如何在StAX中跟踪解析大文件的进度？ [英] How do I keep track of parsing progress of large files in StAX?

问题描述

我正在使用StAX API处理大型（1TB）XML文件。假设我们有一个处理一些元素的循环：

I'm processing large (1TB) XML files using the StAX API. Let's assume we have a loop handling some elements:

XMLInputFactory fac = XMLInputFactory.newInstance();
 XMLStreamReader reader = fac.createXMLStreamReader(new FileReader(inputFile));
   while (true) {
       if (reader.nextTag() == XMLStreamConstants.START_ELEMENT){
            // handle contents
       }
}

如何跟踪大型XML文件中的整体进度？从读取器获取偏移量适用于较小的文件：

How do I keep track of overall progress within the large XML file? Fetching the offset from reader works fine for smaller files:

int offset = reader.getLocation().getCharacterOffset();

但是作为整数偏移，它可能只适用于最大2GB的文件...

but being an Integer offset, it'll probably only work for files up to 2GB...

推荐答案

一个简单的 FilterReader 应该有效。

class ProgressCounter extends FilterReader {
    long progress = 0;

    @Override
    public long skip(long n) throws IOException {
        progress += n;
        return super.skip(n);
    }

    @Override
    public int read(char[] cbuf, int off, int len) throws IOException {
        int red = super.read(cbuf, off, len);
        progress += red;
        return red;
    }

    @Override
    public int read() throws IOException {
        int red = super.read();
        progress += red;
        return red;
    }

    public ProgressCounter(Reader in) {
        super(in);
    }

    public long getProgress () {
        return progress;
    }
}

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