Unexport adapter implementations to make it clear that API interfaces should be used

- this decision was made to follow more idiomatic Go, described in
  https://golang.org/doc/effective_go.html#generality

Change-Id: I341556c792df77ca35a60a1e4afc541482f23734
Signed-off-by: Ondrej Fabry <ofabry@cisco.com>

4 files changed, 54 insertions, 43 deletions

diff --git a/adapter/vppapiclient/stat_client.go b/adapter/vppapiclient/stat_client.go
index 5f3b932..2e2d6db 100644
--- a/adapter/vppapiclient/stat_client.go
+++ b/adapter/vppapiclient/stat_client.go
@@ -161,21 +161,28 @@ var (
 	DefaultStatSocket = "/run/vpp/stats.sock"
 )
 
-// StatClient is the default implementation of StatsAPI.
-type StatClient struct {
+// global VPP stats API client, library vppapiclient only supports
+// single connection at a time
+var globalStatClient *statClient
+
+// stubStatClient is the default implementation of StatsAPI.
+type statClient struct {
 	socketName string
 }
 
 // NewStatClient returns new VPP stats API client.
-func NewStatClient(socketName string) *StatClient {
-	return &StatClient{
+func NewStatClient(socketName string) adapter.StatsAPI {
+	return &statClient{
 		socketName: socketName,
 	}
 }
 
-func (c *StatClient) Connect() error {
-	var sockName string
+func (c *statClient) Connect() error {
+	if globalStatClient != nil {
+		return fmt.Errorf("already connected to stats API, disconnect first")
+	}
 
+	var sockName string
 	if c.socketName == "" {
 		sockName = DefaultStatSocket
 	} else {
@@ -187,15 +194,18 @@ func (c *StatClient) Connect() error {
 		return fmt.Errorf("connecting to VPP stats API failed (rc=%v)", rc)
 	}
 
+	globalStatClient = c
 	return nil
 }
 
-func (c *StatClient) Disconnect() error {
+func (c *statClient) Disconnect() error {
+	globalStatClient = nil
+
 	C.govpp_stat_disconnect()
 	return nil
 }
 
-func (c *StatClient) ListStats(patterns ...string) (stats []string, err error) {
+func (c *statClient) ListStats(patterns ...string) (stats []string, err error) {
 	dir := C.govpp_stat_segment_ls(convertStringSlice(patterns))
 	defer C.govpp_stat_segment_vec_free(unsafe.Pointer(dir))
 
@@ -209,7 +219,7 @@ func (c *StatClient) ListStats(patterns ...string) (stats []string, err error) {
 	return stats, nil
 }
 
-func (c *StatClient) DumpStats(patterns ...string) (stats []*adapter.StatEntry, err error) {
+func (c *statClient) DumpStats(patterns ...string) (stats []*adapter.StatEntry, err error) {
 	dir := C.govpp_stat_segment_ls(convertStringSlice(patterns))
 	defer C.govpp_stat_segment_vec_free(unsafe.Pointer(dir))
 
diff --git a/adapter/vppapiclient/stat_client_stub.go b/adapter/vppapiclient/stat_client_stub.go
index 24f7e13..b42619c 100644
--- a/adapter/vppapiclient/stat_client_stub.go
+++ b/adapter/vppapiclient/stat_client_stub.go
@@ -20,26 +20,26 @@ import (
 	"git.fd.io/govpp.git/adapter"
 )
 
-// StatClient is just an stub adapter that does nothing. It builds only on Windows and OSX, where the real
+// stubStatClient is just an stub adapter that does nothing. It builds only on Windows and OSX, where the real
 // VPP stats API client adapter does not build. Its sole purpose is to make the compiler happy on Windows and OSX.
-type StatClient struct{}
+type stubStatClient struct{}
 
-func NewStatClient(socketName string) *StatClient {
-	return new(StatClient)
+func NewStatClient(socketName string) adapter.StatsAPI {
+	return new(stubStatClient)
 }
 
-func (*StatClient) Connect() error {
+func (*stubStatClient) Connect() error {
 	return adapter.ErrNotImplemented
 }
 
-func (*StatClient) Disconnect() error {
+func (*stubStatClient) Disconnect() error {
 	return nil
 }
 
-func (*StatClient) ListStats(patterns ...string) (statNames []string, err error) {
+func (*stubStatClient) ListStats(patterns ...string) (statNames []string, err error) {
 	return nil, adapter.ErrNotImplemented
 }
 
-func (*StatClient) DumpStats(patterns ...string) ([]*adapter.StatEntry, error) {
+func (*stubStatClient) DumpStats(patterns ...string) ([]*adapter.StatEntry, error) {
 	return nil, adapter.ErrNotImplemented
 }
diff --git a/adapter/vppapiclient/vppapiclient.go b/adapter/vppapiclient/vppapiclient.go
index 34ad199..cf2665a 100644
--- a/adapter/vppapiclient/vppapiclient.go
+++ b/adapter/vppapiclient/vppapiclient.go
@@ -91,25 +91,26 @@ const (
 	vppShmFile = "vpe-api"
 )
 
-// global VPP binary API client adapter context
-var client *VppClient
+// global VPP binary API client, library vppapiclient only supports
+// single connection at a time
+var globalVppClient *vppClient
 
-// VppClient is the default implementation of the VppAPI.
-type VppClient struct {
+// stubVppClient is the default implementation of the VppAPI.
+type vppClient struct {
 	shmPrefix   string
 	msgCallback adapter.MsgCallback
 }
 
 // NewVppClient returns a new VPP binary API client.
-func NewVppClient(shmPrefix string) *VppClient {
-	return &VppClient{
+func NewVppClient(shmPrefix string) adapter.VppAPI {
+	return &vppClient{
 		shmPrefix: shmPrefix,
 	}
 }
 
 // Connect connects the process to VPP.
-func (a *VppClient) Connect() error {
-	if client != nil {
+func (a *vppClient) Connect() error {
+	if globalVppClient != nil {
 		return fmt.Errorf("already connected to binary API, disconnect first")
 	}
 
@@ -124,13 +125,13 @@ func (a *VppClient) Connect() error {
 		return fmt.Errorf("connecting to VPP binary API failed (rc=%v)", rc)
 	}
 
-	client = a
+	globalVppClient = a
 	return nil
 }
 
 // Disconnect disconnects the process from VPP.
-func (a *VppClient) Disconnect() error {
-	client = nil
+func (a *vppClient) Disconnect() error {
+	globalVppClient = nil
 
 	rc := C.govpp_disconnect()
 	if rc != 0 {
@@ -141,7 +142,7 @@ func (a *VppClient) Disconnect() error {
 }
 
 // GetMsgID returns a runtime message ID for the given message name and CRC.
-func (a *VppClient) GetMsgID(msgName string, msgCrc string) (uint16, error) {
+func (a *vppClient) GetMsgID(msgName string, msgCrc string) (uint16, error) {
 	nameAndCrc := C.CString(msgName + "_" + msgCrc)
 	defer C.free(unsafe.Pointer(nameAndCrc))
 
@@ -155,7 +156,7 @@ func (a *VppClient) GetMsgID(msgName string, msgCrc string) (uint16, error) {
 }
 
 // SendMsg sends a binary-encoded message to VPP.
-func (a *VppClient) SendMsg(context uint32, data []byte) error {
+func (a *vppClient) SendMsg(context uint32, data []byte) error {
 	rc := C.govpp_send(C.uint32_t(context), unsafe.Pointer(&data[0]), C.size_t(len(data)))
 	if rc != 0 {
 		return fmt.Errorf("unable to send the message (rc=%v)", rc)
@@ -165,13 +166,13 @@ func (a *VppClient) SendMsg(context uint32, data []byte) error {
 
 // SetMsgCallback sets a callback function that will be called by the adapter
 // whenever a message comes from VPP.
-func (a *VppClient) SetMsgCallback(cb adapter.MsgCallback) {
+func (a *vppClient) SetMsgCallback(cb adapter.MsgCallback) {
 	a.msgCallback = cb
 }
 
 // WaitReady blocks until shared memory for sending
 // binary api calls is present on the file system.
-func (a *VppClient) WaitReady() error {
+func (a *vppClient) WaitReady() error {
 	var path string
 
 	// join the path to the shared memory segment
@@ -219,5 +220,5 @@ func go_msg_callback(msgID C.uint16_t, data unsafe.Pointer, size C.size_t) {
 	sliceHeader := &reflect.SliceHeader{Data: uintptr(data), Len: int(size), Cap: int(size)}
 	byteSlice := *(*[]byte)(unsafe.Pointer(sliceHeader))
 
-	client.msgCallback(uint16(msgID), byteSlice)
+	globalVppClient.msgCallback(uint16(msgID), byteSlice)
 }
diff --git a/adapter/vppapiclient/vppapiclient_stub.go b/adapter/vppapiclient/vppapiclient_stub.go
index 6de89a7..c5566c6 100644
--- a/adapter/vppapiclient/vppapiclient_stub.go
+++ b/adapter/vppapiclient/vppapiclient_stub.go
@@ -20,34 +20,34 @@ import (
 	"git.fd.io/govpp.git/adapter"
 )
 
-// VppClient is just an stub adapter that does nothing. It builds only on Windows and OSX, where the real
+// stubVppClient is just an stub adapter that does nothing. It builds only on Windows and OSX, where the real
 // VPP binary API client adapter does not build. Its sole purpose is to make the compiler happy on Windows and OSX.
-type VppClient struct{}
+type stubVppClient struct{}
 
-func NewVppAdapter(string) *VppClient {
-	return &VppClient{}
+func NewVppClient(string) adapter.VppAPI {
+	return &stubVppClient{}
 }
 
-func (a *VppClient) Connect() error {
+func (a *stubVppClient) Connect() error {
 	return adapter.ErrNotImplemented
 }
 
-func (a *VppClient) Disconnect() error {
+func (a *stubVppClient) Disconnect() error {
 	return nil
 }
 
-func (a *VppClient) GetMsgID(msgName string, msgCrc string) (uint16, error) {
+func (a *stubVppClient) GetMsgID(msgName string, msgCrc string) (uint16, error) {
 	return 0, nil
 }
 
-func (a *VppClient) SendMsg(clientID uint32, data []byte) error {
+func (a *stubVppClient) SendMsg(clientID uint32, data []byte) error {
 	return nil
 }
 
-func (a *VppClient) SetMsgCallback(cb adapter.MsgCallback) {
+func (a *stubVppClient) SetMsgCallback(cb adapter.MsgCallback) {
 	// no op
 }
 
-func (a *VppClient) WaitReady() error {
+func (a *stubVppClient) WaitReady() error {
 	return adapter.ErrNotImplemented
 }