1 /* 2 * P2PFaaS - A framework for FaaS Load Balancing 3 * Copyright (c) 2019 - 2022. Gabriele Proietti Mattia <pm.gabriele@outlook.com> 4 * 5 * This program is free software: you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License as published by 7 * the Free Software Foundation, either version 3 of the License, or 8 * (at your option) any later version. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program. If not, see <https://www.gnu.org/licenses/>. 17 */ 18 19 package utils 20 21 /* 22 * From http://www.golangpatterns.info/concurrency/semaphores 23 */ 24 25 type empty struct{} 26 type Semaphore chan empty 27 28 // P acquires n resources 29 func (s Semaphore) P(n int) { 30 e := empty{} 31 for i := 0; i < n; i++ { 32 s <- e 33 } 34 } 35 36 // V releases n resources 37 func (s Semaphore) V(n int) { 38 for i := 0; i < n; i++ { 39 <-s 40 } 41 } 42 43 /* mutexes */ 44 45 func (s Semaphore) Lock() { 46 s.P(1) 47 } 48 49 func (s Semaphore) Unlock() { 50 s.V(1) 51 } 52 53 /* signal-wait */ 54 55 func (s Semaphore) Signal() { 56 s.V(1) 57 } 58 59 func (s Semaphore) Wait(n int) { 60 s.P(n) 61 } 62