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KeyVal.java
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127 lines (110 loc) · 3.43 KB
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/*
* 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;
}
}