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.zip; import java.io.IOException; import java.util.Calendar; import java.util.Date; import java.util.zip.CRC32; /** * Utility class for handling DOS and Java time conversions. * @Immutable */ public abstract class ZipUtil { /** * Smallest date/time ZIP can handle. */ private static final byte[] DOS_TIME_MIN = ZipLong.getBytes(0x00002100L); /** * Convert a Date object to a DOS date/time field. * @param time the <code>Date</code> to convert * @return the date as a <code>ZipLong</code> */ public static ZipLong toDosTime(Date time) { return new ZipLong(toDosTime(time.getTime())); } /** * Convert a Date object to a DOS date/time field. * * <p>Stolen from InfoZip's <code>fileio.c</code></p> * @param t number of milliseconds since the epoch * @return the date as a byte array */ public static byte[] toDosTime(long t) { Calendar c = Calendar.getInstance(); c.setTimeInMillis(t); int year = c.get(Calendar.YEAR); if (year < 1980) { return copy(DOS_TIME_MIN); // stop callers from changing the array } int month = c.get(Calendar.MONTH) + 1; long value = ((year - 1980) << 25) | (month << 21) | (c.get(Calendar.DAY_OF_MONTH) << 16) | (c.get(Calendar.HOUR_OF_DAY) << 11) | (c.get(Calendar.MINUTE) << 5) | (c.get(Calendar.SECOND) >> 1); return ZipLong.getBytes(value); } /** * Assumes a negative integer really is a positive integer that * has wrapped around and re-creates the original value. * @param i the value to treat as unsigned int. * @return the unsigned int as a long. */ public static long adjustToLong(int i) { if (i < 0) { return 2 * ((long) Integer.MAX_VALUE) + 2 + i; } else { return i; } } /** * Convert a DOS date/time field to a Date object. * * @param zipDosTime contains the stored DOS time. * @return a Date instance corresponding to the given time. */ public static Date fromDosTime(ZipLong zipDosTime) { long dosTime = zipDosTime.getValue(); return new Date(dosToJavaTime(dosTime)); } /** * Converts DOS time to Java time (number of milliseconds since * epoch). */ public static long dosToJavaTime(long dosTime) { Calendar cal = Calendar.getInstance(); // CheckStyle:MagicNumberCheck OFF - no point cal.set(Calendar.YEAR, (int) ((dosTime >> 25) & 0x7f) + 1980); cal.set(Calendar.MONTH, (int) ((dosTime >> 21) & 0x0f) - 1); cal.set(Calendar.DATE, (int) (dosTime >> 16) & 0x1f); cal.set(Calendar.HOUR_OF_DAY, (int) (dosTime >> 11) & 0x1f); cal.set(Calendar.MINUTE, (int) (dosTime >> 5) & 0x3f); cal.set(Calendar.SECOND, (int) (dosTime << 1) & 0x3e); // CheckStyle:MagicNumberCheck ON return cal.getTime().getTime(); } /** * If the entry has Unicode*ExtraFields and the CRCs of the * names/comments match those of the extra fields, transfer the * known Unicode values from the extra field. */ static void setNameAndCommentFromExtraFields(ZipArchiveEntry ze, byte[] originalNameBytes, byte[] commentBytes) { UnicodePathExtraField name = (UnicodePathExtraField) ze.getExtraField(UnicodePathExtraField.UPATH_ID); String originalName = ze.getName(); String newName = getUnicodeStringIfOriginalMatches(name, originalNameBytes); if (newName != null && !originalName.equals(newName)) { ze.setName(newName); } if (commentBytes != null && commentBytes.length > 0) { UnicodeCommentExtraField cmt = (UnicodeCommentExtraField) ze .getExtraField(UnicodeCommentExtraField.UCOM_ID); String newComment = getUnicodeStringIfOriginalMatches(cmt, commentBytes); if (newComment != null) { ze.setComment(newComment); } } } /** * If the stored CRC matches the one of the given name, return the * Unicode name of the given field. * * <p>If the field is null or the CRCs don't match, return null * instead.</p> */ private static String getUnicodeStringIfOriginalMatches(AbstractUnicodeExtraField f, byte[] orig) { if (f != null) { CRC32 crc32 = new CRC32(); crc32.update(orig); long origCRC32 = crc32.getValue(); if (origCRC32 == f.getNameCRC32()) { try { return ZipEncodingHelper.UTF8_ZIP_ENCODING.decode(f.getUnicodeName()); } catch (IOException ex) { // UTF-8 unsupported? should be impossible the // Unicode*ExtraField must contain some bad bytes // TODO log this anywhere? return null; } } } return null; } /** * Create a copy of the given array - or return null if the * argument is null. */ static byte[] copy(byte[] from) { if (from != null) { byte[] to = new byte[from.length]; System.arraycopy(from, 0, to, 0, to.length); return to; } return null; } /** * Whether this library is able to read or write the given entry. */ static boolean canHandleEntryData(ZipArchiveEntry entry) { return supportsEncryptionOf(entry) && supportsMethodOf(entry); } /** * Whether this library supports the encryption used by the given * entry. * * @return true if the entry isn't encrypted at all */ private static boolean supportsEncryptionOf(ZipArchiveEntry entry) { return !entry.getGeneralPurposeBit().usesEncryption(); } /** * Whether this library supports the compression method used by * the given entry. * * @return true if the compression method is STORED or DEFLATED */ private static boolean supportsMethodOf(ZipArchiveEntry entry) { return entry.getMethod() == ZipArchiveEntry.STORED || entry.getMethod() == ZipArchiveEntry.DEFLATED; } /** * Checks whether the entry requires features not (yet) supported * by the library and throws an exception if it does. */ static void checkRequestedFeatures(ZipArchiveEntry ze) throws UnsupportedZipFeatureException { if (!supportsEncryptionOf(ze)) { throw new UnsupportedZipFeatureException(UnsupportedZipFeatureException.Feature.ENCRYPTION, ze); } if (!supportsMethodOf(ze)) { throw new UnsupportedZipFeatureException(UnsupportedZipFeatureException.Feature.METHOD, ze); } } }