Support JSON Path for decoding

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")
+}