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https://github.com/goccy/go-reflect
Zero-allocation reflection library for Go
https://github.com/goccy/go-reflect
go golang golang-library reflection
Last synced: 7 days ago
JSON representation
Zero-allocation reflection library for Go
- Host: GitHub
- URL: https://github.com/goccy/go-reflect
- Owner: goccy
- License: mit
- Created: 2020-07-05T01:28:11.000Z (over 4 years ago)
- Default Branch: master
- Last Pushed: 2023-11-16T23:17:57.000Z (about 1 year ago)
- Last Synced: 2024-10-30T14:50:02.938Z (21 days ago)
- Topics: go, golang, golang-library, reflection
- Language: Go
- Homepage:
- Size: 98.6 KB
- Stars: 525
- Watchers: 9
- Forks: 24
- Open Issues: 5
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
- awesome-list - go-reflect - allocation reflection library for Go | goccy | 283 | (Go)
README
# go-reflect
[](https://pkg.go.dev/github.com/goccy/go-reflect?tab=doc)
[](https://codecov.io/gh/goccy/go-reflect)
[](https://goreportcard.com/report/github.com/goccy/go-reflect)
Zero-allocation reflection library for Go
# Features
- 100% Compatibility APIs with `reflect` library
- No allocation occurs when using the reflect.Type features
- You can choose to escape ( `reflect.ValueOf` ) or noescape ( `reflect.ValueNoEscapeOf` ) when creating reflect.Value
# Status
All the tests in the reflect library have been passed
except the tests that use some private functions.
# Installation
```bash
go get github.com/goccy/go-reflect
```
# How to use
Replace import statement from `reflect` to `github.com/goccy/go-reflect`
```bash
-import "reflect"
+import "github.com/goccy/go-reflect"
```
# Benchmarks
Source https://github.com/goccy/go-reflect/blob/master/benchmark_test.go
## Benchmark about reflect.Type
```
$ go test -bench TypeOf
```
```
goos: darwin
goarch: amd64
pkg: github.com/goccy/go-reflect
Benchmark_TypeOf_Reflect-12 100000000 13.8 ns/op 8 B/op 1 allocs/op
Benchmark_TypeOf_GoReflect-12 2000000000 1.70 ns/op 0 B/op 0 allocs/op
PASS
ok github.com/goccy/go-reflect 5.369s
```
## Benchmark about reflect.Value
```
$ go test -bench ValueOf
```
```
goos: darwin
goarch: amd64
pkg: github.com/goccy/go-reflect
Benchmark_ValueOf_Reflect-12 100000000 13.0 ns/op 8 B/op 1 allocs/op
Benchmark_ValueOf_GoReflect-12 300000000 4.64 ns/op 0 B/op 0 allocs/op
PASS
ok github.com/goccy/go-reflect 3.578s
```
# Real World Example
## Implements Fast Marshaler
I would like to introduce the technique I use for [github.com/goccy/go-json](https://github.com/goccy/go-json).
Using this technique, allocation can be suppressed to once for any marshaler.
Original Source is https://github.com/goccy/go-reflect/blob/master/benchmark_marshaler_test.go
```go
package reflect_test
import (
"errors"
"strconv"
"sync"
"testing"
"unsafe"
"github.com/goccy/go-reflect"
)
var (
typeToEncoderMap sync.Map
bufpool = sync.Pool{
New: func() interface{} {
return &buffer{
b: make([]byte, 0, 1024),
}
},
}
)
type buffer struct {
b []byte
}
type encoder func(*buffer, unsafe.Pointer) error
func Marshal(v interface{}) ([]byte, error) {
// Technique 1.
// Get type information and pointer from interface{} value without allocation.
typ, ptr := reflect.TypeAndPtrOf(v)
typeID := reflect.TypeID(typ)
// Technique 2.
// Reuse the buffer once allocated using sync.Pool
buf := bufpool.Get().(*buffer)
buf.b = buf.b[:0]
defer bufpool.Put(buf)
// Technique 3.
// builds a optimized path by typeID and caches it
if enc, ok := typeToEncoderMap.Load(typeID); ok {
if err := enc.(encoder)(buf, ptr); err != nil {
return nil, err
}
// allocate a new buffer required length only
b := make([]byte, len(buf.b))
copy(b, buf.b)
return b, nil
}
// First time,
// builds a optimized path by type and caches it with typeID.
enc, err := compile(typ)
if err != nil {
return nil, err
}
typeToEncoderMap.Store(typeID, enc)
if err := enc(buf, ptr); err != nil {
return nil, err
}
// allocate a new buffer required length only
b := make([]byte, len(buf.b))
copy(b, buf.b)
return b, nil
}
func compile(typ reflect.Type) (encoder, error) {
switch typ.Kind() {
case reflect.Struct:
return compileStruct(typ)
case reflect.Int:
return compileInt(typ)
}
return nil, errors.New("unsupported type")
}
func compileStruct(typ reflect.Type) (encoder, error) {
encoders := []encoder{}
for i := 0; i < typ.NumField(); i++ {
field := typ.Field(i)
enc, err := compile(field.Type)
if err != nil {
return nil, err
}
offset := field.Offset
encoders = append(encoders, func(buf *buffer, p unsafe.Pointer) error {
return enc(buf, unsafe.Pointer(uintptr(p)+offset))
})
}
return func(buf *buffer, p unsafe.Pointer) error {
buf.b = append(buf.b, '{')
for _, enc := range encoders {
if err := enc(buf, p); err != nil {
return err
}
}
buf.b = append(buf.b, '}')
return nil
}, nil
}
func compileInt(typ reflect.Type) (encoder, error) {
return func(buf *buffer, p unsafe.Pointer) error {
value := *(*int)(p)
buf.b = strconv.AppendInt(buf.b, int64(value), 10)
return nil
}, nil
}
func Benchmark_Marshal(b *testing.B) {
b.ReportAllocs()
for n := 0; n < b.N; n++ {
bytes, err := Marshal(struct{ I int }{10})
if err != nil {
b.Fatal(err)
}
if string(bytes) != "{10}" {
b.Fatal("unexpected error")
}
}
}
```
The benchmark result is as follows.
```bash
$ go test -bench Benchmark_Marshal
goos: darwin
goarch: amd64
pkg: github.com/goccy/go-reflect
Benchmark_Marshal-16 16586372 71.0 ns/op 4 B/op 1 allocs/op
PASS
```