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/*******************************************************************************
* Copyright (c) 2015, 2016 Google, Inc and others.
*
* This program and the accompanying materials
* are made available under the terms of the Eclipse Public License 2.0
* which accompanies this distribution, and is available at
* https://www.eclipse.org/legal/epl-2.0/
*
* SPDX-License-Identifier: EPL-2.0
*
* Contributors:
* Stefan Xenos (Google) - Initial implementation
*******************************************************************************/
package org.eclipse.jdt.internal.core.nd.field;
import org.eclipse.jdt.internal.core.nd.ITypeFactory;
import org.eclipse.jdt.internal.core.nd.Nd;
import org.eclipse.jdt.internal.core.nd.db.Database;
/**
* Used to represent a single field of an object stored in the database. Objects
* which store themselves in the database should store a set of static final
* FieldDefinitions at the top of their class definition to indicate their memory map.
* This serves as a standard way to document the memory map for such structs, provides
* access to the field offsets, and provides a convenience getter.
* <p>
* There are two ways to use this. Callers can either use the "get" method to access
* the value of the field, or can use the public "offset" attribute to perform the reads
* manually. The get function is more convenient but allocates objects and so should
* probably not be used for frequently-accessed fields or primitive types that would
* end up being autoboxed unnecessarily.
*
* @param <T>
*/
public final class Field<T> extends BaseField implements IDestructableField {
public final ITypeFactory<T> factory;
public Field(ITypeFactory<T> objectFactory, String structName, int fieldNumber) {
setFieldName("field " + fieldNumber + ", a " + getClass().getSimpleName() //$NON-NLS-1$//$NON-NLS-2$
+ " in struct " + structName); //$NON-NLS-1$
this.factory = objectFactory;
}
public T get(Nd nd, long address) {
return this.factory.create(nd, address + this.offset);
}
public boolean hasDestructor() {
return this.factory.hasDestructor();
}
@Override
public void destruct(Nd nd, long address) {
this.factory.destruct(nd, address + this.offset);
}
@Override
public int getRecordSize() {
return this.factory.getRecordSize();
}
@Override
public int getAlignment() {
// This sort of field is almost always used for embedding NdStructs within
// other data types. Since most NdStructs allow incoming record pointers, they need to
// be properly aligned. If we ever want to use this sort of field for other data types
// that don't require alignment, we may want to replace this with something smarter
// that can figure out the correct alignment based on the requirements of the actual
// data type.
return Database.BLOCK_SIZE_DELTA;
}
/**
* Creates a new {@link Field} in the given struct with the given type.
*
* @param struct the struct that will contain the newly-created field (must not have had
* {@link StructDef#done()} called on it yet).
* @param fieldType the data type for the contents of the newly created field
* @return the newly-constructed field
*/
public static <T> Field<T> create(StructDef<?> struct, StructDef<T> fieldType) {
Field<T> result = new Field<>(fieldType.getFactory(), struct.getStructName(), struct.getNumFields());
struct.add(result);
struct.addDestructableField(result);
fieldType.addDependency(struct);
return result;
}
}
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