regex.R

# Copyright 2015- Takeshi Arabiki
# License: GNU GPL version 2 or later <http://gnu.org/licenses/gpl.html>
library(Rcpp)

Sys.setenv(PKG_LIBS = "-lpcrecpp")
sourceCpp(code = '
#include <Rcpp.h>     // Rcpp 0.11.3
#include <pcrecpp.h>  // pcrecpp 8.36

// [[Rcpp::export]]
Rcpp::String regexquote(Rcpp::String pattern) {
  return pcrecpp::RE::QuoteMeta(pattern.get_cstring());
}

class Regex {
public:
  pcrecpp::RE re;

  Regex(Rcpp::String pattern) : re("(" + std::string(pattern) + ")", pcrecpp::UTF8()) {
    if (!re.error().empty()) {
      Rcpp::stop("Invalid regular expression: " + re.error());
    }
  }

  ~Regex() {}

  Rcpp::List scan(Rcpp::String str) {
    std::vector<std::vector<std::string> > all_matches;
    pcrecpp::StringPiece input(str.get_cstring());

    int n = re.NumberOfCapturingGroups();
    pcrecpp::Arg** args = new pcrecpp::Arg*[n];
    pcrecpp::Arg* match_ptrs = new pcrecpp::Arg[n];
    std::string* matches = new std::string[n];
    for (int i = 0; i < n; ++i) {
      match_ptrs[i] = &matches[i];
      args[i] = &match_ptrs[i];
    }

    int consumed;
    while (re.DoMatch(input, pcrecpp::RE::UNANCHORED, &consumed, args, n)) {
      all_matches.push_back(std::vector<std::string>(matches, matches + n));
      input.remove_prefix(consumed);
    }
    delete[] args;
    delete[] match_ptrs;
    delete[] matches;

    return Rcpp::wrap(all_matches);
  }
};

RCPP_MODULE(Regex) {
  Rcpp::class_<Regex>("Regex")
    .constructor<Rcpp::String>()
    .method("scan", &Regex::scan)
    ;
}
')