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Apache Commons Compress defines an API for working with compression and archive formats. These include bzip2, gzip, pack200, LZMA, XZ, Snappy, traditional Unix Compress, DEFLATE, DEFLATE64, LZ4, Brotli, Zstandard and ar, cpio, jar, tar, zip, dump, 7z, arj.

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/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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 org.apache.commons.compress.archivers.sevenz;

import java.util.Arrays;

/**
 * The (partially) supported compression/encryption methods used in 7z archives.
 * 
 * All methods with a {@code _FILTER} suffix are used as preprocessors with the goal of creating a better compression ratio with the compressor that comes next
 * in the chain of methods. 7z will in general only allow them to be used together with a "real" compression method but Commons Compress doesn't enforce this.
 * 
 * 
 * The {@code BCJ_} filters work on executable files for the given platform and convert relative addresses to absolute addresses in CALL instructions. This
 * means they are only useful when applied to executables of the chosen platform.
 * 
 */
public enum SevenZMethod {

    /** No compression at all. */
    COPY(new byte[] { (byte) 0x00 }),

    /** LZMA - only supported when reading. */
    LZMA(new byte[] { (byte) 0x03, (byte) 0x01, (byte) 0x01 }),

    /** LZMA2. */
    LZMA2(new byte[] { (byte) 0x21 }),

    /** Deflate. */
    DEFLATE(new byte[] { (byte) 0x04, (byte) 0x01, (byte) 0x08 }),

    /**
     * Deflate64.
     *
     * @since 1.16
     */
    DEFLATE64(new byte[] { (byte) 0x04, (byte) 0x01, (byte) 0x09 }),

    /** BZIP2. */
    BZIP2(new byte[] { (byte) 0x04, (byte) 0x02, (byte) 0x02 }),

    /**
     * AES encryption with a key length of 256 bit using SHA256 for hashes - only supported when reading.
     */
    AES256SHA256(new byte[] { (byte) 0x06, (byte) 0xf1, (byte) 0x07, (byte) 0x01 }),

    /**
     * BCJ x86 platform version 1.
     *
     * @since 1.8
     */
    BCJ_X86_FILTER(new byte[] { 0x03, 0x03, 0x01, 0x03 }),

    /**
     * BCJ PowerPC platform.
     *
     * @since 1.8
     */
    BCJ_PPC_FILTER(new byte[] { 0x03, 0x03, 0x02, 0x05 }),

    /**
     * BCJ I64 platform.
     *
     * @since 1.8
     */
    BCJ_IA64_FILTER(new byte[] { 0x03, 0x03, 0x04, 0x01 }),

    /**
     * BCJ ARM platform.
     *
     * @since 1.8
     */
    BCJ_ARM_FILTER(new byte[] { 0x03, 0x03, 0x05, 0x01 }),

    /**
     * BCJ ARM Thumb platform.
     *
     * @since 1.8
     */
    BCJ_ARM_THUMB_FILTER(new byte[] { 0x03, 0x03, 0x07, 0x01 }),

    /**
     * BCJ Sparc platform.
     *
     * @since 1.8
     */
    BCJ_SPARC_FILTER(new byte[] { 0x03, 0x03, 0x08, 0x05 }),

    /**
     * Delta filter.
     *
     * @since 1.8
     */
    DELTA_FILTER(new byte[] { 0x03 });

    static SevenZMethod byId(final byte[] id) {
        for (final SevenZMethod method : SevenZMethod.class.getEnumConstants()) {
            if (Arrays.equals(method.id, id)) {
                return method;
            }
        }
        return null;
    }

    private final byte[] id;

    SevenZMethod(final byte[] id) {
        this.id = id;
    }

    byte[] getId() {
        return Arrays.copyOf(id, id.length);
    }
}