code: func serializeBlockLoc(loc blockLocation) []byte {
  	// The serialized block location format is:
  	//
  	//  [0:4]  Block file (4 bytes)
  	//  [4:8]  File offset (4 bytes)
  	//  [8:12] Block length (4 bytes)
  	var serializedData [12]byte
  	byteOrder.PutUint32(serializedData[0:4], loc.blockFileNum)
  	byteOrder.PutUint32(serializedData[4:8], loc.fileOffset)
  	byteOrder.PutUint32(serializedData[8:12], loc.blockLen)
  	return serializedData[:]
  }
docs: // serializeBlockLoc returns the serialization of the passed block location.
  // This is data to be stored into the block index metadata for each block.