libgo/go/net/rpc/jsonrpc/client.go

   1 // Copyright 2010 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // Package jsonrpc implements a JSON-RPC 1.0 ClientCodec and ServerCodec
   6 // for the rpc package.
   7 // For JSON-RPC 2.0 support, see https://godoc.org/?q=json-rpc+2.0
   8 package jsonrpc
   9
  10 import (
  11         "encoding/json"
  12         "fmt"
  13         "io"
  14         "net"
  15         "net/rpc"
  16         "sync"
  17 )
  18
  19 type clientCodec struct {
  20         dec *json.Decoder // for reading JSON values
  21         enc *json.Encoder // for writing JSON values
  22         c   io.Closer
  23
  24         // temporary work space
  25         req  clientRequest
  26         resp clientResponse
  27
  28         // JSON-RPC responses include the request id but not the request method.
  29         // Package rpc expects both.
  30         // We save the request method in pending when sending a request
  31         // and then look it up by request ID when filling out the rpc Response.
  32         mutex   sync.Mutex        // protects pending
  33         pending map[uint64]string // map request id to method name
  34 }
  35
  36 // NewClientCodec returns a new rpc.ClientCodec using JSON-RPC on conn.
  37 func NewClientCodec(conn io.ReadWriteCloser) rpc.ClientCodec {
  38         return &clientCodec{
  39                 dec:     json.NewDecoder(conn),
  40                 enc:     json.NewEncoder(conn),
  41                 c:       conn,
  42                 pending: make(map[uint64]string),
  43         }
  44 }
  45
  46 type clientRequest struct {
  47         Method string         `json:"method"`
  48         Params [1]interface{} `json:"params"`
  49         Id     uint64         `json:"id"`
  50 }
  51
  52 func (c *clientCodec) WriteRequest(r *rpc.Request, param interface{}) error {
  53         c.mutex.Lock()
  54         c.pending[r.Seq] = r.ServiceMethod
  55         c.mutex.Unlock()
  56         c.req.Method = r.ServiceMethod
  57         c.req.Params[0] = param
  58         c.req.Id = r.Seq
  59         return c.enc.Encode(&c.req)
  60 }
  61
  62 type clientResponse struct {
  63         Id     uint64           `json:"id"`
  64         Result *json.RawMessage `json:"result"`
  65         Error  interface{}      `json:"error"`
  66 }
  67
  68 func (r *clientResponse) reset() {
  69         r.Id = 0
  70         r.Result = nil
  71         r.Error = nil
  72 }
  73
  74 func (c *clientCodec) ReadResponseHeader(r *rpc.Response) error {
  75         c.resp.reset()
  76         if err := c.dec.Decode(&c.resp); err != nil {
  77                 return err
  78         }
  79
  80         c.mutex.Lock()
  81         r.ServiceMethod = c.pending[c.resp.Id]
  82         delete(c.pending, c.resp.Id)
  83         c.mutex.Unlock()
  84
  85         r.Error = ""
  86         r.Seq = c.resp.Id
  87         if c.resp.Error != nil || c.resp.Result == nil {
  88                 x, ok := c.resp.Error.(string)
  89                 if !ok {
  90                         return fmt.Errorf("invalid error %v", c.resp.Error)
  91                 }
  92                 if x == "" {
  93                         x = "unspecified error"
  94                 }
  95                 r.Error = x
  96         }
  97         return nil
  98 }
  99
 100 func (c *clientCodec) ReadResponseBody(x interface{}) error {
 101         if x == nil {
 102                 return nil
 103         }
 104         return json.Unmarshal(*c.resp.Result, x)
 105 }
 106
 107 func (c *clientCodec) Close() error {
 108         return c.c.Close()
 109 }
 110
 111 // NewClient returns a new rpc.Client to handle requests to the
 112 // set of services at the other end of the connection.
 113 func NewClient(conn io.ReadWriteCloser) *rpc.Client {
 114         return rpc.NewClientWithCodec(NewClientCodec(conn))
 115 }
 116
 117 // Dial connects to a JSON-RPC server at the specified network address.
 118 func Dial(network, address string) (*rpc.Client, error) {
 119         conn, err := net.Dial(network, address)
 120         if err != nil {
 121                 return nil, err
 122         }
 123         return NewClient(conn), err
 124 }