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 */ 019package org.apache.commons.compress.archivers.tar; 020 021import java.io.IOException; 022import java.util.ArrayList; 023import java.util.List; 024 025/** 026 * This class represents a sparse entry in a Tar archive. 027 * 028 * <p> 029 * The C structure for a sparse entry is: 030 * <pre> 031 * struct posix_header { 032 * struct sparse sp[21]; // TarConstants.SPARSELEN_GNU_SPARSE - offset 0 033 * char isextended; // TarConstants.ISEXTENDEDLEN_GNU_SPARSE - offset 504 034 * }; 035 * </pre> 036 * Whereas, "struct sparse" is: 037 * <pre> 038 * struct sparse { 039 * char offset[12]; // offset 0 040 * char numbytes[12]; // offset 12 041 * }; 042 * </pre> 043 * 044 * <p>Each such struct describes a block of data that has actually been written to the archive. The offset describes 045 * where in the extracted file the data is supposed to start and the numbytes provides the length of the block. When 046 * extracting the entry the gaps between the sparse structs are equivalent to areas filled with zero bytes.</p> 047 */ 048 049public class TarArchiveSparseEntry implements TarConstants { 050 /** If an extension sparse header follows. */ 051 private final boolean isExtended; 052 053 private final List<TarArchiveStructSparse> sparseHeaders; 054 055 /** 056 * Construct an entry from an archive's header bytes. File is set 057 * to null. 058 * 059 * @param headerBuf The header bytes from a tar archive entry. 060 * @throws IOException on unknown format 061 */ 062 public TarArchiveSparseEntry(final byte[] headerBuf) throws IOException { 063 int offset = 0; 064 sparseHeaders = new ArrayList<>(TarUtils.readSparseStructs(headerBuf, 0, SPARSE_HEADERS_IN_EXTENSION_HEADER)); 065 offset += SPARSELEN_GNU_SPARSE; 066 isExtended = TarUtils.parseBoolean(headerBuf, offset); 067 } 068 069 public boolean isExtended() { 070 return isExtended; 071 } 072 073 /** 074 * Obtains information about the configuration for the sparse entry. 075 * @since 1.20 076 * @return information about the configuration for the sparse entry. 077 */ 078 public List<TarArchiveStructSparse> getSparseHeaders() { 079 return sparseHeaders; 080 } 081}