core: add database/sql support for more types (#102)

* core: types: add database/sql support for BlockNonce

* common: add database/sql support with Big

New Big type is declared to let big.Int support database/sql by
implementing Scan() and Value() on new type.

1 files changed, 36 insertions, 1 deletions

diff --git a/common/big.go b/common/big.go
index 65d4377bf..dcc5269a7 100644
--- a/common/big.go
+++ b/common/big.go
@@ -16,7 +16,11 @@
 
 package common
 
-import "math/big"
+import (
+	"database/sql/driver"
+	"fmt"
+	"math/big"
+)
 
 // Common big integers often used
 var (
@@ -28,3 +32,34 @@ var (
 	Big256 = big.NewInt(256)
 	Big257 = big.NewInt(257)
 )
+
+// Big support database/sql Scan and Value.
+type Big big.Int
+
+// Scan implements Scanner for database/sql.
+func (b *Big) Scan(src interface{}) error {
+	newB := new(big.Int)
+	switch t := src.(type) {
+	case int64:
+		*b = Big(*newB.SetInt64(t))
+	case uint64:
+		*b = Big(*newB.SetUint64(t))
+	case []byte:
+		*b = Big(*newB.SetBytes(t))
+	case string:
+		v, ok := newB.SetString(t, 10)
+		if !ok {
+			return fmt.Errorf("invalid string format %v", src)
+		}
+		*b = Big(*v)
+	default:
+		return fmt.Errorf("can't scan %T into Big", src)
+	}
+	return nil
+}
+
+// Value implements valuer for database/sql.
+func (b Big) Value() (driver.Value, error) {
+	b2 := big.Int(b)
+	return (&b2).String(), nil
+}