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/*
   Copyright [2015] argonet.co.kr

   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.
*/
/*
 * This software has been developed with reference to
 * the HWP file format open specification by Hancom, Inc.
 * http://www.hancom.co.kr/userofficedata.userofficedataList.do?menuFlag=3
 * 한글과컴퓨터의 한/글 문서 파일(.hwp) 공개 문서를 참고하여 개발하였습니다.
 * 
 * 본 제품은 다음의 소스를 참조하였습니다.
 * https://github.com/cogniti/ruby-hwp/
 */
package com.argo.hwp.utils;

import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;

import org.apache.poi.util.LittleEndian;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class HwpStreamReader {
	private Logger log = LoggerFactory.getLogger(getClass());
	private InputStream input;
	private byte[] buf;

	public HwpStreamReader(InputStream inputStream) {
		this.input = inputStream;
		buf = new byte[4];
	}

	/**
	 * 읽을 데이터가 더 있는가?
	 * 
	 * @return
	 * @throws IOException
	 */
	public boolean available() throws IOException {
		return input.available() > 0;
	}

	/**
	 * unsigned 1 byte
	 * 
	 * @return
	 * @throws IOException
	 */
	public short uint8() throws IOException {
		if (ensure(1) == 0)
			return -1;

		return LittleEndian.getUByte(buf);
	}

	/**
	 * unsigned 2 byte
	 * 
	 * @return
	 * @throws IOException
	 */
	public int uint16() throws IOException {
		if (ensure(2) == 0)
			return -1;

		return LittleEndian.getUShort(buf);
	}

	/**
	 * unsigned 2 byte array
	 * 
	 * @param i
	 * @return
	 * @throws IOException
	 */
	public int[] uint16(int i) throws IOException {
		if (i <= 0)
			throw new IllegalArgumentException();

		int[] uints = new int[i];
		for (int ii = 0; ii < i; ii++) {
			if (ensure(2) == 0)
				throw new EOFException();

			uints[ii] = LittleEndian.getUShort(buf);
		}

		return uints;
	}

	/**
	 * unsigned 4 byte
	 * 
	 * @return
	 * @throws IOException
	 */
	public long uint32() throws IOException {
		if (ensure(4) == 0)
			return -1;

		return LittleEndian.getUInt(buf);
	}

	/**
	 * 
	 * @param n
	 * @return
	 * @throws IOException
	 */
	public long skip(long n) throws IOException {
		return input.skip(n);
	}

	/**
	 * n만큼 skip 하지 못할 경우 IOException 을 발생한다
	 * 
	 * @param n
	 * @throws IOException
	 */
	public void ensureSkip(long n) throws IOException {
		long skipped = skip(n);
		if (n != skipped) {
			log.error("Skip failed {} => {}", n, skipped);
			throw new IOException();
		}
	}

	/**
	 * count만큼 바이트를 읽는다. InflaterInputStream의 경우 한번에 count만큼 read가 안되는 경우가 있다.
	 * 그래서 count만큼 읽을 때까지 루프를 실행한다
	 * 
	 * @param count
	 * @return
	 * @throws IOException
	 * @throws EOFException
	 */
	private int ensure(int count) throws IOException, EOFException {
		int total = 0;
		while (total < count) {
			// if (total > 0) {
			// log.warn("한번에 읽기 실패 {}/{}. 다시 읽기 시도함 {}", total, count, input);
			// }

			int read = input.read(buf, total, count - total);
			if (read <= 0)
				break;

			total += read;
		}

		if (total == 0) {
			// end
		} else if (total < count) {
			// unexpected end
			throw new EOFException();
		}

		return total;
	}
}