io.airlift.drift.transport.netty.codec.ThriftFramedDecoder.java Source code

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Here is the source code for io.airlift.drift.transport.netty.codec.ThriftFramedDecoder.java

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/*
 * Copyright (C) 2018 Facebook, Inc.
 *
 * 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 io.airlift.drift.transport.netty.codec;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;

import java.util.List;
import java.util.Optional;

import static com.google.common.base.Preconditions.checkArgument;
import static java.lang.Math.min;
import static java.lang.Math.toIntExact;
import static java.util.Objects.requireNonNull;

class ThriftFramedDecoder extends ByteToMessageDecoder {
    private final FrameInfoDecoder frameInfoDecoder;
    private final int maxFrameSizeInBytes;

    private Optional<FrameInfo> tooLongFrameInfo = Optional.empty();
    private long tooLongFrameSizeInBytes;
    private long bytesToDiscard;

    public ThriftFramedDecoder(FrameInfoDecoder frameInfoDecoder, int maxFrameSizeInBytes) {
        this.frameInfoDecoder = requireNonNull(frameInfoDecoder, "sequenceIdDecoder is null");
        checkArgument(maxFrameSizeInBytes >= 0, "maxFrameSizeInBytes");
        this.maxFrameSizeInBytes = maxFrameSizeInBytes;
    }

    @Override
    protected void decode(ChannelHandlerContext context, ByteBuf buffer, List<Object> output) {
        decode(buffer).ifPresent(output::add);
    }

    private Optional<ByteBuf> decode(ByteBuf buffer) {
        if (bytesToDiscard > 0) {
            discardTooLongFrame(buffer);
            return Optional.empty();
        }

        int initialReaderIndex = buffer.readerIndex();

        if (buffer.readableBytes() < Integer.BYTES) {
            return Optional.empty();
        }
        long frameSizeInBytes = buffer.readUnsignedInt();

        if (frameSizeInBytes > maxFrameSizeInBytes) {
            // this invocation doesn't move the readerIndex
            Optional<FrameInfo> frameInfo = frameInfoDecoder.tryDecodeFrameInfo(buffer);
            if (frameInfo.isPresent()) {
                tooLongFrameInfo = frameInfo;
                tooLongFrameSizeInBytes = frameSizeInBytes;
                bytesToDiscard = frameSizeInBytes;
                discardTooLongFrame(buffer);
                return Optional.empty();
            }
            // Basic frame info cannot be decoded and the max frame size is already exceeded.
            // Instead of waiting forever, fail without providing the sequence ID.
            if (buffer.readableBytes() >= maxFrameSizeInBytes) {
                tooLongFrameInfo = Optional.empty();
                tooLongFrameSizeInBytes = frameSizeInBytes;
                bytesToDiscard = frameSizeInBytes;
                discardTooLongFrame(buffer);
                return Optional.empty();
            }
            buffer.readerIndex(initialReaderIndex);
            return Optional.empty();
        }

        if (buffer.readableBytes() >= frameSizeInBytes) {
            // toIntExact must be safe, as frameSizeInBytes <= maxFrameSize
            ByteBuf frame = buffer.retainedSlice(buffer.readerIndex(), toIntExact(frameSizeInBytes));
            buffer.readerIndex(buffer.readerIndex() + toIntExact(frameSizeInBytes));
            return Optional.of(frame);
        }

        buffer.readerIndex(initialReaderIndex);
        return Optional.empty();
    }

    private void discardTooLongFrame(ByteBuf buffer) {
        // readableBytes returns int, toIntExact must be safe
        int bytesToSkip = toIntExact(min(bytesToDiscard, buffer.readableBytes()));
        buffer.skipBytes(bytesToSkip);
        bytesToDiscard -= bytesToSkip;

        if (bytesToDiscard == 0) {
            RuntimeException exception = new FrameTooLargeException(tooLongFrameInfo, tooLongFrameSizeInBytes,
                    maxFrameSizeInBytes);
            tooLongFrameInfo = Optional.empty();
            tooLongFrameSizeInBytes = 0;
            throw exception;
        }
    }
}