Book cover

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  1. Introduction
  2. Objects and Classes
  3. Finding Duplicate Files
  4. Matching Patterns
  5. Parsing Text
  6. Running Tests
  7. An Interpreter
  8. Functions and Closures
  9. Protocols
  10. A File Archiver
  11. An HTML Validator
  12. A Template Expander
  13. A Code Linter
  14. Page Layout
  15. Performance Profiling
  16. Object Persistence
  17. Binary Data
  18. A Database
  19. A Build Manager
  20. A Package Manager
  21. Transferring Files
  22. Serving Web Pages
  23. A File Viewer
  24. Undo and Redo
  25. A Virtual Machine
  26. A Debugger
  27. Observers
  28. Generating Documentation
  29. File Compression
  30. A File Cache
  31. Object-Relational Mapper
  32. Concurrency
  33. Conclusion
  1. Bibliography
  2. Bonus Material
  3. Syllabus
  4. License
  5. Code of Conduct
  6. Contributing
  7. Glossary
  8. Colophon
  9. Index

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GitHub repository

File Compression

  • FIXME

Terms defined: nybble

FIXME: create file compressor

Issue 144

  • First idea: number the tokens in the file and replace each with its number
    • Use blank-nonblank tokenization (which inadvertently captures punctuation)
    • compress.py
    • Test with text of introduction to this book: makes things worse
  • So store as binary
    • binary.py
    • Better, but still larger than the original
    • In fact, our binary compression is worse when tested every chapter
  • Look at statistics
    • frequency.py and frequency.svg
    • Lots of words only occur once (long tail)
    • Single space occurs over 1600 times
  • Use variable-length encoding Chapter 17
    • Use nybbles (half-bytes)
    • Most common seven values are 0000 through 0111
    • Next 49 are (1…, 0…)
    • 343 are (1…, 1…, 0…)
    • Calculate compression before implementing
    • varlen_calc.py tells us we can get the introduction from 13240 bytes to 10281 (approximately 1.3X)
    • But gzip can do 2.3X: how?
  • Lempel-Ziv-Storer-Szymanski