// UpTime.cpp : Defines the entry point for the console application.
#include "stdafx.h"

/* define some C99 types for windows */
typedef unsigned __int32 uint32_t;
typedef unsigned __int64 uint64_t;
typedef unsigned __int8 uint8_t;
typedef __int64 int64_t;

/*static*/ char msgstr[21];

#define KEY_SYSTEM	L"2"
#define IDX_UPTIME	674

static void get_boottime(ULARGE_INTEGER *boottime, ULARGE_INTEGER *nowtime) {
	BYTE pbuf[4096];
	PPERF_DATA_BLOCK ppdb = (PPERF_DATA_BLOCK) pbuf;
	DWORD psz = sizeof(pbuf);
	PPERF_OBJECT_TYPE ppot;
	PPERF_COUNTER_DEFINITION ppcd;
	PPERF_COUNTER_BLOCK ppcb;
	DWORD i;

	memset(pbuf, 0, psz);
	nowtime->QuadPart = boottime->QuadPart = 0;	/* 0 = error */

	/* get current 64-bit boottime in 100ns units */
	RegQueryValueExW(HKEY_PERFORMANCE_DATA, KEY_SYSTEM, NULL, NULL, pbuf, &psz);
	RegCloseKey(HKEY_PERFORMANCE_DATA);

	if(memcmp(pbuf, L"PERF", 8)) {
		/* PERF_DATA_BLOCK signature not present */
		return;
	}

	/* parse returned performance data */
	ppot = (PPERF_OBJECT_TYPE) &pbuf[ppdb->HeaderLength];
	ppcd = (PPERF_COUNTER_DEFINITION) &pbuf[ppdb->HeaderLength + ppot->HeaderLength];
	ppcb = (PPERF_COUNTER_BLOCK) &(((uint8_t *)ppot)[ppot->DefinitionLength]);
	nowtime->QuadPart = ppdb->PerfTime100nSec.QuadPart;

	/* get uptime and processor queue length */
	for (i = 0; i < ppot->NumCounters; i++) {
		if (ppcd->CounterNameTitleIndex == IDX_UPTIME) {
			boottime->QuadPart = (int64_t) *(uint64_t *) &(((uint8_t *)ppcb)[ppcd->CounterOffset]);
		}
		ppcd++;
	}
}

int main() {
	ULARGE_INTEGER bt, nt, ut;
	uint32_t days;
	SYSTEMTIME ust;

	get_boottime(&bt, &nt);
	ut.QuadPart = nt.QuadPart - bt.QuadPart;
	FileTimeToSystemTime((FILETIME *) &ut, &ust);

	ut.QuadPart /= 864000000000;

	days = (uint32_t) ut.QuadPart;
	if(days > 1) {
		sprintf(msgstr, "\r\n   %d days, %02d:%02d:%02d\r\n", days, ust.wHour, ust.wMinute, ust.wSecond);
	}else if(days == 1) {
		sprintf(msgstr, "\r\n   1 day, %02d:%02d:%02d\r\n", ust.wHour, ust.wMinute, ust.wSecond);
	}else{
		sprintf(msgstr, "\r\n   0 days, %02d:%02d:%02d\r\n", ust.wHour, ust.wMinute, ust.wSecond);
	}
	printf(msgstr);
 return 0;
}