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package arbo
import (
"crypto/sha256"
"math/big"
"github.com/iden3/go-iden3-crypto/poseidon"
"golang.org/x/crypto/blake2b"
)
var (
// TypeHashSha256 represents the label for the HashFunction of Sha256
TypeHashSha256 = []byte("sha256")
// TypeHashPoseidon represents the label for the HashFunction of
// Poseidon
TypeHashPoseidon = []byte("poseidon")
// TypeHashBlake2b represents the label for the HashFunction of Blake2b
TypeHashBlake2b = []byte("blake2b")
// HashFunctionSha256 contains the HashSha256 struct which implements
// the HashFunction interface
HashFunctionSha256 HashSha256
// HashFunctionPoseidon contains the HashPoseidon struct which implements
// the HashFunction interface
HashFunctionPoseidon HashPoseidon
// HashFunctionBlake2b contains the HashBlake2b struct which implements
// the HashFunction interface
HashFunctionBlake2b HashBlake2b
)
// Once Generics are at Go, this will be updated (August 2021
// https://blog.golang.org/generics-next-step)
// HashFunction defines the interface that is expected for a hash function to be
// used in a generic way in the Tree.
type HashFunction interface {
Type() []byte
Len() int
Hash(...[]byte) ([]byte, error)
// CheckInput checks if the input is valid without computing the hash
// CheckInput(...[]byte) error
}
// HashSha256 implements the HashFunction interface for the Sha256 hash
type HashSha256 struct{}
// Type returns the type of HashFunction for the HashSha256
func (f HashSha256) Type() []byte {
return TypeHashSha256
}
// Len returns the length of the Hash output
func (f HashSha256) Len() int {
return 32 //nolint:gomnd
}
// Hash implements the hash method for the HashFunction HashSha256
func (f HashSha256) Hash(b ...[]byte) ([]byte, error) {
var toHash []byte
for i := 0; i < len(b); i++ {
toHash = append(toHash, b[i]...)
}
h := sha256.Sum256(toHash)
return h[:], nil
}
// HashPoseidon implements the HashFunction interface for the Poseidon hash
type HashPoseidon struct{}
// Type returns the type of HashFunction for the HashPoseidon
func (f HashPoseidon) Type() []byte {
return TypeHashPoseidon
}
// Len returns the length of the Hash output
func (f HashPoseidon) Len() int {
return 32 //nolint:gomnd
}
// Hash implements the hash method for the HashFunction HashPoseidon
func (f HashPoseidon) Hash(b ...[]byte) ([]byte, error) {
var toHash []*big.Int
for i := 0; i < len(b); i++ {
bi := BytesToBigInt(b[i])
toHash = append(toHash, bi)
}
h, err := poseidon.Hash(toHash)
if err != nil {
return nil, err
}
hB := BigIntToBytes(f.Len(), h)
return hB, nil
}
// HashBlake2b implements the HashFunction interface for the Blake2b hash
type HashBlake2b struct{}
// Type returns the type of HashFunction for the HashBlake2b
func (f HashBlake2b) Type() []byte {
return TypeHashBlake2b
}
// Len returns the length of the Hash output
func (f HashBlake2b) Len() int {
return 32 //nolint:gomnd
}
// Hash implements the hash method for the HashFunction HashBlake2b
func (f HashBlake2b) Hash(b ...[]byte) ([]byte, error) {
hasher, err := blake2b.New256(nil)
if err != nil {
return nil, err
}
for i := 0; i < len(b); i++ {
if _, err = hasher.Write(b[i]); err != nil {
return nil, err
}
}
return hasher.Sum(nil), nil
}