support hash interface for poseidon; support golang crypto interfaces for bjj

poseidon/poseidon_wrapper.go

@@ -0,0 +1,53 @@
+package poseidon
+
+import (
+	"bytes"
+	"hash"
+)
+
+type digest struct {
+	buf *bytes.Buffer
+}
+
+// NewPoseidon returns the Poseidon hash of the input bytes.
+func NewPoseidon(b []byte) []byte {
+	h := New()
+	h.Write(b)
+	return h.Sum(nil)
+}
+
+// New returns a new hash.Hash computing the Poseidon hash.
+func New() hash.Hash {
+	return &digest{
+		buf: bytes.NewBuffer([]byte{}),
+	}
+}
+
+// Write (via the embedded io.Writer interface) adds more data to the running hash.
+func (d *digest) Write(p []byte) (n int, err error) {
+	return d.buf.Write(p)
+}
+
+// Sum returns the Poseidon checksum of the data.
+func (d *digest) Sum(b []byte) []byte {
+	hahs, err := HashBytes(d.buf.Bytes())
+	if err != nil {
+		panic(err)
+	}
+	return append(b, hahs.Bytes()...)
+}
+
+// Reset resets the Hash to its initial state.
+func (d *digest) Reset() {
+	d.buf.Reset()
+}
+
+// Size returns the number of bytes Sum will return.
+func (d *digest) Size() int {
+	return 32
+}
+
+// BlockSize returns the hash block size.
+func (d *digest) BlockSize() int {
+	return spongeChunkSize
+}