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scanner.go
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scanner.go
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// Copyright (c) Roman Atachiants and contributors. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for details.
package binary
import (
"errors"
"math/big"
"reflect"
"strings"
"sync"
)
// Map of all the schemas we've encountered so far
var schemas = new(sync.Map)
var importCodec = new(sync.Map)
// Scan gets a codec for the type and uses a cached schema if the type was
// previously scanned.
func scan(t reflect.Type) (c Codec, err error) {
// Attempt to load from cache first
if f, ok := importCodec.Load(t.String()); ok {
c = f.(Codec)
return
}
// Attempt to load from cache first
if f, ok := schemas.Load(t); ok {
c = f.(Codec)
return
}
// Scan for the first time
c, err = scanType(t)
if err != nil {
return
}
// Load or store again
if f, ok := schemas.LoadOrStore(t, c); ok {
c = f.(Codec)
return
}
return
}
// ScanType scans the type
func scanType(t reflect.Type) (Codec, error) {
if f, ok := importCodec.Load(t.String()); ok {
return f.(Codec), nil
}
if custom, ok := scanCustomCodec(t); ok {
return custom, nil
}
if custom, ok := scanBinaryMarshaler(t); ok {
return custom, nil
}
switch t.Kind() {
case reflect.Array:
switch t.Elem().Kind() {
case reflect.Uint8:
return new(byteArrayCodec), nil
case reflect.Bool:
return new(boolArrayCodec), nil
case reflect.Uint:
fallthrough
case reflect.Uint16:
fallthrough
case reflect.Uint32:
fallthrough
case reflect.Uint64:
return new(varuintArrayCodec), nil
case reflect.Int:
fallthrough
case reflect.Int8:
fallthrough
case reflect.Int16:
fallthrough
case reflect.Int32:
fallthrough
case reflect.Int64:
return new(varintArrayCodec), nil
}
if t.Elem().Kind() == reflect.Interface {
return new(reflectInterfaceArrayCodec), nil
}else{
elemCodec, err := scanType(t.Elem())
if err != nil {
return nil, err
}
return &reflectArrayCodec{
elemCodec: elemCodec,
}, nil
}
case reflect.Slice:
// Fast-paths for simple numeric slices and string slices
switch t.Elem().Kind() {
case reflect.Uint8:
return new(byteSliceCodec), nil
case reflect.Bool:
return new(boolSliceCodec), nil
case reflect.Uint:
fallthrough
case reflect.Uint16:
fallthrough
case reflect.Uint32:
fallthrough
case reflect.Uint64:
return new(varuintSliceCodec), nil
case reflect.Int:
fallthrough
case reflect.Int8:
fallthrough
case reflect.Int16:
fallthrough
case reflect.Int32:
fallthrough
case reflect.Int64:
return new(varintSliceCodec), nil
default:
if t.Elem().Kind() == reflect.Interface {
return new(reflectInterfaceSliceCodec), nil
}else{
elemCodec, err := scanType(t.Elem())
if err != nil {
return nil, err
}
return &reflectSliceCodec{
elemCodec: elemCodec,
}, nil
}
}
case reflect.Struct:
if f, ok := importCodec.Load(t.String()); ok {
return f.(Codec), nil
}
s := scanStruct(t)
var v reflectStructCodec
for _, i := range s.fields {
field := t.Field(i)
if c, err := scanType(field.Type); err == nil {
v = append(v, fieldCodec{
Index: i,
Codec: c,
})
} else {
return nil, err
}
}
return &v, nil
case reflect.Map:
key, err := scanType(t.Key())
if err != nil {
return nil, err
}
val, err := scanType(t.Elem())
if err != nil {
return nil, err
}
return &reflectMapCodec{
key: key,
val: val,
}, nil
case reflect.String:
return new(stringCodec), nil
case reflect.Bool:
return new(boolCodec), nil
case reflect.Int8:
fallthrough
case reflect.Int16:
fallthrough
case reflect.Int32:
fallthrough
case reflect.Int:
fallthrough
case reflect.Int64:
return new(varintCodec), nil
case reflect.Uint8:
fallthrough
case reflect.Uint16:
fallthrough
case reflect.Uint32:
fallthrough
case reflect.Uint:
fallthrough
case reflect.Uint64:
return new(varuintCodec), nil
case reflect.Complex64:
return new(complex64Codec), nil
case reflect.Complex128:
return new(complex128Codec), nil
case reflect.Float32:
return new(float32Codec), nil
case reflect.Float64:
return new(float64Codec), nil
case reflect.Ptr:
codec, err := scanType(t.Elem())
if err != nil {
return nil, err
}
return &reflectPtrCodec{
Codec:codec,
}, nil
case reflect.Interface:
return &reflectInterfaceCodec{
}, nil
}
return nil, errors.New("binary: unsupported type " + t.String())
}
type scannedStruct struct {
fields []int
}
func scanStruct(t reflect.Type) (meta *scannedStruct) {
l := t.NumField()
meta = new(scannedStruct)
for i := 0; i < l; i++ {
val := t.Field(i).Tag.Get("binary")
if val != "" {
tagsValue := strings.Split(val, ",")
skip := false
for _, val := range tagsValue {
if strings.Contains(val, "ignore"){
skip = true
break
}
}
if skip {
continue
}
}
if t.Field(i).Name == "_" {
continue
}
meta.fields = append(meta.fields, i)
}
return
}
// scanBinaryMarshaler scans whether a type has a custom binary marshaling implemented.
func scanBinaryMarshaler(t reflect.Type) (out *customCodec, ok bool) {
out = new(customCodec)
if m, ok := t.MethodByName("MarshalBinary"); ok {
out.marshaler = &m
} else if m, ok := reflect.PtrTo(t).MethodByName("MarshalBinary"); ok {
out.ptrMarshaler = &m
}
if m, ok := t.MethodByName("UnmarshalBinary"); ok {
out.unmarshaler = &m
} else if m, ok := reflect.PtrTo(t).MethodByName("UnmarshalBinary"); ok {
out.ptrUnmarshaler = &m
}
// Checks whether we have both marshaler and unmarshaler attached
if (out.marshaler != nil || out.ptrMarshaler != nil) && (out.unmarshaler != nil || out.ptrUnmarshaler != nil) {
return out, true
}
return nil, false
}
// scanCustomCodec scans whether a type has a custom codec implemented.
func scanCustomCodec(t reflect.Type) (out Codec, ok bool) {
if m, ok := reflect.PtrTo(t).MethodByName("GetBinaryCodec"); ok {
callable := reflect.New(t).Method(m.Index)
result := callable.Call([]reflect.Value{})
if len(result) == 1 && !result[0].IsNil() {
out, ok = result[0].Interface().(Codec)
return out, ok
}
}
return
}
func ImportCodeC(t reflect.Type, codec Codec) {
if t.Kind() == reflect.Ptr {
panic(errors.New("the type you import is a ptr"))
}
importCodec.Store(t.String(), codec)
}
func init(){
ImportCodeC(reflect.TypeOf(big.Int{}), &bigIntCodec{})
}