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Increase Buffer / Use SequentialScan For Get-FileHash #20881

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PR Summary

This change uses an alternate constructor in Get-FileHash to increase the buffer size to 64 KiB and specifies the SequentialScan option to support scenarios where the kernel / drivers may benefit from knowing the intended read strategy.

PR Context

The current Get-FileHash -Path and Get-FileHash -LiteralPath functions currently use System.IO.File.OpenRead() establish a file stream before computing the hash. This function, in turn, calls the FileStream constructor using a default buffer size of 4KiB. While this buffer size is probably a good general purpose value for opening files not knowing how they are going to be used, it does not incorporate the contextual knowledge we have that we are going to read the entirety of the file into memory and we are going to do so sequentially. In testing, this change has notable benefits as file sizes increased.

PR Checklist

@NoMoreFood
Increase Buffer / Use SequentialScan
8ebb65e 
- Increased file stream buffer to 64 KiB.
- Changed reads to use SequentialScan to support scenarios that optimize based on this.
@pull-request-quantifier Pull Request Quantifier
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This PR has 8 quantified lines of changes. In general, a change size of upto 200 lines is ideal for the best PR experience!

Quantification details 

Label      : Extra Small
Size       : +7 -1
Percentile : 3.2%

Total files changed: 1

Change summary by file extension:
.cs : +7 -1

Change counts above are quantified counts, based on the PullRequestQuantifier customizations.

Why proper sizing of changes matters

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    • Bugs are more likely to be detected.
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How to interpret the change counts in git diff output

  • One line was added: +1 -0
  • One line was deleted: +0 -1
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  • Change percentiles: Change characteristics (addition, deletion, modification)
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@microsoft-github-policy-service microsoft-github-policy-service bot added Review - Needed The PR is being reviewed labels Dec 18, 2023
@microsoft-github-policy-service Microsoft GitHub Policy Service
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This pull request has been automatically marked as Review Needed because it has been there has not been any activity for 7 days.
Maintainer, please provide feedback and/or mark it as Waiting on Author

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@microsoft-github-policy-service Microsoft GitHub Policy Service
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This pull request has been automatically marked as Review Needed because it has been there has not been any activity for 7 days.
Maintainer, please provide feedback and/or mark it as Waiting on Author

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