IndexedByteBlockInfo getBlockInfo(BigInteger index, int fieldOffset) {
		SortedMap<BigInteger, BlockInfo> tailMap = blockInfoMap.tailMap(index);
		if (tailMap.isEmpty()) {
			return null;
		}
		BlockInfo blockInfo = tailMap.get(tailMap.firstKey());
		BigInteger byteIndex = index.multiply(bytesInLine).add(BigInteger.valueOf(fieldOffset));
		if ((byteIndex.compareTo(blockInfo.blockStart) >= 0) &&
			(byteIndex.compareTo(blockInfo.blockEnd) < 0)) {
			return new IndexedByteBlockInfo(index, blockInfo.block,
				byteIndex.subtract(blockInfo.blockStart), 0);
		}
		return null;
	}
Returns block location information about the given index and fieldOffset.
@param index The line index
@param fieldOffset the field offset (in bytes) from the beginning of the line. 
@return The ByteBlockInfo object that contains the block and offset into that block
that is the resulting byte value.
Ghidra/Features/ByteViewer/src/main/java/ghidra/app/plugin/core/byteviewer/IndexMap.java