TaikoL2

TaikoL2 is a core smart contract for the Taiko Alethia rollup, responsible for cross-layer state synchronization, gas pricing via EIP-1559, and bridging support. It ensures L2 remains in sync with L1 and facilitates secure message verification.

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Features

• Anchor L1 State to L2: Ensures L2 block validity by referencing L1 state.
• EIP-1559 Gas Pricing: Dynamically adjusts base fees and gas targets based on L1 data.
• Cross-Layer Bridging: Enables state root anchoring for message verification between L1 and L2.
• Optimized Block Processing: Ensures gas-efficient state transitions.

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Contract Methods

anchorV2

Anchors L1 block details to L2, ensuring state synchronization.

Parameter	Type	Description
_anchorBlockId	uint256	L1 block ID to anchor.
_anchorStateRoot	bytes32	State root of the specified L1 block.
_parentGasUsed	uint256	Gas used in the parent block.
_baseFeeConfig	uint256	Configuration for base fee calculation.

Returns:

• Updates publicInputHash and synchronizes chain data.
• Computes gas parameters using getBasefeeV2.

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getBasefeeV2

Calculates EIP-1559 base fee and updates gas parameters.

Parameter	Type	Description
_parentGasUsed	uint256	Gas used in the parent block.
_baseFeeConfig	uint256	Configuration for EIP-1559 calculations.

Returns:

Return Value	Type	Description
basefee_	uint256	Computed base fee per gas.
newGasTarget_	uint256	Updated gas target.
newGasExcess_	uint256	Updated gas excess.

Technical Details:

• Uses LibEIP1559.calc1559BaseFee to compute the new base fee.
• Adjusts gas targets dynamically using LibEIP1559.adjustExcess.

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getBlockHash

Retrieves the block hash for a given block ID.

Parameter	Type	Description
_blockId	uint256	ID of the block to retrieve.

Returns:

Return Value	Type	Description
blockHash_	bytes32	Hash of the requested block.

Technical Note:

• If the block is older than 256 blocks, _blockhashes mapping is used instead of blockhash().

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Events

Anchored

Emitted when L1 block details are successfully anchored to L2.

Parameter	Type	Description
parentHash	bytes32	Hash of the parent block.
parentGasExcess	uint256	Gas excess used for base fee calculations.

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EIP1559Update

Emitted when gas parameters are updated.

Parameter	Type	Description
oldGasTarget	uint256	Previous gas target.
newGasTarget	uint256	Updated gas target.
oldGasExcess	uint256	Previous gas excess.
newGasExcess	uint256	Updated gas excess.
basefee	uint256	Computed base fee.

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State Variables

Variable	Type	Description
publicInputHash	bytes32	Ensures integrity of public inputs for block verification.
parentGasExcess	uint256	Tracks gas usage exceeding the target for fee adjustments.
lastSyncedBlock	uint256	Stores the most recent L1 block ID synced with L2.
l1ChainId	uint256	Chain ID of L1 (Ethereum).

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Design Considerations

1. State Synchronization

   • Ensures L1-L2 consistency via anchoring.
   • Uses public input hash validation to prevent state mismatches.

2. Gas Efficiency

   • Implements EIP-1559 dynamic gas pricing.
   • Optimizes L2 execution costs based on L1 gas usage.

3. Bridging & Interoperability

   • Stores verified state roots to facilitate cross-layer message verification.
   • Ensures compatibility with bridging mechanisms.

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