Add Vector256 support to the locator

[mvadari]

High Level Overview of Change

Context of Change

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Performance (increase or change in throughput and/or latency)
• Tests (you added tests for code that already exists, or your new feature included in this PR)
• Documentation update
• Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• Release

API Impact

• Public API: New feature (new methods and/or new fields)
• Public API: Breaking change (in general, breaking changes should only impact the next api_version)
• libxrpl change (any change that may affect libxrpl or dependents of libxrpl)
• Peer protocol change (must be backward compatible or bump the peer protocol version)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.8%. Comparing base (209a1a6) to head (ccf1a83).
⚠️ Report is 1 commits behind head on ripple/wasmi-host-functions.

Additional details and impacted files

@@                     Coverage Diff                     @@
##           ripple/wasmi-host-functions   #6131   +/-   ##
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  Coverage                         79.8%   79.8%           
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  Files                              854     854           
  Lines                            73730   73735    +5     
  Branches                          8341    8341           
===========================================================
+ Hits                             58809   58813    +4     
- Misses                           14921   14922    +1     

Files with missing lines	Coverage Δ
src/xrpld/app/wasm/detail/HostFuncImplGetter.cpp	100.0% <100.0%> (ø)

... and 1 file with indirect coverage changes

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[pwang200]

Look good to me, but Olek should take a look.

[Copilot]

Pull request overview

This PR extends the locator functionality in the WASM host functions to support STI_VECTOR256 type fields, enabling WASM smart contracts to access and navigate Vector256 fields (such as CredentialIDs) in transactions and ledger objects.

Key changes:

• Added STI_VECTOR256 as a non-leaf field type that can be indexed like arrays
• Implemented Vector256 element access through the locator with proper index bounds checking
• Extended array length functions to support Vector256 fields

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/xrpld/app/wasm/detail/HostFuncImpl.cpp	Adds Vector256 support to getAnyFieldData, locateField, and array length functions; implements indexing into Vector256 fields using a thread_local temporary STUInt256 wrapper
src/test/app/HostFuncImpl_test.cpp	Adds comprehensive tests for Vector256 field access, including tests for retrieving Vector256 elements via locator, bounds checking, and error handling for non-leaf field access

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[Copilot]

Consider adding a test case for attempting to nest further into a Vector256 element, similar to the test at lines 691-696 for nesting into non-array/object fields. For example, test a locator like {sfCredentialIDs.fieldCode, 0, sfAccount.fieldCode} which should return LOCATOR_MALFORMED since uint256 values (the elements of Vector256) are leaf nodes and cannot be nested into. This would verify that the Vector256 indexing correctly returns a leaf type that cannot be further navigated.

[oleks-rip]

Please put 319-324 into helper function, and use it in other places

[oleks-rip]

I have concern about static variable, if someone later will call that function 2 times it will overwrite the value without any notice. Try this variants.patch patch with variants instead

[oleks-rip]

Please add test with maximum allowed size for STI_VECTOR256

[mvadari]

Please add test with maximum allowed size for STI_VECTOR256

There's no maximum size, it depends on the field.