public boolean isNodeUsed( int nodeIndex ) {
		int block = bitmap[ nodeIndex / 8 ] & 0xff;
		return ( block & ( 1 << 7 - ( nodeIndex  % 8 ) ) ) != 0;
	}
Returns  true if the specified node index is used.
Returns false if the specified node index is free.
@param nodeIndex the node index
@return true if the specified node index is used, false if free
Ghidra/Features/FileFormats/src/main/java/ghidra/file/formats/ios/btree/BTreeMapRecord.java