title: Is there a library for manipulating Excel .xlsb (BIFF12) files without the (slow) COM API (Interop)?
body: <p>I found many Excel 2007/2010 file manipulation libraries on the web, some of them independent of MS Office's COM API. Some free, some for (lots of) cash. Most if not all support the old binary .xls (Excel 97-2003 BIFF8) format as well as the non-binary Office Open XML .xlsx, but .xlsx loads 4 times longer<sup>[1]</sup> than .xlsb, and .xls only supports 256 columns.</p>
  
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  <p>[1] Also .xlsx saves 2 times slower than .xlsb. I tested this on a generated worksheet with 10'000 rows * 1'000 columns = 10'000'000 (10^7) cells of simple chained <code>=…+1</code> formulas:</p>
  
  <pre><code>╭─────────────╥────────┬────────╮
  │              ║ .xlsx  │ .xlsb  │
  ╞══════════════╬════════╪════════╡
  │ loading time ║ 165s   │  43s   │
  ├──────────────╫────────┼────────┤
  │ saving time  ║ 115s   │  61s   │
  ├──────────────╫────────┼────────┤
  │ file size    ║  91 MB │  65 MB │
  ╰─────────────╨────────┴────────╯
  </code></pre>
  
  <p><sub>The test has been executed on a computer running Windows 7, with a Core2Duo 2.3 GHz processor, 4 GB RAM, and a 5400 rpm SATA II hard disk; the computer was under somewhat heavy load from other processes.</sub></p>