CASSGO-2 Marshal big int returns variable length slice.

The marshalBigInt return 8 bytes slice in all cases except for big.Int,
which returns a variable length slice, but should be 8 bytes slice as well.

patch by Mykyta Oleksiienko; reviewed by João Reis for CASSGO-2

CHANGELOG.md

@@ -14,6 +14,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- CASSGO-2
+
 ## [1.7.0] - 2024-09-23
 
 This release is the first after the donation of gocql to the Apache Software Foundation (ASF)

marshal.go

@@ -77,7 +77,7 @@ type Unmarshaler interface {
 //	tinyint, smallint, int      | integer types      |
 //	tinyint, smallint, int      | string             | formatted as base 10 number
 //	bigint, counter             | integer types      |
-//	bigint, counter             | big.Int            |
+//	bigint, counter             | big.Int            | according to cassandra bigint specification the big.Int value limited to int64 size(an eight-byte two's complement integer.)
 //	bigint, counter             | string             | formatted as base 10 number
 //	float                       | float32            |
 //	double                      | float64            |
@@ -671,7 +671,10 @@ func marshalBigInt(info TypeInfo, value interface{}) ([]byte, error) {
 	case uint8:
 		return encBigInt(int64(v)), nil
 	case big.Int:
-		return encBigInt2C(&v), nil
+		if !v.IsInt64() {
+			return nil, marshalErrorf("marshal bigint: value %v out of range", &v)
+		}
+		return encBigInt(v.Int64()), nil
 	case string:
 		i, err := strconv.ParseInt(value.(string), 10, 64)
 		if err != nil {
@@ -773,6 +776,8 @@ func marshalVarint(info TypeInfo, value interface{}) ([]byte, error) {
 			retBytes = make([]byte, 8)
 			binary.BigEndian.PutUint64(retBytes, v)
 		}
+	case big.Int:
+		retBytes = encBigInt2C(&v)
 	default:
 		retBytes, err = marshalBigInt(info, value)
 	}

marshal_test.go

@@ -39,6 +39,8 @@ import (
 	"time"
 
 	"gopkg.in/inf.v0"
+
+	"github.com/stretchr/testify/require"
 )
 
 type AliasInt int
@@ -1349,7 +1351,7 @@ func TestMarshal_Encode(t *testing.T) {
 			}
 		} else {
 			if _, err := Marshal(test.Info, test.Value); err != test.MarshalError {
-				t.Errorf("unmarshalTest[%d] (%v=>%t): %#v returned error %#v, want %#v.", i, test.Info, test.Value, test.Value, err, test.MarshalError)
+				t.Errorf("marshalTest[%d] (%v=>%t): %#v returned error %#v, want %#v.", i, test.Info, test.Value, test.Value, err, test.MarshalError)
 			}
 		}
 	}
@@ -1535,6 +1537,32 @@ func TestMarshalVarint(t *testing.T) {
 	}
 }
 
+func TestMarshalBigInt(t *testing.T) {
+	var testStruct = []struct {
+		Info         TypeInfo
+		Value        interface{}
+		MarshalError error
+	}{
+		{
+			NativeType{proto: 2, typ: TypeBigInt},
+			"-78635384813432117863538481343211",
+			MarshalError("can not marshal string to bigint: strconv.ParseInt: parsing \"-78635384813432117863538481343211\": value out of range"),
+		},
+		{
+			NativeType{proto: 2, typ: TypeBigInt},
+			"922337203685477692259749625974294",
+			MarshalError("can not marshal string to bigint: strconv.ParseInt: parsing \"922337203685477692259749625974294\": value out of range"),
+		},
+	}
+
+	t.Run("testMarshalBigInt", func(t *testing.T) {
+		for _, tc := range testStruct {
+			_, err := Marshal(tc.Info, tc.Value)
+			require.Equal(t, tc.MarshalError, err)
+		}
+	})
+}
+
 func equalStringPointerSlice(leftList, rightList []*string) bool {
 	if len(leftList) != len(rightList) {
 		return false