tendermint/binary/reflect.go

package binary

import (
	"errors"
	"fmt"
	"io"
	"reflect"
	"sync"

	. "github.com/tendermint/tendermint/common"
)

type TypeInfo struct {
	Type reflect.Type // The type

	// Custom encoder/decoder
	Encoder Encoder
	Decoder Decoder

	// If Type is kind reflect.Interface
	ConcreteTypes map[byte]reflect.Type

	// If Type is concrete
	HasTypeByte bool
	TypeByte    byte
}

// e.g. If o is struct{Foo}{}, return is the Foo interface type.
func GetTypeFromStructDeclaration(o interface{}) reflect.Type {
	rt := reflect.TypeOf(o)
	if rt.NumField() != 1 {
		panic("Unexpected number of fields in struct-wrapped declaration of type")
	}
	return rt.Field(0).Type
}

// If o implements HasTypeByte, returns (true, typeByte)
func GetTypeByteFromStruct(o interface{}) (hasTypeByte bool, typeByte byte) {
	if _, ok := o.(HasTypeByte); ok {
		return true, o.(HasTypeByte).TypeByte()
	} else {
		return false, byte(0x00)
	}
}

// If a type implements TypeByte, the byte is included
// as the first byte for encoding and decoding.
// This is primarily used to encode interfaces types.
// The interface should be declared with RegisterInterface()
type HasTypeByte interface {
	TypeByte() byte
}

// NOTE: do not access typeInfos directly, but call GetTypeInfo()
var typeInfosMtx sync.Mutex
var typeInfos = map[reflect.Type]*TypeInfo{}

func GetTypeInfo(rt reflect.Type) *TypeInfo {
	typeInfosMtx.Lock()
	defer typeInfosMtx.Unlock()
	info := typeInfos[rt]
	if info == nil {
		info = &TypeInfo{Type: rt}
		RegisterType(info)
	}
	return info
}

// For use with the RegisterInterface declaration
type ConcreteType struct {
	O interface{}
}

// Must use this to register an interface to properly decode the
// underlying concrete type.
func RegisterInterface(o interface{}, args ...interface{}) *TypeInfo {
	it := GetTypeFromStructDeclaration(o)
	if it.Kind() != reflect.Interface {
		panic("RegisterInterface expects an interface")
	}
	concreteTypes := make(map[byte]reflect.Type, 0)
	for _, arg := range args {
		switch arg.(type) {
		case ConcreteType:
			concreteTypeInfo := arg.(ConcreteType)
			concreteType := reflect.TypeOf(concreteTypeInfo.O)
			hasTypeByte, typeByte := GetTypeByteFromStruct(concreteTypeInfo.O)
			//fmt.Println(Fmt("HasTypeByte: %v typeByte: %X type: %X", hasTypeByte, typeByte, concreteType))
			if !hasTypeByte {
				panic(Fmt("Expected concrete type %v to implement HasTypeByte", concreteType))
			}
			if concreteTypes[typeByte] != nil {
				panic(Fmt("Duplicate TypeByte for type %v and %v", concreteType, concreteTypes[typeByte]))
			}
			concreteTypes[typeByte] = concreteType
		default:
			panic(Fmt("Unexpected argument type %v", reflect.TypeOf(arg)))
		}
	}
	typeInfo := &TypeInfo{
		Type:          it,
		ConcreteTypes: concreteTypes,
	}
	typeInfos[it] = typeInfo
	return typeInfo
}

// Registers and possibly modifies the TypeInfo.
// NOTE: not goroutine safe, so only call upon program init.
func RegisterType(info *TypeInfo) *TypeInfo {

	// Also register the dereferenced struct if info.Type is a pointer.
	// Or, if info.Type is not a pointer, register the pointer.
	var rt, ptrRt reflect.Type
	if info.Type.Kind() == reflect.Ptr {
		rt, ptrRt = info.Type.Elem(), info.Type
	} else {
		rt, ptrRt = info.Type, reflect.PtrTo(info.Type)
	}

	// Register the type info
	typeInfos[rt] = info
	typeInfos[ptrRt] = info

	// See if the type implements HasTypeByte
	if rt.Kind() != reflect.Interface && rt.Implements(reflect.TypeOf((*HasTypeByte)(nil)).Elem()) {
		zero := reflect.Zero(rt)
		typeByte := zero.Interface().(HasTypeByte).TypeByte()
		if info.HasTypeByte && info.TypeByte != typeByte {
			panic(fmt.Sprintf("Type %v expected TypeByte of %X", rt, typeByte))
		} else {
			info.HasTypeByte = true
			info.TypeByte = typeByte
		}
	} else if ptrRt.Implements(reflect.TypeOf((*HasTypeByte)(nil)).Elem()) {
		zero := reflect.Zero(ptrRt)
		typeByte := zero.Interface().(HasTypeByte).TypeByte()
		if info.HasTypeByte && info.TypeByte != typeByte {
			panic(fmt.Sprintf("Type %v expected TypeByte of %X", ptrRt, typeByte))
		} else {
			info.HasTypeByte = true
			info.TypeByte = typeByte
		}
	}

	return info
}

func readReflect(rv reflect.Value, rt reflect.Type, r Unreader, n *int64, err *error) {

	log.Debug("Read reflect", "type", rt)

	// Get typeInfo
	typeInfo := GetTypeInfo(rt)

	// Custom decoder
	if typeInfo.Decoder != nil {
		decoded := typeInfo.Decoder(r, n, err)
		rv.Set(reflect.ValueOf(decoded))
		return
	}

	// Create a new struct if rv is nil pointer.
	if rt.Kind() == reflect.Ptr && rv.IsNil() {
		newRv := reflect.New(rt.Elem())
		rv.Set(newRv)
		rv = newRv
	}

	// Dereference pointer
	// Still addressable, thus settable!
	if rv.Kind() == reflect.Ptr {
		rv, rt = rv.Elem(), rt.Elem()
	}

	// Read TypeByte prefix
	if typeInfo.HasTypeByte {
		typeByte := ReadByte(r, n, err)
		log.Debug("Read typebyte", "typeByte", typeByte)
		if typeByte != typeInfo.TypeByte {
			*err = errors.New(fmt.Sprintf("Expected TypeByte of %X but got %X", typeInfo.TypeByte, typeByte))
			return
		}
	}

	switch rt.Kind() {
	case reflect.Interface:
		typeByte := PeekByte(r, n, err)
		if *err != nil {
			return
		}
		concreteType, ok := typeInfo.ConcreteTypes[typeByte]
		if !ok {
			panic(Fmt("TypeByte %X not registered for interface %v", typeByte, rt))
		}
		newRv := reflect.New(concreteType)
		readReflect(newRv.Elem(), concreteType, r, n, err)
		rv.Set(newRv.Elem())

	case reflect.Slice:
		elemRt := rt.Elem()
		if elemRt.Kind() == reflect.Uint8 {
			// Special case: Byteslices
			byteslice := ReadByteSlice(r, n, err)
			log.Debug("Read byteslice", "bytes", byteslice)
			rv.Set(reflect.ValueOf(byteslice))
		} else {
			// Read length
			length := int(ReadUvarint(r, n, err))
			log.Debug(Fmt("Read length: %v", length))
			sliceRv := reflect.MakeSlice(rt, length, length)
			// Read elems
			for i := 0; i < length; i++ {
				elemRv := sliceRv.Index(i)
				readReflect(elemRv, elemRt, r, n, err)
			}
			rv.Set(sliceRv)
		}

	case reflect.Struct:
		numFields := rt.NumField()
		for i := 0; i < numFields; i++ {
			field := rt.Field(i)
			if field.PkgPath != "" {
				continue
			}
			fieldRv := rv.Field(i)
			readReflect(fieldRv, field.Type, r, n, err)
		}

	case reflect.String:
		str := ReadString(r, n, err)
		log.Debug(Fmt("Read string: %v", str))
		rv.SetString(str)

	case reflect.Int64:
		num := ReadUint64(r, n, err)
		log.Debug(Fmt("Read num: %v", num))
		rv.SetInt(int64(num))

	case reflect.Int32:
		num := ReadUint32(r, n, err)
		log.Debug(Fmt("Read num: %v", num))
		rv.SetInt(int64(num))

	case reflect.Int16:
		num := ReadUint16(r, n, err)
		log.Debug(Fmt("Read num: %v", num))
		rv.SetInt(int64(num))

	case reflect.Int8:
		num := ReadUint8(r, n, err)
		log.Debug(Fmt("Read num: %v", num))
		rv.SetInt(int64(num))

	case reflect.Int:
		num := ReadUvarint(r, n, err)
		log.Debug(Fmt("Read num: %v", num))
		rv.SetInt(int64(num))

	case reflect.Uint64:
		num := ReadUint64(r, n, err)
		log.Debug(Fmt("Read num: %v", num))
		rv.SetUint(uint64(num))

	case reflect.Uint32:
		num := ReadUint32(r, n, err)
		log.Debug(Fmt("Read num: %v", num))
		rv.SetUint(uint64(num))

	case reflect.Uint16:
		num := ReadUint16(r, n, err)
		log.Debug(Fmt("Read num: %v", num))
		rv.SetUint(uint64(num))

	case reflect.Uint8:
		num := ReadUint8(r, n, err)
		log.Debug(Fmt("Read num: %v", num))
		rv.SetUint(uint64(num))

	case reflect.Uint:
		num := ReadUvarint(r, n, err)
		log.Debug(Fmt("Read num: %v", num))
		rv.SetUint(uint64(num))

	default:
		panic(fmt.Sprintf("Unknown field type %v", rt.Kind()))
	}
}

func writeReflect(rv reflect.Value, rt reflect.Type, w io.Writer, n *int64, err *error) {

	// Get typeInfo
	typeInfo := GetTypeInfo(rt)

	// Custom encoder, say for an interface type rt.
	if typeInfo.Encoder != nil {
		typeInfo.Encoder(rv.Interface(), w, n, err)
		return
	}

	// Dereference interface
	if rt.Kind() == reflect.Interface {
		rv = rv.Elem()
		rt = rv.Type()
		// If interface type, get typeInfo of underlying type.
		typeInfo = GetTypeInfo(rt)
	}

	// Dereference pointer
	if rt.Kind() == reflect.Ptr {
		rt = rt.Elem()
		rv = rv.Elem()
		// RegisterType registers the ptr type,
		// so typeInfo is already for the ptr.
	}

	// Write TypeByte prefix
	if typeInfo.HasTypeByte {
		WriteByte(typeInfo.TypeByte, w, n, err)
	}

	switch rt.Kind() {
	case reflect.Slice:
		elemRt := rt.Elem()
		if elemRt.Kind() == reflect.Uint8 {
			// Special case: Byteslices
			byteslice := rv.Bytes()
			WriteByteSlice(byteslice, w, n, err)
		} else {
			// Write length
			length := rv.Len()
			WriteUvarint(uint(length), w, n, err)
			// Write elems
			for i := 0; i < length; i++ {
				elemRv := rv.Index(i)
				writeReflect(elemRv, elemRt, w, n, err)
			}
		}

	case reflect.Struct:
		numFields := rt.NumField()
		for i := 0; i < numFields; i++ {
			field := rt.Field(i)
			if field.PkgPath != "" {
				continue
			}
			fieldRv := rv.Field(i)
			writeReflect(fieldRv, field.Type, w, n, err)
		}

	case reflect.String:
		WriteString(rv.String(), w, n, err)

	case reflect.Int64:
		WriteInt64(rv.Int(), w, n, err)

	case reflect.Int32:
		WriteInt32(int32(rv.Int()), w, n, err)

	case reflect.Int16:
		WriteInt16(int16(rv.Int()), w, n, err)

	case reflect.Int8:
		WriteInt8(int8(rv.Int()), w, n, err)

	case reflect.Int:
		WriteVarint(int(rv.Int()), w, n, err)

	case reflect.Uint64:
		WriteUint64(rv.Uint(), w, n, err)

	case reflect.Uint32:
		WriteUint32(uint32(rv.Uint()), w, n, err)

	case reflect.Uint16:
		WriteUint16(uint16(rv.Uint()), w, n, err)

	case reflect.Uint8:
		WriteUint8(uint8(rv.Uint()), w, n, err)

	case reflect.Uint:
		WriteUvarint(uint(rv.Uint()), w, n, err)

	default:
		panic(fmt.Sprintf("Unknown field type %v", rt.Kind()))
	}
}