/*
 * Copyright (c) 2017, 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 jdk.internal.util.jar;

/**
 * Simple utility methods for checking Jar file attributes.
 */

public class JarAttributes {

    // No can has instance!
    private JarAttributes() {}

    // Statics for hand-coded Boyer-Moore search
    private static final byte[] CLASSPATH_CHARS =
            {'C','L','A','S','S','-','P','A','T','H', ':', ' '};

    // The bad character shift for "class-path: "
    private static final byte[] CLASSPATH_LASTOCC;

    // The good suffix shift for "class-path: "
    private static final byte[] CLASSPATH_OPTOSFT;

    private static final byte[] MULTIRELEASE_CHARS =
            {'M','U','L','T','I','-','R','E','L','E', 'A', 'S', 'E', ':',
                    ' ', 'T', 'R', 'U', 'E'};

    // The bad character shift for "multi-release: true"
    private static final byte[] MULTIRELEASE_LASTOCC;

    // The good suffix shift for "multi-release: true"
    private static final byte[] MULTIRELEASE_OPTOSFT;

    static {
        CLASSPATH_LASTOCC = new byte[64];
        CLASSPATH_OPTOSFT = new byte[12];
        CLASSPATH_LASTOCC[(int)'C' - 32] = 1;
        CLASSPATH_LASTOCC[(int)'L' - 32] = 2;
        CLASSPATH_LASTOCC[(int)'S' - 32] = 5;
        CLASSPATH_LASTOCC[(int)'-' - 32] = 6;
        CLASSPATH_LASTOCC[(int)'P' - 32] = 7;
        CLASSPATH_LASTOCC[(int)'A' - 32] = 8;
        CLASSPATH_LASTOCC[(int)'T' - 32] = 9;
        CLASSPATH_LASTOCC[(int)'H' - 32] = 10;
        CLASSPATH_LASTOCC[(int)':' - 32] = 11;
        CLASSPATH_LASTOCC[(int)' ' - 32] = 12;
        for (int i = 0; i < 11; i++) {
            CLASSPATH_OPTOSFT[i] = 12;
        }
        CLASSPATH_OPTOSFT[11] = 1;

        MULTIRELEASE_LASTOCC = new byte[64];
        MULTIRELEASE_OPTOSFT = new byte[19];
        MULTIRELEASE_LASTOCC[(int)'M' - 32] = 1;
        MULTIRELEASE_LASTOCC[(int)'I' - 32] = 5;
        MULTIRELEASE_LASTOCC[(int)'-' - 32] = 6;
        MULTIRELEASE_LASTOCC[(int)'L' - 32] = 9;
        MULTIRELEASE_LASTOCC[(int)'A' - 32] = 11;
        MULTIRELEASE_LASTOCC[(int)'S' - 32] = 12;
        MULTIRELEASE_LASTOCC[(int)':' - 32] = 14;
        MULTIRELEASE_LASTOCC[(int)' ' - 32] = 15;
        MULTIRELEASE_LASTOCC[(int)'T' - 32] = 16;
        MULTIRELEASE_LASTOCC[(int)'R' - 32] = 17;
        MULTIRELEASE_LASTOCC[(int)'U' - 32] = 18;
        MULTIRELEASE_LASTOCC[(int)'E' - 32] = 19;
        for (int i = 0; i < 17; i++) {
            MULTIRELEASE_OPTOSFT[i] = 19;
        }
        MULTIRELEASE_OPTOSFT[17] = 6;
        MULTIRELEASE_OPTOSFT[18] = 1;
    }

    public static boolean hasClassPathAttribute(final byte[] manifestEntry) {
        return match(CLASSPATH_CHARS, manifestEntry,
                CLASSPATH_LASTOCC, CLASSPATH_OPTOSFT) != -1;
    }

    public static boolean isMultiRelease(final byte[] manifest) {
        // is this a multi-release jar file
        int i = match(MULTIRELEASE_CHARS, manifest, MULTIRELEASE_LASTOCC,
                MULTIRELEASE_OPTOSFT);
        if (i != -1) {
            i += MULTIRELEASE_CHARS.length;
            if (i < manifest.length) {
                byte c = manifest[i++];
                // Check that the value is followed by a newline
                // and does not have a continuation
                if (c == '\n' &&
                        (i == manifest.length || manifest[i] != ' ')) {
                    return true;
                } else if (c == '\r') {
                    if (i == manifest.length) {
                        return true;
                    } else {
                        c = manifest[i++];
                        if (c == '\n') {
                            if (i == manifest.length || manifest[i] != ' ') {
                                return true;
                            }
                        } else if (c != ' ') {
                            return true;
                        }
                    }
                }
            }
        }
        return false;
    }
    /**
     * Returns true if the pattern {@code src} is found in {@code b}.
     * The {@code lastOcc} array is the precomputed bad character shifts.
     * Since there are no repeated substring in our search strings,
     * the good suffix shifts can be replaced with a comparison.
     */
    private static int match(byte[] src, byte[] b, byte[] lastOcc, byte[] optoSft) {
        int len = src.length;
        int last = b.length - len;
        int i = 0;
        next:
        while (i <= last) {
            for (int j = (len - 1); j >= 0; j--) {
                byte c = b[i + j];
                if (c >= ' ' && c <= 'z') {
                    if (c >= 'a') c -= 32; // Canonicalize

                    if (c != src[j]) {
                        // no match
                        int badShift = lastOcc[c - 32];
                        i += Math.max(j + 1 - badShift, optoSft[j]);
                        continue next;
                    }
                } else {
                    // no match, character not valid for name
                    i += len;
                    continue next;
                }
            }
            return i;
        }
        return -1;
    }
}