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package merkletree
import (
"fmt"
"math/big"
"github.com/iden3/go-iden3-crypto/poseidon"
)
// HashElems performs a poseidon hash over the array of ElemBytes.
// Uses poseidon.PoseidonHash to be compatible with the circom circuits
// implementations.
// The maxim slice input size is poseidon.T
func HashElems(elems ...*big.Int) (*Hash, error) {
if len(elems) > poseidon.T {
return nil, fmt.Errorf("HashElems input can not be bigger than %v", poseidon.T)
}
bi, err := BigIntsToPoseidonInput(elems...)
if err != nil {
return nil, err
}
poseidonHash, err := poseidon.PoseidonHash(bi)
if err != nil {
return nil, err
}
return NewHashFromBigInt(poseidonHash), nil
}
// HashElemsKey performs a poseidon hash over the array of ElemBytes.
func HashElemsKey(key *big.Int, elems ...*big.Int) (*Hash, error) {
if len(elems) > poseidon.T-1 {
return nil, fmt.Errorf("HashElemsKey input can not be bigger than %v", poseidon.T-1)
}
if key == nil {
key = new(big.Int).SetInt64(0)
}
bi, err := BigIntsToPoseidonInput(elems...)
if err != nil {
return nil, err
}
copy(bi[len(elems):], []*big.Int{key})
poseidonHash, err := poseidon.PoseidonHash(bi)
if err != nil {
return nil, err
}
return NewHashFromBigInt(poseidonHash), nil
}
// BigIntsToPoseidonInput takes *big.Ints and returns a fixed-length array of the size `poseidon.T`
func BigIntsToPoseidonInput(bigints ...*big.Int) ([poseidon.T]*big.Int, error) {
z := big.NewInt(0)
b := [poseidon.T]*big.Int{z, z, z, z, z, z}
copy(b[:poseidon.T], bigints[:])
return b, nil
}