CodecPool.java
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上传日期:2018-01-08
资源大小:41811k
文件大小:5k
- /**
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements. See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership. The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- package org.apache.hadoop.io.compress;
- import java.util.ArrayList;
- import java.util.HashMap;
- import java.util.List;
- import java.util.Map;
- import org.apache.commons.logging.Log;
- import org.apache.commons.logging.LogFactory;
- import org.apache.hadoop.util.ReflectionUtils;
- /**
- * A global compressor/decompressor pool used to save and reuse
- * (possibly native) compression/decompression codecs.
- */
- public class CodecPool {
- private static final Log LOG = LogFactory.getLog(CodecPool.class);
-
- /**
- * A global compressor pool used to save the expensive
- * construction/destruction of (possibly native) decompression codecs.
- */
- private static final Map<Class<Compressor>, List<Compressor>> compressorPool =
- new HashMap<Class<Compressor>, List<Compressor>>();
-
- /**
- * A global decompressor pool used to save the expensive
- * construction/destruction of (possibly native) decompression codecs.
- */
- private static final Map<Class<Decompressor>, List<Decompressor>> decompressorPool =
- new HashMap<Class<Decompressor>, List<Decompressor>>();
- private static <T> T borrow(Map<Class<T>, List<T>> pool,
- Class<? extends T> codecClass) {
- T codec = null;
-
- // Check if an appropriate codec is available
- synchronized (pool) {
- if (pool.containsKey(codecClass)) {
- List<T> codecList = pool.get(codecClass);
-
- if (codecList != null) {
- synchronized (codecList) {
- if (!codecList.isEmpty()) {
- codec = codecList.remove(codecList.size()-1);
- }
- }
- }
- }
- }
-
- return codec;
- }
- private static <T> void payback(Map<Class<T>, List<T>> pool, T codec) {
- if (codec != null) {
- Class<T> codecClass = ReflectionUtils.getClass(codec);
- synchronized (pool) {
- if (!pool.containsKey(codecClass)) {
- pool.put(codecClass, new ArrayList<T>());
- }
- List<T> codecList = pool.get(codecClass);
- synchronized (codecList) {
- codecList.add(codec);
- }
- }
- }
- }
-
- /**
- * Get a {@link Compressor} for the given {@link CompressionCodec} from the
- * pool or a new one.
- *
- * @param codec the <code>CompressionCodec</code> for which to get the
- * <code>Compressor</code>
- * @return <code>Compressor</code> for the given
- * <code>CompressionCodec</code> from the pool or a new one
- */
- public static Compressor getCompressor(CompressionCodec codec) {
- Compressor compressor = borrow(compressorPool, codec.getCompressorType());
- if (compressor == null) {
- compressor = codec.createCompressor();
- LOG.info("Got brand-new compressor");
- } else {
- LOG.debug("Got recycled compressor");
- }
- return compressor;
- }
-
- /**
- * Get a {@link Decompressor} for the given {@link CompressionCodec} from the
- * pool or a new one.
- *
- * @param codec the <code>CompressionCodec</code> for which to get the
- * <code>Decompressor</code>
- * @return <code>Decompressor</code> for the given
- * <code>CompressionCodec</code> the pool or a new one
- */
- public static Decompressor getDecompressor(CompressionCodec codec) {
- Decompressor decompressor = borrow(decompressorPool, codec.getDecompressorType());
- if (decompressor == null) {
- decompressor = codec.createDecompressor();
- LOG.info("Got brand-new decompressor");
- } else {
- LOG.debug("Got recycled decompressor");
- }
- return decompressor;
- }
-
- /**
- * Return the {@link Compressor} to the pool.
- *
- * @param compressor the <code>Compressor</code> to be returned to the pool
- */
- public static void returnCompressor(Compressor compressor) {
- if (compressor == null) {
- return;
- }
- compressor.reset();
- payback(compressorPool, compressor);
- }
-
- /**
- * Return the {@link Decompressor} to the pool.
- *
- * @param decompressor the <code>Decompressor</code> to be returned to the
- * pool
- */
- public static void returnDecompressor(Decompressor decompressor) {
- if (decompressor == null) {
- return;
- }
- decompressor.reset();
- payback(decompressorPool, decompressor);
- }
- }