PidFile.cpp

/*
** libutil++
** $Id: PidFile.cpp 1653 2016-02-28 19:54:59Z sella $
** Copyright (c) 2011-2016 Digital Genesis, LLC. All Rights Reserved.
** Released under the LGPL Version 2.1 License.
** http://www.digitalgenesis.com
*/

static const char rcsid[] __attribute__((used)) = "$Id: PidFile.cpp 1653 2016-02-28 19:54:59Z sella $";

#include "PidFile.h"

#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <signal.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/file.h>

using namespace sella::util;

PidFile::PidFile(const std::string &file, uid_t uid, gid_t gid) throw () : file(file), uid(uid), gid(gid) {
        assert(!file.empty());
}

PidFile::PidFile(const PidFile &other) : file(other.file), uid(other.uid), gid(other.gid) {
}

PidFile::~PidFile() {
}

PidFile& PidFile::operator=(const PidFile &other) throw () {
        if (this != &other) {
                this->file = other.file;
                this->uid = other.uid;
                this->gid = other.gid;
        }

        return *this;
}

const std::string& PidFile::get(void) const throw () {
        return file;
}

int PidFile::read(void) const throw (PidFileException) {
        int pid;
        FILE *h;

        if ((h = fopen(file.c_str(), "r")) == NULL) {
                THROW(PidFileException, "Failed to open file '%s'", file.c_str());
        }

        if (fscanf(h, "%d", &pid) == EOF) {
                THROW(PidFileException, "Failed to read file '%s'", file.c_str());
        }

        fclose(h);

        return pid;
}

int PidFile::write(void) const throw (PidFileException) {
        int fd, pid;
        FILE *h;

        if ((fd = open(file.c_str(), O_RDWR|O_CREAT, 0644)) == -1 || (h = fdopen(fd, "r+")) == NULL) {
                THROW(PidFileException, "Failed to open or create file '%s'", file.c_str());
        }

        if (flock(fd, LOCK_EX|LOCK_NB) == -1) {
                if (fscanf(h, "%d", &pid) == EOF) {
                        pid = -1;
                }
                fclose(h);

                THROW(PidFileException, "Lock on file '%s' is already held by pid %d", file.c_str(), pid);
        }

        pid = getpid();

        if (fprintf(h, "%d\n", pid) < 1) {
                close(fd);

                THROW2(PidFileException, "Failed to write pid %d to file '%s'", pid, file.c_str());
        }

        fflush(h);

        if (flock(fd, LOCK_UN) == -1) {
                THROW2(PidFileException, "Failed to unlock file '%s'", file.c_str());
        }

        if (uid != (__UID_T_TYPE) -1 || gid != (__GID_T_TYPE) -1) {
                if (fchown(fd, uid, gid) != 0) {
                        THROW2(PidFileException, "Failed to change owner of file '%s' to %d:%d", file.c_str(), uid, gid);
                }
        }

        close(fd);

        return pid;
}

void PidFile::remove(void) const throw (PidFileException) {
        if (unlink(file.c_str()) != 0) {
                THROW2(PidFileException, "Failed to remove file '%s'", file.c_str());
        }
}

bool PidFile::isOwner(void) const throw () {
        int pid;
        
        try {
                pid = read();
        } catch (PidFileException) {
                return false;
        }

        return (pid == getpid());
}

bool PidFile::isLive(void) const throw () {
        int pid;
        
        try {
                pid = read();
        } catch (PidFileException) {
                return false;
        }

        if (pid == getpid()) {
                return true;
        }

        /* Doesn't actually send a signal, but checks for existance. */
        if (pid == 0 || (kill(pid, 0) != 0 && errno == ESRCH)) {
                return false;
        }

        return true;
}

bool PidFile::isFile(void) const throw () {
        FILE *h;

        if ((h = fopen(file.c_str(), "r")) == NULL) {
                return false;
        }

        fclose(h);

        return true;
}

const PidFile::shared PidFile::shared_ptr(const std::string &file, uid_t uid, gid_t gid) throw () {
        return std::make_shared<PidFile>(file, uid, gid);
}

/*
** vim: noet ts=3 sw=3
*/