Method RunPostfix

extern/re2/re2/testing/regexp_generator.cc:192–238

Interprets the postfix command sequence to create a regular expression passed to HandleRegexp. The results of operators like %s|%s are wrapped in (?: ) to avoid needing to maintain a precedence table.

// passed to HandleRegexp.  The results of operators like %s|%s are wrapped
// in (?: ) to avoid needing to maintain a precedence table.
void RegexpGenerator::RunPostfix(const std::vector<std::string>& post) {
  std::stack<std::string> regexps;
  for (size_t i = 0; i < post.size(); i++) {
    switch (CountArgs(post[i])) {
      default:
        LOG(FATAL) << "Bad operator: " << post[i];
      case 0:
        regexps.push(post[i]);
        break;
      case 1: {
        std::string a = regexps.top();
        regexps.pop();
        regexps.push("(?:" + StringPrintf(post[i].c_str(), a.c_str()) + ")");
        break;
      }
      case 2: {
        std::string b = regexps.top();
        regexps.pop();
        std::string a = regexps.top();
        regexps.pop();
        regexps.push("(?:" +
                     StringPrintf(post[i].c_str(), a.c_str(), b.c_str()) +
                     ")");
        break;
      }
    }
  }

  if (regexps.size() != 1) {
    // Internal error - should never happen.
    printf("Bad regexp program:\n");
    for (size_t i = 0; i < post.size(); i++) {
      printf("  %s\n", CEscape(post[i]).c_str());
    }
    printf("Stack after running program:\n");
    while (!regexps.empty()) {
      printf("  %s\n", CEscape(regexps.top()).c_str());
      regexps.pop();
    }
    LOG(FATAL) << "Bad regexp program.";
  }

  HandleRegexp(regexps.top());
  HandleRegexp("^(?:" + regexps.top() + ")$");
  HandleRegexp("^(?:" + regexps.top() + ")");
  HandleRegexp("(?:" + regexps.top() + ")$");
}

// Split s into an vector of strings, one for each UTF-8 character.
std::vector<std::string> Explode(const StringPiece& s) {