c++ - 从监听器中检索 antlr4 解析器中跳过的空格

Question

我正在尝试从已解析的消息构造一个对象。我正在使用 Antlr4 和 C++我的问题是我需要在词法分析/解析过程中跳过空格，但是当我在 Listener 中构造消息对象时我必须取回它们。这是我的语法

grammar MessageTest;
WS: ('\t' | ' ' | '\r' | '\n' )+ -> skip;

message: 
    messageInfo
    startOfMessage
    messageText+
| EOF;

messageInfo:
    senderName
    filingTime
    receiverName
;

senderName: WORD;

filingTime: DIGITS;

receiverName: WORD;

messageText: ( WORD | DIGITS | ALLOWED_SYMBOLS)+;

startOfMessage: START_OF_MESSAGE_SYMBOL ;

START_OF_MESSAGE_SYMBOL:':';

WORD: LETTER+;

DIGITS: DIGIT+;

LPAREN: '(';
RPAREN: ')';

ALLOWED_SYMBOLS:   '-'| '.' | ',' | '/' | '+' | '?';

fragment LETTER: [A-Z];

fragment DIGIT: [0-9];

所以这个语法运行良好，我的解析树对于以下消息示例是正确的:JOHN0120JANE:HI HOW ARE YOU?我得到了这个解析树:

message (
 messageInfo (
  senderName (
   "JOHN"
  )
  filingTime (
   "0120"
  )
  receiverName (
   "JANE"
  )
 )
 startOfMessage (
  ":"
 )
 messageText (
  "HI"
  "HOW"
  "ARE"
  "YOU"
  "?"
 )
)

问题是当我试图检索整个 messageText 时:HI HOW ARE YOU? 我改为从 MessageTextContext

获取 HIHOWAREYOU?

我做错了什么？

Answer 1

getText() 检索函数从不考虑跳过或隐藏的标记。但是通过使用存储在生成的标记中的索引，很容易获得输入的原始文本(即使只是对应于特定解析规则的范围)。解析规则上下文包含一个开始节点和一个结束节点，因此很容易从上下文转到原始输入，如下所示:

std::string MySQLRecognizerCommon::sourceTextForContext(ParserRuleContext *ctx, bool keepQuotes) {
  return sourceTextForRange(ctx->start, ctx->stop, keepQuotes);
}

//----------------------------------------------------------------------------------------------------------------------

std::string MySQLRecognizerCommon::sourceTextForRange(tree::ParseTree *start, tree::ParseTree *stop, bool keepQuotes) {
  Token *startToken = antlrcpp::is<tree::TerminalNode *>(start) ? dynamic_cast<tree::TerminalNode *>(start)->getSymbol()
                                                                : dynamic_cast<ParserRuleContext *>(start)->start;
  Token *stopToken = antlrcpp::is<tree::TerminalNode *>(stop) ? dynamic_cast<tree::TerminalNode *>(start)->getSymbol()
                                                              : dynamic_cast<ParserRuleContext *>(stop)->stop;
  return sourceTextForRange(startToken, stopToken, keepQuotes);
}

//----------------------------------------------------------------------------------------------------------------------

std::string MySQLRecognizerCommon::sourceTextForRange(Token *start, Token *stop, bool keepQuotes) {
  CharStream *cs = start->getTokenSource()->getInputStream();
  size_t stopIndex = stop != nullptr ? stop->getStopIndex() : std::numeric_limits<size_t>::max();
  std::string result = cs->getText(misc::Interval(start->getStartIndex(), stopIndex));
  if (keepQuotes || result.size() < 2)
    return result;

  char quoteChar = result[0];
  if ((quoteChar == '"' || quoteChar == '`' || quoteChar == '\'') && quoteChar == result.back()) {
    if (quoteChar == '"' || quoteChar == '\'') {
      // Replace any double occurence of the quote char by a single one.
      replaceStringInplace(result, std::string(2, quoteChar), std::string(1, quoteChar));
    }

    return result.substr(1, result.size() - 2);
  }

  return result;
}

此代码专为与 MySQL 一起使用而定制(例如，wrt. 引号字符)，但很容易适应任何其他用例。关键部分是使用标记(例如从解析规则上下文中获取)并从字符输入流中获取原始输入。

代码取自 MySQL Workbench code base .