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/*
 * Copyright (c) 2024, 2024, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * The Universal Permissive License (UPL), Version 1.0
 *
 * Subject to the condition set forth below, permission is hereby granted to any
 * person obtaining a copy of this software, associated documentation and/or
 * data (collectively the "Software"), free of charge and under any and all
 * copyright rights in the Software, and any and all patent rights owned or
 * freely licensable by each licensor hereunder covering either (i) the
 * unmodified Software as contributed to or provided by such licensor, or (ii)
 * the Larger Works (as defined below), to deal in both
 *
 * (a) the Software, and
 *
 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
 * one is included with the Software each a "Larger Work" to which the Software
 * is contributed by such licensors),
 *
 * without restriction, including without limitation the rights to copy, create
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 * Software and the Larger Work(s), and to sublicense the foregoing rights on
 * either these or other terms.
 *
 * This license is subject to the following condition:
 *
 * The above copyright notice and either this complete permission notice or at a
 * minimum a reference to the UPL must be included in all copies or substantial
 * portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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 */

package com.oracle.truffle.regex.tregex.buffer;

public final class IntRingBuffer {

    private final int[] buf;
    private int start = 0;
    private int length = 0;

    public IntRingBuffer(int sizePowerOf2) {
        buf = new int[1 << sizePowerOf2];
    }

    public boolean isEmpty() {
        return length == 0;
    }

    public void clear() {
        start = 0;
        length = 0;
    }

    private int index(int index) {
        assert Integer.bitCount(buf.length) == 1;
        return (start + index) & (buf.length - 1);
    }

    public int first() {
        assert !isEmpty();
        return buf[start];
    }

    public int last() {
        assert !isEmpty();
        return buf[index(length - 1)];
    }

    public void add(int i) {
        assert length < buf.length;
        buf[index(length++)] = i;
    }

    public void addAll(int[] o) {
        assert buf.length >= length + o.length;
        int copyStart = index(length);
        int copyLength = o.length;
        if (copyStart + copyLength > buf.length) {
            copyLength -= (copyStart + copyLength) - buf.length;
            System.arraycopy(o, copyLength, buf, 0, o.length - copyLength);
        }
        System.arraycopy(o, 0, buf, copyStart, copyLength);
        length += o.length;
    }

    public int removeFirst() {
        assert !isEmpty();
        int first = first();
        start = index(1);
        length--;
        return first;
    }
}