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.archivers.ar; import java.io.IOException; import java.io.InputStream; import org.apache.commons.compress.archivers.ArchiveEntry; import org.apache.commons.compress.archivers.ArchiveInputStream; import org.apache.commons.compress.utils.ArchiveUtils; /** * Implements the "ar" archive format as an input stream. * * @NotThreadSafe * */ public class ArArchiveInputStream extends ArchiveInputStream { private final InputStream input; private long offset = 0; private boolean closed; /* * If getNextEnxtry has been called, the entry metadata is stored in * currentEntry. */ private ArArchiveEntry currentEntry = null; // Storage area for extra long names (GNU ar) private byte[] namebuffer = null; /* * The offset where the current entry started. -1 if no entry has been * called */ private long entryOffset = -1; /** * Constructs an Ar input stream with the referenced stream * * @param pInput * the ar input stream */ public ArArchiveInputStream(final InputStream pInput) { input = pInput; closed = false; } /** * Returns the next AR entry in this stream. * * @return the next AR entry. * @throws IOException * if the entry could not be read */ public ArArchiveEntry getNextArEntry() throws IOException { if (currentEntry != null) { final long entryEnd = entryOffset + currentEntry.getLength(); while (offset < entryEnd) { int x = read(); if (x == -1) { // hit EOF before previous entry was complete // TODO: throw an exception instead? return null; } } currentEntry = null; } if (offset == 0) { final byte[] expected = ArchiveUtils.toAsciiBytes(ArArchiveEntry.HEADER); final byte[] realized = new byte[expected.length]; final int read = read(realized); if (read != expected.length) { throw new IOException("failed to read header. Occured at byte: " + getBytesRead()); } for (int i = 0; i < expected.length; i++) { if (expected[i] != realized[i]) { throw new IOException("invalid header " + ArchiveUtils.toAsciiString(realized)); } } } if (offset % 2 != 0 && read() < 0) { // hit eof return null; } if (input.available() == 0) { return null; } final byte[] name = new byte[16]; final byte[] lastmodified = new byte[12]; final byte[] userid = new byte[6]; final byte[] groupid = new byte[6]; final byte[] filemode = new byte[8]; final byte[] length = new byte[10]; read(name); read(lastmodified); read(userid); read(groupid); read(filemode); read(length); { final byte[] expected = ArchiveUtils.toAsciiBytes(ArArchiveEntry.TRAILER); final byte[] realized = new byte[expected.length]; final int read = read(realized); if (read != expected.length) { throw new IOException("failed to read entry trailer. Occured at byte: " + getBytesRead()); } for (int i = 0; i < expected.length; i++) { if (expected[i] != realized[i]) { throw new IOException( "invalid entry trailer. not read the content? Occured at byte: " + getBytesRead()); } } } entryOffset = offset; // GNU ar stores multiple extended filenames in the data section of a file with the name "//", this record is referred to by future headers. A header references an extended filename by storing a "/" followed by a decimal offset to the start of the filename in the extended filename data section. The format of this "//" file itself is simply a list of the long filenames, each separated by one or more LF characters. Note that the decimal offsets are number of characters, not line or string number within the "//" file. // // GNU ar uses a '/' to mark the end of the filename; this allows for the use of spaces without the use of an extended filename. // entry name is stored as ASCII string String temp = ArchiveUtils.toAsciiString(name).trim(); if (temp.equals("//")) { // GNU extended filenames entry int bufflen = asInt(length); // Assume length will fit in an int namebuffer = new byte[bufflen]; int read = read(namebuffer, 0, bufflen); if (read != bufflen) { throw new IOException("Failed to read complete // record: expected=" + bufflen + " read=" + read); } currentEntry = new ArArchiveEntry(temp, bufflen); return getNextArEntry(); } else if (temp.endsWith("/")) { // GNU terminator temp = temp.substring(0, temp.length() - 1); } else if (temp.matches("^/\\d+")) {// GNU long filename ref. int offset = Integer.parseInt(temp.substring(1));// get the offset temp = getExtendedName(offset); // convert to the long name } currentEntry = new ArArchiveEntry(temp, asLong(length), asInt(userid, true), asInt(groupid, true), asInt(filemode, 8), asLong(lastmodified)); return currentEntry; } /** * Get an extended name from the GNU extended name buffer. * * @param offset pointer to entry within the buffer * @return the extended file name; without trailing "/" if present. * @throws IOException if name not found or buffer not set up */ private String getExtendedName(int offset) throws IOException { if (namebuffer == null) { throw new IOException("Cannot process GNU long filename as no // record was found"); } for (int i = offset; i < namebuffer.length; i++) { if (namebuffer[i] == '\012') { if (namebuffer[i - 1] == '/') { i--; // drop trailing / } return ArchiveUtils.toAsciiString(namebuffer, offset, i - offset); } } throw new IOException("Failed to read entry: " + offset); } private long asLong(byte[] input) { return Long.parseLong(new String(input).trim()); } private int asInt(byte[] input) { return asInt(input, 10, false); } private int asInt(byte[] input, boolean treatBlankAsZero) { return asInt(input, 10, treatBlankAsZero); } private int asInt(byte[] input, int base) { return asInt(input, base, false); } private int asInt(byte[] input, int base, boolean treatBlankAsZero) { String string = new String(input).trim(); if (string.length() == 0 && treatBlankAsZero) { return 0; } return Integer.parseInt(string, base); } /* * (non-Javadoc) * * @see * org.apache.commons.compress.archivers.ArchiveInputStream#getNextEntry() */ public ArchiveEntry getNextEntry() throws IOException { return getNextArEntry(); } /* * (non-Javadoc) * * @see java.io.InputStream#close() */ public void close() throws IOException { if (!closed) { closed = true; input.close(); } currentEntry = null; } /* * (non-Javadoc) * * @see java.io.InputStream#read(byte[], int, int) */ public int read(byte[] b, final int off, final int len) throws IOException { int toRead = len; if (currentEntry != null) { final long entryEnd = entryOffset + currentEntry.getLength(); if (len > 0 && entryEnd > offset) { toRead = (int) Math.min(len, entryEnd - offset); } else { return -1; } } final int ret = this.input.read(b, off, toRead); count(ret); offset += (ret > 0 ? ret : 0); return ret; } /** * Checks if the signature matches ASCII "!<arch>" followed by a single LF * control character * * @param signature * the bytes to check * @param length * the number of bytes to check * @return true, if this stream is an Ar archive stream, false otherwise */ public static boolean matches(byte[] signature, int length) { // 3c21 7261 6863 0a3e if (length < 8) { return false; } if (signature[0] != 0x21) { return false; } if (signature[1] != 0x3c) { return false; } if (signature[2] != 0x61) { return false; } if (signature[3] != 0x72) { return false; } if (signature[4] != 0x63) { return false; } if (signature[5] != 0x68) { return false; } if (signature[6] != 0x3e) { return false; } if (signature[7] != 0x0a) { return false; } return true; } }