Wrap Voyager C++ headers in the voyager namespace (fixes #52)

[Sanaullah-Turab]

Description

Voyager's C++ headers were declared in the global namespace instead of a Voyager specific one, which is a problem for anyone wanting to use the C++ library standalone since it risks symbol collisions with other code. This PR wraps all remaining Voyager specific headers in namespace voyager { ... }, following the pattern already used in Metadata.h from an earlier PR, without touching the vendored hnswlib code.

Related Issues

Closes #52

Changes Made

C++

Wrapped the following files in namespace voyager:

• cpp/src/Enums.h
• cpp/src/std_utils.h
• cpp/src/array_utils.h
• cpp/src/E4M3.h
• cpp/src/StreamUtils.h
• cpp/src/Index.h
• cpp/src/TypedIndex.h

hnswlib.h, hnswalg.h, visited_list_pool.h, and Spaces/*.h were left untouched since they are vendored and already scoped under namespace hnswlib.

Updated cpp/test/test_main.cpp to qualify Index, SpaceType, StorageDataType, Metadata, and related test utilities with voyager::.

One deviation worth flagging for review: the vendored hnswalg.h uses the custom InputStream/OutputStream types that just moved into namespace voyager, and I didn't want to edit vendored files to fix this. Instead I added a small alias block at the end of StreamUtils.h:

namespace hnswlib {
  using voyager::InputStream;
  using voyager::OutputStream;
  using voyager::FileOutputStream;
  using voyager::readBinaryPOD;
  using voyager::writeBinaryPOD;
}

This lets hnswalg.h resolve the types inside its own namespace with zero edits to vendored code. Open to a different approach here if maintainers prefer something else.

Also fixed an unrelated small bug I hit along the way: TypedIndex.h had IndexCannotBeShrunkError and IndexFullError incorrectly prefixed with hnswlib::, when those exceptions are actually defined in the global namespace. Removed the incorrect prefix so they resolve correctly.

Python

Updated python/src/bindings.cpp to qualify Index, SpaceType, StorageDataType, Metadata, InputStream, OutputStream, and related utilities with voyager::.

Updated python/src/PythonInputStream.h and python/src/PythonOutputStream.h so their base classes are voyager::InputStream and voyager::OutputStream.

Also fixed a small unrelated bug in tox.ini where tox -e format was running ruff format --diff, which only checks formatting instead of applying it. Removed the --diff flag so the format command actually formats the code.

Java

No changes.

Testing

C++:

• Ran make check-formatting and make format (clang-format v16)
• Built and ran make test via make VoyagerTests
• 3/3 tests passed

Python:

• Ran tox -e format to apply formatting
• Ran tox to build the native extension and run the full test suite
• 5,351 tests passed in around 58 seconds

Checklist

• My code follows the code style of this project.
• I have added and/or updated appropriate documentation (if applicable).
• All new and existing tests pass locally with these changes.
• I have run static code analysis (if available) and resolved any issues.
• I have considered backward compatibility (if applicable).
• I have confirmed that this PR does not introduce any security vulnerabilities.

Additional Comments

The maintainers previously noted they don't guarantee C++ interface compatibility across versions for this exact reason, so this change is expected and welcome rather than a breaking surprise. Happy to adjust the StreamUtils.h alias approach if there's a preferred way to bridge the vendored hnswlib code with the new namespace.