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

Fixes #12256.

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

src/math/big/floatmarsh.go

+// 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
+}

src/math/big/floatmarsh_test.go

+// 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.
+
+package big
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+var floatVals = []string{
+	"0",
+	"1",
+	"0.1",
+	"2.71828",
+	"1234567890",
+	"3.14e1234",
+	"3.14e-1234",
+	"0.738957395793475734757349579759957975985497e100",
+	"0.73895739579347546656564656573475734957975995797598589749859834759476745986795497e100",
+	"inf",
+	"Inf",
+}
+
+func TestFloatJSONEncoding(t *testing.T) {
+	for _, test := range floatVals {
+		for _, sign := range []string{"", "+", "-"} {
+			for _, prec := range []uint{0, 1, 2, 10, 53, 64, 100, 1000} {
+				x := sign + test
+				var tx Float
+				_, _, err := tx.SetPrec(prec).Parse(x, 0)
+				if err != nil {
+					t.Errorf("parsing of %s (prec = %d) failed (invalid test case): %v", x, prec, err)
+					continue
+				}
+				b, err := json.Marshal(&tx)
+				if err != nil {
+					t.Errorf("marshaling of %v (prec = %d) failed: %v", &tx, prec, err)
+					continue
+				}
+				var rx Float
+				rx.SetPrec(prec)
+				if err := json.Unmarshal(b, &rx); err != nil {
+					t.Errorf("unmarshaling of %v (prec = %d) failed: %v", &tx, prec, err)
+					continue
+				}
+				if rx.Cmp(&tx) != 0 {
+					t.Errorf("JSON encoding of %v (prec = %d) failed: got %v want %v", &tx, prec, &rx, &tx)
+				}
+			}
+		}
+	}
+}

src/math/big/intmarsh.go

@@ -42,23 +42,6 @@ func (z *Int) GobDecode(buf []byte) error {
 	return nil
 }
 
-// MarshalJSON implements the json.Marshaler interface.
-func (x *Int) MarshalJSON() ([]byte, error) {
-	if x == nil {
-		return []byte("<nil>"), nil
-	}
-	return x.abs.itoa(x.neg, 10), nil
-}
-
-// UnmarshalJSON implements the json.Unmarshaler interface.
-func (z *Int) UnmarshalJSON(text []byte) error {
-	// TODO(gri): get rid of the []byte/string conversion
-	if _, ok := z.SetString(string(text), 0); !ok {
-		return fmt.Errorf("math/big: cannot unmarshal %q into a *big.Int", text)
-	}
-	return nil
-}
-
 // MarshalText implements the encoding.TextMarshaler interface.
 func (x *Int) MarshalText() (text []byte, err error) {
 	if x == nil {
@@ -75,3 +58,13 @@ func (z *Int) UnmarshalText(text []byte) error {
 	}
 	return nil
 }
+
+// MarshalJSON implements the json.Marshaler interface.
+func (x *Int) MarshalJSON() ([]byte, error) {
+	return x.MarshalText()
+}
+
+// UnmarshalJSON implements the json.Unmarshaler interface.
+func (z *Int) UnmarshalJSON(text []byte) error {
+	return z.UnmarshalText(text)
+}

src/math/big/intmarsh_test.go

@@ -37,10 +37,12 @@ func TestIntGobEncoding(t *testing.T) {
 		tx.SetString(test, 10)
 		if err := enc.Encode(&tx); err != nil {
 			t.Errorf("encoding of %s failed: %s", &tx, err)
+			continue
 		}
 		var rx Int
 		if err := dec.Decode(&rx); err != nil {
 			t.Errorf("decoding of %s failed: %s", &tx, err)
+			continue
 		}
 		if rx.Cmp(&tx) != 0 {
 			t.Errorf("transmission of %s failed: got %s want %s", &tx, &rx, &tx)
@@ -70,7 +72,7 @@ func TestGobEncodingNilIntInSlice(t *testing.T) {
 	}
 	var zero Int
 	if out[0].Cmp(&zero) != 0 {
-		t.Errorf("transmission of (*Int)(nill) failed: got %s want 0", out)
+		t.Fatalf("transmission of (*Int)(nil) failed: got %s want 0", out)
 	}
 }
 
@@ -81,10 +83,12 @@ func TestIntJSONEncoding(t *testing.T) {
 		b, err := json.Marshal(&tx)
 		if err != nil {
 			t.Errorf("marshaling of %s failed: %s", &tx, err)
+			continue
 		}
 		var rx Int
 		if err := json.Unmarshal(b, &rx); err != nil {
 			t.Errorf("unmarshaling of %s failed: %s", &tx, err)
+			continue
 		}
 		if rx.Cmp(&tx) != 0 {
 			t.Errorf("JSON encoding of %s failed: got %s want %s", &tx, &rx, &tx)

src/math/big/ratmarsh.go

@@ -58,15 +58,15 @@ func (z *Rat) GobDecode(buf []byte) error {
 }
 
 // MarshalText implements the encoding.TextMarshaler interface.
-func (r *Rat) MarshalText() (text []byte, err error) {
+func (x *Rat) MarshalText() (text []byte, err error) {
 	// TODO(gri): get rid of the []byte/string conversion
-	return []byte(r.RatString()), nil
+	return []byte(x.RatString()), nil
 }
 
 // UnmarshalText implements the encoding.TextUnmarshaler interface.
-func (r *Rat) UnmarshalText(text []byte) error {
+func (z *Rat) UnmarshalText(text []byte) error {
 	// TODO(gri): get rid of the []byte/string conversion
-	if _, ok := r.SetString(string(text)); !ok {
+	if _, ok := z.SetString(string(text)); !ok {
 		return fmt.Errorf("math/big: cannot unmarshal %q into a *big.Rat", text)
 	}
 	return nil

src/math/big/ratmarsh_test.go

@@ -22,10 +22,12 @@ func TestRatGobEncoding(t *testing.T) {
 		tx.SetString(test + ".14159265")
 		if err := enc.Encode(&tx); err != nil {
 			t.Errorf("encoding of %s failed: %s", &tx, err)
+			continue
 		}
 		var rx Rat
 		if err := dec.Decode(&rx); err != nil {
 			t.Errorf("decoding of %s failed: %s", &tx, err)
+			continue
 		}
 		if rx.Cmp(&tx) != 0 {
 			t.Errorf("transmission of %s failed: got %s want %s", &tx, &rx, &tx)
@@ -55,7 +57,7 @@ func TestGobEncodingNilRatInSlice(t *testing.T) {
 	}
 	var zero Rat
 	if out[0].Cmp(&zero) != 0 {
-		t.Errorf("transmission of (*Int)(nill) failed: got %s want 0", out)
+		t.Fatalf("transmission of (*Int)(nil) failed: got %s want 0", out)
 	}
 }