Excel Zip Decompression Internals

DataLoom Pro parses .xlsx spreadsheets by opening them as standard ZIP packages using System.IO.Compression.

Technical Decompression Steps

  1. Open File Stream: Opens the .xlsx file with sharing permissions enabled (FileShare.ReadWrite).
  2. Locate sharedStrings.xml: Unzips the shared strings table to load all unique text strings into a cache array.
  3. Parse sheet1.xml: Loops through cell nodes, matching coordinates (e.g. A1, B2).
  4. Resolve Value: If the cell contains an index, it looks up the string in the sharedStrings cache; otherwise, it reads the numerical value directly, bypassing Excel COM engines.
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