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common-rpc.go
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common-rpc.go
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package srpc
import (
"context"
"io"
"sync"
"github.com/aperturerobotics/util/broadcast"
"github.com/pkg/errors"
)
// commonRPC contains common logic between server/client rpc.
type commonRPC struct {
// ctx is the context, canceled when the rpc ends.
ctx context.Context
// ctxCancel is called when the rpc ends.
ctxCancel context.CancelFunc
// service is the rpc service
service string
// method is the rpc method
method string
// mtx guards below fields
mtx sync.Mutex
// bcast broadcasts when below fields change
bcast broadcast.Broadcast
// writer is the writer to write messages to
writer PacketWriter
// dataQueue contains incoming data packets.
// note: packets may be len() == 0
dataQueue [][]byte
// dataClosed is a flag set after dataQueue is closed.
// controlled by HandlePacket.
dataClosed bool
// remoteErr is an error set by the remote.
remoteErr error
}
// initCommonRPC initializes the commonRPC.
func initCommonRPC(ctx context.Context, rpc *commonRPC) {
rpc.ctx, rpc.ctxCancel = context.WithCancel(ctx)
}
// Context is canceled when the rpc has finished.
func (c *commonRPC) Context() context.Context {
return c.ctx
}
// Wait waits for the RPC to finish.
func (c *commonRPC) Wait(ctx context.Context) error {
for {
c.mtx.Lock()
if c.dataClosed {
err := c.remoteErr
c.mtx.Unlock()
return err
}
waiter := c.bcast.GetWaitCh()
c.mtx.Unlock()
select {
case <-ctx.Done():
return context.Canceled
case <-waiter:
}
}
}
// ReadOne reads a single message and returns.
//
// returns io.EOF if the stream ended without a packet.
func (c *commonRPC) ReadOne() ([]byte, error) {
var msg []byte
var err error
var ctxDone bool
for {
c.mtx.Lock()
waiter := c.bcast.GetWaitCh()
if ctxDone && !c.dataClosed {
// context must have been canceled locally
c.closeLocked()
err = context.Canceled
c.mtx.Unlock()
return nil, err
}
if len(c.dataQueue) != 0 {
msg = c.dataQueue[0]
c.dataQueue[0] = nil
c.dataQueue = c.dataQueue[1:]
c.mtx.Unlock()
return msg, nil
}
if c.dataClosed || c.remoteErr != nil {
err = c.remoteErr
if err == nil {
err = io.EOF
}
c.mtx.Unlock()
return nil, err
}
c.mtx.Unlock()
select {
case <-c.ctx.Done():
ctxDone = true
case <-waiter:
}
}
}
// WriteCallData writes a call data packet.
func (c *commonRPC) WriteCallData(data []byte, complete bool, err error) error {
if c.writer == nil {
return ErrCompleted
}
outPkt := NewCallDataPacket(data, len(data) == 0, false, nil)
return c.writer.WritePacket(outPkt)
}
// HandleStreamClose handles the incoming stream closing w/ optional error.
func (c *commonRPC) HandleStreamClose(closeErr error) {
c.mtx.Lock()
defer c.mtx.Unlock()
if closeErr != nil && c.remoteErr == nil {
c.remoteErr = closeErr
}
c.dataClosed = true
c.ctxCancel()
if c.writer != nil {
_ = c.writer.Close()
}
c.bcast.Broadcast()
}
// HandleCallCancel handles the call cancel packet.
func (c *commonRPC) HandleCallCancel() error {
c.HandleStreamClose(context.Canceled)
return nil
}
// HandleCallData handles the call data packet.
func (c *commonRPC) HandleCallData(pkt *CallData) error {
c.mtx.Lock()
defer c.mtx.Unlock()
if c.dataClosed {
return ErrCompleted
}
if data := pkt.GetData(); len(data) != 0 || pkt.GetDataIsZero() {
c.dataQueue = append(c.dataQueue, data)
}
complete := pkt.GetComplete()
if err := pkt.GetError(); len(err) != 0 {
complete = true
c.remoteErr = errors.New(err)
}
if complete {
c.dataClosed = true
}
c.bcast.Broadcast()
return nil
}
// WriteCancel writes a call cancel packet.
func (c *commonRPC) WriteCancel() error {
if c.writer != nil {
return c.writer.WritePacket(NewCallCancelPacket())
}
return nil
}
// closeLocked releases resources held by the RPC.
func (c *commonRPC) closeLocked() {
c.dataClosed = true
if c.remoteErr == nil {
c.remoteErr = context.Canceled
}
if c.writer != nil {
_ = c.writer.Close()
}
c.bcast.Broadcast()
c.ctxCancel()
}