Module index_based 

Two-phase index-based deep cloning (matching user’s approach).

Phase 1 (Prepare): Walk through all refs, build HashMap lookup and pos_array Phase 2 (Perform): Walk through again, use pos_array for O(1) lookups

This avoids HashMap lookups during the actual clone, but has overhead:

• Two passes over all data
• Cloning pos_array for each clone operation
• Pre-allocating ref_array

Structs

IndexRef

A reference that supports two-phase cloning.

PerformIndexCloningNode

Perform node - created from PrepareNode for each clone operation.

PrepareIndexCloningNode

Preparation node - built once, stores the reference structure. Uses HashMap to detect shared references.

Functions

clone_refs

Convenience function to clone refs using a prepare node.

prepare_refs

Convenience function to prepare a slice of refs.