github.com/ethereum/go-ethereum@v1.14.3/internal/syncx/mutex.go (about)

     1  // Copyright 2021 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 syncx contains exotic synchronization primitives.
    18  package syncx
    19  
    20  // ClosableMutex is a mutex that can also be closed.
    21  // Once closed, it can never be taken again.
    22  type ClosableMutex struct {
    23  	ch chan struct{}
    24  }
    25  
    26  func NewClosableMutex() *ClosableMutex {
    27  	ch := make(chan struct{}, 1)
    28  	ch <- struct{}{}
    29  	return &ClosableMutex{ch}
    30  }
    31  
    32  // TryLock attempts to lock cm.
    33  // If the mutex is closed, TryLock returns false.
    34  func (cm *ClosableMutex) TryLock() bool {
    35  	_, ok := <-cm.ch
    36  	return ok
    37  }
    38  
    39  // MustLock locks cm.
    40  // If the mutex is closed, MustLock panics.
    41  func (cm *ClosableMutex) MustLock() {
    42  	_, ok := <-cm.ch
    43  	if !ok {
    44  		panic("mutex closed")
    45  	}
    46  }
    47  
    48  // Unlock unlocks cm.
    49  func (cm *ClosableMutex) Unlock() {
    50  	select {
    51  	case cm.ch <- struct{}{}:
    52  	default:
    53  		panic("Unlock of already-unlocked ClosableMutex")
    54  	}
    55  }
    56  
    57  // Close locks the mutex, then closes it.
    58  func (cm *ClosableMutex) Close() {
    59  	_, ok := <-cm.ch
    60  	if !ok {
    61  		panic("Close of already-closed ClosableMutex")
    62  	}
    63  	close(cm.ch)
    64  }