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UnsafeAccess.java
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59 lines (50 loc) · 2 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.lang.Boolean.getBoolean;
import java.lang.reflect.Field;
import sun.misc.Unsafe;
/** Provides access to Unsafe. */
final class UnsafeAccess {
/** Java system property name that can be set to disable unsafe. */
public static final String DISABLE_UNSAFE_PROP = "lmdbjava.disable.unsafe";
/** Indicates whether unsafe use is allowed. */
public static final boolean ALLOW_UNSAFE = !getBoolean(DISABLE_UNSAFE_PROP);
/**
* The actual unsafe. Guaranteed to be non-null if this class can access unsafe and {@link
* #ALLOW_UNSAFE} is true. In other words, this entire class will fail to initialize if unsafe is
* unavailable. This avoids callers from needing to deal with null checks.
*/
static final Unsafe UNSAFE;
/** Unsafe field name (used to reflectively obtain the unsafe instance). */
private static final String FIELD_NAME_THE_UNSAFE = "theUnsafe";
static {
if (!ALLOW_UNSAFE) {
throw new LmdbException("Unsafe disabled by user");
}
try {
final Field field = Unsafe.class.getDeclaredField(FIELD_NAME_THE_UNSAFE);
field.setAccessible(true);
UNSAFE = (Unsafe) field.get(null);
} catch (final NoSuchFieldException
| SecurityException
| IllegalArgumentException
| IllegalAccessException e) {
throw new LmdbException("Unsafe unavailable", e);
}
}
private UnsafeAccess() {}
}