Method PushRepeatOp

extern/re2/re2/parse.cc:475–509

Pushes a repeat operator regexp onto the stack. A valid argument for the operator must already be on the stack. The char c is the name of the operator, for use in error messages.

// A valid argument for the operator must already be on the stack.
// The char c is the name of the operator, for use in error messages.
bool Regexp::ParseState::PushRepeatOp(RegexpOp op, const StringPiece& s,
                                      bool nongreedy) {
  if (stacktop_ == NULL || IsMarker(stacktop_->op())) {
    status_->set_code(kRegexpRepeatArgument);
    status_->set_error_arg(s);
    return false;
  }
  Regexp::ParseFlags fl = flags_;
  if (nongreedy)
    fl = fl ^ NonGreedy;

  // Squash **, ++ and ??. Regexp::Star() et al. handle this too, but
  // they're mostly for use during simplification, not during parsing.
  if (op == stacktop_->op() && fl == stacktop_->parse_flags())
    return true;

  // Squash *+, *?, +*, +?, ?* and ?+. They all squash to *, so because
  // op is a repeat, we just have to check that stacktop_->op() is too,
  // then adjust stacktop_.
  if ((stacktop_->op() == kRegexpStar ||
       stacktop_->op() == kRegexpPlus ||
       stacktop_->op() == kRegexpQuest) &&
      fl == stacktop_->parse_flags()) {
    stacktop_->op_ = kRegexpStar;
    return true;
  }

  Regexp* re = new Regexp(op, fl);
  re->AllocSub(1);
  re->down_ = stacktop_->down_;
  re->sub()[0] = FinishRegexp(stacktop_);
  re->simple_ = re->ComputeSimple();
  stacktop_ = re;
  return true;
}

// RepetitionWalker reports whether the repetition regexp is valid.
// Valid means that the combination of the top-level repetition