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MessagePack for Java is a binary-based efficient object serialization library in Java.

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//
// MessagePack for Java
//
// Copyright (C) 2009 - 2013 FURUHASHI Sadayuki
//
//    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 org.msgpack.unpacker;

import org.msgpack.MessageTypeException;

public final class UnpackerStack {
    private int top;
    private byte[] types;
    private int[] counts;

    public static final int MAX_STACK_SIZE = 128;

    private static final byte TYPE_INVALID = 0;
    private static final byte TYPE_ARRAY = 1;
    private static final byte TYPE_MAP = 2;

    public UnpackerStack() {
        this.top = 0;
        this.types = new byte[MAX_STACK_SIZE];
        this.counts = new int[MAX_STACK_SIZE];
        this.types[0] = TYPE_INVALID;
    }

    public void pushArray(int size) {
        top++;
        types[top] = TYPE_ARRAY;
        counts[top] = size;
    }

    public void pushMap(int size) {
        top++;
        types[top] = TYPE_MAP;
        counts[top] = size * 2;
    }

    /**
     * throws MessageTypeException if stack is invalid
     */
    public void checkCount() {
        if (counts[top] > 0) {
            return;
        }

        if (types[top] == TYPE_ARRAY) {
            throw new MessageTypeException(
                    "Array is end but readArrayEnd() is not called");
        } else if (types[top] == TYPE_MAP) {
            throw new MessageTypeException(
                    "Map is end but readMapEnd() is not called");
        } else { // empty
            return;
        }
    }

    public void reduceCount() {
        counts[top]--;
    }

    public void pop() {
        top--;
    }

    public int getDepth() {
        return top;
    }

    public int getTopCount() {
        return counts[top];
    }

    public boolean topIsArray() {
        return types[top] == TYPE_ARRAY;
    }

    public boolean topIsMap() {
        return types[top] == TYPE_MAP;
    }

    public void clear() {
        top = 0;
    }
}