ultimatepp/bazaar/Signals/Signals.cpp

#include "Signals.h"


////////////////////////////////////////////////////////////////////////////////////
// global Signals object
static One<TSignals> _Signals;

////////////////////////////////////////////////////////////////////////////////////
// global signal handler
void _SignalHandler(int sig, siginfo_t *info, void *v)
{
	Signals().Dispatch(sig, info, v);

} // END ::_SignalHandler()

////////////////////////////////////////////////////////////////////////////////////
// constructor
TSignals::TSignals()
{
	// not(yet) stored instance on file
	StoredInstance = false;

	// we check for a dangling instance, i.e. a lock file without the
	// corresponding process (can happen if you kill the application)
	String LockName = CreateLockName();
	if (!FileExists(LockName))
		return;
	
	// lock exists, we look for corresponding process in proc table
	int pid = 0;
	pid = atoi(FileIn(LockName).GetLine());
	
	// we checks wether the process exists and is accessible
	String CmdLineFile = "/proc/" + AsString(pid) + "/cmdline";
	if(pid == 0 || !FileExists(CmdLineFile))
	{
		// process don't exists or it's not accessible by us;
		// it was a stale lock, just remove it
		FileDelete(LockName);
		return;
	}
	
	// we read the process command line, and look for app name inside
	// FileIn don't work for this file... maybe because is not a normal file
	// we MUST use unix file stuffs
	int f = open(CmdLineFile, O_RDONLY);
	if(f == -1)
	{
		// we haven't access to process data, so it's not
		// the right one. The lock file is stale
		FileDelete(LockName);
		return;
	}
	
	// we gets the file content char by char as (it seems)
	// this file doesn't support seek
	char c;
	String AppName;
	while(read(f, &c, 1) == 1)
		AppName += c;
	close(f);
	AppName = GetFileTitle(AppName);
	if(AppName != GetExeTitle())
		// process app name is different from this one, or we haven't
		// access to it, so we must consider the lock as stale
		FileDelete(LockName);

} // END Constructor TSignals

////////////////////////////////////////////////////////////////////////////////////
// destructor
TSignals::~TSignals()
{
	// removes all handlers
	for (int i = 0; i < CallbackMap.GetCount(); i++)
	{
		int sig = CallbackMap.GetKey(i);

		struct sigaction act;
		act.sa_flags = SA_SIGINFO;
		act.sa_sigaction = (void(*)(int, siginfo_t *, void *))SIG_DFL;
		sigaction(sig, &act, (struct sigaction *)NULL);
	}

	// empties the map
	CallbackMap.Clear();

	// if process had stored instance on file, removes it
	if (StoredInstance)
		FileDelete(CreateLockName());

	StoredInstance = false;

} // END Destructor class TSignals

////////////////////////////////////////////////////////////////////////////////////
// dispatch signals
void TSignals::Dispatch(int sig, siginfo_t *info, void *v)
{
	// gets callback, returns if none found (should not happen)
	int i = CallbackMap.Find(sig);

	if (i < 0)
		return;

	// posts the callback to event loop
	Ctrl::GetActiveWindow()->PostCallback(CallbackMap[i]);

} // END TSignals::Dispatcher()

////////////////////////////////////////////////////////////////////////////////////
// creates lock file name based on user name, app name and display
String TSignals::CreateLockName(void)
{
	if (LockName == "")
		LockName = "/tmp/" + Environment().Get("USER") + "_" + GetExeTitle() + "_" + Environment().Get("DISPLAY") + ".lck";

	return LockName;

} // END TSignals::CreateLockName()

////////////////////////////////////////////////////////////////////////////////////
// add a signal handler
bool TSignals::Handle(int sig, Callback const &cb)
{
	// adds/replaces the handler
	int i;

	if ( (i = CallbackMap.Find(sig)) >= 0)
		CallbackMap[sig] = cb;
	else
		CallbackMap.Add(sig, cb);

	// if needed, hooks the signal to global signal handler
	if (i < 0)
	{

		struct sigaction act;
		act.sa_flags = SA_SIGINFO;
		act.sa_sigaction = _SignalHandler;

		if (sigaction(sig, &act, (struct sigaction *)NULL))
		{
			// an error occurred, just remove the handler
			// from map and return false
			CallbackMap.RemoveKey(sig);
			return false;
		}

		else
			return true;
	}

	return true;

} // END TSignals::Handle()

////////////////////////////////////////////////////////////////////////////////////
// removes a signal handler
bool TSignals::Unhandle(int sig)
{
	// locates signal in map, error if not found
	int i = CallbackMap.Find(sig);

	if (i < 0)
		return false;

	// unhooks signal from global signal handler

	struct sigaction act;

	act.sa_flags = SA_SIGINFO;

	act.sa_sigaction = (void(*)(int, siginfo_t *, void *))SIG_DFL;

	sigaction(sig, &act, (struct sigaction *)NULL);

	// removes signal from map
	CallbackMap.Remove(i);

	return true;

} // END TSignals::Unhandle()

////////////////////////////////////////////////////////////////////////////////////
// stores process info on filesystem
// allowing other process to communicate with it
bool TSignals::StoreInstance(void)
{
	// if already stored, does nothing
	if (StoredInstance)
		return true;

	// first, checks if another instance is running
	// if yes returns false (can't store more than 1 instance)
	if (IsOtherInstanceRunning())
		return false;

	// creates lock file
	FileOut f(CreateLockName());

	// stores current process id on lock file
	f.PutLine(AsString(getpid()));

	f.Close();

	// marks instance as already stored
	StoredInstance = true;

	// all ok
	return true;

} // END TSignals::StoreInstance()

////////////////////////////////////////////////////////////////////////////////////
// checks whether another instance of this process is running
bool TSignals::IsOtherInstanceRunning(void)
{
	// if we stored THIS instance, no other is running
	if (StoredInstance)
		return false;

	// otherwise, check the lock file
	if (FileExists(CreateLockName()))
		return true;

	return false;

} // END TSignals::IsOtherInstanceRunning()

////////////////////////////////////////////////////////////////////////////////////
// sends a signal to another process
bool TSignals::Send(int sig, int procId)
{
	return (kill(procId, sig) == 0);

} // END TSignals::Send()

////////////////////////////////////////////////////////////////////////////////////
// sends a signal to another running instance of this app
bool TSignals::Send(int sig)
{
	// if no other instance running, returns false
	if (!IsOtherInstanceRunning())
		return false;

	// gets pid of other instance
	FileIn f(CreateLockName());

	int pid = atoi(f.GetLine());

	f.Close();

	// sends the signal to process
	return Send(sig, pid);

} // END TSignals::Send()

////////////////////////////////////////////////////////////////////////////////////
// Global signals access
TSignals &Signals(void)
{
	if (_Signals.IsEmpty())
		_Signals = new TSignals;

	return *_Signals;

} // END Signals()