predicateutils

README

Predicate Utils

This package provides simple helpers to pack/unpack byte slices for a predicate transaction, where a byte slice of size N is encoded in the access list of a transaction.

Encoding

A byte slice of size N is encoded as:

1. Slice of N bytes
2. Delimiter byte 0xff
3. Appended 0s to the nearest multiple of 32 bytes

Documentation

Index

• Variables
• func BytesToHashSlice(b []byte) []common.Hash
• func HashSliceToBytes(hashes []common.Hash) []byte
• func PackPredicate(predicate []byte) []byte
• func UnpackPredicate(paddedPredicate []byte) ([]byte, error)

Variables

var PredicateEndByte = byte(0xff)

PredicateEndByte is used as a delimiter for the bytes packed into a precompile predicate. Precompile predicates are encoded in the Access List of transactions in the access tuples which means that its length must be a multiple of 32 (common.HashLength). For messages with a length that does not comply to that, this delimiter is used to append/remove padding.

Functions

func BytesToHashSlice

func BytesToHashSlice(b []byte) []common.Hash

BytesToHashSlice packs [b] into a slice of hash values with zero padding to the right if the length of b is not a multiple of 32.

func HashSliceToBytes

func HashSliceToBytes(hashes []common.Hash) []byte

HashSliceToBytes serializes a []common.Hash into a tightly packed byte array.

func PackPredicate

func PackPredicate(predicate []byte) []byte

PackPredicate packs [predicate] by delimiting the actual message with PredicateEndByte and zero padding to reach a length that is a multiple of 32.

func UnpackPredicate

func UnpackPredicate(paddedPredicate []byte) ([]byte, error)

UnpackPredicate unpacks a predicate by stripping right padded zeroes, checking for the delimter, ensuring there is not excess padding, and returning the original message. Returns an error if it finds an incorrect encoding.