add json decoding for kzg types

crypto/kzg4844/kzg4844.go

@@ -20,21 +20,45 @@ package kzg4844
 import (
 	"embed"
 	"errors"
+	"reflect"
 	"sync/atomic"
+
+	"github.com/ethereum/go-ethereum/common/hexutil"
 )
 
 //go:embed trusted_setup.json
 var content embed.FS
 
+var (
+	blobT       = reflect.TypeOf(Blob{})
+	commitmentT = reflect.TypeOf(Commitment{})
+	proofT      = reflect.TypeOf(Proof{})
+)
+
 // Blob represents a 4844 data blob.
 type Blob [131072]byte
 
+// UnmarshalJSON parses a blob in hex syntax.
+func (b *Blob) UnmarshalJSON(input []byte) error {
+	return hexutil.UnmarshalFixedJSON(blobT, input, b[:])
+}
+
 // Commitment is a serialized commitment to a polynomial.
 type Commitment [48]byte
 
+// UnmarshalJSON parses a commitment in hex syntax.
+func (c *Commitment) UnmarshalJSON(input []byte) error {
+	return hexutil.UnmarshalFixedJSON(commitmentT, input, c[:])
+}
+
 // Proof is a serialized commitment to the quotient polynomial.
 type Proof [48]byte
 
+// UnmarshalJSON parses a proof in hex syntax.
+func (p *Proof) UnmarshalJSON(input []byte) error {
+	return hexutil.UnmarshalFixedJSON(proofT, input, p[:])
+}
+
 // Point is a BLS field element.
 type Point [32]byte