src/com/android/car/systemupdater/UpdateParser.java

/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * 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.android.car.systemupdater;

import android.annotation.NonNull;
import android.annotation.Nullable;
import android.util.Log;

import com.android.internal.util.Preconditions;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.Locale;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;

/** Parse an A/B update zip file. */
class UpdateParser {

    private static final String TAG = "UpdateLayoutFragment";
    private static final String PAYLOAD_BIN_FILE = "payload.bin";
    private static final String PAYLOAD_PROPERTIES = "payload_properties.txt";
    private static final String FILE_URL_PREFIX = "file://";
    private static final int ZIP_FILE_HEADER = 30;

    private UpdateParser() {
    }

    /**
     * Parse a zip file containing a system update and return a non null ParsedUpdate.
     */
    @Nullable
    static ParsedUpdate parse(@NonNull File file) throws IOException {
        Preconditions.checkNotNull(file);

        long payloadOffset = 0;
        long payloadSize = 0;
        boolean payloadFound = false;
        String[] props = null;

        try (ZipFile zipFile = new ZipFile(file)) {
            Enumeration<? extends ZipEntry> entries = zipFile.entries();
            while (entries.hasMoreElements()) {
                ZipEntry entry = entries.nextElement();
                long fileSize = entry.getCompressedSize();
                if (!payloadFound) {
                    payloadOffset += ZIP_FILE_HEADER + entry.getName().length();
                    if (entry.getExtra() != null) {
                        payloadOffset += entry.getExtra().length;
                    }
                }

                if (entry.isDirectory()) {
                    continue;
                } else if (entry.getName().equals(PAYLOAD_BIN_FILE)) {
                    payloadSize = fileSize;
                    payloadFound = true;
                } else if (entry.getName().equals(PAYLOAD_PROPERTIES)) {
                    try (BufferedReader buffer = new BufferedReader(
                            new InputStreamReader(zipFile.getInputStream(entry)))) {
                        props = buffer.lines().toArray(String[]::new);
                    }
                }
                if (!payloadFound) {
                    payloadOffset += fileSize;
                }

                if (Log.isLoggable(TAG, Log.DEBUG)) {
                    Log.d(TAG, String.format("Entry %s", entry.getName()));
                }
            }
        }
        return new ParsedUpdate(file, payloadOffset, payloadSize, props);
    }

    /** Information parsed from an update file. */
    static class ParsedUpdate {
        final String mUrl;
        final long mOffset;
        final long mSize;
        final String[] mProps;

        ParsedUpdate(File file, long offset, long size, String[] props) {
            mUrl = FILE_URL_PREFIX + file.getAbsolutePath();
            mOffset = offset;
            mSize = size;
            mProps = props;
        }

        /** Verify the update information is correct. */
        boolean isValid() {
            return mOffset >= 0 && mSize > 0 && mProps != null;
        }

        @Override
        public String toString() {
            return String.format(Locale.getDefault(),
                    "ParsedUpdate: URL=%s, offset=%d, size=%s, props=%s",
                    mUrl, mOffset, mSize, Arrays.toString(mProps));
        }
    }
}