mirror of https://github.com/poanetwork/gecko.git
349 lines
10 KiB
Go
349 lines
10 KiB
Go
// (c) 2019-2020, Ava Labs, Inc. All rights reserved.
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// See the file LICENSE for licensing terms.
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package codec
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import (
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"errors"
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"fmt"
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"reflect"
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"unicode"
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"github.com/ava-labs/gecko/utils/wrappers"
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)
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const (
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defaultMaxSize = 1 << 18 // default max size, in bytes, of something being marshalled by Marshal()
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defaultMaxSliceLength = 1 << 18 // default max length of a slice being marshalled by Marshal()
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)
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// ErrBadCodec is returned when one tries to perform an operation
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// using an unknown codec
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var (
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errBadCodec = errors.New("wrong or unknown codec used")
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errNil = errors.New("can't marshal nil value")
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errUnmarshalNil = errors.New("can't unmarshal into nil")
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errNeedPointer = errors.New("must unmarshal into a pointer")
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errMarshalUnregisteredType = errors.New("can't marshal an unregistered type")
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errUnmarshalUnregisteredType = errors.New("can't unmarshal an unregistered type")
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errUnknownType = errors.New("don't know how to marshal/unmarshal this type")
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errMarshalUnexportedField = errors.New("can't serialize an unexported field")
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errUnmarshalUnexportedField = errors.New("can't deserialize into an unexported field")
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errOutOfMemory = errors.New("out of memory")
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errSliceTooLarge = errors.New("slice too large")
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)
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// Codec handles marshaling and unmarshaling of structs
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type codec struct {
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maxSize int
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maxSliceLen int
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typeIDToType map[uint32]reflect.Type
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typeToTypeID map[reflect.Type]uint32
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}
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// Codec marshals and unmarshals
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type Codec interface {
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RegisterType(interface{}) error
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Marshal(interface{}) ([]byte, error)
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Unmarshal([]byte, interface{}) error
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}
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// New returns a new codec
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func New(maxSize, maxSliceLen int) Codec {
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return codec{
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maxSize: maxSize,
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maxSliceLen: maxSliceLen,
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typeIDToType: map[uint32]reflect.Type{},
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typeToTypeID: map[reflect.Type]uint32{},
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}
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}
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// NewDefault returns a new codec with reasonable default values
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func NewDefault() Codec { return New(defaultMaxSize, defaultMaxSliceLength) }
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// RegisterType is used to register types that may be unmarshaled into an interface typed value
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// [val] is a value of the type being registered
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func (c codec) RegisterType(val interface{}) error {
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valType := reflect.TypeOf(val)
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if _, exists := c.typeToTypeID[valType]; exists {
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return fmt.Errorf("type %v has already been registered", valType)
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}
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c.typeIDToType[uint32(len(c.typeIDToType))] = reflect.TypeOf(val)
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c.typeToTypeID[valType] = uint32(len(c.typeIDToType) - 1)
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return nil
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}
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// A few notes:
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// 1) See codec_test.go for examples of usage
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// 2) We use "marshal" and "serialize" interchangeably, and "unmarshal" and "deserialize" interchangeably
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// 3) To include a field of a struct in the serialized form, add the tag `serialize:"true"` to it
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// 4) These typed members of a struct may be serialized:
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// bool, string, uint[8,16,32,64, int[8,16,32,64],
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// structs, slices, arrays, interface.
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// structs, slices and arrays can only be serialized if their constituent parts can be.
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// 5) To marshal an interface typed value, you must pass a _pointer_ to the value
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// 6) If you want to be able to unmarshal into an interface typed value,
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// you must call codec.RegisterType([instance of the type that fulfills the interface]).
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// 7) nil slices will be unmarshaled as an empty slice of the appropriate type
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// 8) Serialized fields must be exported
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// Marshal returns the byte representation of [value]
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// If you want to marshal an interface, [value] must be a pointer
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// to the interface
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func (c codec) Marshal(value interface{}) ([]byte, error) {
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if value == nil {
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return nil, errNil
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}
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return c.marshal(reflect.ValueOf(value))
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}
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// Marshal [value] to bytes
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func (c codec) marshal(value reflect.Value) ([]byte, error) {
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p := wrappers.Packer{MaxSize: c.maxSize, Bytes: []byte{}}
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t := value.Type()
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valueKind := value.Kind()
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switch valueKind {
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case reflect.Interface, reflect.Ptr, reflect.Slice:
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if value.IsNil() {
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return nil, errNil
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}
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}
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switch valueKind {
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case reflect.Uint8:
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p.PackByte(uint8(value.Uint()))
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return p.Bytes, p.Err
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case reflect.Int8:
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p.PackByte(uint8(value.Int()))
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return p.Bytes, p.Err
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case reflect.Uint16:
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p.PackShort(uint16(value.Uint()))
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return p.Bytes, p.Err
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case reflect.Int16:
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p.PackShort(uint16(value.Int()))
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return p.Bytes, p.Err
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case reflect.Uint32:
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p.PackInt(uint32(value.Uint()))
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return p.Bytes, p.Err
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case reflect.Int32:
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p.PackInt(uint32(value.Int()))
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return p.Bytes, p.Err
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case reflect.Uint64:
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p.PackLong(value.Uint())
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return p.Bytes, p.Err
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case reflect.Int64:
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p.PackLong(uint64(value.Int()))
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return p.Bytes, p.Err
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case reflect.Uintptr, reflect.Ptr:
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return c.marshal(value.Elem())
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case reflect.String:
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p.PackStr(value.String())
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return p.Bytes, p.Err
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case reflect.Bool:
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p.PackBool(value.Bool())
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return p.Bytes, p.Err
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case reflect.Interface:
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typeID, ok := c.typeToTypeID[reflect.TypeOf(value.Interface())] // Get the type ID of the value being marshaled
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if !ok {
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return nil, fmt.Errorf("can't marshal unregistered type '%v'", reflect.TypeOf(value.Interface()).String())
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}
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p.PackInt(typeID)
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bytes, err := c.Marshal(value.Interface())
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if err != nil {
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return nil, err
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}
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p.PackFixedBytes(bytes)
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if p.Errored() {
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return nil, p.Err
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}
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return p.Bytes, err
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case reflect.Array, reflect.Slice:
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numElts := value.Len() // # elements in the slice/array (assumed to be <= 2^31 - 1)
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// If this is a slice, pack the number of elements in the slice
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if valueKind == reflect.Slice {
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p.PackInt(uint32(numElts))
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}
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for i := 0; i < numElts; i++ { // Pack each element in the slice/array
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eltBytes, err := c.marshal(value.Index(i))
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if err != nil {
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return nil, err
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}
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p.PackFixedBytes(eltBytes)
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}
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return p.Bytes, p.Err
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case reflect.Struct:
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for i := 0; i < t.NumField(); i++ { // Go through all fields of this struct
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field := t.Field(i)
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if !shouldSerialize(field) { // Skip fields we don't need to serialize
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continue
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}
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if unicode.IsLower(rune(field.Name[0])) { // Can only marshal exported fields
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return nil, errMarshalUnexportedField
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}
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fieldVal := value.Field(i) // The field we're serializing
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if fieldVal.Kind() == reflect.Slice && fieldVal.IsNil() {
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p.PackInt(0)
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continue
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}
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fieldBytes, err := c.marshal(fieldVal) // Serialize the field
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if err != nil {
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return nil, err
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}
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p.PackFixedBytes(fieldBytes)
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}
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return p.Bytes, p.Err
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case reflect.Invalid:
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return nil, errUnmarshalNil
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default:
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return nil, errUnknownType
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}
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}
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// Unmarshal unmarshals [bytes] into [dest], where
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// [dest] must be a pointer or interface
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func (c codec) Unmarshal(bytes []byte, dest interface{}) error {
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p := &wrappers.Packer{Bytes: bytes}
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if len(bytes) > c.maxSize {
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return errSliceTooLarge
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}
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if dest == nil {
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return errNil
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}
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destPtr := reflect.ValueOf(dest)
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if destPtr.Kind() != reflect.Ptr {
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return errNeedPointer
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}
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destVal := destPtr.Elem()
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err := c.unmarshal(p, destVal)
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if err != nil {
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return err
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}
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if p.Offset != len(p.Bytes) {
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return fmt.Errorf("has %d leftover bytes after unmarshalling", len(p.Bytes)-p.Offset)
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}
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return nil
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}
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// Unmarshal bytes from [p] into [field]
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// [field] must be addressable
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func (c codec) unmarshal(p *wrappers.Packer, field reflect.Value) error {
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kind := field.Kind()
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switch kind {
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case reflect.Uint8:
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field.SetUint(uint64(p.UnpackByte()))
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case reflect.Int8:
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field.SetInt(int64(p.UnpackByte()))
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case reflect.Uint16:
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field.SetUint(uint64(p.UnpackShort()))
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case reflect.Int16:
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field.SetInt(int64(p.UnpackShort()))
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case reflect.Uint32:
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field.SetUint(uint64(p.UnpackInt()))
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case reflect.Int32:
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field.SetInt(int64(p.UnpackInt()))
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case reflect.Uint64:
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field.SetUint(p.UnpackLong())
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case reflect.Int64:
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field.SetInt(int64(p.UnpackLong()))
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case reflect.Bool:
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field.SetBool(p.UnpackBool())
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case reflect.Slice:
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sliceLen := int(p.UnpackInt()) // number of elements in the slice
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if sliceLen < 0 || sliceLen > c.maxSliceLen {
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return errSliceTooLarge
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}
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// First set [field] to be a slice of the appropriate type/capacity (right now [field] is nil)
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slice := reflect.MakeSlice(field.Type(), sliceLen, sliceLen)
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field.Set(slice)
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// Unmarshal each element into the appropriate index of the slice
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for i := 0; i < sliceLen; i++ {
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if err := c.unmarshal(p, field.Index(i)); err != nil {
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return err
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}
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}
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case reflect.Array:
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for i := 0; i < field.Len(); i++ {
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if err := c.unmarshal(p, field.Index(i)); err != nil {
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return err
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}
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}
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case reflect.String:
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field.SetString(p.UnpackStr())
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case reflect.Interface:
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// Get the type ID
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typeID := p.UnpackInt()
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// Get a struct that implements the interface
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typ, ok := c.typeIDToType[typeID]
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if !ok {
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return errUnmarshalUnregisteredType
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}
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// Ensure struct actually does implement the interface
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fieldType := field.Type()
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if !typ.Implements(fieldType) {
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return fmt.Errorf("%s does not implement interface %s", typ, fieldType)
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}
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concreteInstancePtr := reflect.New(typ) // instance of the proper type
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// Unmarshal into the struct
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if err := c.unmarshal(p, concreteInstancePtr.Elem()); err != nil {
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return err
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}
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// And assign the filled struct to the field
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field.Set(concreteInstancePtr.Elem())
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case reflect.Struct:
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// Type of this struct
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structType := reflect.TypeOf(field.Interface())
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// Go through all the fields and umarshal into each
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for i := 0; i < structType.NumField(); i++ {
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structField := structType.Field(i)
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if !shouldSerialize(structField) { // Skip fields we don't need to unmarshal
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continue
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}
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if unicode.IsLower(rune(structField.Name[0])) { // Only unmarshal into exported field
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return errUnmarshalUnexportedField
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}
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field := field.Field(i) // Get the field
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if err := c.unmarshal(p, field); err != nil { // Unmarshal into the field
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return err
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}
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if p.Errored() { // If there was an error just return immediately
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return p.Err
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}
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}
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case reflect.Ptr:
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// Get the type this pointer points to
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underlyingType := field.Type().Elem()
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// Create a new pointer to a new value of the underlying type
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underlyingValue := reflect.New(underlyingType)
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// Fill the value
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if err := c.unmarshal(p, underlyingValue.Elem()); err != nil {
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return err
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}
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// Assign to the top-level struct's member
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field.Set(underlyingValue)
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case reflect.Invalid:
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return errUnmarshalNil
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default:
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return errUnknownType
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}
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return p.Err
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}
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// Returns true iff [field] should be serialized
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func shouldSerialize(field reflect.StructField) bool {
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if field.Tag.Get("serialize") == "true" {
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return true
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}
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return false
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}
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