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rpc.go
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rpc.go
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// Package msgpackrpc provides a msgpack-rpc codec
package msgpackrpc
import (
"errors"
"github.com/tinylib/msgp/msgp"
)
// The msgpack-rpc specification: https://github.com/msgpack-rpc/msgpack-rpc/blob/master/spec.md
const (
RequestType = 0
ResponseType = 1
NotificationType = 2
RequestPackSize = 4
ResponsePackSize = 4
NotificationPackSize = 3
)
var (
ErrBadPackSize = errors.New("Bad pack size")
ErrBadMessageType = errors.New("Bad message type")
ErrBadErrorType = errors.New("Bad error type")
ErrUnexpectedParams = errors.New("Unexpected params")
ErrNotEncodable = errors.New("Not encodable")
ErrNotDecodable = errors.New("Not decodable")
)
// decodeBody decodes the body of the message.
func decodeBody(r *msgp.Reader, v interface{}) error {
b, ok := v.(msgp.Decodable)
if !ok {
return ErrNotDecodable
}
return msgp.Decode(r, b)
}
// Request is what the client can construct to be sent to the server.
// The params represents the body of the request.
type Request struct {
ID uint32
Method string
Body interface{}
hasBody bool
}
// EncodeMsg encodes the request to writer. The body is expected to
// be an encodable type.
func (r *Request) EncodeMsg(w *msgp.Writer) error {
var bm msgp.Encodable
if r.Body != nil {
var ok bool
bm, ok = r.Body.(msgp.Encodable)
if !ok {
return ErrNotEncodable
}
}
var err error
if err = w.WriteArrayHeader(RequestPackSize); err != nil {
return err
}
if err = w.WriteInt(RequestType); err != nil {
return err
}
if err = w.WriteUint32(r.ID); err != nil {
return err
}
if err = w.WriteString(r.Method); err != nil {
return err
}
// No body to encode. Write a zero-length params array.
if bm == nil {
return w.WriteArrayHeader(0)
}
// 1-item array containing the body.
if err = w.WriteArrayHeader(1); err != nil {
return err
}
return msgp.Encode(w, bm)
}
func (r *Request) DecodeMsg(mr *msgp.Reader) error {
var bm msgp.Decodable
if r.Body != nil {
var ok bool
bm, ok = r.Body.(msgp.Decodable)
if !ok {
return ErrNotDecodable
}
}
if size, err := mr.ReadArrayHeader(); err != nil {
return err
} else if size != RequestPackSize {
return ErrBadPackSize
}
if typ, err := mr.ReadInt(); err != nil {
return err
} else if typ != RequestType {
return ErrBadMessageType
}
id, err := mr.ReadUint32()
if err != nil {
return err
}
r.ID = id
method, err := mr.ReadString()
if err != nil {
return err
}
r.Method = method
// The request body is packed in an array.
l, err := mr.ReadArrayHeader()
if err != nil {
return err
}
if l > 1 {
return ErrUnexpectedParams
} else if l == 0 {
return nil
}
r.hasBody = true
// Skip decoding the body if no value is present to decode into.
// The caller is expected to decode the body or skip it.
if bm != nil {
return decodeBody(mr, bm)
}
return nil
}
type Response struct {
ID uint32
Error string
Body interface{}
hasBody bool
}
func (r *Response) EncodeMsg(w *msgp.Writer) error {
var bm msgp.Encodable
if r.Body != nil {
var ok bool
bm, ok = r.Body.(msgp.Encodable)
if !ok {
return ErrNotEncodable
}
}
var err error
if err = w.WriteArrayHeader(ResponsePackSize); err != nil {
return err
}
if err = w.WriteInt(ResponseType); err != nil {
return err
}
if err = w.WriteUint32(r.ID); err != nil {
return err
}
// No error.
if r.Error == "" {
if err = w.WriteNil(); err != nil {
return err
}
if bm != nil {
return msgp.Encode(w, bm)
}
} else {
if err = w.WriteString(r.Error); err != nil {
return err
}
}
// Write nil body.
return w.WriteNil()
}
func (r *Response) DecodeMsg(mr *msgp.Reader) error {
var bm msgp.Decodable
if r.Body != nil {
var ok bool
bm, ok = r.Body.(msgp.Decodable)
if !ok {
return ErrNotDecodable
}
}
if size, err := mr.ReadArrayHeader(); err != nil {
return err
} else if size != ResponsePackSize {
return ErrBadPackSize
}
if typ, err := mr.ReadInt(); err != nil {
return err
} else if typ != ResponseType {
return ErrBadMessageType
}
id, err := mr.ReadUint32()
if err != nil {
return err
}
r.ID = id
// Error can be nil or a string.
typ, err := mr.NextType()
if err != nil {
return err
}
switch typ {
case msgp.StrType:
s, err := mr.ReadString()
if err != nil {
return err
}
r.Error = s
case msgp.NilType:
if err := mr.ReadNil(); err != nil {
return err
}
r.Error = ""
default:
return ErrBadErrorType
}
// Body can be nil.
typ, err = mr.NextType()
if err != nil {
return err
}
if typ == msgp.NilType {
r.hasBody = false
return mr.ReadNil()
}
r.hasBody = true
// Skip decoding the body if no value is present to decode into.
// The caller is expected to read the body or skip it.
if bm != nil {
return decodeBody(mr, bm)
}
return nil
}
type Notification struct {
Method string
Body interface{}
hasBody bool
}
// EncodeMsg encodes the notification to writer. The body is expected to
// be an encodable type.
func (n *Notification) EncodeMsg(w *msgp.Writer) error {
var bm msgp.Encodable
if n.Body != nil {
var ok bool
bm, ok = n.Body.(msgp.Encodable)
if !ok {
return ErrNotEncodable
}
}
var err error
if err = w.WriteArrayHeader(NotificationPackSize); err != nil {
return err
}
if err = w.WriteInt(NotificationType); err != nil {
return err
}
if err = w.WriteString(n.Method); err != nil {
return err
}
// No body to encode. Write a zero-length params array.
if bm == nil {
return w.WriteArrayHeader(0)
}
// 1-item array containing the body.
if err = w.WriteArrayHeader(1); err != nil {
return err
}
return msgp.Encode(w, bm)
}
func (n *Notification) DecodeMsg(mr *msgp.Reader) error {
var bm msgp.Decodable
if n.Body != nil {
var ok bool
bm, ok = n.Body.(msgp.Decodable)
if !ok {
return ErrNotDecodable
}
}
if size, err := mr.ReadArrayHeader(); err != nil {
return err
} else if size != NotificationPackSize {
return ErrBadPackSize
}
if typ, err := mr.ReadInt(); err != nil {
return err
} else if typ != NotificationType {
return ErrBadMessageType
}
method, err := mr.ReadString()
if err != nil {
return err
}
n.Method = method
// The notification body is packed in an array.
l, err := mr.ReadArrayHeader()
if err != nil {
return err
}
if l > 1 {
return ErrUnexpectedParams
} else if l == 0 {
return nil
}
n.hasBody = true
// Skip decoding the body if no value is present to decode into.
// The caller is expected to decode the body or skip it.
if bm != nil {
return decodeBody(mr, bm)
}
return nil
}