[tor-commits] [tor/master] Merge branch 'ticket31374_029' into ticket31374_035

nickm at torproject.org nickm at torproject.org
Thu Aug 8 19:25:07 UTC 2019


commit b560d94ac0a9ccbc3db7b4a5611ef1ad4ee7628c
Merge: e83eabc9b 3a280b35e
Author: Nick Mathewson <nickm at torproject.org>
Date:   Thu Aug 8 11:46:24 2019 -0400

    Merge branch 'ticket31374_029' into ticket31374_035

 changes/ticket31374        | 4 ++++
 src/lib/time/compat_time.c | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --cc src/lib/time/compat_time.c
index 3d1ffa7af,000000000..98854bad2
mode 100644,000000..100644
--- a/src/lib/time/compat_time.c
+++ b/src/lib/time/compat_time.c
@@@ -1,869 -1,0 +1,869 @@@
 +/* Copyright (c) 2003-2004, Roger Dingledine
 + * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
 + * Copyright (c) 2007-2019, The Tor Project, Inc. */
 +/* See LICENSE for licensing information */
 +
 +/**
 + * \file compat_time.c
 + * \brief Portable wrappers for finding out the current time, running
 + *   timers, etc.
 + **/
 +
 +#define COMPAT_TIME_PRIVATE
 +#include "lib/time/compat_time.h"
 +
 +#include "lib/err/torerr.h"
 +#include "lib/log/log.h"
 +#include "lib/log/util_bug.h"
 +#include "lib/intmath/muldiv.h"
 +#include "lib/intmath/bits.h"
 +#include "lib/fs/winlib.h"
 +#include "lib/wallclock/timeval.h"
 +
 +#ifdef _WIN32
 +#include <winsock2.h>
 +#include <windows.h>
 +#endif
 +
 +#ifdef HAVE_SYS_TYPES_H
 +#include <sys/types.h>
 +#endif
 +#ifdef HAVE_SYS_TIME_H
 +#include <sys/time.h>
 +#endif
 +#ifdef HAVE_UNISTD_H
 +#include <unistd.h>
 +#endif
 +#ifdef TOR_UNIT_TESTS
 +#if !defined(HAVE_USLEEP) && defined(HAVE_SYS_SELECT_H)
 +/* as fallback implementation for tor_sleep_msec */
 +#include <sys/select.h>
 +#endif
 +#endif /* defined(TOR_UNIT_TESTS) */
 +
 +#ifdef __APPLE__
 +#include <mach/mach_time.h>
 +#endif
 +
 +#include <errno.h>
 +#include <stdlib.h>
 +#include <string.h>
 +
 +#ifdef _WIN32
 +#undef HAVE_CLOCK_GETTIME
 +#endif
 +
 +#ifdef TOR_UNIT_TESTS
 +/** Delay for <b>msec</b> milliseconds.  Only used in tests. */
 +void
 +tor_sleep_msec(int msec)
 +{
 +#ifdef _WIN32
 +  Sleep(msec);
 +#elif defined(HAVE_USLEEP)
 +  sleep(msec / 1000);
 +  /* Some usleep()s hate sleeping more than 1 sec */
 +  usleep((msec % 1000) * 1000);
 +#elif defined(HAVE_SYS_SELECT_H)
 +  struct timeval tv = { msec / 1000, (msec % 1000) * 1000};
 +  select(0, NULL, NULL, NULL, &tv);
 +#else
 +  sleep(CEIL_DIV(msec, 1000));
 +#endif /* defined(_WIN32) || ... */
 +}
 +#endif /* defined(TOR_UNIT_TESTS) */
 +
 +#define ONE_MILLION ((int64_t) (1000 * 1000))
 +#define ONE_BILLION ((int64_t) (1000 * 1000 * 1000))
 +
 +/** True iff monotime_init has been called. */
 +static int monotime_initialized = 0;
 +
 +static monotime_t initialized_at;
 +#ifdef MONOTIME_COARSE_FN_IS_DIFFERENT
 +static monotime_coarse_t initialized_at_coarse;
 +#endif
 +
 +#ifdef TOR_UNIT_TESTS
 +/** True if we are running unit tests and overriding the current monotonic
 + * time.  Note that mocked monotonic time might not be monotonic.
 + */
 +static int monotime_mocking_enabled = 0;
 +static monotime_t initialized_at_saved;
 +
 +static int64_t mock_time_nsec = 0;
 +#ifdef MONOTIME_COARSE_FN_IS_DIFFERENT
 +static int64_t mock_time_nsec_coarse = 0;
 +static monotime_coarse_t initialized_at_coarse_saved;
 +#endif
 +
 +void
 +monotime_enable_test_mocking(void)
 +{
 +  if (BUG(monotime_initialized == 0)) {
 +    monotime_init();
 +  }
 +
 +  tor_assert_nonfatal(monotime_mocking_enabled == 0);
 +  monotime_mocking_enabled = 1;
 +  memcpy(&initialized_at_saved,
 +         &initialized_at, sizeof(monotime_t));
 +  memset(&initialized_at, 0, sizeof(monotime_t));
 +#ifdef MONOTIME_COARSE_FN_IS_DIFFERENT
 +  memcpy(&initialized_at_coarse_saved,
 +         &initialized_at_coarse, sizeof(monotime_coarse_t));
 +  memset(&initialized_at_coarse, 0, sizeof(monotime_coarse_t));
 +#endif
 +}
 +
 +void
 +monotime_disable_test_mocking(void)
 +{
 +  tor_assert_nonfatal(monotime_mocking_enabled == 1);
 +  monotime_mocking_enabled = 0;
 +
 +  memcpy(&initialized_at,
 +         &initialized_at_saved, sizeof(monotime_t));
 +#ifdef MONOTIME_COARSE_FN_IS_DIFFERENT
 +  memcpy(&initialized_at_coarse,
 +         &initialized_at_coarse_saved, sizeof(monotime_coarse_t));
 +#endif
 +}
 +
 +void
 +monotime_set_mock_time_nsec(int64_t nsec)
 +{
 +  tor_assert_nonfatal(monotime_mocking_enabled == 1);
 +  mock_time_nsec = nsec;
 +}
 +
 +#ifdef MONOTIME_COARSE_FN_IS_DIFFERENT
 +void
 +monotime_coarse_set_mock_time_nsec(int64_t nsec)
 +{
 +  tor_assert_nonfatal(monotime_mocking_enabled == 1);
 +  mock_time_nsec_coarse = nsec;
 +}
 +#endif /* defined(MONOTIME_COARSE_FN_IS_DIFFERENT) */
 +#endif /* defined(TOR_UNIT_TESTS) */
 +
 +/* "ratchet" functions for monotonic time. */
 +
 +#if defined(_WIN32) || defined(TOR_UNIT_TESTS)
 +
 +/** Protected by lock: last value returned by monotime_get(). */
 +static int64_t last_pctr = 0;
 +/** Protected by lock: offset we must add to monotonic time values. */
 +static int64_t pctr_offset = 0;
 +/* If we are using GetTickCount(), how many times has it rolled over? */
 +static uint32_t rollover_count = 0;
 +/* If we are using GetTickCount(), what's the last value it returned? */
 +static int64_t last_tick_count = 0;
 +
 +/** Helper for windows: Called with a sequence of times that are supposed
 + * to be monotonic; increments them as appropriate so that they actually
 + * _are_ monotonic.
 + *
 + * Caller must hold lock. */
 +STATIC int64_t
 +ratchet_performance_counter(int64_t count_raw)
 +{
 +  /* must hold lock */
 +  const int64_t count_adjusted = count_raw + pctr_offset;
 +
 +  if (PREDICT_UNLIKELY(count_adjusted < last_pctr)) {
 +    /* Monotonicity failed! Pretend no time elapsed. */
 +    pctr_offset = last_pctr - count_raw;
 +    return last_pctr;
 +  } else {
 +    last_pctr = count_adjusted;
 +    return count_adjusted;
 +  }
 +}
 +
 +STATIC int64_t
 +ratchet_coarse_performance_counter(const int64_t count_raw)
 +{
 +  int64_t count = count_raw + (((int64_t)rollover_count) << 32);
 +  while (PREDICT_UNLIKELY(count < last_tick_count)) {
 +    ++rollover_count;
 +    count = count_raw + (((int64_t)rollover_count) << 32);
 +  }
 +  last_tick_count = count;
 +  return count;
 +}
 +#endif /* defined(_WIN32) || defined(TOR_UNIT_TESTS) */
 +
 +#if defined(MONOTIME_USING_GETTIMEOFDAY) || defined(TOR_UNIT_TESTS)
 +static struct timeval last_timeofday = { 0, 0 };
 +static struct timeval timeofday_offset = { 0, 0 };
 +
 +/** Helper for gettimeofday(): Called with a sequence of times that are
 + * supposed to be monotonic; increments them as appropriate so that they
 + * actually _are_ monotonic.
 + *
 + * Caller must hold lock. */
 +STATIC void
 +ratchet_timeval(const struct timeval *timeval_raw, struct timeval *out)
 +{
 +  /* must hold lock */
 +  timeradd(timeval_raw, &timeofday_offset, out);
 +  if (PREDICT_UNLIKELY(timercmp(out, &last_timeofday, OP_LT))) {
 +    /* time ran backwards. Instead, declare that no time occurred. */
 +    timersub(&last_timeofday, timeval_raw, &timeofday_offset);
 +    memcpy(out, &last_timeofday, sizeof(struct timeval));
 +  } else {
 +    memcpy(&last_timeofday, out, sizeof(struct timeval));
 +  }
 +}
 +#endif /* defined(MONOTIME_USING_GETTIMEOFDAY) || defined(TOR_UNIT_TESTS) */
 +
 +#ifdef TOR_UNIT_TESTS
 +/** For testing: reset all the ratchets */
 +void
 +monotime_reset_ratchets_for_testing(void)
 +{
 +  last_pctr = pctr_offset = last_tick_count = 0;
 +  rollover_count = 0;
 +  memset(&last_timeofday, 0, sizeof(struct timeval));
 +  memset(&timeofday_offset, 0, sizeof(struct timeval));
 +}
 +#endif /* defined(TOR_UNIT_TESTS) */
 +
 +#ifdef __APPLE__
 +
 +/** Initialized on startup: tells is how to convert from ticks to
 + * nanoseconds.
 + */
 +static struct mach_timebase_info mach_time_info;
 +static struct mach_timebase_info mach_time_info_msec_cvt;
 +static int32_t mach_time_msec_cvt_threshold;
 +static int monotime_shift = 0;
 +
 +static void
 +monotime_init_internal(void)
 +{
 +  tor_assert(!monotime_initialized);
 +  int r = mach_timebase_info(&mach_time_info);
 +  tor_assert(r == 0);
 +  tor_assert(mach_time_info.denom != 0);
 +
 +  {
 +    // approximate only.
 +    uint64_t ns_per_tick = mach_time_info.numer / mach_time_info.denom;
 +    uint64_t ms_per_tick = ns_per_tick * ONE_MILLION;
 +    // requires that tor_log2(0) == 0.
 +    monotime_shift = tor_log2(ms_per_tick);
 +  }
 +  {
 +    // For converting ticks to milliseconds in a 32-bit-friendly way, we
 +    // will first right-shift by 20, and then multiply by 2048/1953, since
 +    // (1<<20) * 1953/2048 is about 1e6.  We precompute a new numerator and
 +    // denominator here to avoid multiple multiplies.
 +    mach_time_info_msec_cvt.numer = mach_time_info.numer * 2048;
 +    mach_time_info_msec_cvt.denom = mach_time_info.denom * 1953;
 +    // For any value above this amount, we should divide before multiplying,
 +    // to avoid overflow.  For a value below this, we should multiply
 +    // before dividing, to improve accuracy.
 +    mach_time_msec_cvt_threshold = INT32_MAX / mach_time_info_msec_cvt.numer;
 +  }
 +}
 +
 +/**
 + * Set "out" to the most recent monotonic time value
 + */
 +void
 +monotime_get(monotime_t *out)
 +{
 +#ifdef TOR_UNIT_TESTS
 +  if (monotime_mocking_enabled) {
 +    out->abstime_ = (mock_time_nsec * mach_time_info.denom)
 +      / mach_time_info.numer;
 +    return;
 +  }
 +#endif /* defined(TOR_UNIT_TESTS) */
 +  out->abstime_ = mach_absolute_time();
 +}
 +
 +#if defined(HAVE_MACH_APPROXIMATE_TIME)
 +void
 +monotime_coarse_get(monotime_coarse_t *out)
 +{
 +#ifdef TOR_UNIT_TESTS
 +  if (monotime_mocking_enabled) {
 +    out->abstime_ = (mock_time_nsec_coarse * mach_time_info.denom)
 +      / mach_time_info.numer;
 +    return;
 +  }
 +#endif /* defined(TOR_UNIT_TESTS) */
 +  out->abstime_ = mach_approximate_time();
 +}
 +#endif
 +
 +/**
 + * Return the number of nanoseconds between <b>start</b> and <b>end</b>.
 + */
 +int64_t
 +monotime_diff_nsec(const monotime_t *start,
 +                   const monotime_t *end)
 +{
 +  if (BUG(mach_time_info.denom == 0)) {
 +    monotime_init();
 +  }
 +  const int64_t diff_ticks = end->abstime_ - start->abstime_;
 +  const int64_t diff_nsec =
 +    (diff_ticks * mach_time_info.numer) / mach_time_info.denom;
 +  return diff_nsec;
 +}
 +
 +int32_t
 +monotime_coarse_diff_msec32_(const monotime_coarse_t *start,
 +                             const monotime_coarse_t *end)
 +{
 +  if (BUG(mach_time_info.denom == 0)) {
 +    monotime_init();
 +  }
 +  const int64_t diff_ticks = end->abstime_ - start->abstime_;
 +
 +  /* We already require in di_ops.c that right-shift performs a sign-extend. */
 +  const int32_t diff_microticks = (int32_t)(diff_ticks >> 20);
 +
 +  if (diff_microticks >= mach_time_msec_cvt_threshold) {
 +    return (diff_microticks / mach_time_info_msec_cvt.denom) *
 +      mach_time_info_msec_cvt.numer;
 +  } else {
 +    return (diff_microticks * mach_time_info_msec_cvt.numer) /
 +      mach_time_info_msec_cvt.denom;
 +  }
 +}
 +
 +uint32_t
 +monotime_coarse_to_stamp(const monotime_coarse_t *t)
 +{
 +  return (uint32_t)(t->abstime_ >> monotime_shift);
 +}
 +
 +int
 +monotime_is_zero(const monotime_t *val)
 +{
 +  return val->abstime_ == 0;
 +}
 +
 +void
 +monotime_add_msec(monotime_t *out, const monotime_t *val, uint32_t msec)
 +{
 +  const uint64_t nsec = msec * ONE_MILLION;
 +  const uint64_t ticks = (nsec * mach_time_info.denom) / mach_time_info.numer;
 +  out->abstime_ = val->abstime_ + ticks;
 +}
 +
 +/* end of "__APPLE__" */
 +#elif defined(HAVE_CLOCK_GETTIME)
 +
 +#ifdef CLOCK_MONOTONIC_COARSE
 +/**
 + * Which clock should we use for coarse-grained monotonic time? By default
 + * this is CLOCK_MONOTONIC_COARSE, but it might not work -- for example,
 + * if we're compiled with newer Linux headers and then we try to run on
 + * an old Linux kernel. In that case, we will fall back to CLOCK_MONOTONIC.
 + */
 +static int clock_monotonic_coarse = CLOCK_MONOTONIC_COARSE;
 +#endif /* defined(CLOCK_MONOTONIC_COARSE) */
 +
 +static void
 +monotime_init_internal(void)
 +{
 +#ifdef CLOCK_MONOTONIC_COARSE
 +  struct timespec ts;
 +  if (clock_gettime(CLOCK_MONOTONIC_COARSE, &ts) < 0) {
 +    log_info(LD_GENERAL, "CLOCK_MONOTONIC_COARSE isn't working (%s); "
 +             "falling back to CLOCK_MONOTONIC.", strerror(errno));
 +    clock_monotonic_coarse = CLOCK_MONOTONIC;
 +  }
 +#endif /* defined(CLOCK_MONOTONIC_COARSE) */
 +}
 +
 +void
 +monotime_get(monotime_t *out)
 +{
 +#ifdef TOR_UNIT_TESTS
 +  if (monotime_mocking_enabled) {
 +    out->ts_.tv_sec = (time_t) (mock_time_nsec / ONE_BILLION);
 +    out->ts_.tv_nsec = (int) (mock_time_nsec % ONE_BILLION);
 +    return;
 +  }
 +#endif /* defined(TOR_UNIT_TESTS) */
 +  int r = clock_gettime(CLOCK_MONOTONIC, &out->ts_);
 +  tor_assert(r == 0);
 +}
 +
 +#ifdef CLOCK_MONOTONIC_COARSE
 +void
 +monotime_coarse_get(monotime_coarse_t *out)
 +{
 +#ifdef TOR_UNIT_TESTS
 +  if (monotime_mocking_enabled) {
 +    out->ts_.tv_sec = (time_t) (mock_time_nsec_coarse / ONE_BILLION);
 +    out->ts_.tv_nsec = (int) (mock_time_nsec_coarse % ONE_BILLION);
 +    return;
 +  }
 +#endif /* defined(TOR_UNIT_TESTS) */
 +  int r = clock_gettime(clock_monotonic_coarse, &out->ts_);
 +  if (PREDICT_UNLIKELY(r < 0) &&
 +      errno == EINVAL &&
 +      clock_monotonic_coarse == CLOCK_MONOTONIC_COARSE) {
 +    /* We should have caught this at startup in monotime_init_internal!
 +     */
 +    log_warn(LD_BUG, "Falling back to non-coarse monotonic time %s initial "
 +             "system start?", monotime_initialized?"after":"without");
 +    clock_monotonic_coarse = CLOCK_MONOTONIC;
 +    r = clock_gettime(clock_monotonic_coarse, &out->ts_);
 +  }
 +
 +  tor_assert(r == 0);
 +}
 +#endif /* defined(CLOCK_MONOTONIC_COARSE) */
 +
 +int64_t
 +monotime_diff_nsec(const monotime_t *start,
 +                   const monotime_t *end)
 +{
 +  const int64_t diff_sec = end->ts_.tv_sec - start->ts_.tv_sec;
 +  const int64_t diff_nsec = diff_sec * ONE_BILLION +
 +    (end->ts_.tv_nsec - start->ts_.tv_nsec);
 +
 +  return diff_nsec;
 +}
 +
 +int32_t
 +monotime_coarse_diff_msec32_(const monotime_coarse_t *start,
 +                             const monotime_coarse_t *end)
 +{
 +  const int32_t diff_sec = (int32_t)(end->ts_.tv_sec - start->ts_.tv_sec);
 +  const int32_t diff_nsec = (int32_t)(end->ts_.tv_nsec - start->ts_.tv_nsec);
 +  return diff_sec * 1000 + diff_nsec / ONE_MILLION;
 +}
 +
 +/* This value is ONE_BILLION >> 20. */
 +static const uint32_t STAMP_TICKS_PER_SECOND = 953;
 +
 +uint32_t
 +monotime_coarse_to_stamp(const monotime_coarse_t *t)
 +{
 +  uint32_t nsec = (uint32_t)t->ts_.tv_nsec;
 +  uint32_t sec = (uint32_t)t->ts_.tv_sec;
 +
 +  return (sec * STAMP_TICKS_PER_SECOND) + (nsec >> 20);
 +}
 +
 +int
 +monotime_is_zero(const monotime_t *val)
 +{
 +  return val->ts_.tv_sec == 0 && val->ts_.tv_nsec == 0;
 +}
 +
 +void
 +monotime_add_msec(monotime_t *out, const monotime_t *val, uint32_t msec)
 +{
 +  const uint32_t sec = msec / 1000;
 +  const uint32_t msec_remainder = msec % 1000;
 +  out->ts_.tv_sec = val->ts_.tv_sec + sec;
 +  out->ts_.tv_nsec = val->ts_.tv_nsec + (msec_remainder * ONE_MILLION);
 +  if (out->ts_.tv_nsec > ONE_BILLION) {
 +    out->ts_.tv_nsec -= ONE_BILLION;
 +    out->ts_.tv_sec += 1;
 +  }
 +}
 +
 +/* end of "HAVE_CLOCK_GETTIME" */
 +#elif defined (_WIN32)
 +
 +/** Result of QueryPerformanceFrequency, in terms needed to
 + * convert ticks to nanoseconds. */
 +static int64_t nsec_per_tick_numer = 1;
 +static int64_t nsec_per_tick_denom = 1;
 +
 +/** Lock to protect last_pctr and pctr_offset */
 +static CRITICAL_SECTION monotime_lock;
 +/** Lock to protect rollover_count and last_tick_count */
 +static CRITICAL_SECTION monotime_coarse_lock;
 +
 +typedef ULONGLONG (WINAPI *GetTickCount64_fn_t)(void);
 +static GetTickCount64_fn_t GetTickCount64_fn = NULL;
 +
 +static void
 +monotime_init_internal(void)
 +{
 +  tor_assert(!monotime_initialized);
 +  BOOL ok = InitializeCriticalSectionAndSpinCount(&monotime_lock, 200);
 +  tor_assert(ok);
 +  ok = InitializeCriticalSectionAndSpinCount(&monotime_coarse_lock, 200);
 +  tor_assert(ok);
 +  LARGE_INTEGER li;
 +  ok = QueryPerformanceFrequency(&li);
 +  tor_assert(ok);
 +  tor_assert(li.QuadPart);
 +
 +  uint64_t n = ONE_BILLION;
 +  uint64_t d = li.QuadPart;
 +  /* We need to simplify this or we'll probably overflow the int64. */
 +  simplify_fraction64(&n, &d);
 +  tor_assert(n <= INT64_MAX);
 +  tor_assert(d <= INT64_MAX);
 +
 +  nsec_per_tick_numer = (int64_t) n;
 +  nsec_per_tick_denom = (int64_t) d;
 +
 +  last_pctr = 0;
 +  pctr_offset = 0;
 +
 +  HANDLE h = load_windows_system_library(TEXT("kernel32.dll"));
 +  if (h) {
-     GetTickCount64_fn = (GetTickCount64_fn_t)
++    GetTickCount64_fn = (GetTickCount64_fn_t) (void(*)(void))
 +      GetProcAddress(h, "GetTickCount64");
 +  }
 +  // FreeLibrary(h) ?
 +}
 +
 +void
 +monotime_get(monotime_t *out)
 +{
 +  if (BUG(monotime_initialized == 0)) {
 +    monotime_init();
 +  }
 +
 +#ifdef TOR_UNIT_TESTS
 +  if (monotime_mocking_enabled) {
 +    out->pcount_ = (mock_time_nsec * nsec_per_tick_denom)
 +      / nsec_per_tick_numer;
 +    return;
 +  }
 +#endif /* defined(TOR_UNIT_TESTS) */
 +
 +  /* Alas, QueryPerformanceCounter is not always monotonic: see bug list at
 +
 +    https://www.python.org/dev/peps/pep-0418/#windows-queryperformancecounter
 +   */
 +
 +  EnterCriticalSection(&monotime_lock);
 +  LARGE_INTEGER res;
 +  BOOL ok = QueryPerformanceCounter(&res);
 +  tor_assert(ok);
 +  const int64_t count_raw = res.QuadPart;
 +  out->pcount_ = ratchet_performance_counter(count_raw);
 +  LeaveCriticalSection(&monotime_lock);
 +}
 +
 +void
 +monotime_coarse_get(monotime_coarse_t *out)
 +{
 +#ifdef TOR_UNIT_TESTS
 +  if (monotime_mocking_enabled) {
 +    out->tick_count_ = mock_time_nsec_coarse / ONE_MILLION;
 +    return;
 +  }
 +#endif /* defined(TOR_UNIT_TESTS) */
 +
 +  if (GetTickCount64_fn) {
 +    out->tick_count_ = (int64_t)GetTickCount64_fn();
 +  } else {
 +    EnterCriticalSection(&monotime_coarse_lock);
 +    DWORD tick = GetTickCount();
 +    out->tick_count_ = ratchet_coarse_performance_counter(tick);
 +    LeaveCriticalSection(&monotime_coarse_lock);
 +  }
 +}
 +
 +int64_t
 +monotime_diff_nsec(const monotime_t *start,
 +                   const monotime_t *end)
 +{
 +  if (BUG(monotime_initialized == 0)) {
 +    monotime_init();
 +  }
 +  const int64_t diff_ticks = end->pcount_ - start->pcount_;
 +  return (diff_ticks * nsec_per_tick_numer) / nsec_per_tick_denom;
 +}
 +
 +int64_t
 +monotime_coarse_diff_msec(const monotime_coarse_t *start,
 +                          const monotime_coarse_t *end)
 +{
 +  const int64_t diff_ticks = end->tick_count_ - start->tick_count_;
 +  return diff_ticks;
 +}
 +
 +int32_t
 +monotime_coarse_diff_msec32_(const monotime_coarse_t *start,
 +                             const monotime_coarse_t *end)
 +{
 +  return (int32_t)monotime_coarse_diff_msec(start, end);
 +}
 +
 +int64_t
 +monotime_coarse_diff_usec(const monotime_coarse_t *start,
 +                          const monotime_coarse_t *end)
 +{
 +  return monotime_coarse_diff_msec(start, end) * 1000;
 +}
 +
 +int64_t
 +monotime_coarse_diff_nsec(const monotime_coarse_t *start,
 +                          const monotime_coarse_t *end)
 +{
 +  return monotime_coarse_diff_msec(start, end) * ONE_MILLION;
 +}
 +
 +static const uint32_t STAMP_TICKS_PER_SECOND = 1000;
 +
 +uint32_t
 +monotime_coarse_to_stamp(const monotime_coarse_t *t)
 +{
 +  return (uint32_t) t->tick_count_;
 +}
 +
 +int
 +monotime_is_zero(const monotime_t *val)
 +{
 +  return val->pcount_ == 0;
 +}
 +
 +int
 +monotime_coarse_is_zero(const monotime_coarse_t *val)
 +{
 +  return val->tick_count_ == 0;
 +}
 +
 +void
 +monotime_add_msec(monotime_t *out, const monotime_t *val, uint32_t msec)
 +{
 +  const uint64_t nsec = msec * ONE_MILLION;
 +  const uint64_t ticks = (nsec * nsec_per_tick_denom) / nsec_per_tick_numer;
 +  out->pcount_ = val->pcount_ + ticks;
 +}
 +
 +void
 +monotime_coarse_add_msec(monotime_coarse_t *out, const monotime_coarse_t *val,
 +                         uint32_t msec)
 +{
 +  out->tick_count_ = val->tick_count_ + msec;
 +}
 +
 +/* end of "_WIN32" */
 +#elif defined(MONOTIME_USING_GETTIMEOFDAY)
 +
 +static tor_mutex_t monotime_lock;
 +
 +/** Initialize the monotonic timer subsystem. */
 +static void
 +monotime_init_internal(void)
 +{
 +  tor_assert(!monotime_initialized);
 +  tor_mutex_init(&monotime_lock);
 +}
 +
 +void
 +monotime_get(monotime_t *out)
 +{
 +  if (BUG(monotime_initialized == 0)) {
 +    monotime_init();
 +  }
 +
 +  tor_mutex_acquire(&monotime_lock);
 +  struct timeval timeval_raw;
 +  tor_gettimeofday(&timeval_raw);
 +  ratchet_timeval(&timeval_raw, &out->tv_);
 +  tor_mutex_release(&monotime_lock);
 +}
 +
 +int64_t
 +monotime_diff_nsec(const monotime_t *start,
 +                   const monotime_t *end)
 +{
 +  struct timeval diff;
 +  timersub(&end->tv_, &start->tv_, &diff);
 +  return (diff.tv_sec * ONE_BILLION + diff.tv_usec * 1000);
 +}
 +
 +int32_t
 +monotime_coarse_diff_msec32_(const monotime_coarse_t *start,
 +                             const monotime_coarse_t *end)
 +{
 +  struct timeval diff;
 +  timersub(&end->tv_, &start->tv_, &diff);
 +  return diff.tv_sec * 1000 + diff.tv_usec / 1000;
 +}
 +
 +/* This value is ONE_MILLION >> 10. */
 +static const uint32_t STAMP_TICKS_PER_SECOND = 976;
 +
 +uint32_t
 +monotime_coarse_to_stamp(const monotime_coarse_t *t)
 +{
 +  const uint32_t usec = (uint32_t)t->tv_.tv_usec;
 +  const uint32_t sec = (uint32_t)t->tv_.tv_sec;
 +  return (sec * STAMP_TICKS_PER_SECOND) | (nsec >> 10);
 +}
 +
 +int
 +monotime_is_zero(const monotime_t *val)
 +{
 +  return val->tv_.tv_sec == 0 && val->tv_.tv_usec == 0;
 +}
 +
 +void
 +monotime_add_msec(monotime_t *out, const monotime_t *val, uint32_t msec)
 +{
 +  const uint32_t sec = msec / 1000;
 +  const uint32_t msec_remainder = msec % 1000;
 +  out->tv_.tv_sec = val->tv_.tv_sec + sec;
 +  out->tv_.tv_usec = val->tv_.tv_nsec + (msec_remainder * 1000);
 +  if (out->tv_.tv_usec > ONE_MILLION) {
 +    out->tv_.tv_usec -= ONE_MILLION;
 +    out->tv_.tv_sec += 1;
 +  }
 +}
 +
 +/* end of "MONOTIME_USING_GETTIMEOFDAY" */
 +#else
 +#error "No way to implement monotonic timers."
 +#endif /* defined(__APPLE__) || ... */
 +
 +/**
 + * Initialize the monotonic timer subsystem. Must be called before any
 + * monotonic timer functions. This function is idempotent.
 + */
 +void
 +monotime_init(void)
 +{
 +  if (!monotime_initialized) {
 +    monotime_init_internal();
 +    monotime_initialized = 1;
 +    monotime_get(&initialized_at);
 +#ifdef MONOTIME_COARSE_FN_IS_DIFFERENT
 +    monotime_coarse_get(&initialized_at_coarse);
 +#endif
 +  }
 +}
 +
 +void
 +monotime_zero(monotime_t *out)
 +{
 +  memset(out, 0, sizeof(*out));
 +}
 +#ifdef MONOTIME_COARSE_TYPE_IS_DIFFERENT
 +void
 +monotime_coarse_zero(monotime_coarse_t *out)
 +{
 +  memset(out, 0, sizeof(*out));
 +}
 +#endif
 +
 +int64_t
 +monotime_diff_usec(const monotime_t *start,
 +                   const monotime_t *end)
 +{
 +  const int64_t nsec = monotime_diff_nsec(start, end);
 +  return CEIL_DIV(nsec, 1000);
 +}
 +
 +int64_t
 +monotime_diff_msec(const monotime_t *start,
 +                   const monotime_t *end)
 +{
 +  const int64_t nsec = monotime_diff_nsec(start, end);
 +  return CEIL_DIV(nsec, ONE_MILLION);
 +}
 +
 +uint64_t
 +monotime_absolute_nsec(void)
 +{
 +  monotime_t now;
 +  if (BUG(monotime_initialized == 0)) {
 +    monotime_init();
 +  }
 +
 +  monotime_get(&now);
 +  return monotime_diff_nsec(&initialized_at, &now);
 +}
 +
 +uint64_t
 +monotime_absolute_usec(void)
 +{
 +  return monotime_absolute_nsec() / 1000;
 +}
 +
 +uint64_t
 +monotime_absolute_msec(void)
 +{
 +  return monotime_absolute_nsec() / ONE_MILLION;
 +}
 +
 +#ifdef MONOTIME_COARSE_FN_IS_DIFFERENT
 +uint64_t
 +monotime_coarse_absolute_nsec(void)
 +{
 +  if (BUG(monotime_initialized == 0)) {
 +    monotime_init();
 +  }
 +
 +  monotime_coarse_t now;
 +  monotime_coarse_get(&now);
 +  return monotime_coarse_diff_nsec(&initialized_at_coarse, &now);
 +}
 +
 +uint64_t
 +monotime_coarse_absolute_usec(void)
 +{
 +  return monotime_coarse_absolute_nsec() / 1000;
 +}
 +
 +uint64_t
 +monotime_coarse_absolute_msec(void)
 +{
 +  return monotime_coarse_absolute_nsec() / ONE_MILLION;
 +}
 +#else
 +#define initialized_at_coarse initialized_at
 +#endif /* defined(MONOTIME_COARSE_FN_IS_DIFFERENT) */
 +
 +/**
 + * Return the current time "stamp" as described by monotime_coarse_to_stamp.
 + */
 +uint32_t
 +monotime_coarse_get_stamp(void)
 +{
 +  monotime_coarse_t now;
 +  monotime_coarse_get(&now);
 +  return monotime_coarse_to_stamp(&now);
 +}
 +
 +#ifdef __APPLE__
 +uint64_t
 +monotime_coarse_stamp_units_to_approx_msec(uint64_t units)
 +{
 +  /* Recover as much precision as we can. */
 +  uint64_t abstime_diff = (units << monotime_shift);
 +  return (abstime_diff * mach_time_info.numer) /
 +    (mach_time_info.denom * ONE_MILLION);
 +}
 +uint64_t
 +monotime_msec_to_approx_coarse_stamp_units(uint64_t msec)
 +{
 +  uint64_t abstime_val =
 +    (((uint64_t)msec) * ONE_MILLION * mach_time_info.denom) /
 +    mach_time_info.numer;
 +  return abstime_val >> monotime_shift;
 +}
 +#else
 +uint64_t
 +monotime_coarse_stamp_units_to_approx_msec(uint64_t units)
 +{
 +  return (units * 1000) / STAMP_TICKS_PER_SECOND;
 +}
 +uint64_t
 +monotime_msec_to_approx_coarse_stamp_units(uint64_t msec)
 +{
 +  return (msec * STAMP_TICKS_PER_SECOND) / 1000;
 +}
 +#endif





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