avro BinaryDecoder bug ?

[Yang]

if I read on a empty file with BinaryDecoder, I get EOF, good,

but with the current code, if I read it again with the same decoder, I
get a IndexOutofBoundException, not EOF.

it seems that always giving EOF should be a more desirable behavior.

you can see from this test code:

import static org.junit.Assert.assertEquals;

import java.io.IOException;

import org.apache.avro.specific.SpecificRecord;
import org.junit.Test;

import myavro.Apple;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;

import org.apache.avro.io.Decoder;
import org.apache.avro.io.DecoderFactory;
import org.apache.avro.io.Encoder;
import org.apache.avro.io.EncoderFactory;
import org.apache.avro.specific.SpecificDatumReader;
import org.apache.avro.specific.SpecificDatumWriter;

class MyWriter {

    SpecificDatumWriter<SpecificRecord> wr;
    Encoder enc;
    OutputStream ostream;

    public MyWriter() throws FileNotFoundException {
        wr = new SpecificDatumWriter<SpecificRecord>(new Apple().getSchema());
        ostream = new FileOutputStream(new File("/tmp/testavro"));
        enc = EncoderFactory.get().binaryEncoder(ostream, null);
    }

    public synchronized void dump(SpecificRecord event) throws IOException {
        wr.write(event, enc);
        enc.flush();
    }

}

class MyReader {

    SpecificDatumReader<SpecificRecord> rd;
    Decoder dec;
    InputStream istream;

    public MyReader() throws FileNotFoundException {
        rd = new SpecificDatumReader<SpecificRecord>(new Apple().getSchema());
        istream = new FileInputStream(new File("/tmp/testavro"));
        dec = DecoderFactory.get().binaryDecoder(istream, null);
    }

    public synchronized SpecificRecord read() throws IOException {
        Object r = rd.read(null, dec);
        return (SpecificRecord) r;
    }

}

public class AvroWriteAndReadSameTime {
    @Test
    public void testWritingAndReadingAtSameTime() throws Exception {

        MyWriter dumper = new MyWriter();
        final Apple apple = new Apple();
        apple.taste = "sweet";
        dumper.dump(apple);

        final MyReader rd = new MyReader();
        rd.read();


        try {
        rd.read();
        } catch (Exception e) {
            e.printStackTrace();
        }

        // the second one somehow generates a NPE, we hope to get EOF...
        try {
        rd.read();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}





the issue is in BinaryDecoder.readInt(), right now even when it hits
EOF, it still advances the pos pointer.
all the other APIs (readLong readFloat ...) do not do this. changing
to the following  makes it work:


  @Override
  public int readInt() throws IOException {
    ensureBounds(5); // won't throw index out of bounds
    int len = 1;
    int b = buf[pos] & 0xff;
    int n = b & 0x7f;
    if (b > 0x7f) {
      b = buf[pos + len++] & 0xff;
      n ^= (b & 0x7f) << 7;
      if (b > 0x7f) {
        b = buf[pos + len++] & 0xff;
        n ^= (b & 0x7f) << 14;
        if (b > 0x7f) {
          b = buf[pos + len++] & 0xff;
          n ^= (b & 0x7f) << 21;
          if (b > 0x7f) {
            b = buf[pos + len++] & 0xff;
            n ^= (b & 0x7f) << 28;
            if (b > 0x7f) {
              throw new IOException("Invalid int encoding");
            }
          }
        }
      }
    }
    if (pos+len > limit) {
      throw new EOFException();
    }
    pos += len;             //<================== CHANGE, used to be
above the EOF throw

    return (n >>> 1) ^ -(n & 1); // back to two's-complement
  }