Utf8.java

/*
 * 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 com.addthis.basis.chars;

import com.google.common.annotations.Beta;

/**
 * Utf8 utility class.
 */
@Beta
public class Utf8 {

    // 110xxx1x; anything more negative cannot be sequence start (eg. 10xxxxxx)
    public static final byte MIN_MULTI_HEADER = (byte) 0xC2;
    public static final byte MIN_THREE_HEADER = (byte) 0xE0;
    public static final byte MIN_FOUR_HEADER = (byte) 0xF0;

    // these masks only work AFTER the byte is known to be negative
    // they leave only the 1 bit that signals N bytes or greater. Suitable for & >> combos
    public static final byte TWO_BYTE_MASK = (byte) 0x40;
    public static final byte TWO_BYTE_SHIFT = (byte) 6;
    public static final byte THREE_BYTE_MASK = (byte) 0x20;
    public static final byte THREE_BYTE_SHIFT = (byte) 5;
    public static final byte FOUR_BYTE_MASK = (byte) 0x10;
    public static final byte FOUR_BYTE_SHIFT = (byte) 4;

    // xx111111; continuation bytes have 10 as a header and the first two bits should be ignored
    public static final byte CONTINUATION_MASK = (byte) 0x3F;

    public static final byte TWO_BYTE_HEADER_MASK = (byte) 0x1F;
    public static final byte THREE_BYTE_HEADER_MASK = (byte) 0x0F;
    public static final byte FOUR_BYTE_HEADER_MASK = (byte) 0x07;
}