Fix algorithm of struct field detection

decode_compile.go

@@ -260,6 +260,8 @@ func (d *Decoder) removeConflictFields(fieldMap map[string]*structFieldSet, conf
 				dec:         v.dec,
 				offset:      baseOffset + v.offset,
 				isTaggedKey: v.isTaggedKey,
+				key:         k,
+				keyLen:      int64(len(k)),
 			}
 			fieldMap[k] = fieldSet
 			lower := strings.ToLower(k)
@@ -282,6 +284,8 @@ func (d *Decoder) removeConflictFields(fieldMap map[string]*structFieldSet, conf
 					dec:         v.dec,
 					offset:      baseOffset + v.offset,
 					isTaggedKey: v.isTaggedKey,
+					key:         k,
+					keyLen:      int64(len(k)),
 				}
 				fieldMap[k] = fieldSet
 				lower := strings.ToLower(k)
@@ -345,6 +349,8 @@ func (d *Decoder) compileStruct(typ *rtype, structName, fieldName string) (decod
 								dec:         newAnonymousFieldDecoder(pdec.typ, v.offset, v.dec),
 								offset:      field.Offset,
 								isTaggedKey: v.isTaggedKey,
+								key:         k,
+								keyLen:      int64(len(k)),
 							}
 							fieldMap[k] = fieldSet
 							lower := strings.ToLower(k)
@@ -367,6 +373,8 @@ func (d *Decoder) compileStruct(typ *rtype, structName, fieldName string) (decod
 									dec:         newAnonymousFieldDecoder(pdec.typ, v.offset, v.dec),
 									offset:      field.Offset,
 									isTaggedKey: v.isTaggedKey,
+									key:         k,
+									keyLen:      int64(len(k)),
 								}
 								fieldMap[k] = fieldSet
 								lower := strings.ToLower(k)
@@ -388,19 +396,23 @@ func (d *Decoder) compileStruct(typ *rtype, structName, fieldName string) (decod
 			if tag.isString {
 				dec = newWrappedStringDecoder(dec, structName, field.Name)
 			}
-			fieldSet := &structFieldSet{dec: dec, offset: field.Offset, isTaggedKey: tag.isTaggedKey}
+			var key string
 			if tag.key != "" {
-				fieldMap[tag.key] = fieldSet
+				key = tag.key
-				lower := strings.ToLower(tag.key)
-				if _, exists := fieldMap[lower]; !exists {
-					fieldMap[lower] = fieldSet
-				}
 			} else {
-				fieldMap[field.Name] = fieldSet
+				key = field.Name
-				lower := strings.ToLower(field.Name)
+			}
-				if _, exists := fieldMap[lower]; !exists {
+			fieldSet := &structFieldSet{
-					fieldMap[lower] = fieldSet
+				dec:         dec,
-				}
+				offset:      field.Offset,
+				isTaggedKey: tag.isTaggedKey,
+				key:         key,
+				keyLen:      int64(len(key)),
+			}
+			fieldMap[key] = fieldSet
+			lower := strings.ToLower(key)
+			if _, exists := fieldMap[lower]; !exists {
+				fieldMap[lower] = fieldSet
 			}
 		}
 	}

decode_struct.go

@@ -12,6 +12,8 @@ type structFieldSet struct {
 	dec         decoder
 	offset      uintptr
 	isTaggedKey bool
+	key         string
+	keyLen      int64
 }
 
 type structDecoder struct {
@@ -157,6 +159,7 @@ func decodeKeyByBitmapInt8(d *structDecoder, buf []byte, cursor int64) (int64, *
 			keyIdx := 0
 			bitmap := d.keyBitmapInt8
 			keyBitmapLen := len(bitmap)
+			start := cursor
 			for {
 				c := char(b, cursor)
 				switch c {
@@ -164,7 +167,12 @@ func decodeKeyByBitmapInt8(d *structDecoder, buf []byte, cursor int64) (int64, *
 					x := uint64(curBit & -curBit)
 					fieldSetIndex := bitHashTable[(x*0x03F566ED27179461)>>58]
 					field = d.sortedFieldSets[fieldSetIndex]
+					keyLen := cursor - start
 					cursor++
+					if keyLen < field.keyLen {
+						// early match
+						return cursor, nil, nil
+					}
 					return cursor, field, nil
 				case nul:
 					return 0, nil, errUnexpectedEndOfJSON("string", cursor)
@@ -237,6 +245,7 @@ func decodeKeyByBitmapInt16(d *structDecoder, buf []byte, cursor int64) (int64,
 			keyIdx := 0
 			bitmap := d.keyBitmapInt16
 			keyBitmapLen := len(bitmap)
+			start := cursor
 			for {
 				c := char(b, cursor)
 				switch c {
@@ -244,7 +253,12 @@ func decodeKeyByBitmapInt16(d *structDecoder, buf []byte, cursor int64) (int64,
 					x := uint64(curBit & -curBit)
 					fieldSetIndex := bitHashTable[(x*0x03F566ED27179461)>>58]
 					field = d.sortedFieldSets[fieldSetIndex]
+					keyLen := cursor - start
 					cursor++
+					if keyLen < field.keyLen {
+						// early match
+						return cursor, nil, nil
+					}
 					return cursor, field, nil
 				case nul:
 					return 0, nil, errUnexpectedEndOfJSON("string", cursor)
@@ -341,10 +355,13 @@ func decodeKeyByBitmapInt8Stream(d *structDecoder, s *stream) (*structFieldSet,
 					x := uint64(curBit & -curBit)
 					fieldSetIndex := bitHashTable[(x*0x03F566ED27179461)>>58]
 					field = d.sortedFieldSets[fieldSetIndex]
-					b := s.buf[start:s.cursor]
+					keyLen := s.cursor - start
-					key := *(*string)(unsafe.Pointer(&b))
 					s.cursor++
-					return field, key, nil
+					if keyLen < field.keyLen {
+						// early match
+						return nil, field.key, nil
+					}
+					return field, field.key, nil
 				case nul:
 					if s.read() {
 						continue
@@ -441,10 +458,13 @@ func decodeKeyByBitmapInt16Stream(d *structDecoder, s *stream) (*structFieldSet,
 					x := uint64(curBit & -curBit)
 					fieldSetIndex := bitHashTable[(x*0x03F566ED27179461)>>58]
 					field = d.sortedFieldSets[fieldSetIndex]
-					b := s.buf[start:s.cursor]
+					keyLen := s.cursor - start
-					key := *(*string)(unsafe.Pointer(&b))
 					s.cursor++
-					return field, key, nil
+					if keyLen < field.keyLen {
+						// early match
+						return nil, field.key, nil
+					}
+					return field, field.key, nil
 				case nul:
 					if s.read() {
 						continue