LockPatternUtils.java

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed 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 group.pals.android.lib.ui.lockpattern.widget;

import group.pals.android.lib.ui.lockpattern.collect.Lists;

import java.io.UnsupportedEncodingException;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.List;
import java.util.Locale;

/**
 * Utilities for the lock pattern and its settings.
 */
public class LockPatternUtils {

	public static final String Utf8 = "utf-8";
	public static final String Sha1 = "sha-1";

	/**
	 * Deserialize a pattern.
	 * 
	 * @param string The pattern serialized with {@link #patternToString}
	 * @return The pattern.
	 */
	public static List<LockPatternView.Cell> stringToPattern(String string) {
		List<LockPatternView.Cell> result = Lists.newArrayList();

		try {
			final byte[] bytes = string.getBytes(Utf8);
			for (int i = 0; i < bytes.length; i++) {
				byte b = bytes[i];
				result.add(LockPatternView.Cell.of(b / 3, b % 3));
			}
		} catch (UnsupportedEncodingException e) {
			// never catch this
		}

		return result;
	}// stringToPattern()

	/**
	 * Serialize a pattern.
	 * 
	 * @param pattern The pattern.
	 * @return The pattern in string form.
	 */
	public static String patternToString(List<LockPatternView.Cell> pattern) {
		if (pattern == null) {
			return "";
		}
		final int patternSize = pattern.size();

		byte[] res = new byte[patternSize];
		for (int i = 0; i < patternSize; i++) {
			LockPatternView.Cell cell = pattern.get(i);
			res[i] = (byte) (cell.getRow() * 3 + cell.getColumn());
		}
		try {
			return new String(res, Utf8);
		} catch (UnsupportedEncodingException e) {
			// never catch this
			return "";
		}
	}// patternToString()

	/**
	 * Serializes a pattern
	 * 
	 * @param pattern The pattern
	 * @return The SHA-1 string of the pattern got from {@link #patternToString(List)}
	 */
	public static String patternToSha1(List<LockPatternView.Cell> pattern) {
		try {
			MessageDigest md = MessageDigest.getInstance(Sha1);
			md.update(patternToString(pattern).getBytes(Utf8));

			byte[] digest = md.digest();
			BigInteger bi = new BigInteger(1, digest);
			return String.format((Locale) null, "%0" + (digest.length * 2) + "x", bi).toLowerCase(Locale.ENGLISH);
		} catch (NoSuchAlgorithmException e) {
			// never catch this
			return "";
		} catch (UnsupportedEncodingException e) {
			// never catch this
			return "";
		}
	}// patternToSha1()
}