/* Basic TSC compatability helpers, callable from Akaros or Linux. Supports:
 * 		uint64_t read_tsc()
 * 		uint64_t read_tsc_serialized()
 * 		uint64_t get_tsc_freq()
 * 		uint64_t get_tsc_overhead()
 *
 * Note this relies on specifics of procinfo, which isn't stable.  If procinfo
 * changes, this will need to change as well.  You'll know when this doesn't
 * compile (say, if timing_overhead moves).  */

#ifndef _TSC_COMPAT_H
#define _TSC_COMPAT_H

#if defined(__i386__) || defined(__x86_64__)
#else
#error "Platform not supported for read_tsc()"
#endif

#ifdef __cplusplus
	extern "C" {
#endif

#ifdef __ros__

#include <arch/arch.h>
#include <ros/procinfo.h>

static inline uint64_t get_tsc_freq(void)
{
	return __procinfo.tsc_freq;
}

static inline uint64_t get_tsc_overhead(void)
{
	return __procinfo.timing_overhead;
}

#else /* ! _ros_ (linux) */

#include <sys/time.h>
#include <stdint.h>
#include <stdbool.h>

/* Akaros has this helper in ros/common.h. (it returns a bool btw)
 *
 * We wraparound if UINT_MAX < a * b, which is also UINT_MAX / a < b. */
static inline int mult_will_overflow_u64(uint64_t a, uint64_t b)
{
	if (!a)
		return false;
	return (uint64_t)(-1) / a < b;
}

# ifdef __i386__

static inline uint64_t read_tsc(void)
{
	uint64_t tsc;
	asm volatile("rdtsc" : "=A" (tsc));
	return tsc;
}

static inline uint64_t read_tsc_serialized(void)
{
	uint64_t tsc;
	asm volatile("lfence; rdtsc" : "=A" (tsc));
	return tsc;
}

# elif __x86_64__

static inline uint64_t read_tsc(void)
{
	uint32_t lo, hi;
	/* We cannot use "=A", since this would use %rax on x86_64 */
	asm volatile("rdtsc" : "=a" (lo), "=d" (hi));
	return (uint64_t)hi << 32 | lo;
}

static inline uint64_t read_tsc_serialized(void)
{
	uint32_t lo, hi;
	asm volatile("lfence; rdtsc" : "=a" (lo), "=d" (hi));
	return (uint64_t)hi << 32 | lo;
}

# else
#  error "Which arch is this?"
# endif /* __i386__ | __x86_64__ */

static inline uint64_t get_tsc_freq(void)
{
	struct timeval prev;
	struct timeval curr;
	uint64_t beg = read_tsc_serialized();
	gettimeofday(&prev, 0);
	while (1) {
		gettimeofday(&curr, 0);
		if (curr.tv_sec > (prev.tv_sec + 1) ||
			(curr.tv_sec > prev.tv_sec && curr.tv_usec > prev.tv_usec))
			break;
	}
	uint64_t end = read_tsc_serialized();
	return end - beg;
}

/* Don't have a good way to get the overhead on Linux in userspace. */
static inline uint64_t get_tsc_overhead(void)
{
	return 0;
}

static inline uint64_t tsc2sec(uint64_t tsc_time)
{
	return tsc_time / get_tsc_freq();
}

static inline uint64_t tsc2msec(uint64_t tsc_time)
{
	if (mult_will_overflow_u64(tsc_time, 1000))
		return tsc2sec(tsc_time) * 1000;
	else
		return (tsc_time * 1000) / get_tsc_freq();
}

static inline uint64_t tsc2usec(uint64_t tsc_time)
{
	if (mult_will_overflow_u64(tsc_time, 1000000))
		return tsc2msec(tsc_time) * 1000;
	else
		return (tsc_time * 1000000) / get_tsc_freq();
}

static inline uint64_t tsc2nsec(uint64_t tsc_time)
{
	if (mult_will_overflow_u64(tsc_time, 1000000000))
		return tsc2usec(tsc_time) * 1000;
	else
		return (tsc_time * 1000000000) / get_tsc_freq();
}

static inline uint64_t sec2tsc(uint64_t sec)
{
	if (mult_will_overflow_u64(sec, get_tsc_freq()))
		return (uint64_t)(-1);
	else
		return sec * get_tsc_freq();
}

static inline uint64_t msec2tsc(uint64_t msec)
{
	if (mult_will_overflow_u64(msec, get_tsc_freq()))
		return sec2tsc(msec / 1000);
	else
		return (msec * get_tsc_freq()) / 1000;
}

static inline uint64_t usec2tsc(uint64_t usec)
{
	if (mult_will_overflow_u64(usec, get_tsc_freq()))
		return msec2tsc(usec / 1000);
	else
		return (usec * get_tsc_freq()) / 1000000;
}

static inline uint64_t nsec2tsc(uint64_t nsec)
{
	if (mult_will_overflow_u64(nsec, get_tsc_freq()))
		return usec2tsc(nsec / 1000);
	else
		return (nsec * get_tsc_freq()) / 1000000000;
}

#endif /* ! _ros_ */

#ifdef __cplusplus
	}
#endif

#endif /* _TSC_COMPAT_H */