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// Copyright 2016 Google Inc. All rights reserved.
//
// Licensed 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 com.google.archivepatcher.generator;
import com.google.archivepatcher.shared.RandomAccessFileInputStream;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.zip.ZipException;
/**
* A simplified, structural representation of a zip or zip-like (jar, apk, etc) archive. The class
* provides the minimum structural information needed for patch generation and is not suitable as a
* general zip-processing library. In particular, there is little or no verification that any of the
* zip structure is correct or sane; it assumed that the input is sane.
*/
public class MinimalZipArchive {
/**
* Sorts {@link MinimalZipEntry} objects by {@link MinimalZipEntry#getFileOffsetOfLocalEntry()} in
* ascending order.
*/
private static final Comparator<MinimalZipEntry> LOCAL_ENTRY_OFFSET_COMAPRATOR =
new Comparator<MinimalZipEntry>() {
@Override
public int compare(MinimalZipEntry o1, MinimalZipEntry o2) {
return Long.compare(o1.getFileOffsetOfLocalEntry(), o2.getFileOffsetOfLocalEntry());
}
};
/**
* Generate a listing of all of the files in a zip archive in file order and return it. Each entry
* is a {@link MinimalZipEntry}, which has just enough information to generate a patch.
* @param file the zip file to read
* @return such a listing
* @throws IOException if anything goes wrong while reading
*/
public static List<MinimalZipEntry> listEntries(File file) throws IOException {
try (RandomAccessFileInputStream in = new RandomAccessFileInputStream(file)) {
return listEntriesInternal(in);
}
}
/**
* Internal implementation of {@link #listEntries(File)}.
* @param in the input stream to read from
* @return see {@link #listEntries(File)}
* @throws IOException if anything goes wrong while reading
*/
private static List<MinimalZipEntry> listEntriesInternal(RandomAccessFileInputStream in)
throws IOException {
// Step 1: Locate the end-of-central-directory record header.
long offsetOfEocd = MinimalZipParser.locateStartOfEocd(in, 32768);
if (offsetOfEocd == -1) {
// Archive is weird, abort.
throw new ZipException("EOCD record not found in last 32k of archive, giving up");
}
// Step 2: Parse the end-of-central-directory data to locate the central directory itself
in.setRange(offsetOfEocd, in.length() - offsetOfEocd);
MinimalCentralDirectoryMetadata centralDirectoryMetadata = MinimalZipParser.parseEocd(in);
// Step 3: Extract a list of all central directory entries (contiguous data stream)
in.setRange(
centralDirectoryMetadata.getOffsetOfCentralDirectory(),
centralDirectoryMetadata.getLengthOfCentralDirectory());
List<MinimalZipEntry> minimalZipEntries =
new ArrayList<MinimalZipEntry>(centralDirectoryMetadata.getNumEntriesInCentralDirectory());
for (int x = 0; x < centralDirectoryMetadata.getNumEntriesInCentralDirectory(); x++) {
minimalZipEntries.add(MinimalZipParser.parseCentralDirectoryEntry(in));
}
// Step 4: Sort the entries in file order, not central directory order.
Collections.sort(minimalZipEntries, LOCAL_ENTRY_OFFSET_COMAPRATOR);
// Step 5: Seek out each local entry and calculate the offset of the compressed data within
for (int x = 0; x < minimalZipEntries.size(); x++) {
MinimalZipEntry entry = minimalZipEntries.get(x);
long offsetOfNextEntry;
if (x < minimalZipEntries.size() - 1) {
// Don't allow reading past the start of the next entry, for sanity.
offsetOfNextEntry = minimalZipEntries.get(x + 1).getFileOffsetOfLocalEntry();
} else {
// Last entry. Don't allow reading into the central directory, for sanity.
offsetOfNextEntry = centralDirectoryMetadata.getOffsetOfCentralDirectory();
}
long rangeLength = offsetOfNextEntry - entry.getFileOffsetOfLocalEntry();
in.setRange(entry.getFileOffsetOfLocalEntry(), rangeLength);
long relativeDataOffset = MinimalZipParser.parseLocalEntryAndGetCompressedDataOffset(in);
entry.setFileOffsetOfCompressedData(entry.getFileOffsetOfLocalEntry() + relativeDataOffset);
}
// Done!
return minimalZipEntries;
}
}
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