math/big: implement Float.Text(Un)Marshaler

Fixes #12256.

Change-Id: Ie4a3337996da5c060b27530b076048ffead85f3b
Reviewed-on: https://go-review.googlesource.com/15040
Reviewed-by: Alan Donovan <adonovan@google.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/src/math/big/floatmarsh.go b/src/math/big/floatmarsh.go
new file mode 100644
index 0000000000..44987ee03a
--- /dev/null
+++ b/src/math/big/floatmarsh.go
@@ -0,0 +1,33 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements encoding/decoding of Floats.
+
+package big
+
+import "fmt"
+
+// MarshalText implements the encoding.TextMarshaler interface.
+// Only the Float value is marshaled (in full precision), other
+// attributes such as precision or accuracy are ignored.
+func (x *Float) MarshalText() (text []byte, err error) {
+	if x == nil {
+		return []byte("<nil>"), nil
+	}
+	var buf []byte
+	return x.Append(buf, 'g', -1), nil
+}
+
+// UnmarshalText implements the encoding.TextUnmarshaler interface.
+// The result is rounded per the precision and rounding mode of z.
+// If z's precision is 0, it is changed to 64 before rounding takes
+// effect.
+func (z *Float) UnmarshalText(text []byte) error {
+	// TODO(gri): get rid of the []byte/string conversion
+	_, _, err := z.Parse(string(text), 0)
+	if err != nil {
+		err = fmt.Errorf("math/big: cannot unmarshal %q into a *big.Float (%v)", text, err)
+	}
+	return err
+}