filelocker.cpp

#include "filelocker.h"
#include "private/filelocker_impl.h"

#include <sys/stat.h>

#ifndef _MSC_VER
#include <unistd.h>
#include <sys/file.h>
#define _stat stat
#endif

namespace {
	static const int RETRY_INTERVAL_MS = 100;
} // namespace

FileLocker::Impl::Impl(const std::string& filename) :
#ifdef _MSC_VER
	m_handle {NULL},
#else
	m_fd {0},
#endif
	m_filename (filename),
	m_isLocked {false}
{}

FileLocker::FileLocker(const std::string& filename) :
	impl {new Impl {filename}}
{}

FileLocker::~FileLocker()
{
	unlock();
	delete impl;
}

bool FileLocker::lockFileExists() const
{
	struct _stat fileStat;
	int result;

	result = _stat(impl->m_filename.c_str(), &fileStat);
	return result == 0;
}

bool FileLocker::isLocked() const
{
	return impl->m_isLocked;
}

bool FileLocker::lock()
{
	if (impl->m_isLocked) {
		return true;
	}

#ifdef _MSC_VER
	// implementation for windows

	while (1) {
		std::string data = "lockfile";

		SECURITY_ATTRIBUTES securityAtts = { sizeof(SECURITY_ATTRIBUTES), NULL, FALSE };
		impl->m_handle = ::CreateFileA(impl->m_filename.c_str(), GENERIC_WRITE,
																	 FILE_SHARE_READ, &securityAtts, CREATE_NEW, FILE_ATTRIBUTE_NORMAL, NULL);
		if (impl->m_handle == INVALID_HANDLE_VALUE) {
			goto RETRY;
		}
		DWORD bytesWritten = 0;
		if (! WriteFile(impl->m_handle, data.c_str(), static_cast<DWORD> (data.size()), &bytesWritten, NULL) ||
				! FlushFileBuffers(impl->m_handle))
		{
			goto RETRY;
		}

		// success
		break;

RETRY:
		Sleep(RETRY_INTERVAL_MS);
	}

	impl->m_isLocked = true;
	return true;

#else
	// implementation for linux
	impl->m_fd = open(impl->m_filename.c_str(), O_WRONLY | O_CREAT, S_IRWXU);
	if (impl->m_fd == -1) {
		return false;
	}

	int result = flock(impl->m_fd, LOCK_EX);
	if (result != 0){
		return false;
	}
	impl->m_isLocked = true;
	return true;

#endif
}

void FileLocker::unlock()
{
	if (! impl->m_isLocked) {
		return;
	}

#ifdef _MSC_VER
	// implementation for windows

	CloseHandle(impl->m_handle);
	impl->m_handle = NULL;

#else
	// implementation for linux

	close(impl->m_fd);
	impl->m_fd = -1;

#endif
	remove(impl->m_filename.c_str());

	impl->m_isLocked = false;
}