Introduce Stream - experimental API for low-level access to VPP API

Change-Id: I2698e11b76ff55d9730b47d4fee990be93349516
Signed-off-by: Ondrej Fabry <ofabry@cisco.com>

4 files changed, 136 insertions, 79 deletions

diff --git a/api/api.go b/api/api.go
new file mode 100644
index 0000000..977b02e
--- /dev/null
+++ b/api/api.go
@@ -0,0 +1,125 @@
+//  Copyright (c) 2020 Cisco and/or its affiliates.
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at:
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+
+package api
+
+import (
+	"context"
+	"time"
+)
+
+// Connection represents the client connection to VPP API.
+//
+// NOTE: This API is EXPERIMENTAL.
+type Connection interface {
+	// NewStream creates a new stream for sending and receiving messages.
+	// Context can be used to close the stream using cancel or timeout.
+	NewStream(ctx context.Context) (Stream, error)
+
+	// Invoke can be used for a simple request-reply RPC.
+	// It creates stream and calls SendMsg with req and RecvMsg with reply.
+	Invoke(ctx context.Context, req Message, reply Message) error
+}
+
+// Stream provides low-level access for sending and receiving messages.
+// Users should handle correct type and ordering of messages.
+//
+// NOTE: This API is EXPERIMENTAL.
+type Stream interface {
+	// SendMsg sends a message to the client.
+	// It blocks until message is sent to the transport.
+	//
+	// It is safe to have a goroutine calling SendMsg and another goroutine
+	// calling RecvMsg on the same stream at the same time, but it is not safe
+	// to call SendMsg on the same stream in different goroutines.
+	SendMsg(Message) error
+
+	// RecvMsg blocks until a message is received or error occurs.
+	//
+	// It is safe to have a goroutine calling SendMsg and another goroutine
+	// calling RecvMsg on the same stream at the same time, but it is not safe
+	// to call SendMsg on the same stream in different goroutines.
+	RecvMsg() (Message, error)
+
+	// Close closes the stream. Calling SendMsg and RecvMsg will return error
+	// after closing stream.
+	Close() error
+}
+
+// ChannelProvider provides the communication channel with govpp core.
+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)
+
+	// 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(reqChanBufSize, replyChanBufSize int) (Channel, error)
+}
+
+// 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, event Message) (SubscriptionCtx, 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)
+
+	// CheckCompatibility checks the compatiblity for the given messages.
+	// It will return an error if any of the given messages are not compatible.
+	CheckCompatiblity(msgs ...Message) error
+
+	// 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.
+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.
+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)
+}
+
+// SubscriptionCtx is helper interface which allows to control subscription for
+// notification events.
+type SubscriptionCtx interface {
+	// Unsubscribe unsubscribes from receiving the notifications tied to the
+	// subscription context.
+	Unsubscribe() error
+}
diff --git a/api/binapi.go b/api/binapi.go
index 20ddd28..04fdc9e 100644
--- a/api/binapi.go
+++ b/api/binapi.go
@@ -17,7 +17,6 @@ package api
 import (
 	"fmt"
 	"reflect"
-	"time"
 )
 
 // MessageType represents the type of a VPP message.
@@ -56,84 +55,6 @@ type DataType interface {
 	GetTypeName() string
 }
 
-// ChannelProvider provides the communication channel with govpp core.
-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)
-
-	// 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(reqChanBufSize, replyChanBufSize int) (Channel, error)
-}
-
-// 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, event Message) (SubscriptionCtx, 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)
-
-	// CheckCompatibility checks the compatiblity for the given messages.
-	// It will return an error if any of the given messages are not compatible.
-	CheckCompatiblity(msgs ...Message) error
-
-	// 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.
-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.
-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)
-}
-
-// SubscriptionCtx is helper interface which allows to control subscription for
-// notification events.
-type SubscriptionCtx interface {
-	// Unsubscribe unsubscribes from receiving the notifications tied to the
-	// subscription context.
-	Unsubscribe() error
-}
-
-// CompatibilityError is the error type usually returned by CheckCompatibility
-// method of Channel. It contains list of all the compatible/incompatible messages.
-type CompatibilityError struct {
-	CompatibleMessages   []string
-	IncompatibleMessages []string
-}
-
-func (c *CompatibilityError) Error() string {
-	return fmt.Sprintf("%d/%d messages incompatible", len(c.IncompatibleMessages), len(c.CompatibleMessages)+len(c.IncompatibleMessages))
-}
-
 var (
 	registeredMessageTypes = make(map[reflect.Type]string)
 	registeredMessages     = make(map[string]Message)
diff --git a/api/vppapi_errors.go b/api/errors.go
index c9ce3a3..32cc677 100644
--- a/api/vppapi_errors.go
+++ b/api/errors.go
@@ -5,6 +5,17 @@ import (
 	"strconv"
 )
 
+// CompatibilityError is the error type usually returned by CheckCompatibility
+// method of Channel. It contains list of all the compatible/incompatible messages.
+type CompatibilityError struct {
+	CompatibleMessages   []string
+	IncompatibleMessages []string
+}
+
+func (c *CompatibilityError) Error() string {
+	return fmt.Sprintf("%d/%d messages incompatible", len(c.IncompatibleMessages), len(c.CompatibleMessages)+len(c.IncompatibleMessages))
+}
+
 // RetvalToVPPApiError returns error for retval value.
 // Retval 0 returns nil error.
 func RetvalToVPPApiError(retval int32) error {
diff --git a/api/vppapi_errors_test.go b/api/errors_test.go
index 78e1fbf..78e1fbf 100644
--- a/api/vppapi_errors_test.go
+++ b/api/errors_test.go