Small refactoring to make safety clearer

[trask]

Alternatively, I can just add comment explaining that the safety relies on the caller not reusing the byte buffer

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.22%. Comparing base (673f89e) to head (1b9630f).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #8083   +/-   ##
=========================================
  Coverage     90.22%   90.22%           
+ Complexity     7606     7605    -1     
=========================================
  Files           841      841           
  Lines         22938    22939    +1     
  Branches       2291     2291           
=========================================
+ Hits          20695    20697    +2     
+ Misses         1526     1524    -2     
- Partials        717      718    +1     

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