IndexOutOfBoundsException while de-serialization in JAVA for a flatbuffer written in C++

[Ranjith Chungath]

Hi All,

 The following is my fbs file:

===================================

namespace com.helloworld;

table MyObject {

  field1:string;

  field2:[double];

  field3:[double];

  field4:string;

  field5:string;

  field6:string;

}

table MyObjectList {

  objects:[MyObject];

}

root_type MyObjectList;

===================================

The following is my code to serialize the buffer.

===================================

    

    flatbuffers::FlatBufferBuilder fbb

    std::vector< flatbuffers::Offset<MyObject> > objs;

    std::vector<double> vec1 ;  // Initialized with the values : "1.00 0.00 0.00 0.00 0.00 1.00 0.00 0.00 0.00 0.00 1.00 0.00 0.00 0.00 0.09 1.00"

    std::vector<double> vec2 ;  // Initialized with the values : "1.00 0.00 0.00 0.00 0.00 1.00 0.00 0.00 0.00 0.00 1.00 0.00 0.00 -0.04455 0.049 1.00"

    

    for( int i=0; i<objectCount; i++ )

    {

        // Populate the fields

        flatbuffers::Offset<flatbuffers::String> field1 = fbb.CreateString( "field1" );

        flatbuffers::Offset<flatbuffers::Vector<double>> field2 = fbb.CreateVector( vec1 );

        flatbuffers::Offset<flatbuffers::Vector<double>> field3 = fbb.CreateVector( vec1 );

        flatbuffers::Offset<flatbuffers::String> field4 = fbb.CreateString( "field2" );

        flatbuffers::Offset<flatbuffers::String> field5 = fbb.CreateString( "field2" );

        flatbuffers::Offset<flatbuffers::String> field6 = fbb.CreateString( "field2" );        

        // Create the Object

        MyObjectBuilder  obj( fbb );

        obj.add_field6( field5 );

        obj.add_field5( field5 );

        obj.add_field4( field4 );

        obj.add_field3( field3 );

        obj.add_field2( field2 );

        obj.add_field1( field1 );

        // Finished writing the element

        flatbuffers::Offset<MyObject> objOffset = obj.Finish();

        objs.push_back( objOffset );

    }

    // Create the Offset vector of the elements

    flatbuffers::Offset<flatbuffers::Vector<flatbuffers::Offset<MyObject>>> objOffsets = fbb.CreateVector( objs );

    // Build the MyObjectList 

    MyObjectListBuilder listBuffer( fbb );

    listBuffer.add_objects( objOffsets );

    flatbuffers::Offset<MyObjectList> listOffset = listBuffer.Finish();

    // Finish writing the builder with the MyObjectList as root

    fbb.Finish( listOffset );

===================================

The serialization happens without any errors..

But when I de-serialize the buffer through JAVA, I get an IndexOutOfBounds while accessing the fields on any object.

java.lang.IndexOutOfBoundsException

at java.nio.Buffer.checkIndex(Buffer.java:520)

at java.nio.HeapByteBuffer.getShort(HeapByteBuffer.java:289)

at flatbuffers.Table.__offset(Table.java:34)

at com.helloworld.MyObject.field1(MyObject.java:13)

Also, if the number of objects being serialized is less than 10, the de-serialization happens fine. The moment the number of objects becomes 10 or more, the problem appears.

The Java code to de-serialize is given below

===================================

        MyObjectList list = MyObjectList.getRootAsMyObjectList( bb, 0 );

        

        int size = list.objectsLength();        

        for (int i = 0; i < size; i++) {

            MyObject obj = list.objects( i );

            

            String field1 = obj.field1();

            String field4 = obj.field4();

            String field5 = obj.field5();

            String field6 = obj.field6();

            

            System.out.println(" field1 = " + field1 );

            System.out.println(" field4 = " + field4 );

            System.out.println(" field5 = " + field5 );

            System.out.println(" field6 = " + field6 );

        }

===================================

Can you please let me know what is going wrong here. I am thinking the problem is while serializing in the C++ code, but not able to figure out what exactly I am doing wrong. Is there a problem with the way I am creating and writing the Offset of vectors of objects?

Thanks,

Ranjith

[Wouter van Oortmerssen]

The code so far looks correct, but there may be something going wrong in the transport between the two.

In C++, you are transporting GetSize() bytes starting from GetBufferPointer() ? And those bytes then end up at offset 0 in the ByteBuffer?

--
You received this message because you are subscribed to the Google Groups "FlatBuffers" group.
To unsubscribe from this group and stop receiving emails from it, send an email to flatbuffers...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[Ranjith Chungath]

Thank you for your confirmation.

The problem turned out to be the way in which I was transferring the files. It was getting transferred as text instead of binary which caused the problem. Once I corrected that, it worked fine.

Ranjith