taghead.java

YOYOPlayer MP3播放器 java+JMF实现

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package com.hadeslee.audiotag.tag.ape;

import com.hadeslee.yoyoplayer.util.Util;
import java.util.Arrays;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * 内部的私有类,它代表了一个APE标签的头部
 * @author hadeslee
 */
public class TagHead {

    private static Logger log = Logger.getLogger(TagHead.class.getName());
    private byte[] data;//头部的数据
    private boolean valid;//是否是合法的头部
    private int version = 2000;//版本,默认是2000
    private int tagSize;//标签的长度,包括尾标签以及所有的项目,不包括头标签
    private int itemCount;//项目的数量
    private int flag = FOOT;//标签的其它标志,指示它是头部还是尾部
    public static final int HEAD = 0xA0000000;
    public static final int FOOT = 0x80000000;
    public static final int V1=1000;//表示APE的版本号
    public static final int V2=2000;
    private int index;//这个标头的起始点的位置,相对于文件
    public TagHead(byte[] data) {
        this.data = data;
        parseData();
    }

    public TagHead() {
    }

    public int getIndex() {
        return index;
    }

    public void setIndex(int index) {
        this.index = index;
    }

    public byte[] getBytes() {
        //标头总共是32个字节
        byte[] head = new byte[32];
        byte[] temp = {(byte) 'A',
            (byte) 'P',
            (byte) 'E',
            (byte) 'T',
            (byte) 'A',
            (byte) 'G',
            (byte) 'E',
            (byte) 'X'
        };
        //先把头的标量填进去,8字节
        System.arraycopy(temp, 0, head, 0, 8);
        temp = Util.getBytesFromInt(version);
        //再把版本号写进去,4字节
        System.arraycopy(temp, 0, head, 8, 4);
        temp = Util.getBytesFromInt(tagSize);
        log.log(Level.SEVERE,"TAGSIZE="+tagSize);
        //再把标签的长度写进去,4字节
        System.arraycopy(temp, 0, head, 12, 4);
        temp = Util.getBytesFromInt(itemCount);
        //再把标签的数量写进去,4字节
        System.arraycopy(temp, 0, head, 16, 4);
        temp = Util.getBytesFromInt(flag);
        //再把标志写进去,表示是标签头部还是尾部
        System.arraycopy(temp, 0, head, 20, 4);
        //把标志空的8个字节进去,因为默认就是空的,所以不用写了
        //头部或者尾部的数据块已经构造好了
        return head;
    }

    private void parseData() {
        try {
            checkHead();
            checkVersion();
            checkTagSize();
            checkItemCount();
            checkFlag();
            valid = true;
        } catch (Exception exe) {
            log.log(Level.SEVERE, "分析标签异常!");
            valid = false;
        }
    }

    /**
     * 这个标签是否有头标签,因为一般读都是从尾部读过去的
     * @return 是否有头标签,重写的时候有用
     */
    public boolean hasHeader() {
        return ((1 << 31) & flag) != 0;
    }

    /**
     * 检查头部八个字节的的数据是否一样
     */
    private void checkHead() {
        byte[] temp = new byte[8];
        byte[] head = {(byte) 'A',
            (byte) 'P',
            (byte) 'E',
            (byte) 'T',
            (byte) 'A',
            (byte) 'G',
            (byte) 'E',
            (byte) 'X'
        };
        System.arraycopy(data, 0, temp, 0, 8);
        //比较两个头部的数据是否一样,这是第一要素
        if (!Arrays.equals(head, temp)) {
            throw new RuntimeException("头部数据不一样!");
        }
    }

    /**
     * 检查版本号是否合法,必须是1000或者2000
     */
    private void checkVersion() {
        byte[] temp = new byte[4];
        System.arraycopy(data, 8, temp, 0, 4);
        int v = Util.getInt(temp);
        if (v == 2000 || v == 1000) {
            version = v;
            log.log(Level.INFO, "版本号是:" + v);
        } else {
            throw new RuntimeException("版本号不合法!!");
        }
    }

    private void checkTagSize() {
        byte[] temp = new byte[4];
        System.arraycopy(data, 12, temp, 0, 4);
        tagSize = Util.getInt(temp);
        log.log(Level.INFO, "标签大小:" + tagSize);
    }

    private void checkItemCount() {
        byte[] temp = new byte[4];
        System.arraycopy(data, 16, temp, 0, 4);
        itemCount = Util.getInt(temp);
        log.log(Level.INFO, "标签项目数:" + itemCount);
    }

    private void checkFlag() {
        byte[] temp = new byte[4];
        System.arraycopy(data, 20, temp, 0, 4);
        flag = Util.getInt(temp);
        log.log(Level.INFO, "标志:" + flag);
    }

    public void setFlag(int flag) {
        this.flag = flag;
    }

    public void setItemCount(int itemCount) {
        this.itemCount = itemCount;
    }

    public void setTagSize(int tagSize) {
        this.tagSize = tagSize;
    }

    public void setVersion(int version) {
        if(!(version==V1||version==V2)){
            throw new RuntimeException("非法的版本号,只能是V2或者V1.");
        }
        this.version = version;
    }

    public int getFlag() {
        return flag;
    }

    public int getItemCount() {
        return itemCount;
    }

    public int getTagSize() {
        return tagSize;
    }

    public boolean isValid() {
        return valid;
    }

    public int getVersion() {
        return version;
    }

    public static void main(String[] args) {
    }
    }