Module set 

OpenZeppelin’s EnumerableSet implementation for EVM storage using Rust primitives. https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/structs/EnumerableSet.sol

Storage Layout

EnumerableSet uses two storage structures:

• Values Vec: A Vec<T> storing all set elements at keccak256(base_slot)
• Positions Mapping: A Mapping<T, u32> at base_slot + 1 storing 1-indexed positions
  • Position 0 means the value is not in the set
  • Position N means the value is at index N-1 in the values array

Design

Two complementary types:

• Set<T>: Read-only in-memory snapshot. Vec<T> wrapper. Ordered like storage.
• SetHandler<T>: Storage operations.

Usage Patterns

Single Operations (O(1) each)

handler.insert(addr)?;   // Direct storage write
handler.remove(&addr)?;  // Direct storage write
handler.contains(&addr)?; // Direct storage read

Bulk Read

let set: Set<Address> = handler.read()?;
for addr in &set {
    // Iteration preserves storage order
    // set[i] == handler.at(i)
}

Bulk Mutation

let mut vec: Vec<_> = handler.read()?.into();
vec.push(new_addr);
vec.retain(|a| a != &old_addr);
handler.write(vec.into())?;  // `Set::from(vec)` deduplicates

Structs

Set

An ordered set that preserves insertion order.

SetHandler

Type-safe handler for accessing Set<T> in storage.