libgfaservices/common/singleton.c

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/file.h>
#include <unistd.h>
#include "singleton.h"

static int g_fdPid = -1;


int AcquirePidFileLock(const char *pszProcessName, const char *pszPidFile)
{
	int nRet, nRead, fdPid;

	if(g_fdPid >= 0)
	{
		printf("\n%s: Pidfile lock already acquired!\n\n", pszProcessName);
		return 1;
	}

	fdPid = open(pszPidFile, O_CREAT | O_RDWR, 0666);

	if(fdPid < 0)
	{
		printf("Failed to open PID file: %s\n", pszPidFile);
		printf("error: %d\n", errno);
		return 0;
	}

	if((nRet = flock(fdPid, LOCK_EX | LOCK_NB)))
	{
		if(errno == EWOULDBLOCK)
		{
			char szPid[32];
			if((nRead = (int)read(fdPid, szPid, sizeof(szPid) - 1)) > 0)
			{
				szPid[nRead] = '\0';
				printf("\n%s: another instance is already running -> PID: %s\n\n", pszProcessName, szPid);
			}
			else
				printf("\n%s: another instance is already running!\n\n", pszProcessName);
			close(fdPid);
			return 0;
		}
		else
		{
			printf("flock failed with code %d\n", errno);
			close(fdPid);
			return 0;
		}
	}
	else
	{
		char szPid[32];
		int nLen = sprintf(szPid, "%d", getpid());
		write(fdPid, szPid, (size_t)nLen);
		g_fdPid = fdPid;
	}

	return 1;
}

void ReleasePidFileLock(void)
{
	if(g_fdPid >= 0)
	{
		int fdPid = g_fdPid;
		g_fdPid = -1;
		flock(fdPid, LOCK_UN);
		close(fdPid);
	}
}

int GetPidFilePID(const char *pszPidFile)
{
	int nRet = -1;
	char szPid[32];
	ssize_t nRead;
	int fdPid = open(pszPidFile, O_RDONLY, 0666);

	if(fdPid >= 0)
	{
		if((nRead = read(fdPid, szPid, sizeof(szPid) - 1)) > 0)
		{
			szPid[nRead] = '\0';
			nRet = atoi(szPid);
		}
		close(fdPid);
	}

	return nRet;
}