fix: replace deprecated reflect.SliceHeader with unsafe.Slice

[dlevy-msft-sql]

Problem

The UCS-2 string decoding optimization in ucs22str.go uses reflect.SliceHeader which was deprecated in Go 1.21. The deprecation notice recommends using unsafe.Slice instead.

Fix

Replace 7 lines of manual slice header manipulation:

var uint16slice []uint16
uint16Header := (*reflect.SliceHeader)(unsafe.Pointer(&uint16slice))
sourceHeader := (*reflect.SliceHeader)(unsafe.Pointer(&s))
uint16Header.Data = sourceHeader.Data
uint16Header.Len = len(s) / 2
uint16Header.Cap = uint16Header.Len

With a single unsafe.Slice call:

uint16slice := unsafe.Slice((*uint16)(unsafe.Pointer(&s[0])), len(s)/2)

This is equivalent behavior: both reinterpret the underlying []byte as []uint16 for the subsequent utf16.Decode call. The unsafe.Slice version is the recommended modern pattern and lets the compiler/GC properly track the pointer.

Tests

All 17 UCS-2 string conversion tests pass, covering ASCII (lengths 1-9+), Unicode, and emoji inputs.

Fixes #272

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.62%. Comparing base (c10fa99) to head (1784275).

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #366       +/-   ##
===========================================
+ Coverage   80.66%   96.62%   +15.95%     
===========================================
  Files          35       92       +57     
  Lines        6842    74273    +67431     
===========================================
+ Hits         5519    71764    +66245     
- Misses       1055     2176     +1121     
- Partials      268      333       +65     

Flag	Coverage Δ
unittests	96.54% <100.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
ucs22str.go	100.00% <100.00%> (ø)

... and 59 files with indirect coverage changes

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[Copilot]

Pull request overview

Updates the UCS-2 decoding fast/slow-path implementation to remove use of deprecated reflect.SliceHeader in favor of the modern unsafe.Slice API, aligning the driver with Go 1.21+ guidance while preserving the existing optimization approach.

Changes:

• Removed the reflect import and manual reflect.SliceHeader manipulation in ucs22str.go.
• Replaced the byte-slice-to-uint16-slice reinterpretation with a single unsafe.Slice call for the UTF-16 decode slow path.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.