/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sts=2 et sw=2 tw=80:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef vm_MatchPairs_h
#define vm_MatchPairs_h

#include "ds/LifoAlloc.h"
#include "js/AllocPolicy.h"
#include "js/Vector.h"

/*
 * RegExp match results are succinctly represented by pairs of integer
 * indices delimiting (start, limit] segments of the input string.
 *
 * The pair count for a given RegExp match is the capturing parentheses
 * count plus one for the "0 capturing paren" whole text match.
 */

namespace js {

struct MatchPair final {
  int32_t start;
  int32_t limit;

  static constexpr int32_t NoMatch = -1;

  MatchPair() : start(NoMatch), limit(NoMatch) {}

  MatchPair(int32_t start, int32_t limit) : start(start), limit(limit) {}

  size_t length() const {
    MOZ_ASSERT(!isUndefined());
    return limit - start;
  }
  bool isUndefined() const { return start < 0; }

  inline bool check() const {
    MOZ_ASSERT(limit >= start);
    MOZ_ASSERT_IF(start < 0, start == NoMatch);
    MOZ_ASSERT_IF(limit < 0, limit == NoMatch);
    return true;
  }
};

// MachPairs is used as base class for VectorMatchPairs but can also be
// stack-allocated (without a Vector) in JIT code.
class MatchPairs {
 protected:
  /* Length of pairs_. */
  uint32_t pairCount_;

  /* Raw pointer into an allocated MatchPair buffer. */
  MatchPair* pairs_;

 protected:
  /* Not used directly: use VectorMatchPairs. */
  MatchPairs() : pairCount_(0), pairs_(nullptr) {}

 protected:
  /* Functions used by friend classes. */
  friend class RegExpShared;
  friend class RegExpStatics;

  void forgetArray() { pairs_ = nullptr; }

 public:
  void checkAgainst(size_t inputLength) {
#ifdef DEBUG
    for (size_t i = 0; i < pairCount_; i++) {
      const MatchPair& p = (*this)[i];
      MOZ_ASSERT(p.check());
      if (p.isUndefined()) {
        continue;
      }
      MOZ_ASSERT(size_t(p.limit) <= inputLength);
    }
#endif
  }

  /* Querying functions in the style of RegExpStatics. */
  bool empty() const { return pairCount_ == 0; }
  size_t pairCount() const {
    MOZ_ASSERT(pairCount_ > 0);
    return pairCount_;
  }

  static size_t offsetOfPairs() { return offsetof(MatchPairs, pairs_); }
  static size_t offsetOfPairCount() { return offsetof(MatchPairs, pairCount_); }

  int32_t* pairsRaw() { return reinterpret_cast<int32_t*>(pairs_); }

 public:
  size_t length() const { return pairCount_; }

  const MatchPair& operator[](size_t i) const {
    MOZ_ASSERT(i < pairCount_);
    return pairs_[i];
  }
  MatchPair& operator[](size_t i) {
    MOZ_ASSERT(i < pairCount_);
    return pairs_[i];
  }
};

class VectorMatchPairs : public MatchPairs {
  Vector<MatchPair, 10, SystemAllocPolicy> vec_;

 protected:
  friend class RegExpShared;
  friend class RegExpStatics;

  /* MatchPair buffer allocator: set pairs_ and pairCount_. */
  bool allocOrExpandArray(size_t pairCount);

  bool initArrayFrom(VectorMatchPairs& copyFrom);
};

} /* namespace js */

#endif /* vm_MatchPairs_h */