// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package rpc
import (
"bytes"
"context"
"encoding/json"
"errors"
"fmt"
"io"
"reflect"
"strings"
"sync"
"time"
)
const (
vsn = "2.0"
serviceMethodSeparator = "_"
subscribeMethodSuffix = "_subscribe"
unsubscribeMethodSuffix = "_unsubscribe"
notificationMethodSuffix = "_subscription"
defaultWriteTimeout = 10 * time.Second // used if context has no deadline
)
var null = json.RawMessage("null")
type subscriptionResult struct {
ID string `json:"subscription"`
Result json.RawMessage `json:"result,omitempty"`
}
// A value of this type can a JSON-RPC request, notification, successful response or
// error response. Which one it is depends on the fields.
type jsonrpcMessage struct {
Version string `json:"jsonrpc,omitempty"`
ID json.RawMessage `json:"id,omitempty"`
Method string `json:"method,omitempty"`
Params json.RawMessage `json:"params,omitempty"`
Error *jsonError `json:"error,omitempty"`
Result json.RawMessage `json:"result,omitempty"`
}
func (msg *jsonrpcMessage) isNotification() bool {
return msg.ID == nil && msg.Method != ""
}
func (msg *jsonrpcMessage) isCall() bool {
return msg.hasValidID() && msg.Method != ""
}
func (msg *jsonrpcMessage) isResponse() bool {
return msg.hasValidID() && msg.Method == "" && msg.Params == nil && (msg.Result != nil || msg.Error != nil)
}
func (msg *jsonrpcMessage) hasValidID() bool {
return len(msg.ID) > 0 && msg.ID[0] != '{' && msg.ID[0] != '['
}
func (msg *jsonrpcMessage) isSubscribe() bool {
return strings.HasSuffix(msg.Method, subscribeMethodSuffix)
}
func (msg *jsonrpcMessage) isUnsubscribe() bool {
return strings.HasSuffix(msg.Method, unsubscribeMethodSuffix)
}
func (msg *jsonrpcMessage) namespace() string {
elem := strings.SplitN(msg.Method, serviceMethodSeparator, 2)
return elem[0]
}
func (msg *jsonrpcMessage) String() string {
b, _ := json.Marshal(msg)
return string(b)
}
func (msg *jsonrpcMessage) errorResponse(err error) *jsonrpcMessage {
resp := errorMessage(err)
resp.ID = msg.ID
return resp
}
func (msg *jsonrpcMessage) response(result interface{}) *jsonrpcMessage {
enc, err := json.Marshal(result)
if err != nil {
// TODO: wrap with 'internal server error'
return msg.errorResponse(err)
}
return &jsonrpcMessage{Version: vsn, ID: msg.ID, Result: enc}
}
func errorMessage(err error) *jsonrpcMessage {
msg := &jsonrpcMessage{Version: vsn, ID: null, Error: &jsonError{
Code: defaultErrorCode,
Message: err.Error(),
}}
ec, ok := err.(Error)
if ok {
msg.Error.Code = ec.ErrorCode()
}
return msg
}
type jsonError struct {
Code int `json:"code"`
Message string `json:"message"`
Data interface{} `json:"data,omitempty"`
}
func (err *jsonError) Error() string {
if err.Message == "" {
return fmt.Sprintf("json-rpc error %d", err.Code)
}
return err.Message
}
func (err *jsonError) ErrorCode() int {
return err.Code
}
// Conn is a subset of the methods of net.Conn which are sufficient for ServerCodec.
type Conn interface {
io.ReadWriteCloser
SetWriteDeadline(time.Time) error
}
// ConnRemoteAddr wraps the RemoteAddr operation, which returns a description
// of the peer address of a connection. If a Conn also implements ConnRemoteAddr, this
// description is used in log messages.
type ConnRemoteAddr interface {
RemoteAddr() string
}
// connWithRemoteAddr overrides the remote address of a connection.
type connWithRemoteAddr struct {
Conn
addr string
}
func (c connWithRemoteAddr) RemoteAddr() string { return c.addr }
// jsonCodec reads and writes JSON-RPC messages to the underlying connection. It also has
// support for parsing arguments and serializing (result) objects.
type jsonCodec struct {
remoteAddr string
closer sync.Once // close closed channel once
closed chan interface{} // closed on Close
decode func(v interface{}) error // decoder to allow multiple transports
encMu sync.Mutex // guards the encoder
encode func(v interface{}) error // encoder to allow multiple transports
conn Conn
}
// NewCodec creates a new RPC server codec with support for JSON-RPC 2.0 based
// on explicitly given encoding and decoding methods.
func NewCodec(conn Conn, encode, decode func(v interface{}) error) ServerCodec {
codec := &jsonCodec{
closed: make(chan interface{}),
encode: encode,
decode: decode,
conn: conn,
}
if ra, ok := conn.(ConnRemoteAddr); ok {
codec.remoteAddr = ra.RemoteAddr()
}
return codec
}
// NewJSONCodec creates a new RPC server codec with support for JSON-RPC 2.0.
func NewJSONCodec(conn Conn) ServerCodec {
enc := json.NewEncoder(conn)
dec := json.NewDecoder(conn)
dec.UseNumber()
return NewCodec(conn, enc.Encode, dec.Decode)
}
func (c *jsonCodec) RemoteAddr() string {
return c.remoteAddr
}
func (c *jsonCodec) Read() (msg []*jsonrpcMessage, batch bool, err error) {
// Decode the next JSON object in the input stream.
// This verifies basic syntax, etc.
var rawmsg json.RawMessage
if err := c.decode(&rawmsg); err != nil {
return nil, false, err
}
msg, batch = parseMessage(rawmsg)
return msg, batch, nil
}
// Write sends a message to client.
func (c *jsonCodec) Write(ctx context.Context, v interface{}) error {
c.encMu.Lock()
defer c.encMu.Unlock()
deadline, ok := ctx.Deadline()
if !ok {
deadline = time.Now().Add(defaultWriteTimeout)
}
c.conn.SetWriteDeadline(deadline)
return c.encode(v)
}
// Close the underlying connection
func (c *jsonCodec) Close() {
c.closer.Do(func() {
close(c.closed)
c.conn.Close()
})
}
// Closed returns a channel which will be closed when Close is called
func (c *jsonCodec) Closed() <-chan interface{} {
return c.closed
}
// parseMessage parses raw bytes as a (batch of) JSON-RPC message(s). There are no error
// checks in this function because the raw message has already been syntax-checked when it
// is called. Any non-JSON-RPC messages in the input return the zero value of
// jsonrpcMessage.
func parseMessage(raw json.RawMessage) ([]*jsonrpcMessage, bool) {
if !isBatch(raw) {
msgs := []*jsonrpcMessage{{}}
json.Unmarshal(raw, &msgs[0])
return msgs, false
}
dec := json.NewDecoder(bytes.NewReader(raw))
dec.Token() // skip '['
var msgs []*jsonrpcMessage
for dec.More() {
msgs = append(msgs, new(jsonrpcMessage))
dec.Decode(&msgs[len(msgs)-1])
}
return msgs, true
}
// isBatch returns true when the first non-whitespace characters is '['
func isBatch(raw json.RawMessage) bool {
for _, c := range raw {
// skip insignificant whitespace (http://www.ietf.org/rfc/rfc4627.txt)
if c == 0x20 || c == 0x09 || c == 0x0a || c == 0x0d {
continue
}
return c == '['
}
return false
}
// parsePositionalArguments tries to parse the given args to an array of values with the
// given types. It returns the parsed values or an error when the args could not be
// parsed. Missing optional arguments are returned as reflect.Zero values.
func parsePositionalArguments(rawArgs json.RawMessage, types []reflect.Type) ([]reflect.Value, error) {
dec := json.NewDecoder(bytes.NewReader(rawArgs))
var args []reflect.Value
tok, err := dec.Token()
switch {
case err == io.EOF || tok == nil && err == nil:
// "params" is optional and may be empty. Also allow "params":null even though it's
// not in the spec because our own client used to send it.
case err != nil:
return nil, err
case tok == json.Delim('['):
// Read argument array.
if args, err = parseArgumentArray(dec, types); err != nil {
return nil, err
}
default:
return nil, errors.New("non-array args")
}
// Set any missing args to nil.
for i := len(args); i < len(types); i++ {
if types[i].Kind() != reflect.Ptr {
return nil, fmt.Errorf("missing value for required argument %d", i)
}
args = append(args, reflect.Zero(types[i]))
}
return args, nil
}
func parseArgumentArray(dec *json.Decoder, types []reflect.Type) ([]reflect.Value, error) {
args := make([]reflect.Value, 0, len(types))
for i := 0; dec.More(); i++ {
if i >= len(types) {
return args, fmt.Errorf("too many arguments, want at most %d", len(types))
}
argval := reflect.New(types[i])
if err := dec.Decode(argval.Interface()); err != nil {
return args, fmt.Errorf("invalid argument %d: %v", i, err)
}
if argval.IsNil() && types[i].Kind() != reflect.Ptr {
return args, fmt.Errorf("missing value for required argument %d", i)
}
args = append(args, argval.Elem())
}
// Read end of args array.
_, err := dec.Token()
return args, err
}
// parseSubscriptionName extracts the subscription name from an encoded argument array.
func parseSubscriptionName(rawArgs json.RawMessage) (string, error) {
dec := json.NewDecoder(bytes.NewReader(rawArgs))
if tok, _ := dec.Token(); tok != json.Delim('[') {
return "", errors.New("non-array args")
}
v, _ := dec.Token()
method, ok := v.(string)
if !ok {
return "", errors.New("expected subscription name as first argument")
}
return method, nil
}
