github.com/shindo/goofys@v0.24.1-0.20210326210429-9e930f0b2d5c/internal/ticket.go (about)

     1  // Copyright 2016 Ka-Hing Cheung
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package internal
    16  
    17  import (
    18  	"sync"
    19  )
    20  
    21  type Ticket struct {
    22  	Total uint32
    23  
    24  	total       uint32
    25  	outstanding uint32
    26  
    27  	mu   sync.Mutex
    28  	cond *sync.Cond
    29  }
    30  
    31  func (ticket Ticket) Init() *Ticket {
    32  	ticket.cond = sync.NewCond(&ticket.mu)
    33  	ticket.total = ticket.Total
    34  	return &ticket
    35  }
    36  
    37  func (ticket *Ticket) Take(howmany uint32, block bool) (took bool) {
    38  	ticket.mu.Lock()
    39  	defer ticket.mu.Unlock()
    40  
    41  	for ticket.outstanding+howmany > ticket.total {
    42  		if block {
    43  			ticket.cond.Wait()
    44  		} else {
    45  			return
    46  		}
    47  	}
    48  
    49  	ticket.outstanding += howmany
    50  	took = true
    51  	return
    52  }
    53  
    54  func (ticket *Ticket) Return(howmany uint32) {
    55  	ticket.mu.Lock()
    56  	defer ticket.mu.Unlock()
    57  
    58  	ticket.outstanding -= howmany
    59  	ticket.cond.Signal()
    60  }