/*

 * HEIF codec.

 * Copyright (c) 2026 Dirk Farin <dirk.farin@gmail.com>

 *

 * This file is part of libheif.

 *

 * libheif is free software: you can redistribute it and/or modify

 * it under the terms of the GNU Lesser General Public License as

 * published by the Free Software Foundation, either version 3 of

 * the License, or (at your option) any later version.

 *

 * libheif is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with libheif.  If not, see <http://www.gnu.org/licenses/>.

 */

#include "id_creator.h"

#include <cstdint>

namespace {

// The next free id after 'id', i.e. the value a counter should take once 'id'

// has been handed out or reserved. When 'id' is the maximum representable value

// there is no larger id, so the counter becomes 0 == "exhausted" and

// get_new_id() will refuse to hand out another id. Computing this explicitly

// (rather than 'id + 1') keeps the exhausted transition free of the unsigned

// wrap that the 'integer' sanitizer flags, while guaranteeing the counter always

// moves strictly past 'id' so no id is ever handed out twice.

inline uint32_t next_id_after(uint32_t id)

{

  return id == UINT32_MAX ? 0u : id + 1u;

}

}

Result<uint32_t> IDCreator::get_new_id(Namespace ns)

{

  if (m_unif) {

    if (m_next_id_global == 0) {

      return Error(heif_error_Usage_error,

                   heif_suberror_Unspecified,

                   "ID namespace overflow");

    }

    uint32_t id = m_next_id_global;

    m_next_id_global = next_id_after(id);

    return id;

  }

  uint32_t* counter = nullptr;

  switch (ns) {

    case Namespace::item:

      counter = &m_next_id_item;

      break;

    case Namespace::track:

      counter = &m_next_id_track;

      break;

    case Namespace::entity_group:

      counter = &m_next_id_entity_group;

      break;

  }

  if (*counter == 0) {

    return Error(heif_error_Usage_error,

                 heif_suberror_Unspecified,

                 "ID namespace overflow");

  }

  uint32_t id = *counter;

  *counter = next_id_after(id);

  // Keep the global counter ahead of all namespace counters so that switching to

  // unif mode later does not reuse an ID that was already handed out.

  if (m_next_id_global != 0 && id >= m_next_id_global) {

    m_next_id_global = next_id_after(id);

  }

  return id;

}

void IDCreator::mark_id_used(Namespace ns, uint32_t id)

{

  uint32_t* counter = nullptr;

  switch (ns) {

    case Namespace::item:

      counter = &m_next_id_item;

      break;

    case Namespace::track:

      counter = &m_next_id_track;

      break;

    case Namespace::entity_group:

      counter = &m_next_id_entity_group;

      break;

  }

  // A counter value of 0 means "exhausted" (see get_new_id). Advancing past a

  // just-used id keeps get_new_id() from ever handing out the same id again;

  // marking 0xFFFFFFFF used moves the counter to 0 == exhausted.

  if (*counter != 0 && id >= *counter) {

    *counter = next_id_after(id);

  }

  if (m_next_id_global != 0 && id >= m_next_id_global) {

    m_next_id_global = next_id_after(id);

  }

}