https://github.com/ross-spencer/eyeglass

Sample file format for teaching the principles file format development in the digital preservation community
https://github.com/ross-spencer/eyeglass

code4lib digipres file-formats kaitai pedagogy pronom

Last synced: 16 days ago
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Sample file format for teaching the principles file format development in the digital preservation community

• Host: GitHub
• URL: https://github.com/ross-spencer/eyeglass
• Owner: ross-spencer
• Created: 2012-11-07T03:45:08.000Z (over 13 years ago)
• Default Branch: main
• Last Pushed: 2025-03-10T14:44:43.000Z (over 1 year ago)
• Last Synced: 2025-12-25T19:37:41.453Z (6 months ago)
• Topics: code4lib, digipres, file-formats, kaitai, pedagogy, pronom
• Language: Python
• Homepage: https://exponentialdecay.co.uk/blog/genesis-of-a-file-format/
• Size: 30.3 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 1
• Metadata Files:
  • Readme: README.md

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README

          
# eyeglass

Sample 'file format' specification and applications for understanding issues in

digital preservation. The format stores the information required for an eyeglass

prescription for a single patient.

## Specification

    Eyeglass Format Specification 1.0

    ---

    Magic number    - 14 bytes  - String

    Version         - 1 bytes   - Unsigned Char

    Big-endian      - 1 byte    - Bool

    Date/time       - 19 bytes  - String #YYYY-MM-DDTHH:MM:SS

    Expansion room  - 88 bytes  - Undefined

    Sphere          - 8 bytes   - R: Float   L: Float

    Cylinder        - 8 bytes   - R: Float   L: Float

    Axis            - 8 bytes   - R: Integer L: Integer

    Prism           - 8 bytes   - R: Float   L: Float

    Base            - 8 bytes   - R: Float   L: Float

    Distance acuity - 8 bytes   - R: Float   L: Float

    Near acuity     - 8 bytes   - R: Integer L: Integer

    Purpose         - 140 bytes - String

    Observation     - 255 bytes - String

    Next checkup    - 4 bytes   - Float

    End of file     - 4 bytes   - String

The *‘magic number’* identifying the file format will be as follows:

    '\xBB\x0D\x0A\x65\x79\x65\x67\x6C\x61\x73\x73\x1A\x0A\xAB'

The *‘end of file’* sequence terminating the stream will be as follows:

    '\xBB\x65\x6f\x66'

## Further reading

* [exponentialdecay.co.uk/blog/genesis-of-a-file-format][expo-1].

* [exponentialdecay.co.uk/blog/shattering-the-eyeglass][expo-2].

[expo-1]: http://exponentialdecay.co.uk/blog/genesis-of-a-file-format/

[expo-2]: https://exponentialdecay.co.uk/blog/shattering-the-eyeglass/