make api.Channel as interface

Change-Id: I052d241ab09043b1195beebeee99df4d8536621f
Signed-off-by: Vladimir Lavor <vlavor@cisco.com>

1 files changed, 53 insertions, 261 deletions

diff --git a/api/api.go b/api/api.go
index 34e17c1..9c68ab9 100644
--- a/api/api.go
+++ b/api/api.go
@@ -15,11 +15,7 @@
 package api
 
 import (
-	"errors"
-	"fmt"
 	"time"
-
-	"github.com/sirupsen/logrus"
 )
 
 // MessageType represents the type of a VPP message.
@@ -61,11 +57,11 @@ type DataType interface {
 type ChannelProvider interface {
 	// NewAPIChannel returns a new channel for communication with VPP via govpp core.
 	// It uses default buffer sizes for the request and reply Go channels.
-	NewAPIChannel() (*Channel, error)
+	NewAPIChannel() (Channel, error)
 
 	// NewAPIChannelBuffered returns a new channel for communication with VPP via govpp core.
 	// It allows to specify custom buffer sizes for the request and reply Go channels.
-	NewAPIChannelBuffered() (*Channel, error)
+	NewAPIChannelBuffered(reqChanBufSize, replyChanBufSize int) (Channel, error)
 }
 
 // MessageDecoder provides functionality for decoding binary data to generated API messages.
@@ -82,26 +78,57 @@ type MessageIdentifier interface {
 	LookupByID(ID uint16) (string, error)
 }
 
-// Channel is the main communication interface with govpp core. It contains two Go channels, one for sending the requests
-// to VPP and one for receiving the replies from it. The user can access the Go channels directly, or use the helper
-// methods  provided inside of this package. Do not use the same channel from multiple goroutines concurrently,
-// otherwise the responses could mix! Use multiple channels instead.
-type Channel struct {
-	ID uint16 // channel ID
-
-	ReqChan   chan *VppRequest // channel for sending the requests to VPP, closing this channel releases all resources in the ChannelProvider
-	ReplyChan chan *VppReply   // channel where VPP replies are delivered to
-
-	NotifSubsChan      chan *NotifSubscribeRequest // channel for sending notification subscribe requests
-	NotifSubsReplyChan chan error                  // channel where replies to notification subscribe requests are delivered to
-
-	MsgDecoder    MessageDecoder    // used to decode binary data to generated API messages
-	MsgIdentifier MessageIdentifier // used to retrieve message ID of a message
-
-	lastSeqNum uint16 // sequence number of the last sent request
-
-	delayedReply *VppReply     // reply already taken from ReplyChan, buffered for later delivery
-	replyTimeout time.Duration // maximum time that the API waits for a reply from VPP before returning an error, can be set with SetReplyTimeout
+// Channel provides methods for direct communication with VPP channel.
+type Channel interface {
+	// SendRequest asynchronously sends a request to VPP. Returns a request context, that can be used to call ReceiveReply.
+	// In case of any errors by sending, the error will be delivered to ReplyChan (and returned by ReceiveReply).
+	SendRequest(msg Message) RequestCtx
+	// SendMultiRequest asynchronously sends a multipart request (request to which multiple responses are expected) to VPP.
+	// Returns a multipart request context, that can be used to call ReceiveReply.
+	// In case of any errors by sending, the error will be delivered to ReplyChan (and returned by ReceiveReply).
+	SendMultiRequest(msg Message) MultiRequestCtx
+	// SubscribeNotification subscribes for receiving of the specified notification messages via provided Go channel.
+	// Note that the caller is responsible for creating the Go channel with preferred buffer size. If the channel's
+	// buffer is full, the notifications will not be delivered into it.
+	SubscribeNotification(notifChan chan Message, msgFactory func() Message) (*NotifSubscription, error)
+	// UnsubscribeNotification unsubscribes from receiving the notifications tied to the provided notification subscription.
+	UnsubscribeNotification(subscription *NotifSubscription) error
+	// CheckMessageCompatibility checks whether provided messages are compatible with the version of VPP
+	// which the library is connected to.
+	CheckMessageCompatibility(messages ...Message) error
+	// SetReplyTimeout sets the timeout for replies from VPP. It represents the maximum time the API waits for a reply
+	// from VPP before returning an error.
+	SetReplyTimeout(timeout time.Duration)
+	// GetRequestChannel returns request go channel of the VPP channel
+	GetRequestChannel() chan<- *VppRequest
+	// GetReplyChannel returns reply go channel of the VPP channel
+	GetReplyChannel() <-chan *VppReply
+	// GetNotificationChannel returns notification go channel of the VPP channel
+	GetNotificationChannel() chan<- *NotifSubscribeRequest
+	// GetNotificationReplyChannel returns notification reply go channel of the VPP channel
+	GetNotificationReplyChannel() <-chan error
+	// GetMessageDecoder returns message decoder instance
+	GetMessageDecoder() MessageDecoder
+	// GetID returns channel's ID
+	GetID() uint16
+	// Close closes the API channel and releases all API channel-related resources in the ChannelProvider.
+	Close()
+}
+
+// RequestCtx is helper interface which allows to receive reply on request context data
+type RequestCtx interface {
+	// ReceiveReply receives a reply from VPP (blocks until a reply is delivered from VPP, or until an error occurs).
+	// The reply will be decoded into the msg argument. Error will be returned if the response cannot be received or decoded.
+	ReceiveReply(msg Message) error
+}
+
+// MultiRequestCtx is helper interface which allows to receive reply on multi-request context data
+type MultiRequestCtx interface {
+	// ReceiveReply receives a reply from VPP (blocks until a reply is delivered from VPP, or until an error occurs).
+	// The reply will be decoded into the msg argument. If the last reply has been already consumed, lastReplyReceived is
+	// set to true. Do not use the message itself if lastReplyReceived is true - it won't be filled with actual data.
+	// Error will be returned if the response cannot be received or decoded.
+	ReceiveReply(msg Message) (lastReplyReceived bool, err error)
 }
 
 // VppRequest is a request that will be sent to VPP.
@@ -131,238 +158,3 @@ type NotifSubscription struct {
 	NotifChan  chan Message   // channel where notification messages will be delivered to
 	MsgFactory func() Message // function that returns a new instance of the specific message that is expected as a notification
 }
-
-// RequestCtx is a context of a ongoing request (simple one - only one response is expected).
-type RequestCtx struct {
-	ch     *Channel
-	seqNum uint16
-}
-
-// MultiRequestCtx is a context of a ongoing multipart request (multiple responses are expected).
-type MultiRequestCtx struct {
-	ch     *Channel
-	seqNum uint16
-}
-
-const defaultReplyTimeout = time.Second * 1 // default timeout for replies from VPP, can be changed with SetReplyTimeout
-
-// NewChannelInternal returns a new channel structure.
-// Note that this is just a raw channel not yet connected to VPP, it is not intended to be used directly.
-// Use ChannelProvider to get an API channel ready for communication with VPP.
-func NewChannelInternal(id uint16) *Channel {
-	return &Channel{
-		ID:           id,
-		replyTimeout: defaultReplyTimeout,
-	}
-}
-
-// SetReplyTimeout sets the timeout for replies from VPP. It represents the maximum time the API waits for a reply
-// from VPP before returning an error.
-func (ch *Channel) SetReplyTimeout(timeout time.Duration) {
-	ch.replyTimeout = timeout
-}
-
-// Close closes the API channel and releases all API channel-related resources in the ChannelProvider.
-func (ch *Channel) Close() {
-	if ch.ReqChan != nil {
-		close(ch.ReqChan)
-	}
-}
-
-// SendRequest asynchronously sends a request to VPP. Returns a request context, that can be used to call ReceiveReply.
-// In case of any errors by sending, the error will be delivered to ReplyChan (and returned by ReceiveReply).
-func (ch *Channel) SendRequest(msg Message) *RequestCtx {
-	ch.lastSeqNum++
-	ch.ReqChan <- &VppRequest{
-		Message: msg,
-		SeqNum:  ch.lastSeqNum,
-	}
-	return &RequestCtx{ch: ch, seqNum: ch.lastSeqNum}
-}
-
-// ReceiveReply receives a reply from VPP (blocks until a reply is delivered from VPP, or until an error occurs).
-// The reply will be decoded into the msg argument. Error will be returned if the response cannot be received or decoded.
-func (req *RequestCtx) ReceiveReply(msg Message) error {
-	if req == nil || req.ch == nil {
-		return errors.New("invalid request context")
-	}
-
-	lastReplyReceived, err := req.ch.receiveReplyInternal(msg, req.seqNum)
-
-	if lastReplyReceived {
-		err = errors.New("multipart reply recieved while a simple reply expected")
-	}
-	return err
-}
-
-// SendMultiRequest asynchronously sends a multipart request (request to which multiple responses are expected) to VPP.
-// Returns a multipart request context, that can be used to call ReceiveReply.
-// In case of any errors by sending, the error will be delivered to ReplyChan (and returned by ReceiveReply).
-func (ch *Channel) SendMultiRequest(msg Message) *MultiRequestCtx {
-	ch.lastSeqNum++
-	ch.ReqChan <- &VppRequest{
-		Message:   msg,
-		Multipart: true,
-		SeqNum:    ch.lastSeqNum,
-	}
-	return &MultiRequestCtx{ch: ch, seqNum: ch.lastSeqNum}
-}
-
-// ReceiveReply receives a reply from VPP (blocks until a reply is delivered from VPP, or until an error occurs).
-// The reply will be decoded into the msg argument. If the last reply has been already consumed, lastReplyReceived is
-// set to true. Do not use the message itself if lastReplyReceived is true - it won't be filled with actual data.
-// Error will be returned if the response cannot be received or decoded.
-func (req *MultiRequestCtx) ReceiveReply(msg Message) (lastReplyReceived bool, err error) {
-	if req == nil || req.ch == nil {
-		return false, errors.New("invalid request context")
-	}
-
-	return req.ch.receiveReplyInternal(msg, req.seqNum)
-}
-
-// receiveReplyInternal receives a reply from the reply channel into the provided msg structure.
-func (ch *Channel) receiveReplyInternal(msg Message, expSeqNum uint16) (lastReplyReceived bool, err error) {
-	var ignore bool
-	if msg == nil {
-		return false, errors.New("nil message passed in")
-	}
-
-	if ch.delayedReply != nil {
-		// try the delayed reply
-		vppReply := ch.delayedReply
-		ch.delayedReply = nil
-		ignore, lastReplyReceived, err = ch.processReply(vppReply, expSeqNum, msg)
-		if !ignore {
-			return lastReplyReceived, err
-		}
-	}
-
-	timer := time.NewTimer(ch.replyTimeout)
-	for {
-		select {
-		// blocks until a reply comes to ReplyChan or until timeout expires
-		case vppReply := <-ch.ReplyChan:
-			ignore, lastReplyReceived, err = ch.processReply(vppReply, expSeqNum, msg)
-			if ignore {
-				continue
-			}
-			return lastReplyReceived, err
-
-		case <-timer.C:
-			err = fmt.Errorf("no reply received within the timeout period %s", ch.replyTimeout)
-			return false, err
-		}
-	}
-	return
-}
-
-func (ch *Channel) processReply(reply *VppReply, expSeqNum uint16, msg Message) (ignore bool, lastReplyReceived bool, err error) {
-	// check the sequence number
-	cmpSeqNums := compareSeqNumbers(reply.SeqNum, expSeqNum)
-	if cmpSeqNums == -1 {
-		// reply received too late, ignore the message
-		logrus.WithField("sequence-number", reply.SeqNum).Warn(
-			"Received reply to an already closed binary API request")
-		ignore = true
-		return
-	}
-	if cmpSeqNums == 1 {
-		ch.delayedReply = reply
-		err = fmt.Errorf("missing binary API reply with sequence number: %d", expSeqNum)
-		return
-	}
-
-	if reply.Error != nil {
-		err = reply.Error
-		return
-	}
-	if reply.LastReplyReceived {
-		lastReplyReceived = true
-		return
-	}
-
-	// message checks
-	var expMsgID uint16
-	expMsgID, err = ch.MsgIdentifier.GetMessageID(msg)
-	if err != nil {
-		err = fmt.Errorf("message %s with CRC %s is not compatible with the VPP we are connected to",
-			msg.GetMessageName(), msg.GetCrcString())
-		return
-	}
-
-	if reply.MessageID != expMsgID {
-		var msgNameCrc string
-		if nameCrc, err := ch.MsgIdentifier.LookupByID(reply.MessageID); err != nil {
-			msgNameCrc = err.Error()
-		} else {
-			msgNameCrc = nameCrc
-		}
-
-		err = fmt.Errorf("received invalid message ID (seq-num=%d), expected %d (%s), but got %d (%s) "+
-			"(check if multiple goroutines are not sharing single GoVPP channel)",
-			reply.SeqNum, expMsgID, msg.GetMessageName(), reply.MessageID, msgNameCrc)
-		return
-	}
-
-	// decode the message
-	err = ch.MsgDecoder.DecodeMsg(reply.Data, msg)
-	return
-}
-
-// compareSeqNumbers returns -1, 0, 1 if sequence number <seqNum1> precedes, equals to,
-// or succeeds seq. number <seqNum2>.
-// Since sequence numbers cycle in the finite set of size 2^16, the function
-// must assume that the distance between compared sequence numbers is less than
-// (2^16)/2 to determine the order.
-func compareSeqNumbers(seqNum1, seqNum2 uint16) int {
-	// calculate distance from seqNum1 to seqNum2
-	var dist uint16
-	if seqNum1 <= seqNum2 {
-		dist = seqNum2 - seqNum1
-	} else {
-		dist = 0xffff - (seqNum1 - seqNum2 - 1)
-	}
-	if dist == 0 {
-		return 0
-	} else if dist <= 0x8000 {
-		return -1
-	}
-	return 1
-}
-
-// SubscribeNotification subscribes for receiving of the specified notification messages via provided Go channel.
-// Note that the caller is responsible for creating the Go channel with preferred buffer size. If the channel's
-// buffer is full, the notifications will not be delivered into it.
-func (ch *Channel) SubscribeNotification(notifChan chan Message, msgFactory func() Message) (*NotifSubscription, error) {
-	subscription := &NotifSubscription{
-		NotifChan:  notifChan,
-		MsgFactory: msgFactory,
-	}
-	ch.NotifSubsChan <- &NotifSubscribeRequest{
-		Subscription: subscription,
-		Subscribe:    true,
-	}
-	return subscription, <-ch.NotifSubsReplyChan
-}
-
-// UnsubscribeNotification unsubscribes from receiving the notifications tied to the provided notification subscription.
-func (ch *Channel) UnsubscribeNotification(subscription *NotifSubscription) error {
-	ch.NotifSubsChan <- &NotifSubscribeRequest{
-		Subscription: subscription,
-		Subscribe:    false,
-	}
-	return <-ch.NotifSubsReplyChan
-}
-
-// CheckMessageCompatibility checks whether provided messages are compatible with the version of VPP
-// which the library is connected to.
-func (ch *Channel) CheckMessageCompatibility(messages ...Message) error {
-	for _, msg := range messages {
-		_, err := ch.MsgIdentifier.GetMessageID(msg)
-		if err != nil {
-			return fmt.Errorf("message %s with CRC %s is not compatible with the VPP we are connected to",
-				msg.GetMessageName(), msg.GetCrcString())
-		}
-	}
-	return nil
-}