| /* |
| * 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.dump; |
| |
| import java.io.IOException; |
| import org.apache.commons.compress.archivers.zip.ZipEncoding; |
| |
| /** |
| * Various utilities for dump archives. |
| */ |
| class DumpArchiveUtil { |
| /** |
| * Private constructor to prevent instantiation. |
| */ |
| private DumpArchiveUtil() { |
| } |
| |
| /** |
| * Calculate checksum for buffer. |
| * |
| * @param buffer buffer containing tape segment header |
| * @returns checksum |
| */ |
| public static int calculateChecksum(byte[] buffer) { |
| int calc = 0; |
| |
| for (int i = 0; i < 256; i++) { |
| calc += DumpArchiveUtil.convert32(buffer, 4 * i); |
| } |
| |
| return DumpArchiveConstants.CHECKSUM - |
| (calc - DumpArchiveUtil.convert32(buffer, 28)); |
| } |
| |
| /** |
| * Verify that the buffer contains a tape segment header. |
| * |
| * @param buffer |
| */ |
| public static final boolean verify(byte[] buffer) { |
| // verify magic. for now only accept NFS_MAGIC. |
| int magic = convert32(buffer, 24); |
| |
| if (magic != DumpArchiveConstants.NFS_MAGIC) { |
| return false; |
| } |
| |
| //verify checksum... |
| int checksum = convert32(buffer, 28); |
| |
| if (checksum != calculateChecksum(buffer)) { |
| return false; |
| } |
| |
| return true; |
| } |
| |
| /** |
| * Get the ino associated with this buffer. |
| * |
| * @param buffer |
| */ |
| public static final int getIno(byte[] buffer) { |
| return convert32(buffer, 20); |
| } |
| |
| /** |
| * Read 8-byte integer from buffer. |
| * |
| * @param buffer |
| * @param offset |
| * @return the 8-byte entry as a long |
| */ |
| public static final long convert64(byte[] buffer, int offset) { |
| long i = 0; |
| i += (((long) buffer[offset + 7]) << 56); |
| i += (((long) buffer[offset + 6] << 48) & 0x00FF000000000000L); |
| i += (((long) buffer[offset + 5] << 40) & 0x0000FF0000000000L); |
| i += (((long) buffer[offset + 4] << 32) & 0x000000FF00000000L); |
| i += (((long) buffer[offset + 3] << 24) & 0x00000000FF000000L); |
| i += (((long) buffer[offset + 2] << 16) & 0x0000000000FF0000L); |
| i += (((long) buffer[offset + 1] << 8) & 0x000000000000FF00L); |
| i += (buffer[offset] & 0x00000000000000FFL); |
| |
| return i; |
| } |
| |
| /** |
| * Read 4-byte integer from buffer. |
| * |
| * @param buffer |
| * @param offset |
| * @return the 4-byte entry as an int |
| */ |
| public static final int convert32(byte[] buffer, int offset) { |
| int i = 0; |
| i = buffer[offset + 3] << 24; |
| i += (buffer[offset + 2] << 16) & 0x00FF0000; |
| i += (buffer[offset + 1] << 8) & 0x0000FF00; |
| i += buffer[offset] & 0x000000FF; |
| |
| return i; |
| } |
| |
| /** |
| * Read 2-byte integer from buffer. |
| * |
| * @param buffer |
| * @param offset |
| * @return the 2-byte entry as an int |
| */ |
| public static final int convert16(byte[] buffer, int offset) { |
| int i = 0; |
| i += (buffer[offset + 1] << 8) & 0x0000FF00; |
| i += buffer[offset] & 0x000000FF; |
| |
| return i; |
| } |
| |
| /** |
| * Decodes a byte array to a string. |
| */ |
| static String decode(ZipEncoding encoding, byte[] b, int offset, int len) |
| throws IOException { |
| byte[] copy = new byte[len]; |
| System.arraycopy(b, offset, copy, 0, len); |
| return encoding.decode(copy); |
| } |
| } |