/*
 * Copyright © 2016-2025 The LmdbJava Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.lmdbjava;

import static java.util.Objects.requireNonNull;
import static org.lmdbjava.BufferProxy.MDB_VAL_STRUCT_SIZE;
import static org.lmdbjava.Library.RUNTIME;

import jnr.ffi.Pointer;
import jnr.ffi.provider.MemoryManager;

/**
 * Represents off-heap memory holding a key only. Equivalent to {@link KeyVal} without the val part.
 *
 * @param <T> buffer type
 */
final class Key<T> implements AutoCloseable {

  private static final MemoryManager MEM_MGR = RUNTIME.getMemoryManager();
  private boolean closed;
  private final T k;
  private final BufferProxy<T> proxy;
  private final Pointer ptrKey;

  Key(final BufferProxy<T> proxy) {
    requireNonNull(proxy);
    this.proxy = proxy;
    this.k = proxy.allocate();
    ptrKey = MEM_MGR.allocateTemporary(MDB_VAL_STRUCT_SIZE, false);
  }

  @Override
  public void close() {
    if (closed) {
      return;
    }
    closed = true;
    proxy.deallocate(k);
  }

  void keyIn(final T key) {
    proxy.in(key, ptrKey);
  }

  Pointer pointer() {
    return ptrKey;
  }
}