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	/*
	* Copyright (c) 2007, 2011, 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 java.nio.file.attribute;

	import static java.nio.file.attribute.PosixFilePermission.*;
	import java.util.*;

	/**
	* This class consists exclusively of static methods that operate on sets of
	* {@link PosixFilePermission} objects.
	*
	* @since 1.7
	*/

	public final class PosixFilePermissions {
	private PosixFilePermissions() { }

	// Write string representation of permission bits to {@code sb}.
	private static void writeBits(StringBuilder sb, boolean r, boolean w, boolean x) {
	if (r) {
	sb.append('r');
	} else {
	sb.append('-');
	}
	if (w) {
	sb.append('w');
	} else {
	sb.append('-');
	}
	if (x) {
	sb.append('x');
	} else {
	sb.append('-');
	}
	}

	/**
	* Returns the {@code String} representation of a set of permissions. It
	* is guaranteed that the returned {@code String} can be parsed by the
	* {@link #fromString} method.
	*
	* <p> If the set contains {@code null} or elements that are not of type
	* {@code PosixFilePermission} then these elements are ignored.
	*
	* @param perms
	* the set of permissions
	*
	* @return the string representation of the permission set
	*/
	public static String toString(Set<PosixFilePermission> perms) {
	StringBuilder sb = new StringBuilder(9);
	writeBits(sb, perms.contains(OWNER_READ), perms.contains(OWNER_WRITE),
	perms.contains(OWNER_EXECUTE));
	writeBits(sb, perms.contains(GROUP_READ), perms.contains(GROUP_WRITE),
	perms.contains(GROUP_EXECUTE));
	writeBits(sb, perms.contains(OTHERS_READ), perms.contains(OTHERS_WRITE),
	perms.contains(OTHERS_EXECUTE));
	return sb.toString();
	}

	private static boolean isSet(char c, char setValue) {
	if (c == setValue)
	return true;
	if (c == '-')
	return false;
	throw new IllegalArgumentException("Invalid mode");
	}
	private static boolean isR(char c) { return isSet(c, 'r'); }
	private static boolean isW(char c) { return isSet(c, 'w'); }
	private static boolean isX(char c) { return isSet(c, 'x'); }

	/**
	* Returns the set of permissions corresponding to a given {@code String}
	* representation.
	*
	* <p> The {@code perms} parameter is a {@code String} representing the
	* permissions. It has 9 characters that are interpreted as three sets of
	* three. The first set refers to the owner's permissions; the next to the
	* group permissions and the last to others. Within each set, the first
	* character is {@code 'r'} to indicate permission to read, the second
	* character is {@code 'w'} to indicate permission to write, and the third
	* character is {@code 'x'} for execute permission. Where a permission is
	* not set then the corresponding character is set to {@code '-'}.
	*
	* <p> <b>Usage Example:</b>
	* Suppose we require the set of permissions that indicate the owner has read,
	* write, and execute permissions, the group has read and execute permissions
	* and others have none.
	* <pre>
	* Set<PosixFilePermission> perms = PosixFilePermissions.fromString("rwxr-x---");
	* </pre>
	*
	* @param perms
	* string representing a set of permissions
	*
	* @return the resulting set of permissions
	*
	* @throws IllegalArgumentException
	* if the string cannot be converted to a set of permissions
	*
	* @see #toString(Set)
	*/
	public static Set<PosixFilePermission> fromString(String perms) {
	if (perms.length() != 9)
	throw new IllegalArgumentException("Invalid mode");
	Set<PosixFilePermission> result = EnumSet.noneOf(PosixFilePermission.class);
	if (isR(perms.charAt(0))) result.add(OWNER_READ);
	if (isW(perms.charAt(1))) result.add(OWNER_WRITE);
	if (isX(perms.charAt(2))) result.add(OWNER_EXECUTE);
	if (isR(perms.charAt(3))) result.add(GROUP_READ);
	if (isW(perms.charAt(4))) result.add(GROUP_WRITE);
	if (isX(perms.charAt(5))) result.add(GROUP_EXECUTE);
	if (isR(perms.charAt(6))) result.add(OTHERS_READ);
	if (isW(perms.charAt(7))) result.add(OTHERS_WRITE);
	if (isX(perms.charAt(8))) result.add(OTHERS_EXECUTE);
	return result;
	}

	/**
	* Creates a {@link FileAttribute}, encapsulating a copy of the given file
	* permissions, suitable for passing to the {@link java.nio.file.Files#createFile
	* createFile} or {@link java.nio.file.Files#createDirectory createDirectory}
	* methods.
	*
	* @param perms
	* the set of permissions
	*
	* @return an attribute encapsulating the given file permissions with
	* {@link FileAttribute#name name} {@code "posix:permissions"}
	*
	* @throws ClassCastException
	* if the set contains elements that are not of type {@code
	* PosixFilePermission}
	*/
	public static FileAttribute<Set<PosixFilePermission>>
	asFileAttribute(Set<PosixFilePermission> perms)
	{
	// copy set and check for nulls (CCE will be thrown if an element is not
	// a PosixFilePermission)
	perms = new HashSet<PosixFilePermission>(perms);
	for (PosixFilePermission p: perms) {
	if (p == null)
	throw new NullPointerException();
	}
	final Set<PosixFilePermission> value = perms;
	return new FileAttribute<Set<PosixFilePermission>>() {
	@Override
	public String name() {
	return "posix:permissions";
	}
	@Override
	public Set<PosixFilePermission> value() {
	return Collections.unmodifiableSet(value);
	}
	};
	}
	}

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