driver-async/src/main/com/mongodb/async/client/gridfs/helpers/AsynchronousChannelHelper.java
public static AsyncInputStream channelToInputStream(final AsynchronousByteChannel asynchronousByteChannel) {
        notNull("asynchronousByteChannel", asynchronousByteChannel);
        return new AsyncInputStream() {
            @Override
            public void read(final ByteBuffer dst, final SingleResultCallback<Integer> callback) {
                asynchronousByteChannel.read(dst, null, new CompletionHandler<Integer, Object>() {
                    @Override
                    public void completed(final Integer result, final Object attachment) {
                        callback.onResult(result, null);
                    }

                    @Override
                    public void failed(final Throwable exc, final Object attachment) {
                        callback.onResult(null, exc);
                    }
                });
            }

            @Override
            public void skip(final long bytesToSkip, final SingleResultCallback<Long> callback) {
                notNull("callback", callback);
                callback.onResult(0L, null);
            }

            @Override
            public void close(final SingleResultCallback<Void> callback) {
                try {
                    asynchronousByteChannel.close();
                    callback.onResult(null, null);
                } catch (Exception e) {
                    callback.onResult(null, e);
                }
            }
        };
    }
public static AsyncInputStream channelToInputStream(final AsynchronousByteChannel asynchronousByteChannel) {
        notNull("asynchronousByteChannel", asynchronousByteChannel);
        return new AsyncInputStream() {
            @Override
            public void read(final ByteBuffer dst, final SingleResultCallback<Integer> callback) {
                asynchronousByteChannel.read(dst, null, new CompletionHandler<Integer, Object>() {
                    @Override
                    public void completed(final Integer result, final Object attachment) {
                        callback.onResult(result, null);
                    }

                    @Override
                    public void failed(final Throwable exc, final Object attachment) {
                        callback.onResult(null, exc);
                    }
                });
            }

            @Override
            public void skip(final long bytesToSkip, final SingleResultCallback<Long> callback) {
                notNull("callback", callback);
                callback.onResult(0L, null);
            }

            @Override
            public void close(final SingleResultCallback<Void> callback) {
                try {
                    asynchronousByteChannel.close();
                    callback.onResult(null, null);
                } catch (Exception e) {
                    callback.onResult(null, e);
                }
            }
        };
    }
Converts a {@link AsynchronousByteChannel} into a {@link AsyncInputStream}

@param asynchronousByteChannel the AsynchronousByteChannel
@return the AsyncInputStream