rtmp: pull verbosity out of C code

rtmp/rtmp.go

@@ -43,6 +43,7 @@ import "C"
 
 import (
 	"errors"
+	"strconv"
 	"unsafe"
 )
 
@@ -77,9 +78,10 @@ func (s *session) Open() error {
 	if s.rtmp != nil {
 		return errors.New("rtmp: attempt to start already running session")
 	}
-	s.rtmp = C.start_session(s.rtmp, C.CString(s.url), C.uint(s.timeout))
+	var err error
+	s.rtmp, err = C.start_session(s.rtmp, C.CString(s.url), C.uint(s.timeout))
 	if s.rtmp == nil {
-		return errors.New("RTMP start error! Check rtmp log for details!")
+		return err
 	}
 	return nil
 }
@@ -87,10 +89,11 @@ func (s *session) Open() error {
 // Write writes a frame (flv tag) to the rtmp connection
 func (s *session) Write(data []byte) (int, error) {
 	if s.rtmp == nil {
-		return 0, errors.New("rtmp: attempt to write to non-running session")
+		return 0, Err(3)
 	}
-	if C.write_frame(s.rtmp, (*C.char)(unsafe.Pointer(&data[0])), C.uint(len(data))) != 0 {
-		return 0, errors.New("RTMP write error! Check rtmp log for details!")
+	ret := C.write_frame(s.rtmp, (*C.char)(unsafe.Pointer(&data[0])), C.uint(len(data)))
+	if ret != 0 {
+		return 0, Err(ret)
 	}
 	return len(data), nil
 }
@@ -98,12 +101,30 @@ func (s *session) Write(data []byte) (int, error) {
 // Close terminates the rtmp connection
 func (s *session) Close() error {
 	if s.rtmp == nil {
-		return errors.New("Tried to stop rtmp session, but not running!")
+		return Err(3)
 	}
 	ret := C.end_session(s.rtmp)
 	s.rtmp = nil
 	if ret != 0 {
-		return errors.New("RTMP end session error! Check rtmp log for details!")
+		return Err(ret)
 	}
 	return nil
 }
+
+var rtmpErrs = [...]string{
+	1: "rtmp: not connected",
+	2: "rtmp: write error",
+	3: "rtmp: not started",
+}
+
+type Err uint
+
+func (e Err) Error() string {
+	if 0 <= int(e) && int(e) < len(rtmpErrs) {
+		s := rtmpErrs[e]
+		if s != "" {
+			return s
+		}
+	}
+	return "rtmp: " + strconv.Itoa(int(e))
+}