SDP implementation is complete

Support marshaling and unmarshaling session and media descriptions
pion · May 29, 2018 · b2e8189 · b2e8189
1 parent a9220db
commit b2e8189
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Showing 3 changed files with 252 additions and 188 deletions.
diff --git a/internal/sdp/marshal.go b/internal/sdp/marshal.go
@@ -1,55 +1,12 @@
 package sdp
 
-import (
-	"bufio"
-	"strconv"
-	"strings"
+import "strconv"
 
-	"github.com/pkg/errors"
-)
-
-type attributeStatus struct {
-	seen          bool
-	value         string
-	allowMultiple bool
+func kvBuilder(key, value string) string {
+	return key + "=" + value + "\n"
 }
 
-// Detect if the current attribute is ok to be read (detect out of order errors)
-// or if it has already been set
-func attributeValid(statuses []*attributeStatus, attribute string) (err error) {
-	attrFound := false
-	for _, v := range statuses {
-		if attrFound && v.seen {
-			return errors.Errorf("Attribute %s was found, but later attribute %s has already been set", attribute, v.value)
-		}
-
-		if v.value == attribute {
-			if v.seen && !v.allowMultiple {
-				return errors.Errorf("Attribute %s was attempted to be set twice", attribute, v.value)
-			}
-			attrFound = true
-			v.seen = true
-		}
-	}
-	return nil
-}
-
-func nextLine(scanner *bufio.Scanner) (key, value string, scanStatus bool, err error) {
-	if scanStatus = scanner.Scan(); !scanStatus {
-		return key, value, scanStatus, scanner.Err()
-	}
-
-	if len(scanner.Text()) < 3 {
-		return key, value, scanStatus, errors.Errorf("line is not long enough to contain both a key and value: %s", scanner.Text())
-	} else if scanner.Text()[1] != '=' {
-		return key, value, scanStatus, errors.Errorf("line is not a proper key value pair, second character is not `=`: %s", scanner.Text())
-	}
-
-	return string(scanner.Text()[0]), scanner.Text()[2:], scanStatus, err
-}
-
-// Marshaw populates a SessionDescription with a raw string
-//
+// Marshal creates a raw string from a SessionDescription
 // Some lines in each description are REQUIRED and some are OPTIONAL,
 // but all MUST appear in exactly the order given here (the fixed order
 // greatly enhances error detection and allows for a simple parser).
@@ -70,149 +27,45 @@ func nextLine(scanner *bufio.Scanner) (key, value string, scanStatus bool, err e
 // a=* (zero or more session attribute lines)
 // Zero or more media descriptions
 // https://tools.ietf.org/html/rfc4566#section-5
-func (s *SessionDescription) Marshal(raw string) error {
-	earlyEndErr := errors.Errorf("session description ended before all required values were found")
-	orderedSessionAttributes := []*attributeStatus{
-		&attributeStatus{value: "v"},
-		&attributeStatus{value: "o"},
-		&attributeStatus{value: "s"},
-		&attributeStatus{value: "i"},
-		&attributeStatus{value: "u"},
-		&attributeStatus{value: "e"},
-		&attributeStatus{value: "p"},
-		&attributeStatus{value: "c"},
-		&attributeStatus{value: "b", allowMultiple: true},
-		&attributeStatus{value: "t", allowMultiple: true},
-		&attributeStatus{value: "r", allowMultiple: true},
-		&attributeStatus{value: "z", allowMultiple: true},
-		&attributeStatus{value: "k", allowMultiple: true},
-		&attributeStatus{value: "a", allowMultiple: true},
-		&attributeStatus{value: "m", allowMultiple: true},
-	}
-
-	s.Reset()
-	scanner := bufio.NewScanner(strings.NewReader(raw))
-
-	// v=
-	key, value, scanStatus, err := nextLine(scanner)
-	if err != nil {
-		return err
-	} else if !scanStatus {
-		return earlyEndErr
-	} else if key != "v" {
-		return errors.Errorf("v (protocol version) was expected, but not found")
-	} else if s.ProtocolVersion, err = strconv.Atoi(value); err != nil {
-		return errors.Errorf("Failed to take protocol version to int")
-	}
-
-	// o=
-	key, value, scanStatus, err = nextLine(scanner)
-	if err != nil {
-		return err
-	} else if !scanStatus {
-		return earlyEndErr
-	} else if key != "o" {
-		return errors.Errorf("o (originator and session identifier) was expected, but not found")
-	}
-	s.Origin = value
-
-	key, value, scanStatus, err = nextLine(scanner)
-	if err != nil {
-		return err
-	} else if !scanStatus {
-		return earlyEndErr
-	} else if key != "s" {
-		return errors.Errorf("o (session name) was expected, but not found")
+func (s *SessionDescription) Marshal() (raw string) {
+	addIfSet := func(key, value string) {
+		if value != "" {
+			raw += kvBuilder(key, value)
+		}
 	}
-	s.SessionName = value
-
-	const attrAlreadySet string = "attribute %s has already been set"
-	for {
-		key, value, scanStatus, err = nextLine(scanner)
-		if err != nil || !scanStatus {
-			return err
+	addSlice := func(key string, values []string) {
+		for _, v := range values {
+			raw += kvBuilder(key, v)
 		}
+	}
 
-		if err := attributeValid(orderedSessionAttributes, key); err != nil {
-			return err
-		}
+	raw += kvBuilder("v", strconv.Itoa(s.ProtocolVersion))
+	raw += kvBuilder("o", s.Origin)
+	raw += kvBuilder("s", s.SessionName)
 
-		switch key {
-		case "i":
-			s.SessionInformation = value
-		case "u":
-			s.URI = value
-		case "e":
-			s.EmailAddress = value
-		case "p":
-			s.PhoneNumber = value
-		case "c":
-			s.ConnectionData = value
-		case "b":
-			s.Bandwidth = append(s.Bandwidth, value)
-		case "t":
-			s.Timing = append(s.Timing, value)
-		case "r":
-			s.RepeatTimes = append(s.RepeatTimes, value)
-		case "z":
-			s.TimeZones = append(s.TimeZones, value)
-		case "k":
-			s.EncryptionKeys = append(s.EncryptionKeys, value)
-		case "a":
-			s.Attributes = append(s.Attributes, value)
-		case "m":
-			return s.marshalMedias(scanner, value)
-		default:
-			return errors.Errorf("Invalid session attribute: %s")
-		}
-	}
-}
+	addIfSet("i", s.SessionInformation)
+	addIfSet("u", s.URI)
+	addIfSet("e", s.EmailAddress)
+	addIfSet("p", s.PhoneNumber)
+	addIfSet("c", s.ConnectionData)
 
-func (s *SessionDescription) marshalMedias(scanner *bufio.Scanner, firstMediaName string) (err error) {
-	currentMedia := &MediaDescription{MediaName: firstMediaName}
-	orderedMediaAttributes := []*attributeStatus{
-		&attributeStatus{value: "i"},
-		&attributeStatus{value: "c"},
-		&attributeStatus{value: "b", allowMultiple: true},
-		&attributeStatus{value: "k", allowMultiple: true},
-		&attributeStatus{value: "a", allowMultiple: true},
-	}
-	resetMediaAttributes := func() {
-		for _, v := range orderedMediaAttributes {
-			v.seen = false
-		}
-	}
+	addSlice("b", s.Bandwidth)
+	addSlice("t", s.Timing)
+	addSlice("r", s.RepeatTimes)
+	addSlice("z", s.TimeZones)
+	addSlice("k", s.EncryptionKeys)
+	addSlice("a", s.Attributes)
 
-	for {
-		key, value, scanStatus, err := nextLine(scanner)
-		if err != nil || !scanStatus { // This handles EOF, finish current MediaDescription
-			s.MediaDescriptions = append(s.MediaDescriptions, currentMedia)
-			return err
-		}
+	for _, a := range s.MediaDescriptions {
+		raw += kvBuilder("m", a.MediaName)
 
-		if err := attributeValid(orderedMediaAttributes, key); err != nil {
-			return err
-		}
+		addIfSet("i", a.MediaInformation)
+		addIfSet("c", a.ConnectionData)
 
-		switch key {
-		case "m":
-			s.MediaDescriptions = append(s.MediaDescriptions, currentMedia)
-			resetMediaAttributes()
-			currentMedia = &MediaDescription{MediaName: value}
-		case "i":
-			currentMedia.MediaInformation = value
-		case "c":
-			currentMedia.ConnectionData = value
-		case "b":
-			currentMedia.Bandwidth = append(currentMedia.Bandwidth, value)
-		case "k":
-			currentMedia.EncryptionKeys = append(currentMedia.EncryptionKeys, value)
-		case "a":
-			currentMedia.Attributes = append(currentMedia.Attributes, value)
-		default:
-			return errors.Errorf("Invalid media attribute: %s")
-		}
+		addSlice("b", a.Bandwidth)
+		addSlice("k", a.EncryptionKeys)
+		addSlice("a", a.Attributes)
 	}
 
-	return nil
+	return raw
 }