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Source file src/net/rpc/jsonrpc/client.go

Documentation: net/rpc/jsonrpc

     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  }
   125  

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