net.openhft.chronicle.values.Align Maven / Gradle / Ivy
/*
* Copyright 2016-2021 chronicle.software
*
* https://chronicle.software
*
* 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 net.openhft.chronicle.values;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
/**
* Specifies the fields' arrangement in native implementation should be so that the offset to the
* aligned field bytes from the beginning of the instance is a multiple of the specified {@link
* #offset()}, the range of the field's bytes offsets don't cross the specified {@link #dontCross()}
* boundary. This annotation should be put on any single method accessing the field: getter, or
* setter, or adder, etc.
*
*
This annotation guarantees alignment from the beginning of the instance, so to ensure
* alignment in the native memory, the instance as a whole should be aligned by native memory
* addresses to the most coarse alignment of it's fields.
*
*
The default alignment depends on the field type, see {@link #DEFAULT}.
*/
@Target(METHOD)
@Retention(RUNTIME)
@Documented
public @interface Align {
/**
*
* - If the field type is an integer or a floating point primitive, default {@link
* #dontCross()} alignment is equivalent to 1-byte for fields which take {@code <=} 8 bits, 2-byte
* for fields which take {@code <=} 16 bits, 4-byte for fields which take {@code <=} 32 bits, 8-byte for
* fields which take {@code <= } 64 bits. {@link #offset()} alignment is 1-byte for such fields.
* - If the field is another value interface, default {@code offset} alignment is
* {@link ValueModel#recommendedOffsetAlignment()} for this sub-value interface. {@code
* dontCross} default alignment for Value fields is {@link #NO_ALIGNMENT}.
* - If the field is an array, default {@code offset} alignment is equivalent to the
* maximum of it's element {@code offset} or {@code dontCross} alignment, default {@code
* dontCross} for array fields is {@code NO_ALIGNMENT}.
*
* - If the field is of {@link CharSequence} type, default {@code dontCross} alignment
* is {@link #NO_ALIGNMENT}. Default {@code offset} alignment is not applicable for
* {@code CharSequence} fields, must be specified explicitly.
* - If the field is of {@code boolean} type, default alignment is not applicable, both
* {@code offset} and {@code dontCross} alignment values must be specified explicitly.
*
*/
int DEFAULT = -1;
/**
* 0 represents no particular alignment (shouldn't align the field start, shouldn't track
* crossing of any border).
*/
int NO_ALIGNMENT = 0;
/**
* The offset to the field's bytes should be a multiple of the {@code offset}.
*/
int offset() default DEFAULT;
/**
* The field's bytes shouldn't cross the {@code dontCross} boundary.
*/
int dontCross() default DEFAULT;
}