decode: Add DecodeObject and DecodeArray helper methods

1 files changed, 63 insertions, 13 deletions

diff --git a/decode.go b/decode.go
index 98a0e5b..c160192 100644
--- a/decode.go
+++ b/decode.go
@@ -21,12 +21,6 @@ type Decodable interface {
 	DecodeJSON(io.RuneScanner) error
 }
 
-type runeBuffer interface {
-	io.Writer
-	WriteRune(rune) (int, error)
-	Reset()
-}
-
 type decodeStackItem struct {
 	par reflect.Type
 	idx any
@@ -438,7 +432,10 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 			}
 			index := indexStruct(typ)
 			var nameBuf strings.Builder
-			dec.decodeObject(typ, &nameBuf, func() {
+			dec.decodeObject(typ, func() {
+				nameBuf.Reset()
+				dec.decodeString(nil, &nameBuf)
+			}, func() {
 				name := nameBuf.String()
 				dec.stackPush(typ, name)
 				defer dec.stackPop()
@@ -519,7 +516,10 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 					val.Set(reflect.MakeMap(typ))
 				}
 				var nameBuf bytes.Buffer
-				dec.decodeObject(typ, &nameBuf, func() {
+				dec.decodeObject(typ, func() {
+					nameBuf.Reset()
+					dec.decodeString(nil, &nameBuf)
+				}, func() {
 					nameValTyp := typ.Key()
 					nameValPtr := reflect.New(nameValTyp)
 					switch {
@@ -678,7 +678,10 @@ func (dec *Decoder) decodeAny() any {
 		ret := make(map[string]any)
 		typ := reflect.TypeOf(ret)
 		var nameBuf strings.Builder
-		dec.decodeObject(typ, &nameBuf, func() {
+		dec.decodeObject(typ, func() {
+			nameBuf.Reset()
+			dec.decodeString(nil, &nameBuf)
+		}, func() {
 			name := nameBuf.String()
 			dec.stackPush(typ, name)
 			defer dec.stackPop()
@@ -720,7 +723,34 @@ func (dec *Decoder) decodeAny() any {
 	}
 }
 
-func (dec *Decoder) decodeObject(gTyp reflect.Type, nameBuf runeBuffer, decodeKVal func()) {
+// DecodeObject is a helper function for implementing the Decoder interface.
+func DecodeObject(r io.RuneScanner, decodeKey, decodeVal func() error) (err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			if de, ok := r.(decodeError); ok {
+				pub := DecodeError(de)
+				err = &pub
+			} else {
+				panic(r)
+			}
+		}
+	}()
+	dec := NewDecoder(r)
+	dec.decodeObject(nil,
+		func() {
+			if err := decodeKey(); err != nil {
+				dec.panicType("string", nil, err)
+			}
+		},
+		func() {
+			if err := decodeVal(); err != nil {
+				dec.panicType("", nil, err)
+			}
+		})
+	return
+}
+
+func (dec *Decoder) decodeObject(gTyp reflect.Type, decodeKey, decodeVal func()) {
 	dec.expectRuneType('{', RuneTypeObjectBeg, gTyp)
 	_, t := dec.readRune()
 	switch t {
@@ -729,10 +759,9 @@ func (dec *Decoder) decodeObject(gTyp reflect.Type, nameBuf runeBuffer, decodeKV
 	case RuneTypeStringBeg:
 	decodeMember:
 		dec.unreadRune()
-		nameBuf.Reset()
-		dec.decodeString(nil, nameBuf)
+		decodeKey()
 		dec.expectRune(':', RuneTypeObjectColon)
-		decodeKVal()
+		decodeVal()
 		_, t := dec.readRune()
 		switch t {
 		case RuneTypeObjectComma:
@@ -748,6 +777,27 @@ func (dec *Decoder) decodeObject(gTyp reflect.Type, nameBuf runeBuffer, decodeKV
 	}
 }
 
+// DecodeArray is a helper function for implementing the Decoder interface.
+func DecodeArray(r io.RuneScanner, decodeMember func() error) (err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			if de, ok := r.(decodeError); ok {
+				pub := DecodeError(de)
+				err = &pub
+			} else {
+				panic(r)
+			}
+		}
+	}()
+	dec := NewDecoder(r)
+	dec.decodeArray(nil, func() {
+		if err := decodeMember(); err != nil {
+			dec.panicType("array", nil, err)
+		}
+	})
+	return
+}
+
 func (dec *Decoder) decodeArray(gTyp reflect.Type, decodeMember func()) {
 	dec.expectRuneType('[', RuneTypeArrayBeg, gTyp)
 	_, t := dec.readRune()