/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
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 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common
 * Development and Distribution License("CDDL") (collectively, the
 * "License"). You may not use this file except in compliance with the
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 * http://www.netbeans.org/cddl-gplv2.html
 * or nbbuild/licenses/CDDL-GPL-2-CP. See the License for the
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 * particular file as subject to the "Classpath" exception as provided
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 * The Original Software is NetBeans. The Initial Developer of the Original
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package net.minecraftforge.gradle.patching;

import java.io.ByteArrayOutputStream;
import java.util.List;

/**
 * STOLEN FROM diff4j v1.1
 * <p>
 * Base64 utility methods.
 *
 * @author Maros Sandor
 */
class Base64 {

    private Base64() {
    }

    public static byte[] decode(List<String> ls) {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        for (String s : ls) {
            decode(s, bos);
        }
        return bos.toByteArray();
    }

    private static void decode(String s, ByteArrayOutputStream bos) {
        int i = 0;
        int len = s.length();
        while (true) {
            while (i < len && s.charAt(i) <= ' ') {
                i++;
            }
            if (i == len) {
                break;
            }
            int tri = (decode(s.charAt(i)) << 18)
                    + (decode(s.charAt(i + 1)) << 12)
                    + (decode(s.charAt(i + 2)) << 6)
                    + (decode(s.charAt(i + 3)));

            bos.write((tri >> 16) & 255);
            if (s.charAt(i + 2) == '=') {
                break;
            }
            bos.write((tri >> 8) & 255);
            if (s.charAt(i + 3) == '=') {
                break;
            }
            bos.write(tri & 255);

            i += 4;
        }
    }

    private static int decode(char c) {
        if (c >= 'A' && c <= 'Z') {
            return ((int) c) - 65;
        } else if (c >= 'a' && c <= 'z') {
            return ((int) c) - 97 + 26;
        } else if (c >= '0' && c <= '9') {
            return ((int) c) - 48 + 26 + 26;
        } else {
            switch (c) {
                case '+':
                    return 62;
                case '/':
                    return 63;
                case '=':
                    return 0;
                default:
                    throw new RuntimeException("unexpected code: " + c);
            }
        }
    }

}
