dexgen/src/com/android/dexgen/util/Leb128Utils.java

/*
 * Copyright (C) 2008 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 com.android.dexgen.util;

/**
 * LEB128 (little-endian base 128) utilities.
 */
public final class Leb128Utils {
    /**
     * This class is uninstantiable.
     */
    private Leb128Utils() {
        // This space intentionally left blank.
    }

    /**
     * Gets the number of bytes in the unsigned LEB128 encoding of the
     * given value.
     *
     * @param value the value in question
     * @return its write size, in bytes
     */
    public static int unsignedLeb128Size(int value) {
        // TODO: This could be much cleverer.

        int remaining = value >> 7;
        int count = 0;

        while (remaining != 0) {
            remaining >>= 7;
            count++;
        }

        return count + 1;
    }

    /**
     * Gets the number of bytes in the signed LEB128 encoding of the
     * given value.
     *
     * @param value the value in question
     * @return its write size, in bytes
     */
    public static int signedLeb128Size(int value) {
        // TODO: This could be much cleverer.

        int remaining = value >> 7;
        int count = 0;
        boolean hasMore = true;
        int end = ((value & Integer.MIN_VALUE) == 0) ? 0 : -1;

        while (hasMore) {
            hasMore = (remaining != end)
                || ((remaining & 1) != ((value >> 6) & 1));

            value = remaining;
            remaining >>= 7;
            count++;
        }

        return count;
    }
}