github.com/amazechain/amc@v0.1.3/internal/tracers/tracker.go (about)

     1  // Copyright 2023 The AmazeChain Authors
     2  // This file is part of the AmazeChain library.
     3  //
     4  // The AmazeChain 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 AmazeChain 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 AmazeChain library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package tracers
    18  
    19  import (
    20  	"fmt"
    21  	"sync"
    22  )
    23  
    24  // stateTracker is an auxiliary tool used to cache the release functions of all
    25  // used trace states, and to determine whether the creation of trace state needs
    26  // to be paused in case there are too many states waiting for tracing.
    27  type stateTracker struct {
    28  	limit    int                // Maximum number of states allowed waiting for tracing
    29  	oldest   uint64             // The number of the oldest state which is still using for trace
    30  	used     []bool             // List of flags indicating whether the trace state has been used up
    31  	releases []StateReleaseFunc // List of trace state release functions waiting to be called
    32  	cond     *sync.Cond
    33  	lock     *sync.RWMutex
    34  }
    35  
    36  // newStateTracker initializes the tracker with provided state limits and
    37  // the number of the first state that will be used.
    38  func newStateTracker(limit int, oldest uint64) *stateTracker {
    39  	lock := new(sync.RWMutex)
    40  	return &stateTracker{
    41  		limit:  limit,
    42  		oldest: oldest,
    43  		used:   make([]bool, limit),
    44  		cond:   sync.NewCond(lock),
    45  		lock:   lock,
    46  	}
    47  }
    48  
    49  // releaseState marks the state specified by the number as released and caches
    50  // the corresponding release functions internally.
    51  func (t *stateTracker) releaseState(number uint64, release StateReleaseFunc) {
    52  	t.lock.Lock()
    53  	defer t.lock.Unlock()
    54  
    55  	// Set the state as used, the corresponding flag is indexed by
    56  	// the distance between the specified state and the oldest state
    57  	// which is still using for trace.
    58  	t.used[int(number-t.oldest)] = true
    59  
    60  	// If the oldest state is used up, update the oldest marker by moving
    61  	// it to the next state which is not used up.
    62  	if number == t.oldest {
    63  		var count int
    64  		for _, used := range t.used {
    65  			if !used {
    66  				break
    67  			}
    68  			count += 1
    69  		}
    70  		t.oldest += uint64(count)
    71  		copy(t.used, t.used[count:])
    72  
    73  		// Clean up the array tail since they are useless now.
    74  		for i := t.limit - count; i < t.limit; i++ {
    75  			t.used[i] = false
    76  		}
    77  		// Fire the signal to all waiters that oldest marker is updated.
    78  		t.cond.Broadcast()
    79  	}
    80  	t.releases = append(t.releases, release)
    81  }
    82  
    83  // callReleases invokes all cached release functions.
    84  func (t *stateTracker) callReleases() {
    85  	t.lock.Lock()
    86  	defer t.lock.Unlock()
    87  
    88  	for _, release := range t.releases {
    89  		release()
    90  	}
    91  	t.releases = t.releases[:0]
    92  }
    93  
    94  // wait blocks until the accumulated trace states are less than the limit.
    95  func (t *stateTracker) wait(number uint64) error {
    96  	t.lock.Lock()
    97  	defer t.lock.Unlock()
    98  
    99  	for {
   100  		if number < t.oldest {
   101  			return fmt.Errorf("invalid state number %d head %d", number, t.oldest)
   102  		}
   103  		if number < t.oldest+uint64(t.limit) {
   104  			// number is now within limit, wait over
   105  			return nil
   106  		}
   107  		t.cond.Wait()
   108  	}
   109  }