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/*
* Worldvisions Weaver Software:
* Copyright (C) 1997-2002 Net Integration Technologies, Inc.
*
* A simple lockfile class using WvStreams.
*/
#include "wvlockfile.h"
#include "strutils.h"
#include <signal.h>
WvLockFile::WvLockFile(WvStringParm _lockname)
: lockname(_lockname)
{
// nothing special
}
bool WvLockFile::isok()
{
pid_t pid = readpid();
return !pid || pid == getpid();
}
bool WvLockFile::lock()
{
if (!isok())
return false;
WvFile lock(lockname, O_WRONLY|O_CREAT|O_EXCL);
if (!lock.isok())
return false;
lock.print("%s\n", getpid());
return true;
}
bool WvLockFile::unlock()
{
if (!isok())
return false;
unlink(lockname);
return readpid() == 0;
}
pid_t WvLockFile::readpid()
{
char *line;
pid_t pid = 0;
WvString lockdir(getdirname(lockname));
if (access(lockdir, W_OK) < 0
|| (!access(lockname, F_OK) && access(lockname, R_OK) < 0))
return -1; // won't be able to create a lock
else
{
WvFile lock(lockname, O_RDONLY);
line = lock.blocking_getline(-1);
if (line)
{
pid = atoi(line);
if (pid != -1 && kill(pid, 0) < 0 && errno == ESRCH) // no such process
{
// previous lock owner is dead; clean it up.
::unlink(lockname);
return 0;
}
}
else
{
// blank lock file; clean it up.
::unlink(lockname);
return 0;
}
}
return pid;
}
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