<head>
  <script>window.markdeepOptions = {mode: 'script'};</script>
  <script src="https://morgan3d.github.io/markdeep/latest/markdeep.min.js"></script>
  <script id="MathJax-script" async src="https://fastly.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js"></script>
  <script>
    function absFile(url) {
      this.name=url;
      this.slice = async(offset, length) =>{
        const headers = new Headers();
        headers.append('range', 'bytes=' + offset + '-' + ( offset + length -1).toString());

        const opts = {
          credentials: 'include',
          headers    : headers
        };

        const resp = await fetch( this.name, opts );
        return await resp.arrayBuffer();
        //alert(JSON.stringify(resp.headers));
        //return await resp.text();
      }
    }
    
    var file;
    var blocksize = 1024;
    function loadSlice(){
      function render(u8array){
        document.body.innerHTML = window.markdeep.format(new TextDecoder().decode(u8array),true);
        MathJax.typesetPromise();
      }
      function setPageUrl(pageurl){
        let a = document.createElement('a');
        a.href = "i:5c"+pageurl;
        a.click();
      }

      var url;
      var page = 1;
      var extrasize = blocksize; //extrasize should <= blocksize
      let lhash = location.hash;
      if(lhash){
        if("p"!==lhash.charAt(1)){//#offset=&[len]
          let iAmpersand = lhash.indexOf('&',8);
          let offset = parseInt(lhash.substring(8,iAmpersand));
          let len = parseInt(lhash.substring(iAmpersand+1));
          {//update urlInc() url
            let href = location.href;
            let iHash = href.indexOf('#');
            href=href.substring(0,iHash)+"#page="+Math.floor((offset+len)/blocksize);
            setPageUrl(href);
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          file.slice(offset,len).then((buffer)=>{
            let u8 = new Uint8Array(buffer);
            render(u8);
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          return;
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        //#page=
        page = parseInt(lhash.substring(6));
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        setPageUrl(location.href+"#page=1");
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        if(1!=page){
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              iStart = i+1;
              break;
            }
          }
        }
        let iEnd = Math.min(u8len,blocksize);
        limit = Math.min(u8len,blocksize+extrasize);
        for(let i=blocksize+1;i<limit;i=i+2){
          if(10==u8[i] && 10==u8[i-1]) {
            iEnd = i+1;
            break;
          }
        }
        render(u8.slice(iStart,iEnd));
      });

    }
    //?url=#offset=&[len]&page=
    file = new absFile(location.search.substring(5));
    window.addEventListener('hashchange',loadSlice);
  </script>
</head>
<body>
  <script>loadSlice();</script>
</body>