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javabufferbyte
Tony
Tony

Reputation: 3638

Java Bytebuffer overwrite bytes

I've got a ByteBuffer that contains 1024 bytes.

I need to overwrite a short within the buffer at a certain offset at key times.

I know the ByteBuffer class has putShort(), but this doesn't overwrite the data, it simply adds it in, which is causing buffer overflows.

I'm guessing that there isn't a direct way of doing this using the ByteBuffer, can someone possibly suggest a way to do this?

Thanks

Thanks to everyone that replied, seemed it could be done I was just using the wrong version of putShort(). I guess that's what happens when you stare at the same piece of code for six hours.

Thanks again

Upvotes: 1

Views: 3948

Answers (4)

Jean Logeart
Jean Logeart

Reputation: 53829

For your special case, you can modify directly the backing array using the array() method.

Then just insert your two bytes at the proper indexes:

if(myBuffer.hasArray()) {
    byte[] array = myBuffer.array();
    array[index] = (byte) (myShort & 0xff);
    array[index + 1] = (byte) ((myShort >> 8) & 0xff);
}

Upvotes: 1

Evgeniy Dorofeev
Evgeniy Dorofeev

Reputation: 136012

Cannot reproduce the problem, all seems OK

    ByteBuffer bb = ByteBuffer.allocate(20);
    bb.putShort(10, (short)0xffff);
    System.out.println(Arrays.toString(bb.array()));

prints

[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1, -1, 0, 0, 0, 0, 0, 0, 0, 0]

Upvotes: 3

CodeChimp
CodeChimp

Reputation: 8154

I think you can call this version of putShort() that accepts a possition index.

Upvotes: 0

Aubin
Aubin

Reputation: 14853

int p = b.position();
b.position( ZePlace );
p.putShort( ZeValue );
b.position( p );

http://docs.oracle.com/javase/7/docs/api/java/nio/Buffer.html#position%28%29

Upvotes: 1

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