net.minestom.server.network.PolarBufferAccessWidener Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of polar Show documentation

Fast and small world format for Minestom

The newest version!

package net.minestom.server.network;

import org.jetbrains.annotations.ApiStatus;
import org.jetbrains.annotations.NotNull;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;

import static net.minestom.server.network.NetworkBufferImpl.impl;

/**
 * Provides some low level access to the internals of {@link NetworkBuffer}.
 *
 * Do not use this class.
 */
@ApiStatus.Internal
public final class PolarBufferAccessWidener {
    private static final MethodHandle ADDRESS_GETTER;
    private static final MethodHandle ADDRESS_SETTER;

    public static @NotNull NetworkBuffer networkBufferView(@NotNull NetworkBuffer buffer, long start, long length) {
        // We create the buffer with -1 to indicate its a 'dummy' buffer. We do not want to cleaner attached to
        // this buffer to free the backing data. We will later update the address.
        var viewBuffer = new NetworkBufferImpl(-1, length, 0, 0, null, impl(buffer).registries);
        setAddress(impl(viewBuffer), getAddress(impl(buffer)) + start);
        viewBuffer.writeIndex(length);
        viewBuffer.readOnly();
        return viewBuffer;
    }

    public static long networkBufferAddress(@NotNull NetworkBuffer buffer) {
        return getAddress(impl(buffer));
    }

    private static long getAddress(@NotNull NetworkBufferImpl impl) {
        try {
            return (long) ADDRESS_GETTER.invokeExact(impl);
        } catch (Throwable t) {
            throw new RuntimeException(t);
        }
    }

    private static void setAddress(@NotNull NetworkBufferImpl impl, long address) {
        try {
            ADDRESS_SETTER.invokeExact(impl, address);
        } catch (Throwable t) {
            throw new RuntimeException(t);
        }
    }

    static {
        try {
            final var lookup = MethodHandles.privateLookupIn(NetworkBufferImpl.class, MethodHandles.lookup());
            final var field = NetworkBufferImpl.class.getDeclaredField("address");
            ADDRESS_GETTER = lookup.unreflectGetter(field);
            ADDRESS_SETTER = lookup.unreflectSetter(field);
        } catch (IllegalAccessException | NoSuchFieldException e) {
            throw new RuntimeException(e);
        }
    }
}