barrier/lib/arch/CArchTimeWindows.cpp

/*
 * synergy -- mouse and keyboard sharing utility
 * Copyright (C) 2002 Chris Schoeneman, Nick Bolton, Sorin Sbarnea
 * 
 * This package is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * found in the file COPYING that should have accompanied this file.
 * 
 * This package is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

// avoid getting a lot a crap from mmsystem.h that we don't need
#define MMNODRV         // Installable driver support
#define MMNOSOUND       // Sound support
#define MMNOWAVE        // Waveform support
#define MMNOMIDI        // MIDI support
#define MMNOAUX         // Auxiliary audio support
#define MMNOMIXER       // Mixer support
#define MMNOJOY         // Joystick support
#define MMNOMCI         // MCI support
#define MMNOMMIO        // Multimedia file I/O support
#define MMNOMMSYSTEM    // General MMSYSTEM functions

#define WIN32_LEAN_AND_MEAN

#include "CArchTimeWindows.h"
#include <windows.h>
#include <mmsystem.h>

typedef WINMMAPI DWORD (WINAPI *PTimeGetTime)(void);

static double			s_freq       = 0.0;
static HINSTANCE		s_mmInstance = NULL;
static PTimeGetTime		s_tgt        = NULL;


//
// CArchTimeWindows
//

CArchTimeWindows::CArchTimeWindows()
{
	assert(s_freq == 0.0 || s_mmInstance == NULL);

	LARGE_INTEGER freq;
	if (QueryPerformanceFrequency(&freq) && freq.QuadPart != 0) {
		s_freq = 1.0 / static_cast<double>(freq.QuadPart);
	}
	else {
		// load winmm.dll and get timeGetTime
		s_mmInstance = LoadLibrary("winmm");
		if (s_mmInstance != NULL) {
			s_tgt = (PTimeGetTime)GetProcAddress(s_mmInstance, "timeGetTime");
		}
	}
}

CArchTimeWindows::~CArchTimeWindows()
{
	s_freq = 0.0;
	if (s_mmInstance == NULL) {
		FreeLibrary(reinterpret_cast<HMODULE>(s_mmInstance));
		s_tgt        = NULL;
		s_mmInstance = NULL;
	}
}

double
CArchTimeWindows::time()
{
	// get time.  we try three ways, in order of descending precision
	if (s_freq != 0.0) {
		LARGE_INTEGER c;
		QueryPerformanceCounter(&c);
		return s_freq * static_cast<double>(c.QuadPart);
	}
	else if (s_tgt != NULL) {
		return 0.001 * static_cast<double>(s_tgt());
	}
	else {
		return 0.001 * static_cast<double>(GetTickCount());
	}
}