// 返回值： (NonTerminal, int) - Item1: 分析得到的语法树，如果是 null，代表分析失败；Item2: 下一个要扫描的 token
protected override FuncInstructionBase StepMove(int pc, object lastReturned)
{
switch (pc)
{
case 0:
{
if (_startIdx >= _tokens.Count)
{
return(Return(((NonTerminalTree)null, _tokens.Count)));
}
// 一开始一定是非终结符
_ruleList = _bnfDefination.GetRulesForNonTerminal(_currentNonTerminal);
_ruleIdx = 0;
return(Continue());
}
case 1:
{
if (_ruleIdx >= _ruleList.Count)
{
// 没有找到合适的rule
return(Return(((NonTerminalTree)null, _startIdx)));
}
_childs = new ISyntacticAnalysisTree[_ruleList[_ruleIdx].Length];
_currentTokenIdx = _startIdx;
_ruleItemIdx = 0;
return(Continue());
}
case 2:
{
if (_ruleItemIdx >= _ruleList[_ruleIdx].Length)
{
// child 全部填满，可以返回了
return(GoTo(100));
}
// 是否到达末尾
if (_currentTokenIdx == _tokens.Count)
{
if (_ruleList[_ruleIdx][_ruleItemIdx] == TerminalConsts.EndOfFile)
{
// 在规则中应该是末尾
return(GoTo(100));
}
else
{
// TODO: 这里有可能产生式是 ɛ，这样的话即使当前位置是末尾也可以满足要求
++_ruleIdx;
return(GoTo(1));
}
}
if (_ruleList[_ruleIdx][_ruleItemIdx] == TerminalConsts.EndOfFile)
{
// 在规则中应当到达末尾，但是目前没有到达末尾
++_ruleIdx;
return(GoTo(1));
}
else if (_bnfDefination.IsTerminal(_ruleList[_ruleIdx][_ruleItemIdx]))
{
// 根据规则，当前应该是终结符
var currentToken = _tokens[_currentTokenIdx];
if (currentToken.TokenType == _ruleList[_ruleIdx][_ruleItemIdx])
{
_childs[_ruleItemIdx] = new TerminalTree(currentToken);
++_currentTokenIdx;
++_ruleItemIdx;
return(GoTo(2));
}
else
{
++_ruleIdx;
return(GoTo(1));
}
}
else
{
return(Continue());
}
}
case 3:
{
// 当前的 ruleItem 是非终结符
return(CallStackFunc(new ParserFunc(_currentTokenIdx, _ruleList[_ruleIdx][_ruleItemIdx],
_tokens, _bnfDefination, _backtracings)));
}
case 4:
{
var(tree, nextIdx) = ((NonTerminalTree, int))lastReturned;
if (tree == null)
{
++_ruleIdx;
return(GoTo(1));
}
else
{
_childs[_ruleItemIdx] = tree;
_currentTokenIdx = nextIdx;
++_ruleItemIdx;
return(GoTo(2));
}
}
case 100:
{
return(CallWithCurrentContinuation(cont =>
{
_backtracings.Push(cont);
return false;
}));
}
case 101:
{
var shouldSkip = (bool)lastReturned;
if (shouldSkip)
{
++_ruleIdx;
return(GoTo(1));
}
else
{
return(Return((
new NonTerminalTree(_currentNonTerminal, _childs, _ruleList[_ruleIdx]),
_currentTokenIdx
)));
}
}
default:
{
return(null);
}
}
}
