001 /* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, 013 * software distributed under the License is distributed on an 014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 015 * KIND, either express or implied. See the License for the 016 * specific language governing permissions and limitations 017 * under the License. 018 */ 019 package org.apache.commons.compress.compressors.gzip; 020 021 import java.io.IOException; 022 import java.io.InputStream; 023 import java.util.zip.GZIPInputStream; 024 025 import org.apache.commons.compress.compressors.CompressorInputStream; 026 027 /** 028 * Implements the "gz" compression format as an input stream. 029 * This classes wraps the standard java classes for working with gz. 030 */ 031 public class GzipCompressorInputStream extends CompressorInputStream { 032 /* reference to the compressed stream */ 033 private final GZIPInputStream in; 034 035 /** 036 * Constructs a new GZip compressed input stream by the referenced 037 * InputStream. 038 * 039 * @param inputStream the InputStream from which this object should be created of 040 * @throws IOException if the stream could not be created 041 */ 042 public GzipCompressorInputStream(InputStream inputStream) throws IOException { 043 in = new GZIPInputStream(inputStream); 044 } 045 046 /** {@inheritDoc} */ 047 public int read() throws IOException { 048 int read = in.read(); 049 this.count(read < 0 ? -1 : 1); 050 return read; 051 } 052 053 /** 054 * {@inheritDoc} 055 * 056 * @since Apache Commons Compress 1.1 057 */ 058 public int read(byte[] b) throws IOException { 059 int read = in.read(b); 060 this.count(read); 061 return read; 062 } 063 064 /** 065 * {@inheritDoc} 066 * 067 * @since Apache Commons Compress 1.1 068 */ 069 public int read(byte[] b, int from, int length) throws IOException { 070 int read = in.read(b, from, length); 071 this.count(read); 072 return read; 073 } 074 075 /** 076 * Checks if the signature matches what is expected for a gzip file. 077 * 078 * @param signature 079 * the bytes to check 080 * @param length 081 * the number of bytes to check 082 * @return true, if this stream is a gzipped compressed stream, false otherwise 083 * 084 * @since Apache Commons Compress 1.1 085 */ 086 public static boolean matches(byte[] signature, int length) { 087 088 if (length < 2) { 089 return false; 090 } 091 092 if (signature[0] != 31) { 093 return false; 094 } 095 096 if (signature[1] != -117) { 097 return false; 098 } 099 100 return true; 101 } 102 103 }