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/* sane - Scanner Access Now Easy.
Copyright (C) 2005 Gerhard Jaeger
This file is part of the SANE package.
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA.
As a special exception, the authors of SANE give permission for
additional uses of the libraries contained in this release of SANE.
The exception is that, if you link a SANE library with other files
to produce an executable, this does not by itself cause the
resulting executable to be covered by the GNU General Public
License. Your use of that executable is in no way restricted on
account of linking the SANE library code into it.
This exception does not, however, invalidate any other reasons why
the executable file might be covered by the GNU General Public
License.
If you submit changes to SANE to the maintainers to be included in
a subsequent release, you agree by submitting the changes that
those changes may be distributed with this exception intact.
If you write modifications of your own for SANE, it is your choice
whether to permit this exception to apply to your modifications.
If you do not wish that, delete this exception notice.
*/
#include "../include/sane/config.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <signal.h>
#include <limits.h>
#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif
#include <fcntl.h>
#define BACKEND_NAME sanei_access /**< name of this module for debugging */
#include "../include/sane/sane.h"
#include "../include/sane/sanei_debug.h"
#include "../include/sane/sanei_access.h"
#ifndef PATH_MAX
# define PATH_MAX 1024
#endif
#if defined(_WIN32) || defined(HAVE_OS2_H)
# define PATH_SEP '\\'
#else
# define PATH_SEP '/'
#endif
#define REPLACEMENT_CHAR '_'
#define PID_BUFSIZE 50
#define PROCESS_SELF 0
#define PROCESS_DEAD -1
#define PROCESS_OTHER 1
#ifdef ENABLE_LOCKING
/** get the status/owner of a lock file
*
* The function tries to open an existing lockfile. On success, it reads out
* the pid which is stored inside and tries to find out more about the status
* of the process with the corresponding PID.
*
* @param fn - the complete filename of the lockfile to check
* @return
* - PROCESS_SELF - the calling process is owner of the lockfile
* - PROCESS_DEAD - the process who created the lockfile is already dead
* - PROCESS_OTHER - the process who created the lockfile is still alive
*/
static int
get_lock_status( char *fn )
{
char pid_buf[PID_BUFSIZE];
int fd, status;
pid_t pid;
fd = open( fn, O_RDONLY );
if( fd < 0 ) {
DBG( 2, "does_process_exist: open >%s< failed: %s\n",
fn, strerror(errno));
return PROCESS_OTHER;
}
read( fd, pid_buf, (PID_BUFSIZE-1));
pid_buf[PID_BUFSIZE-1] = '\0';
close( fd );
pid_buf[24] = '\0';
pid = strtol( pid_buf, NULL, 10 );
DBG( 2, "does_process_exist: PID %i\n", pid );
status = kill( pid, 0 );
if( status == -1 ) {
if( errno == ESRCH ) {
DBG( 2, "does_process_exist: process %i does not exist!\n", pid );
return PROCESS_DEAD;
}
DBG( 1, "does_process_exist: kill failed: %s\n", strerror(errno));
} else {
DBG( 2, "does_process_exist: process %i does exist!\n", pid );
if( pid == getpid()){
DBG( 2, "does_process_exist: it's me!!!\n" );
return PROCESS_SELF;
}
}
return PROCESS_OTHER;
}
static void
create_lock_filename( char *fn, const char *devname )
{
char *p;
strcpy( fn, STRINGIFY(PATH_SANE_LOCK_DIR)"/LCK.." );
p = &fn[strlen(fn)];
strcat( fn, devname );
while( *p != '\0' ) {
if( *p == PATH_SEP )
*p = REPLACEMENT_CHAR;
p++;
}
DBG( 2, "sanei_access: lockfile name >%s<\n", fn );
}
#endif
void
sanei_access_init( const char *backend )
{
DBG_INIT();
DBG( 2, "sanei_access_init: >%s<\n", backend);
}
SANE_Status
sanei_access_lock( const char *devicename, SANE_Word timeout )
{
#ifdef ENABLE_LOCKING
char fn[PATH_MAX];
char pid_buf[PID_BUFSIZE];
int fd, to, i;
#endif
DBG( 2, "sanei_access_lock: devname >%s<, timeout: %u\n",
devicename, timeout );
#ifndef ENABLE_LOCKING
return SANE_STATUS_GOOD;
#else
to = timeout;
if (to <= 0)
to = 1;
create_lock_filename( fn, devicename );
for (i = 0; i < to; i++) {
fd = open( fn, O_CREAT | O_EXCL | O_WRONLY, 0644 );
if (fd < 0) {
if (errno == EEXIST) {
switch( get_lock_status( fn )) {
case PROCESS_DEAD:
DBG( 2, "sanei_access_lock: "
"deleting old lock file, retrying...\n" );
unlink( fn );
continue;
break;
case PROCESS_SELF:
DBG( 2, "sanei_access_lock: success\n" );
return SANE_STATUS_GOOD;
break;
default:
break;
}
DBG( 2, "sanei_access_lock: lock exists, waiting...\n" );
sleep(1);
} else {
DBG( 1, "sanei_access_lock: open >%s< failed: %s\n",
fn, strerror(errno));
return SANE_STATUS_ACCESS_DENIED;
}
} else {
DBG( 2, "sanei_access_lock: success\n" );
sprintf( pid_buf, "% 11i sane\n", getpid());
write(fd, pid_buf, strlen(pid_buf));
close( fd );
return SANE_STATUS_GOOD;
}
}
DBG( 1, "sanei_access_lock: timeout!\n");
return SANE_STATUS_ACCESS_DENIED;
#endif
}
SANE_Status
sanei_access_unlock( const char *devicename )
{
#ifdef ENABLE_LOCKING
char fn[PATH_MAX];
#endif
DBG( 2, "sanei_access_unlock: devname >%s<\n", devicename );
#ifdef ENABLE_LOCKING
create_lock_filename( fn, devicename );
unlink( fn );
#endif
return SANE_STATUS_GOOD;
}
/* END sanei_access.c .......................................................*/
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