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An unofficial backport of the JDK Classfile API to Java 17
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/*
 * Copyright (c) 2022, 2024, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package io.github.dmlloyd.classfile.impl;

import io.github.dmlloyd.classfile.Attribute;
import io.github.dmlloyd.classfile.AttributeMapper;
import java.util.Arrays;

public class AttributeHolder {
    private static final Attribute[] EMPTY_ATTRIBUTE_ARRAY = {};
    private int attributesCount = 0;
    private Attribute[] attributes = EMPTY_ATTRIBUTE_ARRAY;

    public > void withAttribute(Attribute a) {
        if (a == null)
            return;

        @SuppressWarnings("unchecked")
        AttributeMapper am = (AttributeMapper) a.attributeMapper();
        int attributesCount = this.attributesCount;
        var attributes = this.attributes;
        if (!am.allowMultiple()) {
            // remove if
            for (int i = attributesCount - 1; i >= 0; i--) {
                if (attributes[i].attributeMapper() == am) {
                    attributesCount--;
                    System.arraycopy(attributes, i + 1, attributes, i, attributesCount - i);
                }
            }
        }

        // add attribute
        if (attributesCount >= attributes.length) {
            int newCapacity = attributesCount + 4;
            this.attributes = attributes = Arrays.copyOf(attributes, newCapacity);
        }
        attributes[attributesCount] = a;
        this.attributesCount = attributesCount + 1;
    }

    public int size() {
        return attributesCount;
    }

    public void writeTo(BufWriterImpl buf) {
        int attributesCount = this.attributesCount;
        buf.writeU2(attributesCount);
        for (int i = 0; i < attributesCount; i++) {
            Util.writeAttribute(buf, attributes[i]);
        }
    }

    @SuppressWarnings("unchecked")
    > A get(AttributeMapper am) {
        for (int i = 0; i < attributesCount; i++) {
            Attribute a = attributes[i];
            if (a.attributeMapper() == am)
                return (A) a;
        }
        return null;
    }

    boolean isPresent(AttributeMapper am) {
        for (int i = 0; i < attributesCount; i++) {
            if (attributes[i].attributeMapper() == am)
                return true;
        }
        return false;
    }
}