JBDelegateMetadataLib

Description

This library allows to store metadata for delegates. It allows to store metadata for a large number of delegates, and to retrieve the metadata for a specific delegate, using a lookup table.

Delegate ID

Each new delegate should define a 4 byte ID used to retrieve its metadata. This ID should be unique. We suggest using the first 4 bytes of the code keccak256 hash (using cast k $bytecode or emit log_bytes32(keccak256(type(MyDelegate).creationCode)); for instance).

Metadata structure

Metadata are built as:

• 32B of reserved space for the protocol (left empty)
• a lookup table delegateId: offset, defining the offset of the metadata for each delegate. The offset fits 1 bytes and is the number of word since the begining of the metadata. The ID fits 4 bytes. This table is padded to 32B.
• the metadata for each delegate, padded to 32B each

   +-----------------------+ offset: 0
   | 32B reserved          |
   +-----------------------+ offset: 1 = end of first 32B
   | (delegate1 ID,offset1)|
   | (delegate2 ID,offset2)|
   | 0's padding           |
   +-----------------------+ offset: offset1 = 1 + number of words taken by the padded table
   | delegate 1 metadata1  |
   | 0's padding           |
   +-----------------------+ offset: offset2 = offset1 + number of words taken by the metadata1
   | delegate 2 metadata2  |
   | 0's padding           |
   +-----------------------+ (...)

Usage

Delegate should parse their metadata using the getMetadata function, which takes the delegate id as parameter and returns the metadata as a bytes array.

Frontend should use the helper contract to build metadatas. The createMetadata function takes an array of delegate ids and an array of data, which can be any data type casted to bytes, and returns the encoded metadata.