Add discriminator value check in codec entry Decode

pkg/solana/codec/codec_entry.go

@@ -1,6 +1,7 @@
 package codec
 
 import (
+	"bytes"
 	"fmt"
 	"reflect"
 
@@ -29,6 +30,7 @@ type entry struct {
 	// includeDiscriminator during Encode adds a discriminator to the encoded bytes under an assumption that the provided value didn't have a discriminator.
 	// During Decode includeDiscriminator removes discriminator from bytes under an assumption that the provided struct doesn't need a discriminator.
 	includeDiscriminator bool
+	discriminator        Discriminator
 }
 
 func NewAccountEntry(offchainName string, idlAccount IdlTypeDef, idlTypes IdlTypeDefSlice, includeDiscriminator bool, mod codec.Modifier, builder commonencodings.Builder) (Entry, error) {
@@ -47,10 +49,11 @@ func NewAccountEntry(offchainName string, idlAccount IdlTypeDef, idlTypes IdlTyp
 	return &entry{
 		offchainName:         offchainName,
 		onchainName:          idlAccount.Name,
-		includeDiscriminator: includeDiscriminator,
-		typeCodec:            accCodec,
 		reflectType:          accCodec.GetType(),
+		typeCodec:            accCodec,
 		mod:                  ensureModifier(mod),
+		includeDiscriminator: includeDiscriminator,
+		discriminator:        *NewDiscriminator(idlAccount.Name),
 	}, nil
 }
 
@@ -96,8 +99,7 @@ func (e *entry) Encode(value any, into []byte) ([]byte, error) {
 
 	if e.includeDiscriminator {
 		var byt []byte
-		disc := NewDiscriminator(e.onchainName)
-		encodedDisc, err := disc.Encode(&disc.hashPrefix, byt)
+		encodedDisc, err := e.discriminator.Encode(&e.discriminator.hashPrefix, byt)
 		if err != nil {
 			return nil, err
 		}
@@ -112,6 +114,11 @@ func (e *entry) Decode(encoded []byte) (any, []byte, error) {
 		if len(encoded) < discriminatorLength {
 			return nil, nil, fmt.Errorf("%w: encoded data too short to contain discriminator for offchainName: %q, onchainName: %q", commontypes.ErrInvalidType, e.offchainName, e.onchainName)
 		}
+
+		if !bytes.Equal(e.discriminator.hashPrefix, encoded[:8]) {
+			return nil, nil, fmt.Errorf("%w: encoded data has a bad discriminator %v for offchainName: %q, onchainName: %q", commontypes.ErrInvalidType, encoded[:8], e.offchainName, e.onchainName)
+		}
+
 		encoded = encoded[discriminatorLength:]
 	}
 	return e.typeCodec.Decode(encoded)