FlowState Class — netty Architecture

Source Code

codec-http2/src/main/java/io/netty/handler/codec/http2/DefaultHttp2RemoteFlowController.java lines 271–534

    private final class FlowState implements StreamByteDistributor.StreamState {
        private final Http2Stream stream;
        private final Deque<FlowControlled> pendingWriteQueue;
        private int window;
        private long pendingBytes;
        private boolean markedWritable;

        /**
         * Set to true while a frame is being written, false otherwise.
         */
        private boolean writing;
        /**
         * Set to true if cancel() was called.
         */
        private boolean cancelled;

        FlowState(Http2Stream stream) {
            this.stream = stream;
            pendingWriteQueue = new ArrayDeque<FlowControlled>(2);
        }

        /**
         * Determine if the stream associated with this object is writable.
         * @return {@code true} if the stream associated with this object is writable.
         */
        boolean isWritable() {
            return windowSize() > pendingBytes() && !cancelled;
        }

        /**
         * The stream this state is associated with.
         */
        @Override
        public Http2Stream stream() {
            return stream;
        }

        /**
         * Returns the parameter from the last call to {@link #markedWritability(boolean)}.
         */
        boolean markedWritability() {
            return markedWritable;
        }

        /**
         * Save the state of writability.
         */
        void markedWritability(boolean isWritable) {
            this.markedWritable = isWritable;
        }

        @Override
        public int windowSize() {
            return window;
        }

        /**
         * Reset the window size for this stream.
         */
        void windowSize(int initialWindowSize) {
            window = initialWindowSize;
        }

        /**
         * Write the allocated bytes for this stream.
         * @return the number of bytes written for a stream or {@code -1} if no write occurred.
         */
        int writeAllocatedBytes(int allocated) {
            final int initialAllocated = allocated;
            int writtenBytes;
            // In case an exception is thrown we want to remember it and pass it to cancel(Throwable).
            Throwable cause = null;
            FlowControlled frame;
            try {
                assert !writing;
                writing = true;

                // Write the remainder of frames that we are allowed to
                boolean writeOccurred = false;
                while (!cancelled && (frame = peek()) != null) {
                    int maxBytes = min(allocated, writableWindow());