Overgram/lib/src/main/java/io/github/lonamiwebs/overgram/utils/BinaryReader.java

package io.github.lonamiwebs.overgram.utils;

import io.github.lonamiwebs.overgram.tl.*;

import java.math.BigInteger;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;

public class BinaryReader {
    private final ByteBuffer buffer;

    public BinaryReader(final ByteBuffer buffer) {
        this.buffer = buffer.order(ByteOrder.LITTLE_ENDIAN);
    }

    public int readInt() {
        return buffer.getInt();
    }

    public List<Integer> readIntList() {
        buffer.position(buffer.position() + 4); // vector code
        final int size = buffer.getInt();
        final List<Integer> result = new ArrayList<>(size);
        for (int i = 0; i < size; ++i) {
            result.add(buffer.getInt());
        }
        return result;
    }

    public long readLong() {
        return buffer.getLong();
    }

    public List<Long> readLongList() {
        buffer.position(buffer.position() + 4); // vector code
        final int size = buffer.getInt();
        final List<Long> result = new ArrayList<>(size);
        for (int i = 0; i < size; ++i) {
            result.add(buffer.getLong());
        }
        return result;
    }

    public BigInteger readInt128() {
        final byte[] bytes = new byte[16];
        buffer.get(bytes);
        return new BigInteger(Utils.reversed(bytes));
    }

    public BigInteger readInt256() {
        final byte[] bytes = new byte[32];
        buffer.get(bytes);
        return new BigInteger(Utils.reversed(bytes));
    }

    public double readDouble() {
        return buffer.getDouble();
    }

    public boolean readBoolean() {
        return buffer.getInt() == 0x997275b5;
    }

    public byte[] readBytes() {
        int length;
        int padding;
        final byte first = buffer.get();
        if (first == (byte) 0xfe) {
            buffer.position(buffer.position() - 1);
            length = buffer.getInt() >> 8;
            padding = length % 4;
        } else {
            length = first;
            padding = (length + 1) % 4;
        }

        final byte[] data = new byte[length];
        buffer.get(data);
        if (padding > 0) {
            buffer.position(buffer.position() + 4 - padding);
        }
        return data;
    }

    public List<byte[]> readBytesList() {
        buffer.position(buffer.position() + 4); // vector code
        final int size = buffer.getInt();
        final List<byte[]> result = new ArrayList<>(size);
        for (int i = 0; i < size; ++i) {
            result.add(readBytes());
        }
        return result;
    }

    public String readString() {
        return StandardCharsets.UTF_8.decode(ByteBuffer.wrap(readBytes())).toString();
    }

    public List<String> readStringList() {
        buffer.position(buffer.position() + 4); // vector code
        final int size = buffer.getInt();
        final List<String> result = new ArrayList<>(size);
        for (int i = 0; i < size; ++i) {
            result.add(readString());
        }
        return result;
    }

    public TLObject readTl() throws ClassNotFoundException {
        final int id = readInt();
        final TLObject object;
        switch (id) {
            case RPCResult.CONSTRUCTOR_ID:
                object = new RPCResult();
                break;
            case GzipPacked.CONSTRUCTOR_ID:
                object = new GzipPacked();
                break;
            case MessageContainer.CONSTRUCTOR_ID:
                object = new MessageContainer();
                break;
            default:
                object = Types.getFromId(id);
                break;
        }
        object.deserialize(this);
        return object;
    }

    public List<?> readTlList() throws ClassNotFoundException {
        buffer.position(buffer.position() + 4); // vector code
        final int size = buffer.getInt();
        final List<TLObject> result = new ArrayList<>(size);
        for (int i = 0; i < size; ++i) {
            result.add(readTl());
        }
        return result;
    }

    public int tell() {
        return buffer.position();
    }

    public void seek(final int delta) {
        buffer.position(buffer.position() + delta);
    }

    public void set(final int position) {
        buffer.position(position);
    }

    public byte[] read(final int size) {
        final byte[] result = new byte[size];
        buffer.get(result);
        return result;
    }

    public byte[] read() {
        final byte[] result = new byte[buffer.remaining()];
        buffer.get(result);
        return result;
    }
}