GH-43142: [C++][Parquet] Refactor Encryptor API to use arrow::util::span instead of raw pointers

[adamreeve]

Rationale for this change

See #43142. This is a follow up to #43071 which refactored the Decryptor API and added extra checks to prevent segfaults. This PR makes similar changes to the Encryptor API for consistency and better maintainability.

What changes are included in this PR?

• Change AesEncryptor::Encrypt and Encryptor::Encrypt to use arrow::util::span instead of raw pointers
• Replace the AesEncryptor::CiphertextSizeDelta method with a CiphertextLength method that checks for overflow and abstracts the size difference behaviour away from consumer code for improved readability.

Are these changes tested?

• This is mostly a refactoring of existing code so is covered by existing tests.

Are there any user-facing changes?

No

• GitHub Issue: [C++][Parquet] Refactor Encryptor API to use arrow::util::span instead of raw pointers #43142

[github-actions]

⚠️ GitHub issue #43142 has been automatically assigned in GitHub to PR creator.

[adamreeve]

There's a CI failure due to a segfault running arrow-dataset-file-parquet-encryption-test, but it looks like this is happening on main too, and has been reported in #43057

Given I'm working in this area already I'll take a look and see if I can reproduce this, but I don't think it should be a blocker for this PR.

[pitrou]

LGTM, except for one nit (see comment about int vs. unsigned)

[pitrou]

@github-actions crossbow submit -g cpp

[github-actions]

Revision: 20e1aaf

Submitted crossbow builds: ursacomputing/crossbow @ actions-5626e3c393

Task	Status
test-alpine-linux-cpp
test-build-cpp-fuzz
test-conda-cpp
test-conda-cpp-valgrind
test-cuda-cpp
test-debian-12-cpp-amd64
test-debian-12-cpp-i386
test-fedora-39-cpp
test-ubuntu-20.04-cpp
test-ubuntu-20.04-cpp-bundled
test-ubuntu-20.04-cpp-minimal-with-formats
test-ubuntu-20.04-cpp-thread-sanitizer
test-ubuntu-22.04-cpp
test-ubuntu-22.04-cpp-20
test-ubuntu-22.04-cpp-emscripten
test-ubuntu-22.04-cpp-no-threading
test-ubuntu-24.04-cpp
test-ubuntu-24.04-cpp-gcc-14

[pitrou]

Thanks again for doing this @adamreeve !

[pitrou]

@raulcd This is 17.0.0 material if you ever need to cut another RC.

[raulcd]

This is 17.0.0 material if you ever need to cut another RC.

I've added the backport-candidate label to the issue

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 4 benchmarking runs that have been run so far on merge-commit 6e438e6.

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 2 possible false positives for unstable benchmarks that are known to sometimes produce them.