使用VTD-XML将大XML文件拆分为小块时出现异常

我正在开发一个小程序,将一个非常大的XML文件(超过2Gb)分成小块。

在研究了许多库之后,我选择了VTD-XML(对大文件使用VTDGenHuge),并开始开发一些代码测试。但是当我读取文件的段字节时,我遇到了一个问题。

我得到偏移和长度:

            long [] l = vn.getElementFragment();

然后我得到结果信息:

            int offset = (int) (l[0] >> 64);
            int len = new Integer("" + l[1]);

最后,我尝试提取字节段以将其写入另一个文件:

            b = new byte[len];
            fis.read(b, offset, len); **//<===== this is the exception problem**

但我正在学习java。lang.IndexOutOfBoundsException

此外,当我为字节数组(例如新字节[400])分配一个固定数字时,程序结束正常,但输出文件已损坏。

我的代码:

    File fo = new File("\\path\\post_people.xml");
    FileOutputStream fos = new FileOutputStream(fo);

    int count = 0;

    File f = new File("\\path\\people.xml");
    FileInputStream fis = new FileInputStream(f);
    byte[] b;

    VTDGenHuge vg = new VTDGenHuge();
    if (vg.parseFile("\\path\\people.xml", false, VTDGenHuge.MEM_MAPPED)){

        VTDNavHuge vn = vg.getNav();

        AutoPilotHuge ap = new AutoPilotHuge();
        ap.bind(vn);
        ap.selectXPath("/people/person"); //here it could be posible add another condition

        while (ap.evalXPath() != -1) {
            long [] l = vn.getElementFragment();
            int offset = (int) (l[0] >> 64);
            int len = new Integer("" + l[1]);
            b = new byte[len];
            fis.read(b, offset, len); //<===== this is the line problem

            fos.write(b); // writing the fragment out into other file

            count++;

            if (count == 3) { //this is just a test
                break;
            }

        }

    }

XML文件示例:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<people>
    <person>
        <name>Nombre 0</name>
        <lastName>ApPaterno 1</lastName>
        <birthdate>2017-11-10T10:20:44.926-05:00</birthdate>
        <age>0</age>
        <address>
            <streetType>Tipo Calle 0</streetType>
            <streetName>Nombre de Calle 0</streetName>
            <number>0</number>
        </address>
    </person>
    <person>
        <name>Nombre 1</name>
        <lastName>ApPaterno 1</lastName>
        <birthdate>2017-11-10T10:20:44.926-05:00</birthdate>
        <age>1</age>
        <address>
            <streetType>Tipo Calle 1</streetType>
            <streetName>Nombre de Calle 1</streetName>
            <number>1</number>
        </address>
    </person>
</people>

拜托,你们能帮帮我吗?

更新和解决方案:

最后,我应该修改的片段代码如下:

long [] l = vn.getElementFragment();
int offset = (int) (l[0] >> 64);
int len = new Integer("" + l[1]);
b = new byte[len];

fis.getChannel().position(0); //must return to position 0
fis.skip(offset); //must move to offset position
fis.read(b, 0, len);