public static int collectVarData(final List<Token> tokens, final int index, final List<Token> varData)
    {
        return collect(Signal.BEGIN_VAR_DATA, tokens, index, varData);
    }
Collect the var data for a message.

@param tokens  for the message.
@param index   index at which to begin.
@param varData to collect the var data tokens into.
@return resulting index.
sbe-tool/src/main/java/uk/co/real_logic/sbe/ir/GenerationUtil.java