
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#ifndef sanei_access_h
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#define sanei_access_h
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#include "../include/sane/config.h"
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#include "../include/sane/sane.h"
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/** Initialize sanei_access.
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*
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* This function must be called before any other sanei_access function.
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*
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* @param backend - backend name, who uses this lib
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*/
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extern void sanei_access_init( const char * backend );
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/** Set a lock.
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*
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* The function tries to open/create exclusively a lock file in
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* $PATH_SANE_LOCK_DIR/lock/sane.
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* If the file could be created successfully, the function fills in the
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* process ID.
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* The complete filename of the lockfile is created as follows:
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* $PATH_SANE_LOCK_DIR/lock/LCK..<devicename>
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* If the lock could not be set, the function tries it until the timeout
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* period has been elapsed.
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*
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* @param devicename - unique part of the lockfile name
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* @param timeout - time in seconds to try to set a lock
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* @return
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* - SANE_STATUS_GOOD - if the lock has been successfully set
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* - SANE_STATUS_ACCESS_DENIED - the lock could not set
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*/
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extern SANE_Status sanei_access_lock( const char * devicename, SANE_Word timeout );
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/** Unlock a previously set lock.
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*
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* The function tries to unlock a previously created lock. The lockfile will be
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* closed and removed.
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*
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* @param devicename - part of the lockfile name, use for sanei_acess_lock()
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* @return
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* - SANE_STATUS_GOOD - currently the one and only return value
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*/
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extern SANE_Status sanei_access_unlock( const char * devicename );
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#endif /* sanei_access_h */
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@ -0,0 +1,209 @@
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/* sane - Scanner Access Now Easy.
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Copyright (C) 2005 Gerhard Jaeger
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This file is part of the SANE package.
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place - Suite 330, Boston,
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MA 02111-1307, USA.
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As a special exception, the authors of SANE give permission for
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additional uses of the libraries contained in this release of SANE.
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The exception is that, if you link a SANE library with other files
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to produce an executable, this does not by itself cause the
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resulting executable to be covered by the GNU General Public
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License. Your use of that executable is in no way restricted on
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account of linking the SANE library code into it.
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This exception does not, however, invalidate any other reasons why
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the executable file might be covered by the GNU General Public
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License.
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If you submit changes to SANE to the maintainers to be included in
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a subsequent release, you agree by submitting the changes that
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those changes may be distributed with this exception intact.
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If you write modifications of your own for SANE, it is your choice
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whether to permit this exception to apply to your modifications.
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If you do not wish that, delete this exception notice.
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*/
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#include "../include/sane/config.h"
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <signal.h>
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#include <limits.h>
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#ifdef HAVE_UNISTD_H
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# include <unistd.h>
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#endif
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#include <fcntl.h>
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#define BACKEND_NAME sanei_access /**< name of this module for debugging */
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#include "../include/sane/sane.h"
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#include "../include/sane/sanei_debug.h"
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#include "../include/sane/sanei_access.h"
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#define PID_BUFSIZE 50
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#define PROCESS_SELF 0
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#define PROCESS_DEAD -1
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#define PROCESS_OTHER 1
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#ifdef ENABLE_LOCKING
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/** get the status/owner of a lock file
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*
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* The function tries to open an existing lockfile. On success, it reads out
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* the pid which is stored inside and tries to find out more about the status
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* of the process with the corresponding PID.
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*
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* @param fn - the complete filename of the lockfile to check
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* @return
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* - PROCESS_SELF - the calling process is owner of the lockfile
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* - PROCESS_DEAD - the process who created the lockfile is already dead
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* - PROCESS_OTHER - the process who created the lockfile is still alive
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*/
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static int
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get_lock_status( char *fn )
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{
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char pid_buf[PID_BUFSIZE];
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int fd, status;
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pid_t pid;
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fd = open( fn, O_RDONLY );
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if( fd < 0 ) {
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DBG( 2, "does_process_exist: open >%s< failed: %s\n",
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fn, strerror(errno));
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return PROCESS_OTHER;
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}
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read( fd, pid_buf, (PID_BUFSIZE-1));
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pid_buf[PID_BUFSIZE-1] = '\0';
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close( fd );
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pid_buf[24] = '\0';
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pid = strtol( pid_buf, NULL, 10 );
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DBG( 2, "does_process_exist: PID %i\n", pid );
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status = kill( pid, 0 );
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if( status == -1 ) {
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if( errno == ESRCH ) {
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DBG( 2, "does_process_exist: process %i does not exist!\n", pid );
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return PROCESS_DEAD;
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}
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DBG( 1, "does_process_exist: kill failed: %s\n", strerror(errno));
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} else {
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DBG( 2, "does_process_exist: process %i does exist!\n", pid );
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if( pid == getpid()){
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DBG( 2, "does_process_exist: it's me!!!\n" );
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return PROCESS_SELF;
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}
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}
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return PROCESS_OTHER;
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}
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static void
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create_lock_filename( char *fn, const char *devname )
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{
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strcpy( fn, STRINGIFY(PATH_SANE_LOCK_DIR)"/lock/sane/LCK.." );
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strcat( fn, devname );
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}
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#endif
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void
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sanei_access_init( const char *backend )
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{
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DBG_INIT();
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DBG( 2, "sanei_access_init: >%s<\n", backend);
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}
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SANE_Status
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sanei_access_lock( const char *devicename, SANE_Word timeout )
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{
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#ifdef ENABLE_LOCKING
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char fn[PATH_MAX];
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char pid_buf[PID_BUFSIZE];
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int fd, to, i;
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#endif
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DBG( 2, "sanei_access_lock: devname >%s<, timeout: %u\n",
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devicename, timeout );
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#ifndef ENABLE_LOCKING
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return SANE_STATUS_GOOD;
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#else
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to = timeout;
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if (to <= 0)
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to = 1;
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create_lock_filename( fn, devicename );
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for (i = 0; i < to; i++) {
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fd = open( fn, O_CREAT | O_EXCL | O_WRONLY, 0644 );
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if (fd < 0) {
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if (errno == EEXIST) {
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switch( get_lock_status( fn )) {
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case PROCESS_DEAD:
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DBG( 2, "sanei_access_lock: "
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"deleting old lock file, retrying...\n" );
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unlink( fn );
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continue;
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break;
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case PROCESS_SELF:
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DBG( 2, "sanei_access_lock: success\n" );
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return SANE_STATUS_GOOD;
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break;
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default:
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break;
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}
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DBG( 2, "sanei_access_lock: lock exists, waiting...\n" );
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sleep(1);
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} else {
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DBG( 1, "sanei_access_lock: open >%s< failed: %s\n",
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fn, strerror(errno));
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return SANE_STATUS_ACCESS_DENIED;
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}
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} else {
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DBG( 2, "sanei_access_lock: success\n" );
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sprintf( pid_buf, "% 11i sane\n", getpid());
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write(fd, pid_buf, strlen(pid_buf));
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close( fd );
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return SANE_STATUS_GOOD;
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}
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}
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DBG( 1, "sanei_access_lock: timeout!\n");
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return SANE_STATUS_ACCESS_DENIED;
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#endif
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}
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SANE_Status
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sanei_access_unlock( const char *devicename )
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{
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#ifdef ENABLE_LOCKING
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char fn[PATH_MAX];
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#endif
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DBG( 2, "sanei_access_unlock: devname >%s<\n", devicename );
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#ifdef ENABLE_LOCKING
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create_lock_filename( fn, devicename );
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unlink( fn );
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#endif
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return SANE_STATUS_GOOD;
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}
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/* END sanei_access.c .......................................................*/
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