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TaikoL2

TaikoL2 is a smart contract that handles cross-layer message verification and manages EIP-1559 gas pricing for Taiko operations. It is used to anchor the latest L1 block details to L2 for cross-layer communication, manage EIP-1559 parameters for gas pricing, and store verified L1 block information.

Core Purpose

  1. Anchor: Due to Taiko’s based rollup nature, each L2 block requires anchoring to the latest L1 block details. The first transaction of every block must perform this anchor, or all calls will revert with L2_PUBLIC_INPUT_HASH_MISMATCH.

  2. Gas Pricing: The contract calculates EIP-1559 base fee and updates gas parameters dynamically for optimal gas pricing using key inputs such as _parentGasUsed and _baseFeeConfig.

  3. State Synchronization: The contract ensures L2 remains in sync with L1 by storing verified block information and updating state data like block hashes and timestamps.

  4. Bridging Support: It plays a crucial role in L1-L2 bridging, anchoring state roots to enable secure and efficient communication between layers. For more, visit the Bridging page.

Key Functions

anchorV2

  • Purpose: Anchors the latest L1 block details to L2, enabling cross-layer message verification.

  • Parameters:

    • _anchorBlockId: The L1 block ID to anchor.
    • _anchorStateRoot: State root of the specified L1 block.
    • _parentGasUsed: Gas usage in the parent block.
    • _baseFeeConfig: Configuration for base fee calculation.

  • Mechanism: Verifies and updates the publicInputHash, calculates the base fee and gas excess using getBasefeeV2, and synchronizes chain data.

getBasefeeV2

  • Purpose: Computes the EIP-1559 base fee and updates gas parameters like gas excess and gas target.

  • Parameters:

    • _parentGasUsed: Gas used in the parent block.
    • _baseFeeConfig: Configuration for EIP-1559 calculations.

  • Returns:

    • basefee_: Calculated base fee per gas.
    • newGasTarget_: Updated gas target.
    • newGasExcess_: Updated gas excess.

  • Technical Details: Uses LibEIP1559.calc1559BaseFee and LibEIP1559.adjustExcess for precise gas pricing dynamics.

getBlockHash

  • Purpose: Fetches the block hash for a specified block ID.

  • Technical Note: If the block ID is too old (not in the last 256 blocks), it uses an internal mapping (_blockhashes) to retrieve stored hashes.

Key Events

  1. Anchored Emitted when L1 block details are successfully anchored to L2.

    Parameters:

    • parentHash: Hash of the parent block.
    • parentGasExcess: Gas excess for base fee calculation.

  2. EIP1559Update Emitted when gas parameters (e.g., target, excess, base fee) are updated.

    Parameters:

    • oldGasTarget: Previous gas target.
    • newGasTarget: Updated gas target.
    • oldGasExcess: Previous gas excess.
    • newGasExcess: Updated gas excess.
    • basefee: Calculated base fee.

Important Data Structures

State Variables

  1. publicInputHash: Validates the integrity of public inputs for block verification.

  2. parentGasExcess: Tracks gas usage exceeding the target for dynamic base fee adjustment.

  3. lastSyncedBlock: Stores the ID of the most recent L1 block synced with L2.

  4. l1ChainId: Chain ID of the base layer (L1).