1 /* 2 * Copyright (C) 2014 Square, Inc. 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 package okio; 17 18 /** 19 * A collection of unused segments, necessary to avoid GC churn and zero-fill. 20 * This pool is a thread-safe static singleton. 21 */ 22 final class SegmentPool { 23 /** The maximum number of bytes to pool. */ 24 // TODO: Is 64 KiB a good maximum size? Do we ever have that many idle segments? 25 static final long MAX_SIZE = 64 * 1024; // 64 KiB. 26 27 /** Singly-linked list of segments. */ 28 static Segment next; 29 30 /** Total bytes in this pool. */ 31 static long byteCount; 32 33 private SegmentPool() { 34 } 35 36 static Segment take() { 37 synchronized (SegmentPool.class) { 38 if (next != null) { 39 Segment result = next; 40 next = result.next; 41 result.next = null; 42 byteCount -= Segment.SIZE; 43 return result; 44 } 45 } 46 return new Segment(); // Pool is empty. Don't zero-fill while holding a lock. 47 } 48 49 static void recycle(Segment segment) { 50 if (segment.next != null || segment.prev != null) throw new IllegalArgumentException(); 51 if (segment.shared) return; // This segment cannot be recycled. 52 synchronized (SegmentPool.class) { 53 if (byteCount + Segment.SIZE > MAX_SIZE) return; // Pool is full. 54 byteCount += Segment.SIZE; 55 segment.next = next; 56 segment.pos = segment.limit = 0; 57 next = segment; 58 } 59 } 60 } 61
