encoding/json: fix and optimize marshal for quoted string

Since Go 1.2 every string can be marshaled to JSON without error even if it contains invalid UTF-8 byte sequences. Therefore there is no need to use Marshal again for the only reason of enclosing the string in double quotes. Not using Marshal here also removes the error check as there has not been a way for Marshal to fail anyway. name old time/op new time/op delta Issue34127-4 360ns ± 3% 200ns ± 3% -44.56% (p=0.008 n=5+5) name old alloc/op new alloc/op delta Issue34127-4 56.0B ± 0% 40.0B ± 0% -28.57% (p=0.008 n=5+5) name old allocs/op new allocs/op delta Issue34127-4 3.00 ± 0% 2.00 ± 0% -33.33% (p=0.008 n=5+5) Fixes #34154 Change-Id: Ib60dc11980f9b20d8bef2982de7168943d632263 GitHub-Last-Rev: 9b0ac1d4c5318b6bf9ed7930320f2bd755f9939c GitHub-Pull-Request: golang/go#34127 Reviewed-on: https://go-review.googlesource.com/c/go/+/193604 Reviewed-by: Daniel Martí <[email protected]> Run-TryBot: Daniel Martí <[email protected]> TryBot-Result: Gobot Gobot <[email protected]>
e-nikolov · Sep 11, 2019 · c3bfbe7 · c3bfbe7
1 parent 56765a6
commit c3bfbe7
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Showing 3 changed files with 31 additions and 5 deletions.
diff --git a/json/bench_test.go b/json/bench_test.go
@@ -297,6 +297,22 @@ func BenchmarkIssue10335(b *testing.B) {
 	})
 }
 
+func BenchmarkIssue34127(b *testing.B) {
+	b.ReportAllocs()
+	j := struct {
+		Bar string `json:"bar,string"`
+	}{
+		Bar: `foobar`,
+	}
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			if _, err := Marshal(&j); err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+}
+
 func BenchmarkUnmapped(b *testing.B) {
 	b.ReportAllocs()
 	j := []byte(`{"s": "hello", "y": 2, "o": {"x": 0}, "a": [1, 99, {"x": 1}]}`)

diff --git a/json/encode.go b/json/encode.go
@@ -600,11 +600,11 @@ func stringEncoder(e *encodeState, v reflect.Value, opts encOpts) {
 		return
 	}
 	if opts.quoted {
-		sb, err := Marshal(v.String())
-		if err != nil {
-			e.error(err)
-		}
-		e.string(string(sb), opts.escapeHTML)
+		b := make([]byte, 0, v.Len()+2)
+		b = append(b, '"')
+		b = append(b, []byte(v.String())...)
+		b = append(b, '"')
+		e.stringBytes(b, opts.escapeHTML)
 	} else {
 		e.string(v.String(), opts.escapeHTML)
 	}

diff --git a/json/stream_test.go b/json/stream_test.go
@@ -118,6 +118,11 @@ func TestEncoderSetEscapeHTML(t *testing.T) {
 		Ptr    strPtrMarshaler
 	}{`"<str>"`, `"<str>"`}
 
+	// https://golang.org/issue/34154
+	stringOption := struct {
+		Bar string `json:"bar,string"`
+	}{`<html>foobar</html>`}
+
 	for _, tt := range []struct {
 		name       string
 		v          interface{}
@@ -137,6 +142,11 @@ func TestEncoderSetEscapeHTML(t *testing.T) {
 			`{"NonPtr":"\u003cstr\u003e","Ptr":"\u003cstr\u003e"}`,
 			`{"NonPtr":"<str>","Ptr":"<str>"}`,
 		},
+		{
+			"stringOption", stringOption,
+			`{"bar":"\"\u003chtml\u003efoobar\u003c/html\u003e\""}`,
+			`{"bar":"\"<html>foobar</html>\""}`,
+		},
 	} {
 		var buf bytes.Buffer
 		enc := NewEncoder(&buf)