private void readAsync()

in src/main/java/org/apache/commons/io/input/ReadAheadInputStream.java [378:456]
63 lines of code
12 McCabe index (conditional complexity)

    private void readAsync() throws IOException {
        stateChangeLock.lock();
        final byte[] arr;
        try {
            arr = readAheadBuffer.array();
            if (endOfStream || readInProgress) {
                return;
            }
            checkReadException();
            readAheadBuffer.position(0);
            readAheadBuffer.flip();
            readInProgress = true;
        } finally {
            stateChangeLock.unlock();
        }
        executorService.execute(() -> {
            stateChangeLock.lock();
            try {
                if (isClosed) {
                    readInProgress = false;
                    return;
                }
                // Flip this so that the close method will not close the underlying input stream when we
                // are reading.
                isReading = true;
            } finally {
                stateChangeLock.unlock();
            }

            // Please note that it is safe to release the lock and read into the read ahead buffer
            // because either of following two conditions will hold:
            //
            // 1. The active buffer has data available to read so the reader will not read from the read ahead buffer.
            //
            // 2. This is the first time read is called or the active buffer is exhausted, in that case the reader waits
            // for this async read to complete.
            //
            // So there is no race condition in both the situations.
            int read = 0;
            int off = 0;
            int len = arr.length;
            Throwable exception = null;
            try {
                // try to fill the read ahead buffer.
                // if a reader is waiting, possibly return early.
                do {
                    read = in.read(arr, off, len);
                    if (read <= 0) {
                        break;
                    }
                    off += read;
                    len -= read;
                } while (len > 0 && !isWaiting.get());
            } catch (final Throwable ex) {
                exception = ex;
                if (ex instanceof Error) {
                    // `readException` may not be reported to the user. Rethrow Error to make sure at least
                    // The user can see Error in UncaughtExceptionHandler.
                    throw (Error) ex;
                }
            } finally {
                stateChangeLock.lock();
                try {
                    readAheadBuffer.limit(off);
                    if (read < 0 || exception instanceof EOFException) {
                        endOfStream = true;
                    } else if (exception != null) {
                        readAborted = true;
                        readException = exception;
                    }
                    readInProgress = false;
                    signalAsyncReadComplete();
                } finally {
                    stateChangeLock.unlock();
                }
                closeUnderlyingInputStreamIfNecessary();
            }
        });
    }