1 /* 2 Copyright 2017 The Kubernetes Authors. 3 4 Licensed under the Apache License, Version 2.0 (the "License"); 5 you may not use this file except in compliance with the License. 6 You may obtain a copy of the License at 7 8 http://www.apache.org/licenses/LICENSE-2.0 9 10 Unless required by applicable law or agreed to in writing, software 11 distributed under the License is distributed on an "AS IS" BASIS, 12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 See the License for the specific language governing permissions and 14 limitations under the License. 15 */ 16 17 package buffer 18 19 // RingGrowing is a growing ring buffer. 20 // Not thread safe. 21 type RingGrowing struct { 22 data []interface{} 23 n int // Size of Data 24 beg int // First available element 25 readable int // Number of data items available 26 } 27 28 // NewRingGrowing constructs a new RingGrowing instance with provided parameters. 29 func NewRingGrowing(initialSize int) *RingGrowing { 30 return &RingGrowing{ 31 data: make([]interface{}, initialSize), 32 n: initialSize, 33 } 34 } 35 36 // ReadOne reads (consumes) first item from the buffer if it is available, otherwise returns false. 37 func (r *RingGrowing) ReadOne() (data interface{}, ok bool) { 38 if r.readable == 0 { 39 return nil, false 40 } 41 r.readable-- 42 element := r.data[r.beg] 43 r.data[r.beg] = nil // Remove reference to the object to help GC 44 if r.beg == r.n-1 { 45 // Was the last element 46 r.beg = 0 47 } else { 48 r.beg++ 49 } 50 return element, true 51 } 52 53 // WriteOne adds an item to the end of the buffer, growing it if it is full. 54 func (r *RingGrowing) WriteOne(data interface{}) { 55 if r.readable == r.n { 56 // Time to grow 57 newN := r.n * 2 58 newData := make([]interface{}, newN) 59 to := r.beg + r.readable 60 if to <= r.n { 61 copy(newData, r.data[r.beg:to]) 62 } else { 63 copied := copy(newData, r.data[r.beg:]) 64 copy(newData[copied:], r.data[:(to%r.n)]) 65 } 66 r.beg = 0 67 r.data = newData 68 r.n = newN 69 } 70 r.data[(r.readable+r.beg)%r.n] = data 71 r.readable++ 72 } 73