MemoryDataSourceImpl#map changes the position of the data ByteBuffer

[michschn]

When parsing a IsoFile from an MemoryDataSourceImpl, I always get errors like:

java.lang.RuntimeException: java.lang.IllegalArgumentException: Bad position (limit 41958): 1769172853
at java.nio.Buffer.positionImpl(Buffer.java:364)
at java.nio.Buffer.position(Buffer.java:358)
at com.googlecode.mp4parser.MemoryDataSourceImpl.positio...

This seems to be caused by map(...) implementation changing the data's position.

Restoring the position fixes the issue:
public ByteBuffer map(long startPosition, long size) throws IOException {
int oldPosition = data.position();
data.position(l2i(startPosition));
ByteBuffer result = data.slice();
result.limit(l2i(size));
data.position(oldPosition);
return result;
}