[GitHub] [daffodil-vscode] scholarsmate commented on issue #311: Handle different logical byte sizes and bit ordering

[GitBox <gi...@apache.org>]

scholarsmate commented on issue #311:
URL: https://github.com/apache/daffodil-vscode/issues/311#issuecomment-1262726725

   The workflow for 7-bit ASCII and LSB at a lower offset, the user would select Bit for Offset, which would force the encoding to be binary, 7 would be selected as the logical byte size, and Lower Offset would be selected for the LSB.  Then the user would click and drag to select the bit offset range (the UI will force the range to be in multiples of the logical byte size).  In the second viewport, the user will see the range selected as 7-bit bytes (behind the scenes, the logical byte is left padded to fill an 8-bit byte so that we can display the byte values).  Overwrites are pretty straight-forward except the values given must fit inside the logical bytes (for 7-bit bytes, that's 0 - 127 decimal).  Inserts are complex since memory and files use 8-bit bytes and inserting 7 bits in the middle of the file means shifting all the bits right and creating a new byte at the end of the file to handle the overflow.  This can be a massive amount of change, especially when editing large file
 s where the inserts are not done near the end of the file.  Delete is similarly complex.
   
   I think for the initial implementation, that we only allow inserts and deletes when the byte size is 8-bits and we're byte aligned.


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