Method prefix

java/com/google/re2j/Prog.java:63–77

(StringBuilder prefix)

  // regexp must start with, and a boolean which is true if the prefix is the
  // entire match.  The string is returned by appending to |prefix|.
  boolean prefix(StringBuilder prefix) {
    Inst i = skipNop(start);

    // Avoid allocation of buffer if prefix is empty.
    if (!Inst.isRuneOp(i.op) || i.runes.length != 1) {
      return i.op == Inst.MATCH; // (append "" to prefix)
    }

    // Have prefix; gather characters.
    while (Inst.isRuneOp(i.op) && i.runes.length == 1 && (i.arg & RE2.FOLD_CASE) == 0) {
      prefix.appendCodePoint(i.runes[0]); // an int, not a byte.
      i = skipNop(i.out);
    }
    return i.op == Inst.MATCH;
  }

  // startCond() returns the leading empty-width conditions that must be true
  // in any match.  It returns -1 (all bits set) if no matches are possible.