SimpleApkV2

SimpleApkV2.java

// package me.piebridge;

import java.io.IOException;
import java.io.RandomAccessFile;
import java.math.BigInteger;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.Arrays;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Created by thom on 2018/5/31.
 */
public class SimpleApkV2 {

    private SimpleApkV2() {

    }

    private static abstract class ApkV2Parser {

        private final String sourceDir;

        ApkV2Parser(String sourceDir) {
            this.sourceDir = sourceDir;
            parse();
        }

        private void parse() {
            final byte[] apkSignV2 = {'A', 'P', 'K', ' ', 'S', 'i', 'g', ' ',
                    'B', 'l', 'o', 'c', 'k', ' ', '4', '2'};
            try (
                    RandomAccessFile apk = new RandomAccessFile(sourceDir, "r")
            ) {
                ByteBuffer buffer = ByteBuffer.allocate(0x10);
                buffer.order(ByteOrder.LITTLE_ENDIAN);

                apk.seek(apk.length() - 0x6);
                apk.readFully(buffer.array(), 0x0, 0x6);
                int offset = buffer.getInt();
                if (buffer.getShort() != 0) {
                    return;
                }
                apk.seek(offset - 0x10);
                apk.readFully(buffer.array(), 0x0, 0x10);
                if (!Arrays.equals(apkSignV2, buffer.array())) {
                    return;
                }

                // Read and compare size fields
                apk.seek(offset - 0x18);
                apk.readFully(buffer.array(), 0x0, 0x8);
                buffer.rewind();
                int size = (int) buffer.getLong();

                ByteBuffer block = ByteBuffer.allocate(size + 0x8);
                block.order(ByteOrder.LITTLE_ENDIAN);
                apk.seek(offset - block.capacity());
                apk.readFully(block.array(), 0x0, block.capacity());

                if (size != block.getLong()) {
                    return;
                }

                while (block.remaining() > 0x18) {
                    size = (int) block.getLong();
                    int id = block.getInt();
                    int newPosition = block.position() + size - 0x4;
                    if (handle(id, size, block)) {
                        return;
                    }
                    block.position(newPosition);
                }
            } catch (IOException ignore) {
                // do nothing
            }
        }

        protected abstract boolean handle(int id, int size, ByteBuffer block);

    }

    public static void main(String[] args) {
        new DummyParser(args[0]);
    }

    private static class DummyParser extends ApkV2Parser {

        private static final char[] HEX = {
                '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
        };

        DummyParser(String sourceDir) {
            super(sourceDir);
        }

        @Override
        protected boolean handle(int id, int size, ByteBuffer block) {
            if (id == 0x7109871a) {
                System.out.println("id: " + Integer.toHexString(id) + "(sign v2), size: " + size);
            } else if (id == 0xf05368c0) {
                System.out.println("id: " + Integer.toHexString(id) + "(sign v3), size: " + size);
            } else if (id == 0x42726577) {
                System.out.println("id: " + Integer.toHexString(id) + "(padding), size: " + size);
            } else if (id == 0x71777777) {
                byte[] bytes = new byte[size - 0x4];
                block.get(bytes, 0, bytes.length);
                String channel = new String(bytes);
                System.out.println("id: " + Integer.toHexString(id) + "(channel), " + channel);
            } else {
                System.out.println("id: " + Integer.toHexString(id) + "(unknown), size: " + size);
                byte[] bytes = new byte[size - 0x4];
                block.get(bytes, 0, bytes.length);
                System.out.println("    " + hex(bytes));
            }

            return false;
        }

        private static String hex(byte[] bytes) {
            StringBuilder sb = new StringBuilder(bytes.length * 2);
            for (byte b : bytes) {
                sb.append(HEX[(b >> 4) & 0xf]);
                sb.append(HEX[b & 0xf]);
            }
            return sb.toString();
        }

    }

}