termux-app

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/*
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 * Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.  Oracle designates this
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 * particular file as subject to the "Classpath" exception as provided
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 * by Oracle in the LICENSE file that accompanied this code.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * or visit www.oracle.com if you need additional information or have any
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 * questions.
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 */
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package com.termux.shared.file.filesystem;
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import static com.termux.shared.file.filesystem.FilePermission.*;
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import java.util.*;
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/**
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 * This class consists exclusively of static methods that operate on sets of
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 * {@link FilePermission} objects.
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 *
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 * https://cs.android.com/android/platform/superproject/+/android-11.0.0_r3:libcore/ojluni/src/main/java/java/nio/file/attribute/PosixFilePermissions.java
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 *
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 * @since 1.7
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 */
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public final class FilePermissions {
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    private FilePermissions() { }
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    // Write string representation of permission bits to {@code sb}.
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    private static void writeBits(StringBuilder sb, boolean r, boolean w, boolean x) {
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        if (r) {
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            sb.append('r');
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        } else {
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            sb.append('-');
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        }
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        if (w) {
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            sb.append('w');
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        } else {
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            sb.append('-');
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        }
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        if (x) {
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            sb.append('x');
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        } else {
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            sb.append('-');
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        }
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    }
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    /**
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     * Returns the {@code String} representation of a set of permissions. It
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     * is guaranteed that the returned {@code String} can be parsed by the
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     * {@link #fromString} method.
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     *
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     * <p> If the set contains {@code null} or elements that are not of type
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     * {@code FilePermission} then these elements are ignored.
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     *
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     * @param   perms
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     *          the set of permissions
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     *
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     * @return  the string representation of the permission set
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     */
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    public static String toString(Set<FilePermission> perms) {
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        StringBuilder sb = new StringBuilder(9);
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        writeBits(sb, perms.contains(OWNER_READ), perms.contains(OWNER_WRITE),
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            perms.contains(OWNER_EXECUTE));
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        writeBits(sb, perms.contains(GROUP_READ), perms.contains(GROUP_WRITE),
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            perms.contains(GROUP_EXECUTE));
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        writeBits(sb, perms.contains(OTHERS_READ), perms.contains(OTHERS_WRITE),
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            perms.contains(OTHERS_EXECUTE));
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        return sb.toString();
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    }
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    private static boolean isSet(char c, char setValue) {
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        if (c == setValue)
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            return true;
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        if (c == '-')
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            return false;
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        throw new IllegalArgumentException("Invalid mode");
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    }
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    private static boolean isR(char c) { return isSet(c, 'r'); }
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    private static boolean isW(char c) { return isSet(c, 'w'); }
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    private static boolean isX(char c) { return isSet(c, 'x'); }
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    /**
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     * Returns the set of permissions corresponding to a given {@code String}
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     * representation.
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     *
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     * <p> The {@code perms} parameter is a {@code String} representing the
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     * permissions. It has 9 characters that are interpreted as three sets of
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     * three. The first set refers to the owner's permissions; the next to the
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     * group permissions and the last to others. Within each set, the first
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     * character is {@code 'r'} to indicate permission to read, the second
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     * character is {@code 'w'} to indicate permission to write, and the third
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     * character is {@code 'x'} for execute permission. Where a permission is
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     * not set then the corresponding character is set to {@code '-'}.
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     *
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     * <p> <b>Usage Example:</b>
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     * Suppose we require the set of permissions that indicate the owner has read,
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     * write, and execute permissions, the group has read and execute permissions
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     * and others have none.
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     * <pre>
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     *   Set&lt;FilePermission&gt; perms = FilePermissions.fromString("rwxr-x---");
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     * </pre>
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     *
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     * @param   perms
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     *          string representing a set of permissions
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     *
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     * @return  the resulting set of permissions
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     *
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     * @throws  IllegalArgumentException
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     *          if the string cannot be converted to a set of permissions
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     *
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     * @see #toString(Set)
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     */
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    public static Set<FilePermission> fromString(String perms) {
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        if (perms.length() != 9)
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            throw new IllegalArgumentException("Invalid mode");
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        Set<FilePermission> result = EnumSet.noneOf(FilePermission.class);
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        if (isR(perms.charAt(0))) result.add(OWNER_READ);
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        if (isW(perms.charAt(1))) result.add(OWNER_WRITE);
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        if (isX(perms.charAt(2))) result.add(OWNER_EXECUTE);
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        if (isR(perms.charAt(3))) result.add(GROUP_READ);
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        if (isW(perms.charAt(4))) result.add(GROUP_WRITE);
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        if (isX(perms.charAt(5))) result.add(GROUP_EXECUTE);
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        if (isR(perms.charAt(6))) result.add(OTHERS_READ);
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        if (isW(perms.charAt(7))) result.add(OTHERS_WRITE);
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        if (isX(perms.charAt(8))) result.add(OTHERS_EXECUTE);
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        return result;
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    }
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}
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