PackExt.java

/*
 * Copyright (C) 2013, Google Inc.
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
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package org.eclipse.jgit.internal.storage.pack;

/**
 * A pack file extension.
 */
public class PackExt {
    private static volatile PackExt[] VALUES = new PackExt[] {};

    /** A pack file extension. */
    public static final PackExt PACK = newPackExt("pack"); //$NON-NLS-1$

    /** A pack index file extension. */
    public static final PackExt INDEX = newPackExt("idx"); //$NON-NLS-1$

    /** A keep pack file extension. */
    public static final PackExt KEEP = newPackExt("keep"); //$NON-NLS-1$

    /** A pack bitmap index file extension. */
    public static final PackExt BITMAP_INDEX = newPackExt("bitmap"); //$NON-NLS-1$

    /** A reftable file. */
    public static final PackExt REFTABLE = newPackExt("ref"); //$NON-NLS-1$

    /**
     * Get all of the PackExt values.
     *
     * @return all of the PackExt values.
     */
    public static PackExt[] values() {
        return VALUES;
    }

    /**
     * Returns a PackExt for the file extension and registers it in the values
     * array.
     *
     * @param ext
     *            the file extension.
     * @return the PackExt for the ext
     */
    public synchronized static PackExt newPackExt(String ext) {
        PackExt[] dst = new PackExt[VALUES.length + 1];
        for (int i = 0; i < VALUES.length; i++) {
            PackExt packExt = VALUES[i];
            if (packExt.getExtension().equals(ext))
                return packExt;
            dst[i] = packExt;
        }
        if (VALUES.length >= 32)
            throw new IllegalStateException(
                    "maximum number of pack extensions exceeded"); //$NON-NLS-1$

        PackExt value = new PackExt(ext, VALUES.length);
        dst[VALUES.length] = value;
        VALUES = dst;
        return value;
    }

    private final String ext;

    private final int pos;

    private PackExt(String ext, int pos) {
        this.ext = ext;
        this.pos = pos;
    }

    /**
     * Get the file extension.
     *
     * @return the file extension.
     */
    public String getExtension() {
        return ext;
    }

    /**
     * Get the position of the extension in the values array.
     *
     * @return the position of the extension in the values array.
     */
    public int getPosition() {
        return pos;
    }

    /**
     * Get the bit mask of the extension e.g {@code 1 << getPosition()}.
     *
     * @return the bit mask of the extension e.g {@code 1 << getPosition()}.
     */
    public int getBit() {
        return 1 << getPosition();
    }

    /** {@inheritDoc} */
    @Override
    public String toString() {
        return String.format("PackExt[%s, bit=0x%s]", getExtension(), //$NON-NLS-1$
                Integer.toHexString(getBit()));
    }
}