Avoid doing type switching in inner functions

The CPU profiler tells me that the encoder is spending a lot of time on
type switches.

1 files changed, 20 insertions, 20 deletions

diff --git a/decode.go b/decode.go
index 7ae723c..91be865 100644
--- a/decode.go
+++ b/decode.go
@@ -565,7 +565,7 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 					if dec.disallowUnknownFields {
 						dec.panicType("", typ, fmt.Errorf("json: unknown field %q", name))
 					}
-					dec.scan(io.Discard)
+					dec.scan(internal.Discard)
 					return
 				}
 				field := index.byPos[idx]
@@ -749,7 +749,7 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 					dec.decode(mValPtr.Elem(), false)
 					val.Index(i).Set(mValPtr.Elem())
 				} else {
-					dec.scan(io.Discard)
+					dec.scan(internal.Discard)
 				}
 				i++
 			})
@@ -773,18 +773,18 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 	}
 }
 
-func (dec *Decoder) scan(out io.Writer) {
+func (dec *Decoder) scan(out internal.RuneWriter) {
 	limiter := dec.limitingScanner()
 	for {
 		c, _, err := limiter.ReadRune()
 		if err == io.EOF {
 			return
 		}
-		_, _ = writeRune(out, c)
+		_, _ = out.WriteRune(c)
 	}
 }
 
-func (dec *Decoder) scanNumber(gTyp reflect.Type, out io.Writer) {
+func (dec *Decoder) scanNumber(gTyp reflect.Type, out internal.RuneWriter) {
 	if t := dec.peekRuneType(); !t.IsNumber() {
 		dec.panicType(t.JSONType(), gTyp, nil)
 	}
@@ -991,34 +991,34 @@ func (dec *Decoder) decodeArray(gTyp reflect.Type, decodeMember func()) {
 	}
 }
 
-func (dec *Decoder) decodeString(gTyp reflect.Type, out io.Writer) {
+func (dec *Decoder) decodeString(gTyp reflect.Type, out internal.RuneWriter) {
 	dec.expectRuneType('"', internal.RuneTypeStringBeg, gTyp)
 	var uhex [4]byte
 	for {
 		c, t := dec.readRune()
 		switch t {
 		case internal.RuneTypeStringChar:
-			_, _ = writeRune(out, c)
+			_, _ = out.WriteRune(c)
 		case internal.RuneTypeStringEsc, internal.RuneTypeStringEscU:
 			// do nothing
 		case internal.RuneTypeStringEsc1:
 			switch c {
 			case '"':
-				_, _ = writeRune(out, '"')
+				_, _ = out.WriteRune('"')
 			case '\\':
-				_, _ = writeRune(out, '\\')
+				_, _ = out.WriteRune('\\')
 			case '/':
-				_, _ = writeRune(out, '/')
+				_, _ = out.WriteRune('/')
 			case 'b':
-				_, _ = writeRune(out, '\b')
+				_, _ = out.WriteRune('\b')
 			case 'f':
-				_, _ = writeRune(out, '\f')
+				_, _ = out.WriteRune('\f')
 			case 'n':
-				_, _ = writeRune(out, '\n')
+				_, _ = out.WriteRune('\n')
 			case 'r':
-				_, _ = writeRune(out, '\r')
+				_, _ = out.WriteRune('\r')
 			case 't':
-				_, _ = writeRune(out, '\t')
+				_, _ = out.WriteRune('\t')
 			default:
 				panic("should not happen")
 			}
@@ -1038,12 +1038,12 @@ func (dec *Decoder) decodeString(gTyp reflect.Type, out io.Writer) {
 		handleUnicode:
 			if utf16.IsSurrogate(c) {
 				if dec.peekRuneType() != internal.RuneTypeStringEsc {
-					_, _ = writeRune(out, utf8.RuneError)
+					_, _ = out.WriteRune(utf8.RuneError)
 					break
 				}
 				dec.expectRune('\\', internal.RuneTypeStringEsc)
 				if dec.peekRuneType() != internal.RuneTypeStringEscU {
-					_, _ = writeRune(out, utf8.RuneError)
+					_, _ = out.WriteRune(utf8.RuneError)
 					break
 				}
 				dec.expectRune('u', internal.RuneTypeStringEscU)
@@ -1063,13 +1063,13 @@ func (dec *Decoder) decodeString(gTyp reflect.Type, out io.Writer) {
 					rune(uhex[3])<<0
 				d := utf16.DecodeRune(c, c2)
 				if d == utf8.RuneError {
-					_, _ = writeRune(out, utf8.RuneError)
+					_, _ = out.WriteRune(utf8.RuneError)
 					c = c2
 					goto handleUnicode
 				}
-				_, _ = writeRune(out, d)
+				_, _ = out.WriteRune(d)
 			} else {
-				_, _ = writeRune(out, c)
+				_, _ = out.WriteRune(c)
 			}
 		case internal.RuneTypeStringEnd:
 			return