github.com/luckypickle/go-ethereum-vet@v1.14.2/common/mclock/simclock.go (about)

     1  // Copyright 2018 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package mclock
    18  
    19  import (
    20  	"sync"
    21  	"time"
    22  )
    23  
    24  // Simulated implements a virtual Clock for reproducible time-sensitive tests. It
    25  // simulates a scheduler on a virtual timescale where actual processing takes zero time.
    26  //
    27  // The virtual clock doesn't advance on its own, call Run to advance it and execute timers.
    28  // Since there is no way to influence the Go scheduler, testing timeout behaviour involving
    29  // goroutines needs special care. A good way to test such timeouts is as follows: First
    30  // perform the action that is supposed to time out. Ensure that the timer you want to test
    31  // is created. Then run the clock until after the timeout. Finally observe the effect of
    32  // the timeout using a channel or semaphore.
    33  type Simulated struct {
    34  	now       AbsTime
    35  	scheduled []event
    36  	mu        sync.RWMutex
    37  	cond      *sync.Cond
    38  }
    39  
    40  type event struct {
    41  	do func()
    42  	at AbsTime
    43  }
    44  
    45  // Run moves the clock by the given duration, executing all timers before that duration.
    46  func (s *Simulated) Run(d time.Duration) {
    47  	s.mu.Lock()
    48  	defer s.mu.Unlock()
    49  	s.init()
    50  
    51  	end := s.now + AbsTime(d)
    52  	for len(s.scheduled) > 0 {
    53  		ev := s.scheduled[0]
    54  		if ev.at > end {
    55  			break
    56  		}
    57  		s.now = ev.at
    58  		ev.do()
    59  		s.scheduled = s.scheduled[1:]
    60  	}
    61  	s.now = end
    62  }
    63  
    64  func (s *Simulated) ActiveTimers() int {
    65  	s.mu.RLock()
    66  	defer s.mu.RUnlock()
    67  
    68  	return len(s.scheduled)
    69  }
    70  
    71  func (s *Simulated) WaitForTimers(n int) {
    72  	s.mu.Lock()
    73  	defer s.mu.Unlock()
    74  	s.init()
    75  
    76  	for len(s.scheduled) < n {
    77  		s.cond.Wait()
    78  	}
    79  }
    80  
    81  // Now implements Clock.
    82  func (s *Simulated) Now() AbsTime {
    83  	s.mu.RLock()
    84  	defer s.mu.RUnlock()
    85  
    86  	return s.now
    87  }
    88  
    89  // Sleep implements Clock.
    90  func (s *Simulated) Sleep(d time.Duration) {
    91  	<-s.After(d)
    92  }
    93  
    94  // After implements Clock.
    95  func (s *Simulated) After(d time.Duration) <-chan time.Time {
    96  	after := make(chan time.Time, 1)
    97  	s.insert(d, func() {
    98  		after <- (time.Time{}).Add(time.Duration(s.now))
    99  	})
   100  	return after
   101  }
   102  
   103  func (s *Simulated) insert(d time.Duration, do func()) {
   104  	s.mu.Lock()
   105  	defer s.mu.Unlock()
   106  	s.init()
   107  
   108  	at := s.now + AbsTime(d)
   109  	l, h := 0, len(s.scheduled)
   110  	ll := h
   111  	for l != h {
   112  		m := (l + h) / 2
   113  		if at < s.scheduled[m].at {
   114  			h = m
   115  		} else {
   116  			l = m + 1
   117  		}
   118  	}
   119  	s.scheduled = append(s.scheduled, event{})
   120  	copy(s.scheduled[l+1:], s.scheduled[l:ll])
   121  	s.scheduled[l] = event{do: do, at: at}
   122  	s.cond.Broadcast()
   123  }
   124  
   125  func (s *Simulated) init() {
   126  	if s.cond == nil {
   127  		s.cond = sync.NewCond(&s.mu)
   128  	}
   129  }