[1/N] Chunk encoding optimization: Support encoding format with gnark (…

…#617)

encoding/serialization.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/gob"
 	"encoding/json"
+	"errors"
 	"fmt"
 
 	"github.com/consensys/gnark-crypto/ecc/bn254"
@@ -22,6 +23,41 @@ func (c *Frame) Deserialize(data []byte) (*Frame, error) {
 	return c, err
 }
 
+func (c *Frame) SerializeGnark() ([]byte, error) {
+	coded := make([]byte, 0, bn254.SizeOfG1AffineCompressed+BYTES_PER_SYMBOL*len(c.Coeffs))
+	// This is compressed format with just 32 bytes.
+	proofBytes := c.Proof.Bytes()
+	coded = append(coded, proofBytes[:]...)
+	for _, coeff := range c.Coeffs {
+		coded = append(coded, coeff.Marshal()...)
+	}
+	return coded, nil
+}
+
+func (c *Frame) DeserializeGnark(data []byte) (*Frame, error) {
+	var f Frame
+	buf := data
+	err := f.Proof.Unmarshal(buf[:bn254.SizeOfG1AffineCompressed])
+	if err != nil {
+		return nil, err
+	}
+	buf = buf[bn254.SizeOfG1AffineCompressed:]
+	if len(buf)%BYTES_PER_SYMBOL != 0 {
+		return nil, errors.New("invalid chunk length")
+	}
+	f.Coeffs = make([]Symbol, len(buf)/BYTES_PER_SYMBOL)
+	i := 0
+	for len(buf) > 0 {
+		if len(buf) < BYTES_PER_SYMBOL {
+			return nil, errors.New("invalid chunk length")
+		}
+		f.Coeffs[i].Unmarshal(buf[:BYTES_PER_SYMBOL])
+		i++
+		buf = buf[BYTES_PER_SYMBOL:]
+	}
+	return &f, nil
+}
+
 func (f *Frame) Encode() ([]byte, error) {
 	var buf bytes.Buffer
 	enc := gob.NewEncoder(&buf)

encoding/serialization_test.go

@@ -0,0 +1,47 @@
+package encoding_test
+
+import (
+	"testing"
+
+	"github.com/Layr-Labs/eigenda/encoding"
+	"github.com/consensys/gnark-crypto/ecc/bn254/fp"
+	"github.com/consensys/gnark-crypto/ecc/bn254/fr"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSerDeserGnark(t *testing.T) {
+	var XCoord, YCoord fp.Element
+	_, err := XCoord.SetString("21661178944771197726808973281966770251114553549453983978976194544185382599016")
+	assert.NoError(t, err)
+	_, err = YCoord.SetString("9207254729396071334325696286939045899948985698134704137261649190717970615186")
+	assert.NoError(t, err)
+
+	numCoeffs := 64
+	var f encoding.Frame
+	f.Proof = encoding.Proof{
+		X: XCoord,
+		Y: YCoord,
+	}
+	for i := 0; i < numCoeffs; i++ {
+		f.Coeffs = append(f.Coeffs, fr.NewElement(uint64(i)))
+	}
+
+	gnark, err := f.SerializeGnark()
+	assert.Nil(t, err)
+	// The gnark encoding via f.Serialize() will generate less bytes
+	// than gob.
+	assert.Equal(t, 32*(1+numCoeffs), len(gnark))
+	gob, err := f.Serialize()
+	assert.Nil(t, err)
+	// 2080 with gnark v.s. 2574 with gob
+	assert.Equal(t, 2574, len(gob))
+
+	// Verify the deserialization can get back original data
+	c, err := new(encoding.Frame).DeserializeGnark(gnark)
+	assert.Nil(t, err)
+	assert.True(t, f.Proof.Equal(&c.Proof))
+	assert.Equal(t, len(f.Coeffs), len(c.Coeffs))
+	for i := 0; i < len(f.Coeffs); i++ {
+		assert.True(t, f.Coeffs[i].Equal(&c.Coeffs[i]))
+	}
+}