Queue

Overview

The Queue contract provides a shared foundation for time-gated asset processing in systems like DepositQueue and RedeemQueue. It tracks user requests via timestamped checkpoints and processes them using oracle-based pricing.

This abstract module is not directly deployable but is designed to be extended by concrete implementations, which define the behavior of _handleReport and allowed user actions (deposit / redeem functions).

Purpose

  • Serves as a modular base for deposit/redeem queues

  • Enforces Vault request processing initially triggered by Oracle

  • Stores timestamped user action traces via Checkpoints.Trace224

  • Ensures vault-controlled access and proper report validation

Derived contracts

  • DepositQueue: handles queued deposits after a delay

  • RedeemQueue: handles redemption requests similarly

Use Cases

  • Prevents manipulation by requiring delayed processing relative to price updates

Storage Structure

struct QueueStorage {
  address asset;              // Token/ETH managed by this queue
  address vault;              // Vault that owns this queue
  Checkpoints.Trace224 timestamps; // Timeline of requests
}

  • asset: token used for this queue (ERC20 or native ETH)

  • vault: only this address can call handleReport(...)

  • timestamps: request history used in the implementations

Initialization

function __Queue_init(address asset_, address vault_) internal

  • Must be called by child contracts

  • Initializes asset, vault, and creates a starting checkpoint

Oracle Integration

function handleReport(uint224 priceD18, uint32 timestamp) external

  • Called by the vault when an oracle report is available

  • Verifies:

    • Caller is the vault

    • Price is non-zero

    • Timestamp is in the past (timestamp < block.timestamp)

  • Internally delegates to _handleReport(...) (must be implemented by child)

Abstract Hook

function _handleReport(uint224 priceD18, uint32 timestamp) internal virtual

Must be implemented by child classes to:

  • Read and process requests from _timestamps()

  • Apply pricing logic to convert shares↔assets

  • Mint/burn shares, transfer tokens, etc.

View Functions

Function
Description

vault()

Returns the controlling vault address

asset()

Returns the ERC20/native token used by the queue

canBeRemoved()

Not implemented in Queue (optional for children)

Internal Helpers

Function
Description

_timestamps()

Returns the internal Checkpoints.Trace224 structure

_queueStorage()

Loads queue storage using custom storage slot

_queueStorageSlot

Computed using SlotLibrary to prevent conflicts

Events

event ReportHandled(uint224 priceD18, uint32 timestamp)

  • Emitted when handleReport() completes

  • Signals that all eligible requests up to timestamp were processed

Errors

Error
Reason

ZeroValue()

Called with 0 address or value

Forbidden()

Caller not authorized (e.g., not the vault)

InvalidReport()

Oracle report is zero-priced or timestamp is invalid

QueuePaused()

Reserved for future ACL/pause integration

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