Owner Two Step Transfer Module

Two-step ERC-173 ownership transfer logic

Key Features

• Implements ERC-173 two-step ownership transfer logic.
• All functions are internal, intended for use by other facets within a diamond.
• Utilizes diamond storage pattern for ownership state management.
• Emits OwnershipTransferStarted and OwnershipTransferred events for off-chain monitoring.

Module Usage

This module provides internal functions for use in your custom facets. Import it to access shared logic and storage.

Overview

This module provides internal functions for initiating and accepting ERC-173 ownership transfers. Facets can integrate this module to manage ownership changes within the diamond. Ownership changes are finalized through a two-step process, ensuring that the new owner explicitly accepts the transfer.

Storage

OwnerStorage

storage-location: erc8042:erc173.owner

Definition

struct OwnerStorage {
  address owner;
}

---

PendingOwnerStorage

storage-location: erc8042:erc173.owner.pending

Definition

struct PendingOwnerStorage {
  address pendingOwner;
}

State Variables

Property	Type	Description
OWNER_STORAGE_POSITION	bytes32	Diamond storage slot position for this module (Value: keccak256("erc173.owner"))
PENDING_OWNER_STORAGE_POSITION	bytes32	Diamond storage slot position for this module (Value: keccak256("erc173.owner.pending"))

Functions

acceptOwnership

Finalizes ownership transfer. Only the pending owner can call this function.

function acceptOwnership() ;

---

getOwnerStorage

Returns a pointer to the Owner storage struct. Uses inline assembly to access the storage slot defined by OWNER_STORAGE_POSITION.

function getOwnerStorage() pure returns (OwnerStorage storage s);

Returns:

Property	Type	Description
s	OwnerStorage	The OwnerStorage struct in storage.

---

getPendingOwnerStorage

Returns a pointer to the PendingOwner storage struct. Uses inline assembly to access the storage slot defined by PENDING_OWNER_STORAGE_POSITION.

function getPendingOwnerStorage() pure returns (PendingOwnerStorage storage s);

Returns:

Property	Type	Description
s	PendingOwnerStorage	The PendingOwnerStorage struct in storage.

---

transferOwnership

Initiates a two-step ownership transfer.

function transferOwnership(address _newOwner) ;

Parameters:

Property	Type	Description
_newOwner	address	The address of the new owner of the contract.

Events

Emitted when ownership transfer is initiated (pending owner set).

Signature:

event OwnershipTransferStarted(address indexed _previousOwner, address indexed _newOwner);

Emitted when ownership transfer is finalized.

Signature:

event OwnershipTransferred(address indexed _previousOwner, address indexed _newOwner);

Errors

Signature:

error OwnerUnauthorizedAccount();

Best Practices

Best Practice

• Ensure the transferOwnership function is called only by the current owner to prevent unauthorized transfer initiation.
• Verify that acceptOwnership is called by the correct pending owner before finalizing the transfer.
• Handle the OwnerUnauthorizedAccount error, which is emitted when unauthorized accounts attempt to perform ownership-related actions.

Integration Notes

Shared Storage

This module interacts with two primary storage slots within the diamond's shared storage: OWNER_STORAGE_POSITION for the current owner and PENDING_OWNER_STORAGE_POSITION for the pending owner. The getOwnerStorage and getPendingOwnerStorage functions provide direct access pointers to these storage locations using inline assembly. Changes made via transferOwnership and acceptOwnership modify these shared storage slots, making them immediately visible to any other facet that accesses the same storage positions.

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Last updated:March 13, 2026