Class Utils

java/com/google/re2j/Utils.java:12–205

Various constants and helper utilities.

 * Various constants and helper utilities.
 */
abstract class Utils {

  static final int[] EMPTY_INTS = {};

  // Returns true iff |c| is an ASCII letter or decimal digit.
  static boolean isalnum(int c) {
    return ('0' <= c && c <= '9') || ('A' <= c && c <= 'Z') || ('a' <= c && c <= 'z');
  }

  // If |c| is an ASCII hex digit, returns its value, otherwise -1.
  static int unhex(int c) {
    if ('0' <= c && c <= '9') {
      return c - '0';
    }
    if ('a' <= c && c <= 'f') {
      return c - 'a' + 10;
    }
    if ('A' <= c && c <= 'F') {
      return c - 'A' + 10;
    }
    return -1;
  }

  private static final String METACHARACTERS = "\\.+*?()|[]{}^$";

  // Appends a RE2 literal to |out| for rune |rune|,
  // with regexp metacharacters escaped.
  static void escapeRune(StringBuilder out, int rune) {
    if (Unicode.isPrint(rune)) {
      if (METACHARACTERS.indexOf((char) rune) >= 0) {
        out.append('\\');
      }
      out.appendCodePoint(rune);
      return;
    }

    switch (rune) {
      case '"':
        out.append("\\\"");
        break;
      case '\\':
        out.append("\\\\");
        break;
      case '\t':
        out.append("\\t");
        break;
      case '\n':
        out.append("\\n");
        break;
      case '\r':
        out.append("\\r");
        break;
      case '\b':
        out.append("\\b");
        break;
      case '\f':
        out.append("\\f");
        break;