ID3V1 and ID3v1.1 tag writing support

README.md

@@ -45,6 +45,28 @@ func main() {
 
 ## Encoding ID3v1.1
 ```
+	f, err := os.OpenFile("/path/to/file/myfile.mp3",os.O_WRONLY, os.ModePerm)
+	if err != nil {
+		panic(err)
+	}
+	defer f.Close()
+
+    // create your tags struct
+	tags := ID3v11Tags{
+		SongName: "mysong",
+		Artist:   "me",
+		Album:    "my album",
+		Year:     2021,
+		Comment:  "Cool song",
+        Track:    1,
+		Genre:    "Christian Gangsta Rap", // list of genres see "id3v1genres.go"
+	}
+
+    // write given tags in file
+	err = WriteID3v11Tags(f, tags)
+	if err != nil {
+		panic(err)
+	}
 ```
 
 # Testing

id3v10.go

@@ -2,6 +2,7 @@ package id3ed
 
 import (
 	"bytes"
+	"encoding/binary"
 	"fmt"
 	"io"
 	"strconv"
@@ -71,8 +72,11 @@ func GetID3v1Tags(rs io.ReadSeeker) (*ID3v1Tags, error) {
 	if err != nil {
 		return nil, err
 	}
-	// genre is one byte by specification
+	genreInt, err := binary.ReadVarint(bytes.NewBuffer(genreByte))
-	genre, exists := id3v1genres[int(genreByte[0])]
+	if err != nil {
+		return nil, err
+	}
+	genre, exists := id3v1genres[int(genreInt)]
 	if !exists {
 		genre = ""
 	}
@@ -88,8 +92,58 @@ func GetID3v1Tags(rs io.ReadSeeker) (*ID3v1Tags, error) {
 }
 
 // Writes given ID3v1.0 tags to dst
-func SetID3v1Tags(dst io.WriteSeeker, tags ID3v11Tags) error {
+func WriteID3v1Tags(dst io.WriteSeeker, tags ID3v1Tags) error {
 	dst.Seek(0, io.SeekEnd)
 
+	// TAG
+	_, err := dst.Write([]byte("TAG"))
+	if err != nil {
+		return err
+	}
+
+	// Song name
+	err = writeToExtend(dst, []byte(tags.SongName), 30)
+	if err != nil {
+		return err
+	}
+
+	// Artist
+	err = writeToExtend(dst, []byte(tags.Artist), 30)
+	if err != nil {
+		return err
+	}
+
+	// Album
+	err = writeToExtend(dst, []byte(tags.Album), 30)
+	if err != nil {
+		return err
+	}
+
+	// Year
+	err = writeToExtend(dst, []byte(fmt.Sprint(tags.Year)), 4)
+	if err != nil {
+		return err
+	}
+
+	// Comment
+	err = writeToExtend(dst, []byte(tags.Comment), 30)
+	if err != nil {
+		return err
+	}
+
+	// Genre
+	genreCode := getKey(id3v1genres, tags.Genre)
+	if genreCode == -1 {
+		// if no genre found - encode genre code as 255
+		genreCode = 255
+	}
+	genrebyte := make([]byte, 1)
+	binary.PutVarint(genrebyte, int64(genreCode))
+
+	_, err = dst.Write(genrebyte)
+	if err != nil {
+		return err
+	}
+
 	return nil
 }

id3v10_test.go

@@ -6,7 +6,7 @@ import (
 )
 
 func TestGetID3v1Tags(t *testing.T) {
-	testfile, err := os.Open("./testData/testmp3id3v1.mp3")
+	testfile, err := os.Open("./testData/testread.mp3")
 	if err != nil {
 		t.Errorf("could not open file for testing: %s", err)
 	}
@@ -19,3 +19,40 @@ func TestGetID3v1Tags(t *testing.T) {
 		t.Errorf("GetID3v1Tags failed: expected %s; got %s", "Comment here ", tags.Comment)
 	}
 }
+
+func TestWriteID3v1Tags(t *testing.T) {
+	os.Remove("./testData/testwrite.mp3")
+
+	f, err := os.Create("./testData/testwrite.mp3")
+	if err != nil {
+		t.Errorf("%s", err)
+	}
+	defer f.Close()
+
+	tags := ID3v1Tags{
+		SongName: "testsong",
+		Artist:   "testartist",
+		Album:    "testalbum",
+		Year:     727,
+		Comment:  "testcomment",
+		Genre:    "Blues",
+	}
+
+	err = WriteID3v1Tags(f, tags)
+	if err != nil {
+		t.Errorf("WriteID3v1Tags failed: %s", err)
+	}
+
+	readTags, err := GetID3v1Tags(f)
+	if err != nil {
+		t.Errorf("%s", err)
+	}
+
+	if readTags.Album != "testalbum" {
+		t.Errorf("WriteID3v1Tags failed: expected %s; got %s", "testalbum", readTags.Album)
+	}
+
+	if readTags.Year != 727 {
+		t.Errorf("WriteID3v1Tags failed: expected %d; got %d", 727, readTags.Year)
+	}
+}

id3v11.go

@@ -2,6 +2,7 @@ package id3ed
 
 import (
 	"bytes"
+	"encoding/binary"
 	"fmt"
 	"io"
 	"strconv"
@@ -75,15 +76,20 @@ func GetID3v11Tags(rs io.ReadSeeker) (*ID3v11Tags, error) {
 		return nil, err
 	}
 
-	// track is one byte by specification
+	track, err := binary.ReadVarint(bytes.NewBuffer(trackByte))
-	track := int(trackByte[0])
+	if err != nil {
+		return nil, err
+	}
 
 	genreByte, err := read(rs, 1)
 	if err != nil {
 		return nil, err
 	}
-	// genre is one byte by specification
+	genreInt, err := binary.ReadVarint(bytes.NewBuffer(genreByte))
-	genre, exists := id3v1genres[int(genreByte[0])]
+	if err != nil {
+		return nil, err
+	}
+	genre, exists := id3v1genres[int(genreInt)]
 	if !exists {
 		genre = ""
 	}
@@ -94,14 +100,78 @@ func GetID3v11Tags(rs io.ReadSeeker) (*ID3v11Tags, error) {
 		Album:    album,
 		Year:     year,
 		Comment:  comment,
-		Track:    track,
+		Track:    int(track),
 		Genre:    genre,
 	}, nil
 }
 
 // Writes given ID3v1.1 tags to dst
-func SetID3v11Tags(dst io.WriteSeeker, tags ID3v11Tags) error {
+func WriteID3v11Tags(dst io.WriteSeeker, tags ID3v11Tags) error {
 	dst.Seek(0, io.SeekEnd)
 
+	// TAG
+	_, err := dst.Write([]byte("TAG"))
+	if err != nil {
+		return fmt.Errorf("could not write to dst: %s", err)
+	}
+
+	// Song name
+	err = writeToExtend(dst, []byte(tags.SongName), 30)
+	if err != nil {
+		return fmt.Errorf("could not write to dst: %s", err)
+	}
+
+	// Artist
+	err = writeToExtend(dst, []byte(tags.Artist), 30)
+	if err != nil {
+		return fmt.Errorf("could not write to dst: %s", err)
+	}
+
+	// Album
+	err = writeToExtend(dst, []byte(tags.Album), 30)
+	if err != nil {
+		return fmt.Errorf("could not write to dst: %s", err)
+	}
+
+	// Year
+	err = writeToExtend(dst, []byte(fmt.Sprint(tags.Year)), 4)
+	if err != nil {
+		return fmt.Errorf("could not write to dst: %s", err)
+	}
+
+	// Comment
+	err = writeToExtend(dst, []byte(tags.Comment), 28)
+	if err != nil {
+		return fmt.Errorf("could not write to dst: %s", err)
+	}
+
+	_, err = dst.Write([]byte{0})
+	if err != nil {
+		return fmt.Errorf("could not write to dst: %s", err)
+	}
+
+	// Track
+	trackBytes := make([]byte, 1)
+	binary.PutVarint(trackBytes, int64(tags.Track))
+	// binary.BigEndian.PutUint16(trackBytes, uint16(tags.Track))
+	_, err = dst.Write(trackBytes)
+	if err != nil {
+		return fmt.Errorf("could not write to dst: %s", err)
+	}
+
+	//Genre
+	genreCode := getKey(id3v1genres, tags.Genre)
+	if genreCode == -1 {
+		// if no genre found - encode genre code as 255
+		genreCode = 255
+	}
+	genrebyte := make([]byte, 1)
+	binary.PutVarint(genrebyte, int64(genreCode))
+
+	err = writeToExtend(dst, genrebyte, 1)
+	if err != nil {
+		return fmt.Errorf("could not write to dst: %s", err)
+	}
+
 	return nil
 }

id3v11_test.go

@@ -7,21 +7,63 @@ import (
 )
 
 func TestGetID3v11Tags(t *testing.T) {
-	testfile, err := os.Open("./testData/testmp3id3v1.mp3")
+	testfile, err := os.Open("./testData/testread.mp3")
 	if err != nil {
 		t.Errorf("could not open file for testing: %s", err)
 	}
 	mp3tags, err := GetID3v11Tags(testfile)
 	if err != nil {
-		t.Errorf("GetID3v1Tags failed: %s", err)
+		t.Errorf("GetID3v11Tags failed: %s", err)
 	}
 
 	if mp3tags.Artist != "Artist" {
 		fmt.Printf("%v", mp3tags.Artist)
-		t.Errorf("GetID3v1Tags has failed:  expected %v; got %v", "Artist", mp3tags.Artist)
+		t.Errorf("GetID3v11Tags failed:  expected %s; got %s", "Artist", mp3tags.Artist)
 	}
 
-	if mp3tags.Track != 8 {
+	if mp3tags.Track != 4 {
-		t.Errorf("GetID3v1Tags has failed: expected %v; got %v", 8, mp3tags.Track)
+		t.Errorf("GetID3v11Tags failed: expected %d; got %d", 4, mp3tags.Track)
+	}
+}
+
+func TestWriteID3v11Tags(t *testing.T) {
+	os.Remove("./testData/testwrite.mp3")
+
+	f, err := os.Create("./testData/testwrite.mp3")
+	if err != nil {
+		t.Errorf("%s", err)
+	}
+	defer f.Close()
+
+	tags := ID3v11Tags{
+		SongName: "testsong",
+		Artist:   "testartist",
+		Album:    "testalbum",
+		Year:     727,
+		Comment:  "testcomment",
+		Track:    5,
+		Genre:    "Blues",
+	}
+
+	err = WriteID3v11Tags(f, tags)
+	if err != nil {
+		t.Errorf("WriteID3v1Tags failed: %s", err)
+	}
+
+	readTags, err := GetID3v11Tags(f)
+	if err != nil {
+		t.Errorf("%s", err)
+	}
+
+	if readTags.Album != "testalbum" {
+		t.Errorf("WriteID3v11Tags failed: expected %s; got %s", "testalbum", readTags.Album)
+	}
+
+	if readTags.Year != 727 {
+		t.Errorf("WriteID3v11Tags failed: expected %d; got %d", 727, readTags.Year)
+	}
+
+	if readTags.Track != 5 {
+		t.Errorf("WriteID3v11Tags failed: expected %d; got %d", 5, readTags.Track)
 	}
 }

util.go

@@ -1,6 +1,7 @@
 package id3ed
 
 import (
+	"bytes"
 	"fmt"
 	"io"
 )
@@ -35,3 +36,43 @@ func readToString(rs io.Reader, n int) (string, error) {
 
 	return readString, nil
 }
+
+// Writes data to wr, if len(data) is less than lenNeeded - adds null bytes until written lenNeeded bytes
+func writeToExtend(wr io.Writer, data []byte, lenNeeded int) error {
+	if len(data) > lenNeeded {
+		return fmt.Errorf("length of given data bytes is bigger than length needed")
+	}
+
+	buff := new(bytes.Buffer)
+	for i := 0; i < lenNeeded; i++ {
+		if i < len(data) {
+			err := buff.WriteByte(data[i])
+			if err != nil {
+				return err
+			}
+		} else {
+			err := buff.WriteByte(0)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	_, err := wr.Write(buff.Bytes())
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Returns found key (int) in provided map by value (string);
+// If key does not exist in map - returns -1
+func getKey(mp map[int]string, givenValue string) int {
+	for key, value := range mp {
+		if value == givenValue {
+			return key
+		}
+	}
+	return -1
+}