github.com/lianghucheng/zrddz@v0.0.0-20200923083010-c71f680932e2/src/gopkg.in/mgo.v2/queue.go (about) 1 // mgo - MongoDB driver for Go 2 // 3 // Copyright (c) 2010-2012 - Gustavo Niemeyer <gustavo@niemeyer.net> 4 // 5 // All rights reserved. 6 // 7 // Redistribution and use in source and binary forms, with or without 8 // modification, are permitted provided that the following conditions are met: 9 // 10 // 1. Redistributions of source code must retain the above copyright notice, this 11 // list of conditions and the following disclaimer. 12 // 2. Redistributions in binary form must reproduce the above copyright notice, 13 // this list of conditions and the following disclaimer in the documentation 14 // and/or other materials provided with the distribution. 15 // 16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 17 // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 18 // WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 19 // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR 20 // ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 21 // (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 22 // LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 23 // ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 25 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 27 package mgo 28 29 type queue struct { 30 elems []interface{} 31 nelems, popi, pushi int 32 } 33 34 func (q *queue) Len() int { 35 return q.nelems 36 } 37 38 func (q *queue) Push(elem interface{}) { 39 //debugf("Pushing(pushi=%d popi=%d cap=%d): %#v\n", 40 // q.pushi, q.popi, len(q.elems), elem) 41 if q.nelems == len(q.elems) { 42 q.expand() 43 } 44 q.elems[q.pushi] = elem 45 q.nelems++ 46 q.pushi = (q.pushi + 1) % len(q.elems) 47 //debugf(" Pushed(pushi=%d popi=%d cap=%d): %#v\n", 48 // q.pushi, q.popi, len(q.elems), elem) 49 } 50 51 func (q *queue) Pop() (elem interface{}) { 52 //debugf("Popping(pushi=%d popi=%d cap=%d)\n", 53 // q.pushi, q.popi, len(q.elems)) 54 if q.nelems == 0 { 55 return nil 56 } 57 elem = q.elems[q.popi] 58 q.elems[q.popi] = nil // Help GC. 59 q.nelems-- 60 q.popi = (q.popi + 1) % len(q.elems) 61 //debugf(" Popped(pushi=%d popi=%d cap=%d): %#v\n", 62 // q.pushi, q.popi, len(q.elems), elem) 63 return elem 64 } 65 66 func (q *queue) expand() { 67 curcap := len(q.elems) 68 var newcap int 69 if curcap == 0 { 70 newcap = 8 71 } else if curcap < 1024 { 72 newcap = curcap * 2 73 } else { 74 newcap = curcap + (curcap / 4) 75 } 76 elems := make([]interface{}, newcap) 77 78 if q.popi == 0 { 79 copy(elems, q.elems) 80 q.pushi = curcap 81 } else { 82 newpopi := newcap - (curcap - q.popi) 83 copy(elems, q.elems[:q.popi]) 84 copy(elems[newpopi:], q.elems[q.popi:]) 85 q.popi = newpopi 86 } 87 for i := range q.elems { 88 q.elems[i] = nil // Help GC. 89 } 90 q.elems = elems 91 }