[zanmato1984]

Rationale for this change

inverse_permutation and scatter currently accept only signed integer indices, requiring unnecessary casts for unsigned arrays. This PR adds unsigned support while reducing generated code size.

What changes are included in this PR?

• Accept signed and unsigned integer indices in both functions.
• Allow unsigned inverse-permutation output types, with the default still following the input type.
• Share input handling by bit width and validity generation by output width, while retaining specialized output writes.
• Reduce the swizzle object's code section from 432,480 to 185,204 bytes (about 57.2% smaller, Apple Clang/O2).
• Preserve signed-index checks and uint64 bounds diagnostics, and update the C++ and Python-facing documentation.

Are these changes tested?

Added unit tests for unsigned types, index bounds, sliced/chunked inputs, and validity bitmap boundaries.

Are there any user-facing changes?

Unsigned integer indices are now accepted. For example, inverse permutation of uint8 [2, null, 0, 1] returns uint8 [2, 3, 0, null].

No breaking API changes.

Was AI used for this PR?

The changes were thoroughly reviewed by a human with AI assistance.

PR code and description written by:

• Human
• AI

Reviewed before submission by:

• Human
• AI
• Not reviewed

• GitHub Issue: [C++][Compute] inverse_permutation and scatter should accept unsigned integers #54920

[github-actions]

⚠️ GitHub issue #54920 has been automatically assigned in GitHub to PR creator.

[Copilot]

🟢 Approval recommended

Static review found no blocking issues in dispatch, bounds checks, or validity generation, with added tests covering key boundary cases.

No open issues 🎉

What changed in this PR

Adds unsigned integer support to C++ compute functions inverse_permutation and scatter, addressing GH-54920 while reducing generated code size.

Changes:

• Accept signed and unsigned indices, and allow unsigned inverse-permutation outputs.
• Share input processing and validity generation by integer width while preserving bounds checks.
• Expand boundary, sliced-array, and chunked-array tests and update public documentation.

File	Description
python/​pyarrow/​_compute.pyx	Document unsigned inverse-permutation output support.
docs/​source/​cpp/​compute.rst	List integer input and output support.
cpp/​src/​arrow/​compute/​kernels/​vector_swizzle.cc	Add unsigned support and consolidate kernel implementations.
cpp/​src/​arrow/​compute/​kernels/​vector_swizzle_test.cc	Expand integer-type and boundary-case coverage.
cpp/​src/​arrow/​compute/​api_vector.h	Document signed and unsigned integer support.

_{Review effort: Balanced}