如何在vert.x中泵送具有偏移量和长度的流？

Question

I'm porting a kotlin rest server to Vert.x, but I have some trouble finding an alternative to InputStream.skip() , OutputStream.write(buffer, 0, len) and how to append to a file on disk.

Is it possible using the Pump.pump() ? Do I have to override the ReadStream and WriteStream ?

My old code is:

    val fromOffset = FROM_OFFSET.getLongParam(req, false, 0)
    val toOffset = TO_OFFSET.getLongParam(req, false, -1)

    val component = repository.getComponent(contRep, docId, compId)

    component.inputStream.use { input ->
        res.outputStream.use { output ->
            input.skip(fromOffset)
            val buffer = ByteArray(64 * 1024)
            var len: Int
            var read = 0
            do {
                len = input.read(buffer)

                // Check offset
                read += len
                if (toOffset in 0..(read - 1))
                    len -= (read - toOffset).toInt()

                if (len > 0) output.write(buffer, 0, len)

            } while (len > 0)
        }
    }

And, to append to a file:

    inputStream.use { appendStream ->
        FileOutputStream(componentFile, true).use { outputStream ->
            appendStream.copyTo(outputStream)
        }
    }

Thanks in advance

Answer 1

You can open a file in append mode. Then when you call write the buffer goes to the end of the file:

vertx.fileSystem().open(fileName, new OpenOptions().setAppend(true), ar -> {
  if (ar.succeeded()) {
    AsyncFile writestream = ar.result();
    // If you write here it will be at the end of the file
  }
});

For skipping, just use AsyncFile#setReadPos :

vertx.fileSystem().open(fileToRead, new OpenOptions(), ar -> {
  if (ar.succeeded()) {
    AsyncFile readstream = ar.result();
    rs.setReadPos(offset);
  }
}

When this is done you can use the usual pump code:

Pump pump = Pump.pump(readstream, writestream);
readstream.endHandler(v -> {
  // Done
});
pump.start();

These are all Java snippets but you'll easily convert to Kotlin syntax.