[storage/adb/current] adb::ordered::current (provides exclusion proof support)

[roberto-bayardo]

This PR creates a variant of adb::current called adb::ordered::Current that supports key exclusion proofs.

TODO:

• current_ordered_init benchmark
• adb_current_ordered_operations fuzz test

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Pull Request Overview

This PR introduces an ordered variant of the current authenticated database (ADB) that supports key exclusion proofs. The main purpose is to extend the existing unordered current ADB implementation with ordered key capabilities, allowing users to prove that specific keys do not exist in the database.

Key changes include:

• Creation of a new adb::current::ordered module with exclusion proof functionality
• Refactoring of the existing current ADB to separate ordered and unordered variants
• Addition of helper methods for empty MMR root computation and ordered key operations

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
storage/src/mmr/mem.rs	Added empty_mmr_root helper method and corresponding test
storage/src/mmr/hasher.rs	Updated test to use new empty MMR root helper
storage/src/mmr/grafting.rs	Fixed documentation reference from specific type to module
storage/src/adb/mod.rs	Added KeyExists error variant for exclusion proof failures
storage/src/adb/current/unordered.rs	Updated to use new shared verification function and added next_key field
storage/src/adb/current/ordered.rs	New implementation of ordered current ADB with exclusion proof support
storage/src/adb/current/mod.rs	Refactored to support both ordered and unordered variants, added shared verification functions
storage/src/adb/benches/current_init.rs	Updated import to use unordered variant
storage/src/adb/any/fixed/unordered.rs	Added is_empty helper method
storage/src/adb/any/fixed/ordered.rs	Made fields and methods public for use by current ordered implementation
storage/fuzz/fuzz_targets/adb_current_operations.rs	Updated import to use unordered variant

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[Copilot]

Incomplete comment on line 657. The comment 'Make sure the' appears to be cut off and should be completed or removed.

Suggested change

// Make sure the

[codecov]

Codecov Report

❌ Patch coverage is 96.27907% with 40 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.27%. Comparing base (2dd0dae) to head (ca42d14).

Files with missing lines	Patch %	Lines
storage/src/adb/current/ordered.rs	98.29%	17 Missing ⚠️
storage/src/adb/current/mod.rs	72.34%	13 Missing ⚠️
storage/src/adb/any/fixed/ordered.rs	37.50%	10 Missing ⚠️

@@            Coverage Diff             @@
##             main    #1799      +/-   ##
==========================================
+ Coverage   92.21%   92.27%   +0.05%     
==========================================
  Files         308      309       +1     
  Lines       81255    82320    +1065     
==========================================
+ Hits        74931    75960    +1029     
- Misses       6324     6360      +36     

Files with missing lines	Coverage Δ
storage/src/adb/any/fixed/unordered.rs	95.11% <100.00%> (+0.01%)	⬆️
storage/src/adb/current/unordered.rs	92.62% <100.00%> (+0.04%)	⬆️
storage/src/adb/mod.rs	95.45% <ø> (ø)
storage/src/mmr/grafting.rs	86.25% <ø> (ø)
storage/src/mmr/hasher.rs	93.70% <100.00%> (+0.04%)	⬆️
storage/src/mmr/mem.rs	93.03% <100.00%> (+0.03%)	⬆️
storage/src/adb/any/fixed/ordered.rs	96.04% <37.50%> (-0.54%)	⬇️
storage/src/adb/current/mod.rs	80.43% <72.34%> (-6.53%)	⬇️
storage/src/adb/current/ordered.rs	98.29% <98.29%> (ø)

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