LabelUtils

Title: DotNS Label Utilities Library

Canonical keccak labelhash and .dot-TLD namehash helpers shared by every DotNS contract that derives node identifiers from user-supplied labels.

Exists so that the identical inline-assembly keccak sequences don't need to live in every controller, registrar, or resolver. Every caller that maps a label to an on-chain node goes through this library, which is the single source of truth for how a label hashes.

Deliberate non-goals:

Validation (single-label checks, min-length rules, availability): each caller owns its own validation policy alongside its own interface-declared errors. Centralising validation here would require centralising the error types, which breaks interface-level error ownership.
Lowercase ASCII letters/digits/hyphen rules with hyphen-position constraints live in @custom:function StringUtils.isSingleLabel; this library treats the input as opaque bytes once a caller has run its own checks.

Note: security-contact: admin@parity.io

Functions

labelhash

Computes keccak256(bytes(label)) via memory-safe scratch space.

function labelhash(string calldata label) internal pure returns (bytes32 hash);

Parameters

Name	Type	Description
`label`	`string`	Label string.

Returns

Name	Type	Description
`hash`	`bytes32`	`keccak256(bytes(label))`.

labelhashMemory

Computes keccak256(bytes(label)) for a memory string.

Overload used by call sites that hold the label in memory (e.g. the registrar's transfer sync path reading _labels[tokenId]). Same semantics as @custom:function labelhash, different calldata shape.

function labelhashMemory(string memory label) internal pure returns (bytes32 hash);

Parameters

Name	Type	Description
`label`	`string`	Label string held in memory.

Returns

Name	Type	Description
`hash`	`bytes32`	`keccak256(bytes(label))`.

namehashUnder

Computes namehash(parent, labelhash) against an arbitrary parent.

General form of @custom:function namehash; use when the parent is not the .dot TLD (e.g. subnode derivation under a non-TLD parent in the forward registry, or a PoP namespace root). For top-level .dot registrations prefer

Note: function: namehash which hard-codes DOT_NODE.

function namehashUnder(bytes32 parent, bytes32 labelhash_)
    internal
    pure
    returns (bytes32 node);

Parameters

Name	Type	Description
`parent`	`bytes32`	Parent node.
`labelhash_`	`bytes32`	`keccak256(bytes(label))`.

Returns

Name	Type	Description
`node`	`bytes32`	`namehash(parent, labelhash)`.

namehash

Computes namehash(DOT_NODE, labelhash) via memory-safe scratch space.

Specialised to the .dot TLD; cheaper than @custom:function namehashUnder because the parent constant is folded in at compile time.

function namehash(bytes32 labelhash_) internal pure returns (bytes32 node);

Parameters

Name	Type	Description
`labelhash_`	`bytes32`	`keccak256(bytes(label))`.

Returns

Name	Type	Description
`node`	`bytes32`	The node identifier under the `.dot` TLD.

deriveNode

Derives (labelhash, node) from a label in one call.

Convenience combinator for registration flows: hashes the label exactly once and returns both identifiers callers need without recomputing.

function deriveNode(string calldata label) internal pure returns (bytes32 hash, bytes32 node);

Parameters

Name	Type	Description
`label`	`string`	Label string.

Returns

Name	Type	Description
`hash`	`bytes32`	`keccak256(bytes(label))`.
`node`	`bytes32`	`namehash(DOT_NODE, hash)`.

stripDotTld

Strips the configured .dot TLD suffix from a stored full name.

Returns the empty string when the input does not end in the TLD; callers treat an empty return as a "do not trust this record" signal.

function stripDotTld(string memory fullName) internal pure returns (string memory label);