Class Prog

java/com/google/re2j/Prog.java:17–179

A Prog is a compiled regular expression program.

 * A Prog is a compiled regular expression program.
 */
final class Prog {

  Inst[] inst = new Inst[10];
  int instSize = 0;
  int start; // index of start instruction
  int numCap = 2; // number of CAPTURE insts in re
  // 2 => implicit ( and ) for whole match $0

  // Constructs an empty program.
  Prog() {}

  // Returns the instruction at the specified pc.
  // Precondition: pc > 0 && pc < numInst().
  Inst getInst(int pc) {
    return inst[pc];
  }

  // Returns the number of instructions in this program.
  int numInst() {
    return instSize;
  }

  // Adds a new instruction to this program, with operator |op| and |pc| equal
  // to |numInst()|.
  void addInst(int op) {
    if (instSize >= inst.length) {
      inst = Arrays.copyOf(inst, inst.length * 2);
    }
    inst[instSize] = new Inst(op);
    instSize++;
  }

  // skipNop() follows any no-op or capturing instructions and returns the
  // resulting instruction.
  Inst skipNop(int pc) {
    Inst i = inst[pc];
    while (i.op == Inst.NOP || i.op == Inst.CAPTURE) {
      i = inst[pc];
      pc = i.out;
    }
    return i;
  }

  // prefix() returns a pair of a literal string that all matches for the
  // 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);