League\CommonMark\Block\Parser\FencedCodeParser::parse PHP Method

    public function parse(ContextInterface $context, Cursor $cursor)
    {
        if ($cursor->isIndented()) {
            return false;
        }
        $previousState = $cursor->saveState();
        $indent = $cursor->advanceToFirstNonSpace();
        $fence = $cursor->match('/^`{3,}(?!.*`)|^~{3,}(?!.*~)/');
        if (is_null($fence)) {
            $cursor->restoreState($previousState);
            return false;
        }
        // fenced code block
        $fenceLength = strlen($fence);
        $context->addBlock(new FencedCode($fenceLength, $fence[0], $indent));
        return true;
    }