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| 1 | +package rpcstream |
| 2 | + |
| 3 | +import ( |
| 4 | + "context" |
| 5 | + "errors" |
| 6 | + |
| 7 | + "github.com/aperturerobotics/starpc/srpc" |
| 8 | +) |
| 9 | + |
| 10 | +// RpcStream implements a RPC call stream over a RPC call. Used to implement |
| 11 | +// sub-components which have a different set of services & calls available. |
| 12 | +type RpcStream interface { |
| 13 | + srpc.Stream |
| 14 | + Send(*Packet) error |
| 15 | + Recv() (*Packet, error) |
| 16 | +} |
| 17 | + |
| 18 | +// RpcStreamGetter returns the Mux for the component ID from the remote. |
| 19 | +type RpcStreamGetter func(ctx context.Context, componentID string) (srpc.Mux, error) |
| 20 | + |
| 21 | +// RpcStreamCaller is a function which starts the RpcStream call. |
| 22 | +type RpcStreamCaller func(ctx context.Context) (RpcStream, error) |
| 23 | + |
| 24 | +// NewRpcStreamOpenStream constructs an OpenStream function with a RpcStream. |
| 25 | +func NewRpcStreamOpenStream(componentID string, rpcCaller RpcStreamCaller) srpc.OpenStreamFunc { |
| 26 | + return func(ctx context.Context, msgHandler srpc.PacketHandler) (srpc.Writer, error) { |
| 27 | + // open the rpc stream |
| 28 | + rpcStream, err := rpcCaller(ctx) |
| 29 | + if err != nil { |
| 30 | + return nil, err |
| 31 | + } |
| 32 | + |
| 33 | + // write the component id |
| 34 | + err = rpcStream.Send(&Packet{ |
| 35 | + Body: &Packet_Init{ |
| 36 | + Init: &RpcStreamInit{ |
| 37 | + ComponentId: componentID, |
| 38 | + }, |
| 39 | + }, |
| 40 | + }) |
| 41 | + if err != nil { |
| 42 | + _ = rpcStream.Close() |
| 43 | + return nil, err |
| 44 | + } |
| 45 | + |
| 46 | + // initialize the rpc |
| 47 | + rw := NewRpcStreamReadWriter(rpcStream, msgHandler) |
| 48 | + |
| 49 | + // start the read pump |
| 50 | + go func() { |
| 51 | + err := rw.ReadPump() |
| 52 | + if err != nil { |
| 53 | + _ = rw.Close() |
| 54 | + } |
| 55 | + }() |
| 56 | + |
| 57 | + // return the writer |
| 58 | + return rw, nil |
| 59 | + } |
| 60 | +} |
| 61 | + |
| 62 | +// HandleRpcStream handles an incoming RPC stream (remote is the initiator). |
| 63 | +func HandleRpcStream(stream RpcStream, getter RpcStreamGetter) error { |
| 64 | + // Read the "init" packet. |
| 65 | + initPkt, err := stream.Recv() |
| 66 | + if err != nil { |
| 67 | + return err |
| 68 | + } |
| 69 | + initInner, ok := initPkt.GetBody().(*Packet_Init) |
| 70 | + if !ok || initInner.Init == nil { |
| 71 | + return errors.New("expected init packet") |
| 72 | + } |
| 73 | + componentID := initInner.Init.GetComponentId() |
| 74 | + if componentID == "" { |
| 75 | + return errors.New("invalid init packet: empty component id") |
| 76 | + } |
| 77 | + |
| 78 | + // lookup the server for this component id |
| 79 | + ctx := stream.Context() |
| 80 | + mux, err := getter(ctx, componentID) |
| 81 | + if err != nil { |
| 82 | + return err |
| 83 | + } |
| 84 | + if mux == nil { |
| 85 | + return errors.New("no server for that component") |
| 86 | + } |
| 87 | + |
| 88 | + // handle the rpc |
| 89 | + serverRPC := srpc.NewServerRPC(ctx, mux) |
| 90 | + prw := NewRpcStreamReadWriter(stream, serverRPC.HandlePacket) |
| 91 | + serverRPC.SetWriter(prw) |
| 92 | + err = prw.ReadPump() |
| 93 | + _ = prw.Close() |
| 94 | + return err |
| 95 | +} |
| 96 | + |
| 97 | +// RpcStreamReadWriter reads and writes packets from a RpcStream. |
| 98 | +type RpcStreamReadWriter struct { |
| 99 | + // stream is the RpcStream |
| 100 | + stream RpcStream |
| 101 | + // cb is the callback |
| 102 | + cb srpc.PacketHandler |
| 103 | +} |
| 104 | + |
| 105 | +// NewRpcStreamReadWriter constructs a new read/writer. |
| 106 | +func NewRpcStreamReadWriter(stream RpcStream, cb srpc.PacketHandler) *RpcStreamReadWriter { |
| 107 | + return &RpcStreamReadWriter{stream: stream, cb: cb} |
| 108 | +} |
| 109 | + |
| 110 | +// WritePacket writes a packet to the writer. |
| 111 | +func (r *RpcStreamReadWriter) WritePacket(p *srpc.Packet) error { |
| 112 | + data, err := p.MarshalVT() |
| 113 | + if err != nil { |
| 114 | + return err |
| 115 | + } |
| 116 | + return r.stream.Send(&Packet{ |
| 117 | + Body: &Packet_Data{ |
| 118 | + Data: data, |
| 119 | + }, |
| 120 | + }) |
| 121 | +} |
| 122 | + |
| 123 | +// ReadPump executes the read pump in a goroutine. |
| 124 | +func (r *RpcStreamReadWriter) ReadPump() error { |
| 125 | + for { |
| 126 | + rpcStreamPkt, err := r.stream.Recv() |
| 127 | + if err != nil { |
| 128 | + return err |
| 129 | + } |
| 130 | + dataPkt, ok := rpcStreamPkt.GetBody().(*Packet_Data) |
| 131 | + if !ok { |
| 132 | + return errors.New("expected data packet") |
| 133 | + } |
| 134 | + pkt := &srpc.Packet{} |
| 135 | + if err := pkt.UnmarshalVT(dataPkt.Data); err != nil { |
| 136 | + return err |
| 137 | + } |
| 138 | + if err := r.cb(pkt); err != nil { |
| 139 | + return err |
| 140 | + } |
| 141 | + } |
| 142 | +} |
| 143 | + |
| 144 | +// Close closes the packet rw. |
| 145 | +func (r *RpcStreamReadWriter) Close() error { |
| 146 | + return r.stream.Close() |
| 147 | +} |
| 148 | + |
| 149 | +// _ is a type assertion |
| 150 | +var _ srpc.Writer = (*RpcStreamReadWriter)(nil) |
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