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Filename : instr_time.h
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/*-------------------------------------------------------------------------
 *
 * instr_time.h
 *	  portable high-precision interval timing
 *
 * This file provides an abstraction layer to hide portability issues in
 * interval timing.  On Unix we use gettimeofday(), but on Windows that
 * gives a low-precision result so we must use QueryPerformanceCounter()
 * instead.  These macros also give some breathing room to use other
 * high-precision-timing APIs on yet other platforms.
 *
 * The basic data type is instr_time, which all callers should treat as an
 * opaque typedef.  instr_time can store either an absolute time (of
 * unspecified reference time) or an interval.  The operations provided
 * for it are:
 *
 * INSTR_TIME_IS_ZERO(t)			is t equal to zero?
 *
 * INSTR_TIME_SET_ZERO(t)			set t to zero (memset is acceptable too)
 *
 * INSTR_TIME_SET_CURRENT(t)		set t to current time
 *
 * INSTR_TIME_ADD(x, y)				x += y
 *
 * INSTR_TIME_SUBTRACT(x, y)		x -= y
 *
 * INSTR_TIME_ACCUM_DIFF(x, y, z)	x += (y - z)
 *
 * INSTR_TIME_GET_DOUBLE(t)			convert t to double (in seconds)
 *
 * INSTR_TIME_GET_MILLISEC(t)		convert t to double (in milliseconds)
 *
 * INSTR_TIME_GET_MICROSEC(t)		convert t to uint64 (in microseconds)
 *
 * Note that INSTR_TIME_SUBTRACT and INSTR_TIME_ACCUM_DIFF convert
 * absolute times to intervals.  The INSTR_TIME_GET_xxx operations are
 * only useful on intervals.
 *
 * When summing multiple measurements, it's recommended to leave the
 * running sum in instr_time form (ie, use INSTR_TIME_ADD or
 * INSTR_TIME_ACCUM_DIFF) and convert to a result format only at the end.
 *
 * Beware of multiple evaluations of the macro arguments.
 *
 *
 * Copyright (c) 2001-2012, PostgreSQL Global Development Group
 *
 * src/include/portability/instr_time.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef INSTR_TIME_H
#define INSTR_TIME_H

#ifndef WIN32

#include <sys/time.h>

typedef struct timeval instr_time;

#define INSTR_TIME_IS_ZERO(t)	((t).tv_usec == 0 && (t).tv_sec == 0)

#define INSTR_TIME_SET_ZERO(t)	((t).tv_sec = 0, (t).tv_usec = 0)

#define INSTR_TIME_SET_CURRENT(t)	gettimeofday(&(t), NULL)

#define INSTR_TIME_ADD(x,y) \
	do { \
		(x).tv_sec += (y).tv_sec; \
		(x).tv_usec += (y).tv_usec; \
		/* Normalize */ \
		while ((x).tv_usec >= 1000000) \
		{ \
			(x).tv_usec -= 1000000; \
			(x).tv_sec++; \
		} \
	} while (0)

#define INSTR_TIME_SUBTRACT(x,y) \
	do { \
		(x).tv_sec -= (y).tv_sec; \
		(x).tv_usec -= (y).tv_usec; \
		/* Normalize */ \
		while ((x).tv_usec < 0) \
		{ \
			(x).tv_usec += 1000000; \
			(x).tv_sec--; \
		} \
	} while (0)

#define INSTR_TIME_ACCUM_DIFF(x,y,z) \
	do { \
		(x).tv_sec += (y).tv_sec - (z).tv_sec; \
		(x).tv_usec += (y).tv_usec - (z).tv_usec; \
		/* Normalize after each add to avoid overflow/underflow of tv_usec */ \
		while ((x).tv_usec < 0) \
		{ \
			(x).tv_usec += 1000000; \
			(x).tv_sec--; \
		} \
		while ((x).tv_usec >= 1000000) \
		{ \
			(x).tv_usec -= 1000000; \
			(x).tv_sec++; \
		} \
	} while (0)

#define INSTR_TIME_GET_DOUBLE(t) \
	(((double) (t).tv_sec) + ((double) (t).tv_usec) / 1000000.0)

#define INSTR_TIME_GET_MILLISEC(t) \
	(((double) (t).tv_sec * 1000.0) + ((double) (t).tv_usec) / 1000.0)

#define INSTR_TIME_GET_MICROSEC(t) \
	(((uint64) (t).tv_sec * (uint64) 1000000) + (uint64) (t).tv_usec)
#else							/* WIN32 */

typedef LARGE_INTEGER instr_time;

#define INSTR_TIME_IS_ZERO(t)	((t).QuadPart == 0)

#define INSTR_TIME_SET_ZERO(t)	((t).QuadPart = 0)

#define INSTR_TIME_SET_CURRENT(t)	QueryPerformanceCounter(&(t))

#define INSTR_TIME_ADD(x,y) \
	((x).QuadPart += (y).QuadPart)

#define INSTR_TIME_SUBTRACT(x,y) \
	((x).QuadPart -= (y).QuadPart)

#define INSTR_TIME_ACCUM_DIFF(x,y,z) \
	((x).QuadPart += (y).QuadPart - (z).QuadPart)

#define INSTR_TIME_GET_DOUBLE(t) \
	(((double) (t).QuadPart) / GetTimerFrequency())

#define INSTR_TIME_GET_MILLISEC(t) \
	(((double) (t).QuadPart * 1000.0) / GetTimerFrequency())

#define INSTR_TIME_GET_MICROSEC(t) \
	((uint64) (((double) (t).QuadPart * 1000000.0) / GetTimerFrequency()))

static inline double
GetTimerFrequency(void)
{
	LARGE_INTEGER f;

	QueryPerformanceFrequency(&f);
	return (double) f.QuadPart;
}
#endif   /* WIN32 */

#endif   /* INSTR_TIME_H */