encoding/json: add Decoder.Buffered accessor to get overread data
Otherwise it's impossible to know how much data from the
json.Decoder's underlying Reader was actually consumed.
The old fix from golang.org/issue/1955 just added docs. This
provides an actual mechanism.
Update #1955
R=golang-dev, adg, rsc
CC=golang-dev
https://golang.org/cl/7181053
diff --git a/src/pkg/encoding/json/stream.go b/src/pkg/encoding/json/stream.go
index 9592467..00f4726 100644
--- a/src/pkg/encoding/json/stream.go
+++ b/src/pkg/encoding/json/stream.go
@@ -5,6 +5,7 @@
package json
import (
+ "bytes"
"errors"
"io"
)
@@ -58,6 +59,12 @@
return err
}
+// Buffered returns a reader of the data remaining in the Decoder's
+// buffer. The reader is valid until the next call to Decode.
+func (dec *Decoder) Buffered() io.Reader {
+ return bytes.NewReader(dec.buf)
+}
+
// readValue reads a JSON value into dec.buf.
// It returns the length of the encoding.
func (dec *Decoder) readValue() (int, error) {
diff --git a/src/pkg/encoding/json/stream_test.go b/src/pkg/encoding/json/stream_test.go
index 4d66f55..07c9e1d 100644
--- a/src/pkg/encoding/json/stream_test.go
+++ b/src/pkg/encoding/json/stream_test.go
@@ -6,8 +6,10 @@
import (
"bytes"
+ "io/ioutil"
"net"
"reflect"
+ "strings"
"testing"
)
@@ -83,6 +85,28 @@
}
}
+func TestDecoderBuffered(t *testing.T) {
+ r := strings.NewReader(`{"Name": "Gopher"} extra `)
+ var m struct {
+ Name string
+ }
+ d := NewDecoder(r)
+ err := d.Decode(&m)
+ if err != nil {
+ t.Fatal(err)
+ }
+ if m.Name != "Gopher" {
+ t.Errorf("Name = %q; want Gopher", m.Name)
+ }
+ rest, err := ioutil.ReadAll(d.Buffered())
+ if err != nil {
+ t.Fatal(err)
+ }
+ if g, w := string(rest), " extra "; g != w {
+ t.Errorf("Remaining = %q; want %q", g, w)
+ }
+}
+
func nlines(s string, n int) string {
if n <= 0 {
return ""
