/*

* 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.BufferProxy.STRUCT_FIELD_OFFSET_SIZE;

import static org.lmdbjava.Library.RUNTIME;

import jnr.ffi.Pointer;

import jnr.ffi.provider.MemoryManager;

/**

* Represents off-heap memory holding a key and value pair.

*

* @param <T> buffer type

*/

final class KeyVal<T> implements AutoCloseable {

private static final MemoryManager MEM_MGR = RUNTIME.getMemoryManager();

private boolean closed;

private T k;

private final BufferProxy<T> proxy;

private final Pointer ptrArray;

private final Pointer ptrKey;

private final Pointer ptrVal;

private T v;

KeyVal(final BufferProxy<T> proxy) {

requireNonNull(proxy);

this.proxy = proxy;

this.k = proxy.allocate();

this.v = proxy.allocate();

ptrKey = MEM_MGR.allocateTemporary(MDB_VAL_STRUCT_SIZE, false);

ptrArray = MEM_MGR.allocateTemporary(MDB_VAL_STRUCT_SIZE * 2, false);

ptrVal = ptrArray.slice(0, MDB_VAL_STRUCT_SIZE);

}

@Override

public void close() {

if (closed) {

return;

}

closed = true;

proxy.deallocate(k);

proxy.deallocate(v);

}

T key() {

return k;

}

Pointer keyIn(final T key) {

return proxy.in(key, ptrKey);

}

T keyOut() {

k = proxy.out(k, ptrKey);

return k;

}

Pointer pointerKey() {

return ptrKey;

}

Pointer pointerVal() {

return ptrVal;

}

T val() {

return v;

}

Pointer valIn(final T val) {

return proxy.in(val, ptrVal);

}

Pointer valIn(final int size) {

return proxy.in(v, size, ptrVal);

}

/**

* Prepares an array suitable for presentation as the data argument to a <code>MDB_MULTIPLE</code>

* put.

*

* <p>The returned array is equivalent of two <code>MDB_val</code>s as follows:

*

* <ul>

* <li>ptrVal1.data = pointer to the data address of passed buffer

* <li>ptrVal1.size = size of each individual data element

* <li>ptrVal2.data = unused

* <li>ptrVal2.size = number of data elements (as passed to this method)

* </ul>

*

* @param val a user-provided buffer with data elements (required)

* @param elements number of data elements the user has provided

* @return a properly-prepared pointer to an array for the operation

*/

Pointer valInMulti(final T val, final int elements) {

final long ptrVal2SizeOff = MDB_VAL_STRUCT_SIZE + STRUCT_FIELD_OFFSET_SIZE;

ptrArray.putLong(ptrVal2SizeOff, elements); // ptrVal2.size

proxy.in(val, ptrVal); // ptrVal1.data

final long totalBufferSize = ptrVal.getLong(STRUCT_FIELD_OFFSET_SIZE);

final long elemSize = totalBufferSize / elements;

ptrVal.putLong(STRUCT_FIELD_OFFSET_SIZE, elemSize); // ptrVal1.size

return ptrArray;

}

T valOut() {

v = proxy.out(v, ptrVal);

return v;

}

}