/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/* Apache Harmony HEADER because the code in this class comes mostly from ZipFile, ZipEntry and
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* ZipConstants from android libcore.
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*/
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package androidx.multidex;
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import java.io.File;
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import java.io.IOException;
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import java.io.RandomAccessFile;
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import java.util.zip.CRC32;
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import java.util.zip.ZipException;
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/**
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* Tools to build a quick partial crc of zip files.
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*/
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final class ZipUtil {
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static class CentralDirectory {
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long offset;
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long size;
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}
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/* redefine those constant here because of bug 13721174 preventing to compile using the
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* constants defined in ZipFile */
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private static final int ENDHDR = 22;
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private static final int ENDSIG = 0x6054b50;
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/**
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* Size of reading buffers.
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*/
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private static final int BUFFER_SIZE = 0x4000;
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/**
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* Compute crc32 of the central directory of an apk. The central directory contains
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* the crc32 of each entries in the zip so the computed result is considered valid for the whole
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* zip file. Does not support zip64 nor multidisk but it should be OK for now since ZipFile does
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* not either.
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*/
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static long getZipCrc(File apk) throws IOException {
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RandomAccessFile raf = new RandomAccessFile(apk, "r");
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try {
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CentralDirectory dir = findCentralDirectory(raf);
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return computeCrcOfCentralDir(raf, dir);
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} finally {
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raf.close();
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}
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}
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/* Package visible for testing */
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static CentralDirectory findCentralDirectory(RandomAccessFile raf) throws IOException,
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ZipException {
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long scanOffset = raf.length() - ENDHDR;
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if (scanOffset < 0) {
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throw new ZipException("File too short to be a zip file: " + raf.length());
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}
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long stopOffset = scanOffset - 0x10000 /* ".ZIP file comment"'s max length */;
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if (stopOffset < 0) {
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stopOffset = 0;
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}
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int endSig = Integer.reverseBytes(ENDSIG);
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while (true) {
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raf.seek(scanOffset);
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if (raf.readInt() == endSig) {
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break;
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}
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scanOffset--;
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if (scanOffset < stopOffset) {
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throw new ZipException("End Of Central Directory signature not found");
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}
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}
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// Read the End Of Central Directory. ENDHDR includes the signature
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// bytes,
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// which we've already read.
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// Pull out the information we need.
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raf.skipBytes(2); // diskNumber
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raf.skipBytes(2); // diskWithCentralDir
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raf.skipBytes(2); // numEntries
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raf.skipBytes(2); // totalNumEntries
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CentralDirectory dir = new CentralDirectory();
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dir.size = Integer.reverseBytes(raf.readInt()) & 0xFFFFFFFFL;
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dir.offset = Integer.reverseBytes(raf.readInt()) & 0xFFFFFFFFL;
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return dir;
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}
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/* Package visible for testing */
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static long computeCrcOfCentralDir(RandomAccessFile raf, CentralDirectory dir)
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throws IOException {
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CRC32 crc = new CRC32();
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long stillToRead = dir.size;
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raf.seek(dir.offset);
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int length = (int) Math.min(BUFFER_SIZE, stillToRead);
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byte[] buffer = new byte[BUFFER_SIZE];
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length = raf.read(buffer, 0, length);
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while (length != -1) {
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crc.update(buffer, 0, length);
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stillToRead -= length;
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if (stillToRead == 0) {
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break;
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}
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length = (int) Math.min(BUFFER_SIZE, stillToRead);
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length = raf.read(buffer, 0, length);
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}
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return crc.getValue();
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}
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}
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