1 files changed, 44 insertions, 0 deletions
diff --git a/src/database/sql/convert.go b/src/database/sql/convert.go
index 7a3b5fa7da..4c056a1eda 100644
--- a/src/database/sql/convert.go
+++ b/src/database/sql/convert.go
@@ -288,6 +288,11 @@ func convertAssignRows(dest, src interface{}, rows *Rows) error {
 			*d = s.AppendFormat((*d)[:0], time.RFC3339Nano)
 			return nil
 		}
+	case decimalDecompose:
+		switch d := dest.(type) {
+		case decimalCompose:
+			return d.Compose(s.Decompose(nil))
+		}
 	case nil:
 		switch d := dest.(type) {
 		case *interface{}:
@@ -553,3 +558,42 @@ func callValuerValue(vr driver.Valuer) (v driver.Value, err error) {
 	}
 	return vr.Value()
 }
+
+// decimal composes or decomposes a decimal value to and from individual parts.
+// There are four parts: a boolean negative flag, a form byte with three possible states
+// (finite=0, infinite=1, NaN=2), a base-2 big-endian integer
+// coefficient (also known as a significand) as a []byte, and an int32 exponent.
+// These are composed into a final value as "decimal = (neg) (form=finite) coefficient * 10 ^ exponent".
+// A zero length coefficient is a zero value.
+// The big-endian integer coefficent stores the most significant byte first (at coefficent[0]).
+// If the form is not finite the coefficient and exponent should be ignored.
+// The negative parameter may be set to true for any form, although implementations are not required
+// to respect the negative parameter in the non-finite form.
+//
+// Implementations may choose to set the negative parameter to true on a zero or NaN value,
+// but implementations that do not differentiate between negative and positive
+// zero or NaN values should ignore the negative parameter without error.
+// If an implementation does not support Infinity it may be converted into a NaN without error.
+// If a value is set that is larger than what is supported by an implementation,
+// an error must be returned.
+// Implementations must return an error if a NaN or Infinity is attempted to be set while neither
+// are supported.
+//
+// NOTE(kardianos): This is an experimental interface. See https://golang.org/issue/30870
+type decimal interface {
+	decimalDecompose
+	decimalCompose
+}
+
+type decimalDecompose interface {
+	// Decompose returns the internal decimal state in parts.
+	// If the provided buf has sufficient capacity, buf may be returned as the coefficient with
+	// the value set and length set as appropriate.
+	Decompose(buf []byte) (form byte, negative bool, coefficient []byte, exponent int32)
+}
+
+type decimalCompose interface {
+	// Compose sets the internal decimal value from parts. If the value cannot be
+	// represented then an error should be returned.
+	Compose(form byte, negative bool, coefficient []byte, exponent int32) error
+}