Java tutorial
/* * 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.commons.compress.compressors.gzip; import java.util.HashMap; import java.util.Locale; import java.util.Map; /** * Utility code for the gzip compression format. * @ThreadSafe */ public class GzipUtils { /** * Map from common filename suffixes to the suffixes that identify gzipped * versions of those file types. For example: from ".tar" to ".tgz". */ private static final Map compressSuffix = new HashMap(); /** * Map from common filename suffixes of gzipped files to the corresponding * suffixes of uncompressed files. For example: from ".tgz" to ".tar". * <p> * This map also contains gzip-specific suffixes like ".gz" and "-z". * These suffixes are mapped to the empty string, as they should simply * be removed from the filename when the file is uncompressed. */ private static final Map uncompressSuffix = new HashMap(); static { compressSuffix.put(".tar", ".tgz"); compressSuffix.put(".svg", ".svgz"); compressSuffix.put(".cpio", ".cpgz"); compressSuffix.put(".wmf", ".wmz"); compressSuffix.put(".emf", ".emz"); uncompressSuffix.put(".tgz", ".tar"); uncompressSuffix.put(".taz", ".tar"); uncompressSuffix.put(".svgz", ".svg"); uncompressSuffix.put(".cpgz", ".cpio"); uncompressSuffix.put(".wmz", ".wmf"); uncompressSuffix.put(".emz", ".emf"); uncompressSuffix.put(".gz", ""); uncompressSuffix.put(".z", ""); uncompressSuffix.put("-gz", ""); uncompressSuffix.put("-z", ""); uncompressSuffix.put("_z", ""); } // N.B. if any shorter or longer keys are added, ensure the for loop limits are changed /** Private constructor to prevent instantiation of this utility class. */ private GzipUtils() { } /** * Detects common gzip suffixes in the given filename. * * @param filename name of a file * @return <code>true</code> if the filename has a common gzip suffix, * <code>false</code> otherwise */ public static boolean isCompressedFilename(String filename) { String lower = filename.toLowerCase(Locale.ENGLISH); int n = lower.length(); // Shortest suffix is two letters (_z), longest is five (.svgz) for (int i = 2; i <= 5 && i < n; i++) { if (uncompressSuffix.containsKey(lower.substring(n - i))) { return true; } } return false; } /** * Maps the given name of a gzip-compressed file to the name that the * file should have after uncompression. Commonly used file type specific * suffixes like ".tgz" or ".svgz" are automatically detected and * correctly mapped. For example the name "package.tgz" is mapped to * "package.tar". And any filenames with the generic ".gz" suffix * (or any other generic gzip suffix) is mapped to a name without that * suffix. If no gzip suffix is detected, then the filename is returned * unmapped. * * @param filename name of a file * @return name of the corresponding uncompressed file */ public static String getUncompressedFilename(String filename) { String lower = filename.toLowerCase(Locale.ENGLISH); int n = lower.length(); // Shortest suffix is two letters (_z), longest is five (.svgz) for (int i = 2; i <= 5 && i < n; i++) { Object suffix = uncompressSuffix.get(lower.substring(n - i)); if (suffix != null) { return filename.substring(0, n - i) + suffix; } } return filename; } /** * Maps the given filename to the name that the file should have after * compression with gzip. Common file types with custom suffixes for * compressed versions are automatically detected and correctly mapped. * For example the name "package.tar" is mapped to "package.tgz". If no * custom mapping is applicable, then the default ".gz" suffix is appended * to the filename. * * @param filename name of a file * @return name of the corresponding compressed file */ public static String getCompressedFilename(String filename) { String lower = filename.toLowerCase(Locale.ENGLISH); int n = lower.length(); // Shortest suffix is four letters (.svg), longest is five (.cpio) for (int i = 4; i <= 5 && i < n; i++) { Object suffix = compressSuffix.get(lower.substring(n - i)); if (suffix != null) { return filename.substring(0, n - i) + suffix; } } // No custom suffix found, just append the default .gz return filename + ".gz"; } }