GH-49959: [C++][Parquet] Avoid unbounded temp alloc in BYTE_STREAM_SPLIT decoder

[pitrou]

Rationale for this change

The BYTE_STREAM_SPLIT encoder and decoder allocate a SmallVector to hold the addresses of the different streams. While this is valid for small number of streams (which is most or all legitimate use cases), very large numbers of streams (e.g. FLBA(100000000)) can trigger a huge temporary memory allocation.

This issue was found by OSS-Fuzz: https://issues.oss-fuzz.com/issues/511575321

What changes are included in this PR?

1. When the width of the BYTE_STREAM_SPLIT-encoded type is larger than a predefined constant, switch to a slower implementation that doesn't need any temporary allocation
2. When encoding or decoding 0 values, avoid some pointless setup work
3. Add tests for the two conditions above

Are these changes tested?

Yes, by additional unit tests and by additional fuzz regression file.

Are there any user-facing changes?

• GitHub Issue: [C++][Parquet] Avoid unbounded temp alloc in BYTE_STREAM_SPLIT decoder #49959

[pitrou]

@github-actions crossbow submit -g cpp

[github-actions]

Revision: 14e16db

Submitted crossbow builds: ursacomputing/crossbow @ actions-51f44d0cee

Task	Status
example-cpp-minimal-build-static
example-cpp-minimal-build-static-system-dependency
example-cpp-tutorial
test-build-cpp-fuzz
test-conda-cpp
test-conda-cpp-valgrind
test-debian-13-cpp-amd64
test-debian-13-cpp-i386
test-debian-experimental-cpp-gcc-15
test-fedora-42-cpp
test-ubuntu-22.04-cpp
test-ubuntu-22.04-cpp-bundled
test-ubuntu-22.04-cpp-emscripten
test-ubuntu-22.04-cpp-no-threading
test-ubuntu-24.04-cpp
test-ubuntu-24.04-cpp-bundled-offline
test-ubuntu-24.04-cpp-gcc-13-bundled
test-ubuntu-24.04-cpp-gcc-14
test-ubuntu-24.04-cpp-minimal-with-formats
test-ubuntu-24.04-cpp-thread-sanitizer