Support JSON Path

Makefile

@@ -22,7 +22,7 @@ cover-html: cover
 
 .PHONY: lint
 lint: golangci-lint
-	golangci-lint run
+	$(BIN_DIR)/golangci-lint run
 
 golangci-lint: | $(BIN_DIR)
 	@{ \

benchmarks/path_test.go

@@ -0,0 +1,24 @@
+package benchmark
+
+import (
+	"testing"
+
+	gojson "github.com/goccy/go-json"
+)
+
+func Benchmark_Decode_SmallStruct_UnmarshalPath_GoJson(b *testing.B) {
+	path, err := gojson.CreatePath("$.st")
+	if err != nil {
+		b.Fatal(err)
+	}
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		var v int
+		if err := path.Unmarshal(SmallFixture, &v); err != nil {
+			b.Fatal(err)
+		}
+		if v != 1 {
+			b.Fatal("failed to unmarshal path")
+		}
+	}
+}

decode.go

@@ -83,6 +83,34 @@ func unmarshalContext(ctx context.Context, data []byte, v interface{}, optFuncs
 	return validateEndBuf(src, cursor)
 }
 
+var (
+	pathDecoder = decoder.NewPathDecoder()
+)
+
+func extractFromPath(path *Path, data []byte, optFuncs ...DecodeOptionFunc) ([][]byte, error) {
+	src := make([]byte, len(data)+1) // append nul byte to the end
+	copy(src, data)
+
+	ctx := decoder.TakeRuntimeContext()
+	ctx.Buf = src
+	ctx.Option.Flags = 0
+	ctx.Option.Flags |= decoder.PathOption
+	ctx.Option.Path = path.path
+	for _, optFunc := range optFuncs {
+		optFunc(ctx.Option)
+	}
+	paths, cursor, err := pathDecoder.DecodePath(ctx, 0, 0)
+	if err != nil {
+		decoder.ReleaseRuntimeContext(ctx)
+		return nil, err
+	}
+	decoder.ReleaseRuntimeContext(ctx)
+	if err := validateEndBuf(src, cursor); err != nil {
+		return nil, err
+	}
+	return paths, nil
+}
+
 func unmarshalNoEscape(data []byte, v interface{}, optFuncs ...DecodeOptionFunc) error {
 	src := make([]byte, len(data)+1) // append nul byte to the end
 	copy(src, data)

error.go

@@ -37,3 +37,5 @@ type UnmarshalTypeError = errors.UnmarshalTypeError
 type UnsupportedTypeError = errors.UnsupportedTypeError
 
 type UnsupportedValueError = errors.UnsupportedValueError
+
+type PathError = errors.PathError

internal/decoder/anonymous_field.go

@@ -35,3 +35,7 @@ func (d *anonymousFieldDecoder) Decode(ctx *RuntimeContext, cursor, depth int64,
 	p = *(*unsafe.Pointer)(p)
 	return d.dec.Decode(ctx, cursor, depth, unsafe.Pointer(uintptr(p)+d.offset))
 }
+
+func (d *anonymousFieldDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	return d.dec.DecodePath(ctx, cursor, depth)
+}

internal/decoder/array.go

@@ -1,6 +1,7 @@
 package decoder
 
 import (
+	"fmt"
 	"unsafe"
 
 	"github.com/goccy/go-json/internal/errors"
@@ -167,3 +168,7 @@ func (d *arrayDecoder) Decode(ctx *RuntimeContext, cursor, depth int64, p unsafe
 		}
 	}
 }
+
+func (d *arrayDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	return nil, 0, fmt.Errorf("json: array decoder does not support decode path")
+}

internal/decoder/assign.go

@@ -0,0 +1,438 @@
+package decoder
+
+import (
+	"fmt"
+	"reflect"
+	"strconv"
+)
+
+var (
+	nilValue = reflect.ValueOf(nil)
+)
+
+func AssignValue(src, dst reflect.Value) error {
+	if dst.Type().Kind() != reflect.Ptr {
+		return fmt.Errorf("invalid dst type. required pointer type: %T", dst.Type())
+	}
+	casted, err := castValue(dst.Elem().Type(), src)
+	if err != nil {
+		return err
+	}
+	dst.Elem().Set(casted)
+	return nil
+}
+
+func castValue(t reflect.Type, v reflect.Value) (reflect.Value, error) {
+	switch t.Kind() {
+	case reflect.Int:
+		vv, err := castInt(v)
+		if err != nil {
+			return nilValue, err
+		}
+		return reflect.ValueOf(int(vv.Int())), nil
+	case reflect.Int8:
+		vv, err := castInt(v)
+		if err != nil {
+			return nilValue, err
+		}
+		return reflect.ValueOf(int8(vv.Int())), nil
+	case reflect.Int16:
+		vv, err := castInt(v)
+		if err != nil {
+			return nilValue, err
+		}
+		return reflect.ValueOf(int16(vv.Int())), nil
+	case reflect.Int32:
+		vv, err := castInt(v)
+		if err != nil {
+			return nilValue, err
+		}
+		return reflect.ValueOf(int32(vv.Int())), nil
+	case reflect.Int64:
+		return castInt(v)
+	case reflect.Uint:
+		vv, err := castUint(v)
+		if err != nil {
+			return nilValue, err
+		}
+		return reflect.ValueOf(uint(vv.Uint())), nil
+	case reflect.Uint8:
+		vv, err := castUint(v)
+		if err != nil {
+			return nilValue, err
+		}
+		return reflect.ValueOf(uint8(vv.Uint())), nil
+	case reflect.Uint16:
+		vv, err := castUint(v)
+		if err != nil {
+			return nilValue, err
+		}
+		return reflect.ValueOf(uint16(vv.Uint())), nil
+	case reflect.Uint32:
+		vv, err := castUint(v)
+		if err != nil {
+			return nilValue, err
+		}
+		return reflect.ValueOf(uint32(vv.Uint())), nil
+	case reflect.Uint64:
+		return castUint(v)
+	case reflect.Uintptr:
+		vv, err := castUint(v)
+		if err != nil {
+			return nilValue, err
+		}
+		return reflect.ValueOf(uintptr(vv.Uint())), nil
+	case reflect.String:
+		return castString(v)
+	case reflect.Bool:
+		return castBool(v)
+	case reflect.Float32:
+		vv, err := castFloat(v)
+		if err != nil {
+			return nilValue, err
+		}
+		return reflect.ValueOf(float32(vv.Float())), nil
+	case reflect.Float64:
+		return castFloat(v)
+	case reflect.Array:
+		return castArray(t, v)
+	case reflect.Slice:
+		return castSlice(t, v)
+	case reflect.Map:
+		return castMap(t, v)
+	case reflect.Struct:
+		return castStruct(t, v)
+	}
+	return v, nil
+}
+
+func castInt(v reflect.Value) (reflect.Value, error) {
+	switch v.Type().Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return v, nil
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return reflect.ValueOf(int64(v.Uint())), nil
+	case reflect.String:
+		i64, err := strconv.ParseInt(v.String(), 10, 64)
+		if err != nil {
+			return nilValue, err
+		}
+		return reflect.ValueOf(i64), nil
+	case reflect.Bool:
+		if v.Bool() {
+			return reflect.ValueOf(int64(1)), nil
+		}
+		return reflect.ValueOf(int64(0)), nil
+	case reflect.Float32, reflect.Float64:
+		return reflect.ValueOf(int64(v.Float())), nil
+	case reflect.Array:
+		if v.Len() > 0 {
+			return castInt(v.Index(0))
+		}
+		return nilValue, fmt.Errorf("failed to cast to int64 from empty array")
+	case reflect.Slice:
+		if v.Len() > 0 {
+			return castInt(v.Index(0))
+		}
+		return nilValue, fmt.Errorf("failed to cast to int64 from empty slice")
+	case reflect.Interface:
+		return castInt(reflect.ValueOf(v.Interface()))
+	case reflect.Map:
+		return nilValue, fmt.Errorf("failed to cast to int64 from map")
+	case reflect.Struct:
+		return nilValue, fmt.Errorf("failed to cast to int64 from struct")
+	case reflect.Ptr:
+		return castInt(v.Elem())
+	}
+	return nilValue, fmt.Errorf("failed to cast to int64 from %s", v.Type().Kind())
+}
+
+func castUint(v reflect.Value) (reflect.Value, error) {
+	switch v.Type().Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return reflect.ValueOf(uint64(v.Int())), nil
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return v, nil
+	case reflect.String:
+		u64, err := strconv.ParseUint(v.String(), 10, 64)
+		if err != nil {
+			return nilValue, err
+		}
+		return reflect.ValueOf(u64), nil
+	case reflect.Bool:
+		if v.Bool() {
+			return reflect.ValueOf(uint64(1)), nil
+		}
+		return reflect.ValueOf(uint64(0)), nil
+	case reflect.Float32, reflect.Float64:
+		return reflect.ValueOf(uint64(v.Float())), nil
+	case reflect.Array:
+		if v.Len() > 0 {
+			return castUint(v.Index(0))
+		}
+		return nilValue, fmt.Errorf("failed to cast to uint64 from empty array")
+	case reflect.Slice:
+		if v.Len() > 0 {
+			return castUint(v.Index(0))
+		}
+		return nilValue, fmt.Errorf("failed to cast to uint64 from empty slice")
+	case reflect.Interface:
+		return castUint(reflect.ValueOf(v.Interface()))
+	case reflect.Map:
+		return nilValue, fmt.Errorf("failed to cast to uint64 from map")
+	case reflect.Struct:
+		return nilValue, fmt.Errorf("failed to cast to uint64 from struct")
+	case reflect.Ptr:
+		return castUint(v.Elem())
+	}
+	return nilValue, fmt.Errorf("failed to cast to uint64 from %s", v.Type().Kind())
+}
+
+func castString(v reflect.Value) (reflect.Value, error) {
+	switch v.Type().Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return reflect.ValueOf(fmt.Sprint(v.Int())), nil
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return reflect.ValueOf(fmt.Sprint(v.Uint())), nil
+	case reflect.String:
+		return v, nil
+	case reflect.Bool:
+		if v.Bool() {
+			return reflect.ValueOf("true"), nil
+		}
+		return reflect.ValueOf("false"), nil
+	case reflect.Float32, reflect.Float64:
+		return reflect.ValueOf(fmt.Sprint(v.Float())), nil
+	case reflect.Array:
+		if v.Len() > 0 {
+			return castString(v.Index(0))
+		}
+		return nilValue, fmt.Errorf("failed to cast to string from empty array")
+	case reflect.Slice:
+		if v.Len() > 0 {
+			return castString(v.Index(0))
+		}
+		return nilValue, fmt.Errorf("failed to cast to string from empty slice")
+	case reflect.Interface:
+		return castString(reflect.ValueOf(v.Interface()))
+	case reflect.Map:
+		return nilValue, fmt.Errorf("failed to cast to string from map")
+	case reflect.Struct:
+		return nilValue, fmt.Errorf("failed to cast to string from struct")
+	case reflect.Ptr:
+		return castString(v.Elem())
+	}
+	return nilValue, fmt.Errorf("failed to cast to string from %s", v.Type().Kind())
+}
+
+func castBool(v reflect.Value) (reflect.Value, error) {
+	switch v.Type().Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		switch v.Int() {
+		case 0:
+			return reflect.ValueOf(false), nil
+		case 1:
+			return reflect.ValueOf(true), nil
+		}
+		return nilValue, fmt.Errorf("failed to cast to bool from %d", v.Int())
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		switch v.Uint() {
+		case 0:
+			return reflect.ValueOf(false), nil
+		case 1:
+			return reflect.ValueOf(true), nil
+		}
+		return nilValue, fmt.Errorf("failed to cast to bool from %d", v.Uint())
+	case reflect.String:
+		b, err := strconv.ParseBool(v.String())
+		if err != nil {
+			return nilValue, err
+		}
+		return reflect.ValueOf(b), nil
+	case reflect.Bool:
+		return v, nil
+	case reflect.Float32, reflect.Float64:
+		switch v.Float() {
+		case 0:
+			return reflect.ValueOf(false), nil
+		case 1:
+			return reflect.ValueOf(true), nil
+		}
+		return nilValue, fmt.Errorf("failed to cast to bool from %f", v.Float())
+	case reflect.Array:
+		if v.Len() > 0 {
+			return castBool(v.Index(0))
+		}
+		return nilValue, fmt.Errorf("failed to cast to string from empty array")
+	case reflect.Slice:
+		if v.Len() > 0 {
+			return castBool(v.Index(0))
+		}
+		return nilValue, fmt.Errorf("failed to cast to string from empty slice")
+	case reflect.Interface:
+		return castBool(reflect.ValueOf(v.Interface()))
+	case reflect.Map:
+		return nilValue, fmt.Errorf("failed to cast to string from map")
+	case reflect.Struct:
+		return nilValue, fmt.Errorf("failed to cast to string from struct")
+	case reflect.Ptr:
+		return castBool(v.Elem())
+	}
+	return nilValue, fmt.Errorf("failed to cast to bool from %s", v.Type().Kind())
+}
+
+func castFloat(v reflect.Value) (reflect.Value, error) {
+	switch v.Type().Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return reflect.ValueOf(float64(v.Int())), nil
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return reflect.ValueOf(float64(v.Uint())), nil
+	case reflect.String:
+		f64, err := strconv.ParseFloat(v.String(), 64)
+		if err != nil {
+			return nilValue, err
+		}
+		return reflect.ValueOf(f64), nil
+	case reflect.Bool:
+		if v.Bool() {
+			return reflect.ValueOf(float64(1)), nil
+		}
+		return reflect.ValueOf(float64(0)), nil
+	case reflect.Float32, reflect.Float64:
+		return v, nil
+	case reflect.Array:
+		if v.Len() > 0 {
+			return castFloat(v.Index(0))
+		}
+		return nilValue, fmt.Errorf("failed to cast to float64 from empty array")
+	case reflect.Slice:
+		if v.Len() > 0 {
+			return castFloat(v.Index(0))
+		}
+		return nilValue, fmt.Errorf("failed to cast to float64 from empty slice")
+	case reflect.Interface:
+		return castFloat(reflect.ValueOf(v.Interface()))
+	case reflect.Map:
+		return nilValue, fmt.Errorf("failed to cast to float64 from map")
+	case reflect.Struct:
+		return nilValue, fmt.Errorf("failed to cast to float64 from struct")
+	case reflect.Ptr:
+		return castFloat(v.Elem())
+	}
+	return nilValue, fmt.Errorf("failed to cast to float64 from %s", v.Type().Kind())
+}
+
+func castArray(t reflect.Type, v reflect.Value) (reflect.Value, error) {
+	kind := v.Type().Kind()
+	if kind == reflect.Interface {
+		return castArray(t, reflect.ValueOf(v.Interface()))
+	}
+	if kind != reflect.Slice && kind != reflect.Array {
+		return nilValue, fmt.Errorf("failed to cast to array from %s", kind)
+	}
+	if t.Elem() == v.Type().Elem() {
+		return v, nil
+	}
+	if t.Len() != v.Len() {
+		return nilValue, fmt.Errorf("failed to cast [%d]array from slice of %d length", t.Len(), v.Len())
+	}
+	ret := reflect.New(t).Elem()
+	for i := 0; i < v.Len(); i++ {
+		vv, err := castValue(t.Elem(), v.Index(i))
+		if err != nil {
+			return nilValue, err
+		}
+		ret.Index(i).Set(vv)
+	}
+	return ret, nil
+}
+
+func castSlice(t reflect.Type, v reflect.Value) (reflect.Value, error) {
+	kind := v.Type().Kind()
+	if kind == reflect.Interface {
+		return castSlice(t, reflect.ValueOf(v.Interface()))
+	}
+	if kind != reflect.Slice && kind != reflect.Array {
+		return nilValue, fmt.Errorf("failed to cast to slice from %s", kind)
+	}
+	if t.Elem() == v.Type().Elem() {
+		return v, nil
+	}
+	ret := reflect.MakeSlice(t, v.Len(), v.Len())
+	for i := 0; i < v.Len(); i++ {
+		vv, err := castValue(t.Elem(), v.Index(i))
+		if err != nil {
+			return nilValue, err
+		}
+		ret.Index(i).Set(vv)
+	}
+	return ret, nil
+}
+
+func castMap(t reflect.Type, v reflect.Value) (reflect.Value, error) {
+	ret := reflect.MakeMap(t)
+	switch v.Type().Kind() {
+	case reflect.Map:
+		iter := v.MapRange()
+		for iter.Next() {
+			key, err := castValue(t.Key(), iter.Key())
+			if err != nil {
+				return nilValue, err
+			}
+			value, err := castValue(t.Elem(), iter.Value())
+			if err != nil {
+				return nilValue, err
+			}
+			ret.SetMapIndex(key, value)
+		}
+		return ret, nil
+	case reflect.Interface:
+		return castMap(t, reflect.ValueOf(v.Interface()))
+	case reflect.Slice:
+		if v.Len() > 0 {
+			return castMap(t, v.Index(0))
+		}
+		return nilValue, fmt.Errorf("failed to cast to map from empty slice")
+	}
+	return nilValue, fmt.Errorf("failed to cast to map from %s", v.Type().Kind())
+}
+
+func castStruct(t reflect.Type, v reflect.Value) (reflect.Value, error) {
+	ret := reflect.New(t).Elem()
+	switch v.Type().Kind() {
+	case reflect.Map:
+		iter := v.MapRange()
+		for iter.Next() {
+			key := iter.Key()
+			k, err := castString(key)
+			if err != nil {
+				return nilValue, err
+			}
+			fieldName := k.String()
+			field, ok := t.FieldByName(fieldName)
+			if ok {
+				value, err := castValue(field.Type, iter.Value())
+				if err != nil {
+					return nilValue, err
+				}
+				ret.FieldByName(fieldName).Set(value)
+			}
+		}
+		return ret, nil
+	case reflect.Struct:
+		for i := 0; i < v.Type().NumField(); i++ {
+			name := v.Type().Field(i).Name
+			ret.FieldByName(name).Set(v.FieldByName(name))
+		}
+		return ret, nil
+	case reflect.Interface:
+		return castStruct(t, reflect.ValueOf(v.Interface()))
+	case reflect.Slice:
+		if v.Len() > 0 {
+			return castStruct(t, v.Index(0))
+		}
+		return nilValue, fmt.Errorf("failed to cast to struct from empty slice")
+	default:
+		return nilValue, fmt.Errorf("failed to cast to struct from %s", v.Type().Kind())
+	}
+}

internal/decoder/bool.go

@@ -1,6 +1,7 @@
 package decoder
 
 import (
+	"fmt"
 	"unsafe"
 
 	"github.com/goccy/go-json/internal/errors"
@@ -76,3 +77,7 @@ func (d *boolDecoder) Decode(ctx *RuntimeContext, cursor, depth int64, p unsafe.
 	}
 	return 0, errors.ErrUnexpectedEndOfJSON("bool", cursor)
 }
+
+func (d *boolDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	return nil, 0, fmt.Errorf("json: bool decoder does not support decode path")
+}

internal/decoder/bytes.go

@@ -2,6 +2,7 @@ package decoder
 
 import (
 	"encoding/base64"
+	"fmt"
 	"unsafe"
 
 	"github.com/goccy/go-json/internal/errors"
@@ -78,6 +79,10 @@ func (d *bytesDecoder) Decode(ctx *RuntimeContext, cursor, depth int64, p unsafe
 	return cursor, nil
 }
 
+func (d *bytesDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	return nil, 0, fmt.Errorf("json: []byte decoder does not support decode path")
+}
+
 func (d *bytesDecoder) decodeStreamBinary(s *Stream, depth int64, p unsafe.Pointer) ([]byte, error) {
 	c := s.skipWhiteSpace()
 	if c == '[' {

internal/decoder/float.go

@@ -156,3 +156,15 @@ func (d *floatDecoder) Decode(ctx *RuntimeContext, cursor, depth int64, p unsafe
 	d.op(p, f64)
 	return cursor, nil
 }
+
+func (d *floatDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	buf := ctx.Buf
+	bytes, c, err := d.decodeByte(buf, cursor)
+	if err != nil {
+		return nil, 0, err
+	}
+	if bytes == nil {
+		return [][]byte{nullbytes}, c, nil
+	}
+	return [][]byte{bytes}, c, nil
+}

internal/decoder/func.go

@@ -2,6 +2,7 @@ package decoder
 
 import (
 	"bytes"
+	"fmt"
 	"unsafe"
 
 	"github.com/goccy/go-json/internal/errors"
@@ -139,3 +140,7 @@ func (d *funcDecoder) Decode(ctx *RuntimeContext, cursor, depth int64, p unsafe.
 	}
 	return cursor, errors.ErrInvalidBeginningOfValue(buf[cursor], cursor)
 }
+
+func (d *funcDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	return nil, 0, fmt.Errorf("json: func decoder does not support decode path")
+}

internal/decoder/int.go

@@ -240,3 +240,7 @@ func (d *intDecoder) Decode(ctx *RuntimeContext, cursor, depth int64, p unsafe.P
 	d.op(p, i64)
 	return cursor, nil
 }
+
+func (d *intDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	return nil, 0, fmt.Errorf("json: int decoder does not support decode path")
+}

internal/decoder/interface.go

@@ -94,6 +94,7 @@ func (d *interfaceDecoder) numDecoder(s *Stream) Decoder {
 
 var (
 	emptyInterfaceType = runtime.Type2RType(reflect.TypeOf((*interface{})(nil)).Elem())
+	EmptyInterfaceType = emptyInterfaceType
 	interfaceMapType   = runtime.Type2RType(
 		reflect.TypeOf((*map[string]interface{})(nil)).Elem(),
 	)
@@ -456,3 +457,72 @@ func (d *interfaceDecoder) decodeEmptyInterface(ctx *RuntimeContext, cursor, dep
 	}
 	return cursor, errors.ErrInvalidBeginningOfValue(buf[cursor], cursor)
 }
+
+func NewPathDecoder() Decoder {
+	ifaceDecoder := &interfaceDecoder{
+		typ:        emptyInterfaceType,
+		structName: "",
+		fieldName:  "",
+		floatDecoder: newFloatDecoder("", "", func(p unsafe.Pointer, v float64) {
+			*(*interface{})(p) = v
+		}),
+		numberDecoder: newNumberDecoder("", "", func(p unsafe.Pointer, v json.Number) {
+			*(*interface{})(p) = v
+		}),
+		stringDecoder: newStringDecoder("", ""),
+	}
+	ifaceDecoder.sliceDecoder = newSliceDecoder(
+		ifaceDecoder,
+		emptyInterfaceType,
+		emptyInterfaceType.Size(),
+		"", "",
+	)
+	ifaceDecoder.mapDecoder = newMapDecoder(
+		interfaceMapType,
+		stringType,
+		ifaceDecoder.stringDecoder,
+		interfaceMapType.Elem(),
+		ifaceDecoder,
+		"", "",
+	)
+	return ifaceDecoder
+}
+
+var (
+	truebytes  = []byte("true")
+	falsebytes = []byte("false")
+)
+
+func (d *interfaceDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	buf := ctx.Buf
+	cursor = skipWhiteSpace(buf, cursor)
+	switch buf[cursor] {
+	case '{':
+		return d.mapDecoder.DecodePath(ctx, cursor, depth)
+	case '[':
+		return d.sliceDecoder.DecodePath(ctx, cursor, depth)
+	case '-', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+		return d.floatDecoder.DecodePath(ctx, cursor, depth)
+	case '"':
+		return d.stringDecoder.DecodePath(ctx, cursor, depth)
+	case 't':
+		if err := validateTrue(buf, cursor); err != nil {
+			return nil, 0, err
+		}
+		cursor += 4
+		return [][]byte{truebytes}, cursor, nil
+	case 'f':
+		if err := validateFalse(buf, cursor); err != nil {
+			return nil, 0, err
+		}
+		cursor += 5
+		return [][]byte{falsebytes}, cursor, nil
+	case 'n':
+		if err := validateNull(buf, cursor); err != nil {
+			return nil, 0, err
+		}
+		cursor += 4
+		return [][]byte{nullbytes}, cursor, nil
+	}
+	return nil, cursor, errors.ErrInvalidBeginningOfValue(buf[cursor], cursor)
+}

internal/decoder/invalid.go

@@ -43,3 +43,13 @@ func (d *invalidDecoder) Decode(ctx *RuntimeContext, cursor, depth int64, p unsa
 		Field:  d.fieldName,
 	}
 }
+
+func (d *invalidDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	return nil, 0, &errors.UnmarshalTypeError{
+		Value:  "object",
+		Type:   runtime.RType2Type(d.typ),
+		Offset: cursor,
+		Struct: d.structName,
+		Field:  d.fieldName,
+	}
+}

internal/decoder/map.go

@@ -185,3 +185,95 @@ func (d *mapDecoder) Decode(ctx *RuntimeContext, cursor, depth int64, p unsafe.P
 		cursor++
 	}
 }
+
+func (d *mapDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	buf := ctx.Buf
+	depth++
+	if depth > maxDecodeNestingDepth {
+		return nil, 0, errors.ErrExceededMaxDepth(buf[cursor], cursor)
+	}
+
+	cursor = skipWhiteSpace(buf, cursor)
+	buflen := int64(len(buf))
+	if buflen < 2 {
+		return nil, 0, errors.ErrExpected("{} for map", cursor)
+	}
+	switch buf[cursor] {
+	case 'n':
+		if err := validateNull(buf, cursor); err != nil {
+			return nil, 0, err
+		}
+		cursor += 4
+		return [][]byte{nullbytes}, cursor, nil
+	case '{':
+	default:
+		return nil, 0, errors.ErrExpected("{ character for map value", cursor)
+	}
+	cursor++
+	cursor = skipWhiteSpace(buf, cursor)
+	if buf[cursor] == '}' {
+		cursor++
+		return nil, cursor, nil
+	}
+	keyDecoder, ok := d.keyDecoder.(*stringDecoder)
+	if !ok {
+		return nil, 0, &errors.UnmarshalTypeError{
+			Value:  "string",
+			Type:   reflect.TypeOf(""),
+			Offset: cursor,
+			Struct: d.structName,
+			Field:  d.fieldName,
+		}
+	}
+	ret := [][]byte{}
+	for {
+		key, keyCursor, err := keyDecoder.decodeByte(buf, cursor)
+		if err != nil {
+			return nil, 0, err
+		}
+		cursor = skipWhiteSpace(buf, keyCursor)
+		if buf[cursor] != ':' {
+			return nil, 0, errors.ErrExpected("colon after object key", cursor)
+		}
+		cursor++
+		child, found, err := ctx.Option.Path.Field(string(key))
+		if err != nil {
+			return nil, 0, err
+		}
+		if found {
+			if child != nil {
+				oldPath := ctx.Option.Path.node
+				ctx.Option.Path.node = child
+				paths, c, err := d.valueDecoder.DecodePath(ctx, cursor, depth)
+				if err != nil {
+					return nil, 0, err
+				}
+				ctx.Option.Path.node = oldPath
+				ret = append(ret, paths...)
+				cursor = c
+			} else {
+				start := cursor
+				end, err := skipValue(buf, cursor, depth)
+				if err != nil {
+					return nil, 0, err
+				}
+				ret = append(ret, buf[start:end])
+				cursor = end
+			}
+		} else {
+			c, err := skipValue(buf, cursor, depth)
+			if err != nil {
+				return nil, 0, err
+			}
+			cursor = skipWhiteSpace(buf, c)
+		}
+		if buf[cursor] == '}' {
+			cursor++
+			return ret, cursor, nil
+		}
+		if buf[cursor] != ',' {
+			return nil, 0, errors.ErrExpected("comma after object value", cursor)
+		}
+		cursor++
+	}
+}

internal/decoder/number.go

@@ -51,6 +51,17 @@ func (d *numberDecoder) Decode(ctx *RuntimeContext, cursor, depth int64, p unsaf
 	return cursor, nil
 }
 
+func (d *numberDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	bytes, c, err := d.decodeByte(ctx.Buf, cursor)
+	if err != nil {
+		return nil, 0, err
+	}
+	if bytes == nil {
+		return [][]byte{nullbytes}, c, nil
+	}
+	return [][]byte{bytes}, c, nil
+}
+
 func (d *numberDecoder) decodeStreamByte(s *Stream) ([]byte, error) {
 	start := s.cursor
 	for {

internal/decoder/option.go

@@ -7,9 +7,11 @@ type OptionFlags uint8
 const (
 	FirstWinOption OptionFlags = 1 << iota
 	ContextOption
+	PathOption
 )
 
 type Option struct {
 	Flags   OptionFlags
 	Context context.Context
+	Path    *Path
 }

internal/decoder/path.go

@@ -0,0 +1,653 @@
+package decoder
+
+import (
+	"fmt"
+	"reflect"
+	"strconv"
+
+	"github.com/goccy/go-json/internal/errors"
+	"github.com/goccy/go-json/internal/runtime"
+)
+
+type PathString string
+
+func (s PathString) Build() (*Path, error) {
+	builder := new(PathBuilder)
+	return builder.Build([]rune(s))
+}
+
+type PathBuilder struct {
+	root                    PathNode
+	node                    PathNode
+	singleQuotePathSelector bool
+	doubleQuotePathSelector bool
+}
+
+func (b *PathBuilder) Build(buf []rune) (*Path, error) {
+	node, err := b.build(buf)
+	if err != nil {
+		return nil, err
+	}
+	return &Path{
+		node:                    node,
+		SingleQuotePathSelector: b.singleQuotePathSelector,
+		DoubleQuotePathSelector: b.doubleQuotePathSelector,
+	}, nil
+}
+
+func (b *PathBuilder) build(buf []rune) (PathNode, error) {
+	if len(buf) == 0 {
+		return nil, errors.ErrEmptyPath()
+	}
+	if buf[0] != '$' {
+		return nil, errors.ErrInvalidPath("JSON Path must start with a $ character")
+	}
+	if len(buf) == 1 {
+		return nil, nil
+	}
+	buf = buf[1:]
+	offset, err := b.buildNext(buf)
+	if err != nil {
+		return nil, err
+	}
+	if len(buf) > offset {
+		return nil, errors.ErrInvalidPath("remain invalid path %q", buf[offset:])
+	}
+	return b.root, nil
+}
+
+func (b *PathBuilder) buildNextCharIfExists(buf []rune, cursor int) (int, error) {
+	if len(buf) > cursor+1 {
+		offset, err := b.buildNext(buf[cursor+1:])
+		if err != nil {
+			return 0, err
+		}
+		return cursor + 1 + offset, nil
+	}
+	return cursor, nil
+}
+
+func (b *PathBuilder) buildNext(buf []rune) (int, error) {
+	switch buf[0] {
+	case '.':
+		if len(buf) == 1 {
+			return 0, errors.ErrInvalidPath("JSON Path ends with dot character")
+		}
+		offset, err := b.buildSelector(buf[1:])
+		if err != nil {
+			return 0, err
+		}
+		return offset + 1, nil
+	case '[':
+		if len(buf) == 1 {
+			return 0, errors.ErrInvalidPath("JSON Path ends with left bracket character")
+		}
+		offset, err := b.buildIndex(buf[1:])
+		if err != nil {
+			return 0, err
+		}
+		return offset + 1, nil
+	default:
+		return 0, errors.ErrInvalidPath("expect dot or left bracket character. but found %c character", buf[0])
+	}
+}
+
+func (b *PathBuilder) buildSelector(buf []rune) (int, error) {
+	switch buf[0] {
+	case '.':
+		if len(buf) == 1 {
+			return 0, errors.ErrInvalidPath("JSON Path ends with double dot character")
+		}
+		offset, err := b.buildPathRecursive(buf[1:])
+		if err != nil {
+			return 0, err
+		}
+		return 1 + offset, nil
+	case '[', ']', '$', '*':
+		return 0, errors.ErrInvalidPath("found invalid path character %c after dot", buf[0])
+	}
+	for cursor := 0; cursor < len(buf); cursor++ {
+		switch buf[cursor] {
+		case '$', '*', ']':
+			return 0, errors.ErrInvalidPath("found %c character in field selector context", buf[cursor])
+		case '.':
+			if cursor+1 >= len(buf) {
+				return 0, errors.ErrInvalidPath("JSON Path ends with dot character")
+			}
+			selector := buf[:cursor]
+			b.addSelectorNode(string(selector))
+			offset, err := b.buildSelector(buf[cursor+1:])
+			if err != nil {
+				return 0, err
+			}
+			return cursor + 1 + offset, nil
+		case '[':
+			if cursor+1 >= len(buf) {
+				return 0, errors.ErrInvalidPath("JSON Path ends with left bracket character")
+			}
+			selector := buf[:cursor]
+			b.addSelectorNode(string(selector))
+			offset, err := b.buildIndex(buf[cursor+1:])
+			if err != nil {
+				return 0, err
+			}
+			return cursor + 1 + offset, nil
+		case '"':
+			if cursor+1 >= len(buf) {
+				return 0, errors.ErrInvalidPath("JSON Path ends with double quote character")
+			}
+			offset, err := b.buildQuoteSelector(buf[cursor+1:], DoubleQuotePathSelector)
+			if err != nil {
+				return 0, err
+			}
+			return cursor + 1 + offset, nil
+		}
+	}
+	b.addSelectorNode(string(buf))
+	return len(buf), nil
+}
+
+func (b *PathBuilder) buildQuoteSelector(buf []rune, sel QuotePathSelector) (int, error) {
+	switch buf[0] {
+	case '[', ']', '$', '.', '*', '\'', '"':
+		return 0, errors.ErrInvalidPath("found invalid path character %c after quote", buf[0])
+	}
+	for cursor := 0; cursor < len(buf); cursor++ {
+		switch buf[cursor] {
+		case '\'':
+			if sel != SingleQuotePathSelector {
+				return 0, errors.ErrInvalidPath("found double quote character in field selector with single quote context")
+			}
+			if len(buf) <= cursor+1 {
+				return 0, errors.ErrInvalidPath("JSON Path ends with single quote character in field selector context")
+			}
+			if buf[cursor+1] != ']' {
+				return 0, errors.ErrInvalidPath("expect right bracket for field selector with single quote but found %c", buf[cursor+1])
+			}
+			selector := buf[:cursor]
+			b.addSelectorNode(string(selector))
+			return b.buildNextCharIfExists(buf, cursor+1)
+		case '"':
+			if sel != DoubleQuotePathSelector {
+				return 0, errors.ErrInvalidPath("found single quote character in field selector with double quote context")
+			}
+			selector := buf[:cursor]
+			b.addSelectorNode(string(selector))
+			return b.buildNextCharIfExists(buf, cursor)
+		}
+	}
+	return 0, errors.ErrInvalidPath("couldn't find quote character in selector quote path context")
+}
+
+func (b *PathBuilder) buildPathRecursive(buf []rune) (int, error) {
+	switch buf[0] {
+	case '.', '[', ']', '$', '*':
+		return 0, errors.ErrInvalidPath("found invalid path character %c after double dot", buf[0])
+	}
+	for cursor := 0; cursor < len(buf); cursor++ {
+		switch buf[cursor] {
+		case '$', '*', ']':
+			return 0, errors.ErrInvalidPath("found %c character in field selector context", buf[cursor])
+		case '.':
+			if cursor+1 >= len(buf) {
+				return 0, errors.ErrInvalidPath("JSON Path ends with dot character")
+			}
+			selector := buf[:cursor]
+			b.addRecursiveNode(string(selector))
+			offset, err := b.buildSelector(buf[cursor+1:])
+			if err != nil {
+				return 0, err
+			}
+			return cursor + 1 + offset, nil
+		case '[':
+			if cursor+1 >= len(buf) {
+				return 0, errors.ErrInvalidPath("JSON Path ends with left bracket character")
+			}
+			selector := buf[:cursor]
+			b.addRecursiveNode(string(selector))
+			offset, err := b.buildIndex(buf[cursor+1:])
+			if err != nil {
+				return 0, err
+			}
+			return cursor + 1 + offset, nil
+		}
+	}
+	b.addRecursiveNode(string(buf))
+	return len(buf), nil
+}
+
+func (b *PathBuilder) buildIndex(buf []rune) (int, error) {
+	switch buf[0] {
+	case '.', '[', ']', '$':
+		return 0, errors.ErrInvalidPath("found invalid path character %c after left bracket", buf[0])
+	case '\'':
+		if len(buf) == 1 {
+			return 0, errors.ErrInvalidPath("JSON Path ends with single quote character")
+		}
+		offset, err := b.buildQuoteSelector(buf[1:], SingleQuotePathSelector)
+		if err != nil {
+			return 0, err
+		}
+		return 1 + offset, nil
+	case '*':
+		if len(buf) == 1 {
+			return 0, errors.ErrInvalidPath("JSON Path ends with star character")
+		}
+		if buf[1] != ']' {
+			return 0, errors.ErrInvalidPath("expect right bracket character for index all path but found %c character", buf[1])
+		}
+		b.addIndexAllNode()
+		offset := len("*]")
+		if len(buf) > 2 {
+			buildOffset, err := b.buildNext(buf[2:])
+			if err != nil {
+				return 0, err
+			}
+			return offset + buildOffset, nil
+		}
+		return offset, nil
+	}
+
+	for cursor := 0; cursor < len(buf); cursor++ {
+		switch buf[cursor] {
+		case ']':
+			index, err := strconv.ParseInt(string(buf[:cursor]), 10, 64)
+			if err != nil {
+				return 0, errors.ErrInvalidPath("%q is unexpected index path", buf[:cursor])
+			}
+			b.addIndexNode(int(index))
+			return b.buildNextCharIfExists(buf, cursor)
+		}
+	}
+	return 0, errors.ErrInvalidPath("couldn't find right bracket character in index path context")
+}
+
+func (b *PathBuilder) addIndexAllNode() {
+	node := newPathIndexAllNode()
+	if b.root == nil {
+		b.root = node
+		b.node = node
+	} else {
+		b.node = b.node.chain(node)
+	}
+}
+
+func (b *PathBuilder) addRecursiveNode(selector string) {
+	node := newPathRecursiveNode(selector)
+	if b.root == nil {
+		b.root = node
+		b.node = node
+	} else {
+		b.node = b.node.chain(node)
+	}
+}
+
+func (b *PathBuilder) addSelectorNode(name string) {
+	node := newPathSelectorNode(name)
+	if b.root == nil {
+		b.root = node
+		b.node = node
+	} else {
+		b.node = b.node.chain(node)
+	}
+}
+
+func (b *PathBuilder) addIndexNode(idx int) {
+	node := newPathIndexNode(idx)
+	if b.root == nil {
+		b.root = node
+		b.node = node
+	} else {
+		b.node = b.node.chain(node)
+	}
+}
+
+type QuotePathSelector int
+
+const (
+	SingleQuotePathSelector QuotePathSelector = 1
+	DoubleQuotePathSelector QuotePathSelector = 2
+)
+
+type Path struct {
+	node                    PathNode
+	SingleQuotePathSelector bool
+	DoubleQuotePathSelector bool
+}
+
+func (p *Path) Field(sel string) (PathNode, bool, error) {
+	return p.node.Field(sel)
+}
+
+func (p *Path) Get(src, dst reflect.Value) error {
+	return p.node.Get(src, dst)
+}
+
+type PathNode interface {
+	fmt.Stringer
+	Index(idx int) (PathNode, bool, error)
+	Field(fieldName string) (PathNode, bool, error)
+	Get(src, dst reflect.Value) error
+	chain(PathNode) PathNode
+	target() bool
+	single() bool
+}
+
+type BasePathNode struct {
+	child PathNode
+}
+
+func (n *BasePathNode) chain(node PathNode) PathNode {
+	n.child = node
+	return node
+}
+
+func (n *BasePathNode) target() bool {
+	return n.child == nil
+}
+
+func (n *BasePathNode) single() bool {
+	return true
+}
+
+type PathSelectorNode struct {
+	*BasePathNode
+	selector string
+}
+
+func newPathSelectorNode(selector string) *PathSelectorNode {
+	return &PathSelectorNode{
+		BasePathNode: &BasePathNode{},
+		selector:     selector,
+	}
+}
+
+func (n *PathSelectorNode) Index(idx int) (PathNode, bool, error) {
+	return nil, false, &errors.PathError{}
+}
+
+func (n *PathSelectorNode) Field(fieldName string) (PathNode, bool, error) {
+	if n.selector == fieldName {
+		return n.child, true, nil
+	}
+	return nil, false, nil
+}
+
+func (n *PathSelectorNode) Get(src, dst reflect.Value) error {
+	switch src.Type().Kind() {
+	case reflect.Map:
+		iter := src.MapRange()
+		for iter.Next() {
+			key, ok := iter.Key().Interface().(string)
+			if !ok {
+				return fmt.Errorf("invalid map key type %T", src.Type().Key())
+			}
+			child, found, err := n.Field(key)
+			if err != nil {
+				return err
+			}
+			if found {
+				if child != nil {
+					return child.Get(iter.Value(), dst)
+				}
+				return AssignValue(iter.Value(), dst)
+			}
+		}
+	case reflect.Struct:
+		typ := src.Type()
+		for i := 0; i < typ.Len(); i++ {
+			tag := runtime.StructTagFromField(typ.Field(i))
+			child, found, err := n.Field(tag.Key)
+			if err != nil {
+				return err
+			}
+			if found {
+				if child != nil {
+					return child.Get(src.Field(i), dst)
+				}
+				return AssignValue(src.Field(i), dst)
+			}
+		}
+	case reflect.Ptr:
+		return n.Get(src.Elem(), dst)
+	case reflect.Interface:
+		return n.Get(reflect.ValueOf(src.Interface()), dst)
+	case reflect.Float64, reflect.String, reflect.Bool:
+		return AssignValue(src, dst)
+	}
+	return fmt.Errorf("failed to get %s value from %s", n.selector, src.Type())
+}
+
+func (n *PathSelectorNode) String() string {
+	s := fmt.Sprintf(".%s", n.selector)
+	if n.child != nil {
+		s += n.child.String()
+	}
+	return s
+}
+
+type PathIndexNode struct {
+	*BasePathNode
+	selector int
+}
+
+func newPathIndexNode(selector int) *PathIndexNode {
+	return &PathIndexNode{
+		BasePathNode: &BasePathNode{},
+		selector:     selector,
+	}
+}
+
+func (n *PathIndexNode) Index(idx int) (PathNode, bool, error) {
+	if n.selector == idx {
+		return n.child, true, nil
+	}
+	return nil, false, nil
+}
+
+func (n *PathIndexNode) Field(fieldName string) (PathNode, bool, error) {
+	return nil, false, &errors.PathError{}
+}
+
+func (n *PathIndexNode) Get(src, dst reflect.Value) error {
+	switch src.Type().Kind() {
+	case reflect.Array, reflect.Slice:
+		if src.Len() > n.selector {
+			if n.child != nil {
+				return n.child.Get(src.Index(n.selector), dst)
+			}
+			return AssignValue(src.Index(n.selector), dst)
+		}
+	case reflect.Ptr:
+		return n.Get(src.Elem(), dst)
+	case reflect.Interface:
+		return n.Get(reflect.ValueOf(src.Interface()), dst)
+	}
+	return fmt.Errorf("failed to get [%d] value from %s", n.selector, src.Type())
+}
+
+func (n *PathIndexNode) String() string {
+	s := fmt.Sprintf("[%d]", n.selector)
+	if n.child != nil {
+		s += n.child.String()
+	}
+	return s
+}
+
+type PathIndexAllNode struct {
+	*BasePathNode
+}
+
+func newPathIndexAllNode() *PathIndexAllNode {
+	return &PathIndexAllNode{
+		BasePathNode: &BasePathNode{},
+	}
+}
+
+func (n *PathIndexAllNode) Index(idx int) (PathNode, bool, error) {
+	return n.child, true, nil
+}
+
+func (n *PathIndexAllNode) Field(fieldName string) (PathNode, bool, error) {
+	return nil, false, &errors.PathError{}
+}
+
+func (n *PathIndexAllNode) Get(src, dst reflect.Value) error {
+	switch src.Type().Kind() {
+	case reflect.Array, reflect.Slice:
+		var arr []interface{}
+		for i := 0; i < src.Len(); i++ {
+			var v interface{}
+			rv := reflect.ValueOf(&v)
+			if n.child != nil {
+				if err := n.child.Get(src.Index(i), rv); err != nil {
+					return err
+				}
+			} else {
+				if err := AssignValue(src.Index(i), rv); err != nil {
+					return err
+				}
+			}
+			arr = append(arr, v)
+		}
+		if err := AssignValue(reflect.ValueOf(arr), dst); err != nil {
+			return err
+		}
+		return nil
+	case reflect.Ptr:
+		return n.Get(src.Elem(), dst)
+	case reflect.Interface:
+		return n.Get(reflect.ValueOf(src.Interface()), dst)
+	}
+	return fmt.Errorf("failed to get all value from %s", src.Type())
+}
+
+func (n *PathIndexAllNode) String() string {
+	s := "[*]"
+	if n.child != nil {
+		s += n.child.String()
+	}
+	return s
+}
+
+type PathRecursiveNode struct {
+	*BasePathNode
+	selector string
+}
+
+func newPathRecursiveNode(selector string) *PathRecursiveNode {
+	node := newPathSelectorNode(selector)
+	return &PathRecursiveNode{
+		BasePathNode: &BasePathNode{
+			child: node,
+		},
+		selector: selector,
+	}
+}
+
+func (n *PathRecursiveNode) Field(fieldName string) (PathNode, bool, error) {
+	if n.selector == fieldName {
+		return n.child, true, nil
+	}
+	return nil, false, nil
+}
+
+func (n *PathRecursiveNode) Index(_ int) (PathNode, bool, error) {
+	return n, true, nil
+}
+
+func valueToSliceValue(v interface{}) []interface{} {
+	rv := reflect.ValueOf(v)
+	ret := []interface{}{}
+	if rv.Type().Kind() == reflect.Slice || rv.Type().Kind() == reflect.Array {
+		for i := 0; i < rv.Len(); i++ {
+			ret = append(ret, rv.Index(i).Interface())
+		}
+		return ret
+	}
+	return []interface{}{v}
+}
+
+func (n *PathRecursiveNode) Get(src, dst reflect.Value) error {
+	if n.child == nil {
+		return fmt.Errorf("failed to get by recursive path ..%s", n.selector)
+	}
+	var arr []interface{}
+	switch src.Type().Kind() {
+	case reflect.Map:
+		iter := src.MapRange()
+		for iter.Next() {
+			key, ok := iter.Key().Interface().(string)
+			if !ok {
+				return fmt.Errorf("invalid map key type %T", src.Type().Key())
+			}
+			child, found, err := n.Field(key)
+			if err != nil {
+				return err
+			}
+			if found {
+				var v interface{}
+				rv := reflect.ValueOf(&v)
+				_ = child.Get(iter.Value(), rv)
+				arr = append(arr, valueToSliceValue(v)...)
+			} else {
+				var v interface{}
+				rv := reflect.ValueOf(&v)
+				_ = n.Get(iter.Value(), rv)
+				if v != nil {
+					arr = append(arr, valueToSliceValue(v)...)
+				}
+			}
+		}
+		_ = AssignValue(reflect.ValueOf(arr), dst)
+		return nil
+	case reflect.Struct:
+		typ := src.Type()
+		for i := 0; i < typ.Len(); i++ {
+			tag := runtime.StructTagFromField(typ.Field(i))
+			child, found, err := n.Field(tag.Key)
+			if err != nil {
+				return err
+			}
+			if found {
+				var v interface{}
+				rv := reflect.ValueOf(&v)
+				_ = child.Get(src.Field(i), rv)
+				arr = append(arr, valueToSliceValue(v)...)
+			} else {
+				var v interface{}
+				rv := reflect.ValueOf(&v)
+				_ = n.Get(src.Field(i), rv)
+				if v != nil {
+					arr = append(arr, valueToSliceValue(v)...)
+				}
+			}
+		}
+		_ = AssignValue(reflect.ValueOf(arr), dst)
+		return nil
+	case reflect.Array, reflect.Slice:
+		for i := 0; i < src.Len(); i++ {
+			var v interface{}
+			rv := reflect.ValueOf(&v)
+			_ = n.Get(src.Index(i), rv)
+			if v != nil {
+				arr = append(arr, valueToSliceValue(v)...)
+			}
+		}
+		_ = AssignValue(reflect.ValueOf(arr), dst)
+		return nil
+	case reflect.Ptr:
+		return n.Get(src.Elem(), dst)
+	case reflect.Interface:
+		return n.Get(reflect.ValueOf(src.Interface()), dst)
+	}
+	return fmt.Errorf("failed to get %s value from %s", n.selector, src.Type())
+}
+
+func (n *PathRecursiveNode) String() string {
+	s := fmt.Sprintf("..%s", n.selector)
+	if n.child != nil {
+		s += n.child.String()
+	}
+	return s
+}

internal/decoder/ptr.go

@@ -1,6 +1,7 @@
 package decoder
 
 import (
+	"fmt"
 	"unsafe"
 
 	"github.com/goccy/go-json/internal/runtime"
@@ -34,6 +35,10 @@ func (d *ptrDecoder) contentDecoder() Decoder {
 //go:linkname unsafe_New reflect.unsafe_New
 func unsafe_New(*runtime.Type) unsafe.Pointer
 
+func UnsafeNew(t *runtime.Type) unsafe.Pointer {
+	return unsafe_New(t)
+}
+
 func (d *ptrDecoder) DecodeStream(s *Stream, depth int64, p unsafe.Pointer) error {
 	if s.skipWhiteSpace() == nul {
 		s.read()
@@ -85,3 +90,7 @@ func (d *ptrDecoder) Decode(ctx *RuntimeContext, cursor, depth int64, p unsafe.P
 	cursor = c
 	return cursor, nil
 }
+
+func (d *ptrDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	return nil, 0, fmt.Errorf("json: ptr decoder does not support decode path")
+}

internal/decoder/slice.go

@@ -299,3 +299,80 @@ func (d *sliceDecoder) Decode(ctx *RuntimeContext, cursor, depth int64, p unsafe
 		}
 	}
 }
+
+func (d *sliceDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	buf := ctx.Buf
+	depth++
+	if depth > maxDecodeNestingDepth {
+		return nil, 0, errors.ErrExceededMaxDepth(buf[cursor], cursor)
+	}
+
+	ret := [][]byte{}
+	for {
+		switch buf[cursor] {
+		case ' ', '\n', '\t', '\r':
+			cursor++
+			continue
+		case 'n':
+			if err := validateNull(buf, cursor); err != nil {
+				return nil, 0, err
+			}
+			cursor += 4
+			return [][]byte{nullbytes}, cursor, nil
+		case '[':
+			cursor++
+			cursor = skipWhiteSpace(buf, cursor)
+			if buf[cursor] == ']' {
+				cursor++
+				return ret, cursor, nil
+			}
+			idx := 0
+			for {
+				child, found, err := ctx.Option.Path.node.Index(idx)
+				if err != nil {
+					return nil, 0, err
+				}
+				if found {
+					if child != nil {
+						oldPath := ctx.Option.Path.node
+						ctx.Option.Path.node = child
+						paths, c, err := d.valueDecoder.DecodePath(ctx, cursor, depth)
+						if err != nil {
+							return nil, 0, err
+						}
+						ctx.Option.Path.node = oldPath
+						ret = append(ret, paths...)
+						cursor = c
+					} else {
+						start := cursor
+						end, err := skipValue(buf, cursor, depth)
+						if err != nil {
+							return nil, 0, err
+						}
+						ret = append(ret, buf[start:end])
+					}
+				} else {
+					c, err := skipValue(buf, cursor, depth)
+					if err != nil {
+						return nil, 0, err
+					}
+					cursor = skipWhiteSpace(buf, c)
+				}
+				switch buf[cursor] {
+				case ']':
+					cursor++
+					return ret, cursor, nil
+				case ',':
+					idx++
+				default:
+					return nil, 0, errors.ErrInvalidCharacter(buf[cursor], "slice", cursor)
+				}
+				cursor++
+			}
+		case '-', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+			return nil, 0, d.errNumber(cursor)
+		default:
+			return nil, 0, errors.ErrUnexpectedEndOfJSON("slice", cursor)
+		}
+	}
+}

internal/decoder/string.go

@@ -60,6 +60,17 @@ func (d *stringDecoder) Decode(ctx *RuntimeContext, cursor, depth int64, p unsaf
 	return cursor, nil
 }
 
+func (d *stringDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	bytes, c, err := d.decodeByte(ctx.Buf, cursor)
+	if err != nil {
+		return nil, 0, err
+	}
+	if bytes == nil {
+		return [][]byte{nullbytes}, c, nil
+	}
+	return [][]byte{bytes}, c, nil
+}
+
 var (
 	hexToInt = [256]int{
 		'0': 0,

internal/decoder/struct.go

@@ -817,3 +817,7 @@ func (d *structDecoder) Decode(ctx *RuntimeContext, cursor, depth int64, p unsaf
 		cursor++
 	}
 }
+
+func (d *structDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	return nil, 0, fmt.Errorf("json: struct decoder does not support decode path")
+}

internal/decoder/type.go

@@ -10,6 +10,7 @@ import (
 
 type Decoder interface {
 	Decode(*RuntimeContext, int64, int64, unsafe.Pointer) (int64, error)
+	DecodePath(*RuntimeContext, int64, int64) ([][]byte, int64, error)
 	DecodeStream(*Stream, int64, unsafe.Pointer) error
 }
 

internal/decoder/uint.go

@@ -188,3 +188,7 @@ func (d *uintDecoder) Decode(ctx *RuntimeContext, cursor, depth int64, p unsafe.
 	d.op(p, u64)
 	return cursor, nil
 }
+
+func (d *uintDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	return nil, 0, fmt.Errorf("json: uint decoder does not support decode path")
+}

internal/decoder/unmarshal_json.go

@@ -3,6 +3,7 @@ package decoder
 import (
 	"context"
 	"encoding/json"
+	"fmt"
 	"unsafe"
 
 	"github.com/goccy/go-json/internal/errors"
@@ -97,3 +98,7 @@ func (d *unmarshalJSONDecoder) Decode(ctx *RuntimeContext, cursor, depth int64,
 	}
 	return end, nil
 }
+
+func (d *unmarshalJSONDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	return nil, 0, fmt.Errorf("json: unmarshal json decoder does not support decode path")
+}

internal/decoder/unmarshal_text.go

@@ -3,6 +3,7 @@ package decoder
 import (
 	"bytes"
 	"encoding"
+	"fmt"
 	"unicode"
 	"unicode/utf16"
 	"unicode/utf8"
@@ -142,6 +143,10 @@ func (d *unmarshalTextDecoder) Decode(ctx *RuntimeContext, cursor, depth int64,
 	return end, nil
 }
 
+func (d *unmarshalTextDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	return nil, 0, fmt.Errorf("json: unmarshal text decoder does not support decode path")
+}
+
 func unquoteBytes(s []byte) (t []byte, ok bool) {
 	length := len(s)
 	if length < 2 || s[0] != '"' || s[length-1] != '"' {

internal/decoder/wrapped_string.go

@@ -1,6 +1,7 @@
 package decoder
 
 import (
+	"fmt"
 	"reflect"
 	"unsafe"
 
@@ -66,3 +67,7 @@ func (d *wrappedStringDecoder) Decode(ctx *RuntimeContext, cursor, depth int64,
 	ctx.Buf = oldBuf
 	return c, nil
 }
+
+func (d *wrappedStringDecoder) DecodePath(ctx *RuntimeContext, cursor, depth int64) ([][]byte, int64, error) {
+	return nil, 0, fmt.Errorf("json: wrapped string decoder does not support decode path")
+}

internal/errors/error.go

@@ -162,3 +162,22 @@ func ErrInvalidBeginningOfValue(c byte, cursor int64) *SyntaxError {
 		Offset: cursor,
 	}
 }
+
+type PathError struct {
+	msg string
+}
+
+func (e *PathError) Error() string {
+	return fmt.Sprintf("json: invalid path format: %s", e.msg)
+}
+
+func ErrInvalidPath(msg string, args ...interface{}) *PathError {
+	if len(args) != 0 {
+		return &PathError{msg: fmt.Sprintf(msg, args...)}
+	}
+	return &PathError{msg: msg}
+}
+
+func ErrEmptyPath() *PathError {
+	return &PathError{msg: "path is empty"}
+}

path.go

@@ -0,0 +1,73 @@
+package json
+
+import (
+	"reflect"
+
+	"github.com/goccy/go-json/internal/decoder"
+)
+
+// CreatePath creates JSON Path.
+//
+// JSON Path rule
+// $   : root object or element. The JSON Path format must start with this operator, which refers to the outermost level of the JSON-formatted string.
+// .   : child operator. You can identify child values using dot-notation.
+// ..  : recursive descent.
+// []  : subscript operator. If the JSON object is an array, you can use brackets to specify the array index.
+// [*] : all objects/elements for array.
+//
+// Reserved words must be properly escaped when included in Path.
+// Escale Rule
+// single quote style escape: e.g.) `$['a.b'].c`
+// double quote style escape: e.g.) `$."a.b".c`
+func CreatePath(p string) (*Path, error) {
+	path, err := decoder.PathString(p).Build()
+	if err != nil {
+		return nil, err
+	}
+	return &Path{path: path}, nil
+}
+
+// Path represents JSON Path.
+type Path struct {
+	path *decoder.Path
+}
+
+// UsedSingleQuotePathSelector whether single quote-based escaping was done when building the JSON Path.
+func (p *Path) UsedSingleQuotePathSelector() bool {
+	return p.path.SingleQuotePathSelector
+}
+
+// UsedSingleQuotePathSelector whether double quote-based escaping was done when building the JSON Path.
+func (p *Path) UsedDoubleQuotePathSelector() bool {
+	return p.path.DoubleQuotePathSelector
+}
+
+// Extract extracts a specific JSON string.
+func (p *Path) Extract(data []byte, optFuncs ...DecodeOptionFunc) ([][]byte, error) {
+	return extractFromPath(p, data, optFuncs...)
+}
+
+// Unmarshal extract and decode the value of the part corresponding to JSON Path from the input data.
+func (p *Path) Unmarshal(data []byte, v interface{}, optFuncs ...DecodeOptionFunc) error {
+	contents, err := extractFromPath(p, data, optFuncs...)
+	if err != nil {
+		return err
+	}
+	results := make([]interface{}, 0, len(contents))
+	for _, content := range contents {
+		var result interface{}
+		if err := Unmarshal(content, &result); err != nil {
+			return err
+		}
+		results = append(results, result)
+	}
+	if err := decoder.AssignValue(reflect.ValueOf(results), reflect.ValueOf(v)); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Get extract and substitute the value of the part corresponding to JSON Path from the input value.
+func (p *Path) Get(src, dst interface{}) error {
+	return p.path.Get(reflect.ValueOf(src), reflect.ValueOf(dst))
+}

path_test.go

@@ -0,0 +1,234 @@
+package json_test
+
+import (
+	"bytes"
+	"reflect"
+	"sort"
+	"testing"
+
+	"github.com/goccy/go-json"
+)
+
+func TestExtractPath(t *testing.T) {
+	src := []byte(`{"a":{"b":10,"c":true},"b":"text"}`)
+	t.Run("$.a.b", func(t *testing.T) {
+		path, err := json.CreatePath("$.a.b")
+		if err != nil {
+			t.Fatal(err)
+		}
+		contents, err := path.Extract(src)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if len(contents) != 1 {
+			t.Fatal("failed to extract")
+		}
+		if !bytes.Equal(contents[0], []byte("10")) {
+			t.Fatal("failed to extract")
+		}
+	})
+	t.Run("$.b", func(t *testing.T) {
+		path, err := json.CreatePath("$.b")
+		if err != nil {
+			t.Fatal(err)
+		}
+		contents, err := path.Extract(src)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if len(contents) != 1 {
+			t.Fatal("failed to extract")
+		}
+		if !bytes.Equal(contents[0], []byte(`"text"`)) {
+			t.Fatal("failed to extract")
+		}
+	})
+	t.Run("$.a", func(t *testing.T) {
+		path, err := json.CreatePath("$.a")
+		if err != nil {
+			t.Fatal(err)
+		}
+		contents, err := path.Extract(src)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if len(contents) != 1 {
+			t.Fatal("failed to extract")
+		}
+		if !bytes.Equal(contents[0], []byte(`{"b":10,"c":true}`)) {
+			t.Fatal("failed to extract")
+		}
+	})
+}
+
+func TestUnmarshalPath(t *testing.T) {
+	t.Run("int", func(t *testing.T) {
+		src := []byte(`{"a":{"b":10,"c":true},"b":"text"}`)
+		t.Run("success", func(t *testing.T) {
+			path, err := json.CreatePath("$.a.b")
+			if err != nil {
+				t.Fatal(err)
+			}
+			var v int
+			if err := path.Unmarshal(src, &v); err != nil {
+				t.Fatal(err)
+			}
+			if v != 10 {
+				t.Fatal("failed to unmarshal path")
+			}
+		})
+		t.Run("failure", func(t *testing.T) {
+			path, err := json.CreatePath("$.a.c")
+			if err != nil {
+				t.Fatal(err)
+			}
+			var v map[string]interface{}
+			if err := path.Unmarshal(src, &v); err == nil {
+				t.Fatal("expected error")
+			}
+		})
+	})
+	t.Run("bool", func(t *testing.T) {
+		src := []byte(`{"a":{"b":10,"c":true},"b":"text"}`)
+		t.Run("success", func(t *testing.T) {
+			path, err := json.CreatePath("$.a.c")
+			if err != nil {
+				t.Fatal(err)
+			}
+			var v bool
+			if err := path.Unmarshal(src, &v); err != nil {
+				t.Fatal(err)
+			}
+			if !v {
+				t.Fatal("failed to unmarshal path")
+			}
+		})
+		t.Run("failure", func(t *testing.T) {
+			path, err := json.CreatePath("$.a.b")
+			if err != nil {
+				t.Fatal(err)
+			}
+			var v bool
+			if err := path.Unmarshal(src, &v); err == nil {
+				t.Fatal("expected error")
+			}
+		})
+	})
+	t.Run("map", func(t *testing.T) {
+		src := []byte(`{"a":{"b":10,"c":true},"b":"text"}`)
+		t.Run("success", func(t *testing.T) {
+			path, err := json.CreatePath("$.a")
+			if err != nil {
+				t.Fatal(err)
+			}
+			var v map[string]interface{}
+			if err := path.Unmarshal(src, &v); err != nil {
+				t.Fatal(err)
+			}
+			if len(v) != 2 {
+				t.Fatal("failed to decode map")
+			}
+		})
+	})
+
+	t.Run("path with single quote selector", func(t *testing.T) {
+		path, err := json.CreatePath("$['a.b'].c")
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		var v string
+		if err := path.Unmarshal([]byte(`{"a.b": {"c": "world"}}`), &v); err != nil {
+			t.Fatal(err)
+		}
+		if v != "world" {
+			t.Fatal("failed to unmarshal path")
+		}
+	})
+	t.Run("path with double quote selector", func(t *testing.T) {
+		path, err := json.CreatePath(`$."a.b".c`)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		var v string
+		if err := path.Unmarshal([]byte(`{"a.b": {"c": "world"}}`), &v); err != nil {
+			t.Fatal(err)
+		}
+		if v != "world" {
+			t.Fatal("failed to unmarshal path")
+		}
+	})
+}
+
+func TestGetPath(t *testing.T) {
+	t.Run("selector", func(t *testing.T) {
+		var v interface{}
+		if err := json.Unmarshal([]byte(`{"a":{"b":10,"c":true},"b":"text"}`), &v); err != nil {
+			t.Fatal(err)
+		}
+		path, err := json.CreatePath("$.a.b")
+		if err != nil {
+			t.Fatal(err)
+		}
+		var b int
+		if err := path.Get(v, &b); err != nil {
+			t.Fatal(err)
+		}
+		if b != 10 {
+			t.Fatalf("failed to decode by json.Get")
+		}
+	})
+	t.Run("index", func(t *testing.T) {
+		var v interface{}
+		if err := json.Unmarshal([]byte(`{"a":[{"b":10,"c":true},{"b":"text"}]}`), &v); err != nil {
+			t.Fatal(err)
+		}
+		path, err := json.CreatePath("$.a[0].b")
+		if err != nil {
+			t.Fatal(err)
+		}
+		var b int
+		if err := path.Get(v, &b); err != nil {
+			t.Fatal(err)
+		}
+		if b != 10 {
+			t.Fatalf("failed to decode by json.Get")
+		}
+	})
+	t.Run("indexAll", func(t *testing.T) {
+		var v interface{}
+		if err := json.Unmarshal([]byte(`{"a":[{"b":1,"c":true},{"b":2},{"b":3}]}`), &v); err != nil {
+			t.Fatal(err)
+		}
+		path, err := json.CreatePath("$.a[*].b")
+		if err != nil {
+			t.Fatal(err)
+		}
+		var b []int
+		if err := path.Get(v, &b); err != nil {
+			t.Fatal(err)
+		}
+		if !reflect.DeepEqual(b, []int{1, 2, 3}) {
+			t.Fatalf("failed to decode by json.Get")
+		}
+	})
+	t.Run("recursive", func(t *testing.T) {
+		var v interface{}
+		if err := json.Unmarshal([]byte(`{"a":[{"b":1,"c":true},{"b":2},{"b":3}],"a2":{"b":4}}`), &v); err != nil {
+			t.Fatal(err)
+		}
+		path, err := json.CreatePath("$..b")
+		if err != nil {
+			t.Fatal(err)
+		}
+		var b []int
+		if err := path.Get(v, &b); err != nil {
+			t.Fatal(err)
+		}
+		sort.Ints(b)
+		if !reflect.DeepEqual(b, []int{1, 2, 3, 4}) {
+			t.Fatalf("failed to decode by json.Get")
+		}
+	})
+}