time.h   [plain text]

/*
 * Copyright (c) 2008-2011 Apple Inc. All rights reserved.
 *
 * @APPLE_APACHE_LICENSE_HEADER_START@
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * @APPLE_APACHE_LICENSE_HEADER_END@
 */

/*
 * IMPORTANT: This header file describes INTERNAL interfaces to libdispatch
 * which are subject to change in future releases of Mac OS X. Any applications
 * relying on these interfaces WILL break.
 */

#ifndef __DISPATCH_SHIMS_TIME__
#define __DISPATCH_SHIMS_TIME__

#ifndef __DISPATCH_INDIRECT__
#error "Please #include <dispatch/dispatch.h> instead of this file directly."
#endif

uint64_t _dispatch_get_nanoseconds(void);

#if defined(__i386__) || defined(__x86_64__) || !HAVE_MACH_ABSOLUTE_TIME
// x86 currently implements mach time in nanoseconds
// this is NOT likely to change
#define _dispatch_time_mach2nano(x) ({x;})
#define _dispatch_time_nano2mach(x) ({x;})
#else
typedef struct _dispatch_host_time_data_s {
	long double frac;
	bool ratio_1_to_1;
	dispatch_once_t pred;
} _dispatch_host_time_data_s;
extern _dispatch_host_time_data_s _dispatch_host_time_data;
void _dispatch_get_host_time_init(void *context);

static inline uint64_t
_dispatch_time_mach2nano(uint64_t machtime)
{
	_dispatch_host_time_data_s *const data = &_dispatch_host_time_data;
	dispatch_once_f(&data->pred, NULL, _dispatch_get_host_time_init);

	return machtime * data->frac;
}

static inline int64_t
_dispatch_time_nano2mach(int64_t nsec)
{
	_dispatch_host_time_data_s *const data = &_dispatch_host_time_data;
	dispatch_once_f(&data->pred, NULL, _dispatch_get_host_time_init);

	if (slowpath(_dispatch_host_time_data.ratio_1_to_1)) {
		return nsec;
	}

	long double big_tmp = nsec;

	// Divide by tbi.numer/tbi.denom to convert nsec to Mach absolute time
	big_tmp /= data->frac;

	// Clamp to a 64bit signed int
	if (slowpath(big_tmp > INT64_MAX)) {
		return INT64_MAX;
	}
	if (slowpath(big_tmp < INT64_MIN)) {
		return INT64_MIN;
	}
	return big_tmp;
}
#endif

static inline uint64_t
_dispatch_absolute_time(void)
{
#if !HAVE_MACH_ABSOLUTE_TIME
	struct timespec ts;
	int ret;

#if HAVE_DECL_CLOCK_UPTIME
	ret = clock_gettime(CLOCK_UPTIME, &ts);
#elif HAVE_DECL_CLOCK_MONOTONIC
	ret = clock_gettime(CLOCK_MONOTONIC, &ts);
#else
#error "clock_gettime: no supported absolute time clock"
#endif
	(void)dispatch_assume_zero(ret);

	/* XXXRW: Some kind of overflow detection needed? */
	return (ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec);
#else
	return mach_absolute_time();
#endif
}

#endif