Added checks for already existing ID3v1.x tags

README.md

@@ -1,12 +1,20 @@
 # ID3ED (ID3 - Encoder - Decoder)
 ## Library for encoding/decoding ID3 tags
 
+---
+
+# Under construction !
+
+---
+
 # Installation 
 
 ```
 go get github.com/Unbewohnte/id3ed
 ```
 
+---
+
 # Usage
 
 ## Decoding ID3v1.1
@@ -33,10 +41,8 @@ func main() {
     // print all tags
     fmt.Printf("%+v",mp3tags)
 
-    // get a certain tag from "getter" function
-    songname := mp3tags.GetSongName()
+    songname := mp3tags.SongName
 
-    // get a certain tag from struct field
     genre := mp3tags.Genre
 
     // etc.
@@ -52,7 +58,7 @@ func main() {
 	defer f.Close()
 
     // create your tags struct
-	tags := ID3v11Tags{
+	tags := &ID3v11Tags{
 		SongName: "mysong",
 		Artist:   "me",
 		Album:    "my album",
@@ -62,13 +68,15 @@ func main() {
 		Genre:    "Christian Gangsta Rap", // list of genres see "id3v1genres.go"
 	}
 
-    // write given tags in file
-	err = WriteID3v11Tags(f, tags)
+    // write given tags to file
+	err = WriteID3v11ToFile(f, tags)
 	if err != nil {
 		panic(err)
 	}
 ```
 
+---
+
 # Testing
 
 ```
@@ -80,5 +88,4 @@ go test -v
 ```
 to get a verbose output
 
-# Under construction !
-## Bugs are a possibility rn in this state, the package is still not tested properly 
+---

id3v10.go

@@ -5,6 +5,7 @@ import (
 	"encoding/binary"
 	"fmt"
 	"io"
+	"os"
 	"strconv"
 )
 
@@ -91,8 +92,8 @@ func GetID3v1Tags(rs io.ReadSeeker) (*ID3v1Tags, error) {
 	}, nil
 }
 
-// Writes given ID3v1.0 tags to dst
-func WriteID3v1Tags(dst io.WriteSeeker, tags ID3v1Tags) error {
+// Writes given ID3v1.0 tags to given io.ReadWriteSeeker.
+func WriteID3v1Tags(dst io.WriteSeeker, tags *ID3v1Tags) error {
 	dst.Seek(0, io.SeekEnd)
 
 	// TAG
@@ -147,3 +148,45 @@ func WriteID3v1Tags(dst io.WriteSeeker, tags ID3v1Tags) error {
 
 	return nil
 }
+
+// Checks for existing ID3v1 tag in file, if present - removes it and replaces with provided tags
+func WriteID3v1ToFile(f *os.File, tags *ID3v1Tags) error {
+	defer f.Close()
+
+	// check for existing ID3v1 tag
+	f.Seek(-int64(ID3V1SIZE), io.SeekEnd)
+
+	tag, err := read(f, 3)
+	if err != nil {
+		return err
+	}
+
+	if !bytes.Equal(tag, []byte("TAG")) {
+		// no existing tag, just write given tags
+		err = WriteID3v1Tags(f, tags)
+		if err != nil {
+			return err
+		}
+		return nil
+	}
+
+	// does contain ID3v1 tag. Removing it
+	fStats, err := f.Stat()
+	if err != nil {
+		return err
+	}
+
+	err = f.Truncate(fStats.Size() - int64(ID3V1SIZE))
+	if err != nil {
+		return nil
+	}
+
+	// writing new tags
+	err = WriteID3v1Tags(f, tags)
+	if err != nil {
+		return err
+	}
+
+	return nil
+
+}

id3v10_test.go

@@ -5,8 +5,17 @@ import (
 	"testing"
 )
 
+var TESTv1TAGS = &ID3v1Tags{
+	SongName: "testsong",
+	Artist:   "testartist",
+	Album:    "testalbum",
+	Year:     727,
+	Comment:  "testcomment",
+	Genre:    "Blues",
+}
+
 func TestGetID3v1Tags(t *testing.T) {
-	testfile, err := os.Open("./testData/testread.mp3")
+	testfile, err := os.Open("./testData/testreadv1.mp3")
 	if err != nil {
 		t.Errorf("could not open file for testing: %s", err)
 	}
@@ -21,22 +30,15 @@ func TestGetID3v1Tags(t *testing.T) {
 }
 
 func TestWriteID3v1Tags(t *testing.T) {
-	os.Remove("./testData/testwrite.mp3")
+	os.Remove("./testData/testwritev1.mp3")
 
-	f, err := os.Create("./testData/testwrite.mp3")
+	f, err := os.Create("./testData/testwritev1.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",
-	}
+	tags := TESTv1TAGS
 
 	err = WriteID3v1Tags(f, tags)
 	if err != nil {
@@ -56,3 +58,18 @@ func TestWriteID3v1Tags(t *testing.T) {
 		t.Errorf("WriteID3v1Tags failed: expected %d; got %d", 727, readTags.Year)
 	}
 }
+
+func TestWriteID3v1ToFile(t *testing.T) {
+	f, err := os.Open("./testData/testwritev1.mp3")
+	if err != nil {
+		t.Errorf("%s", err)
+	}
+
+	tags := TESTv1TAGS
+
+	err = WriteID3v1ToFile(f, tags)
+	if err != nil {
+		t.Errorf("WriteID3v1ToFile failed: %s", err)
+	}
+
+}

id3v11.go

@@ -5,6 +5,7 @@ import (
 	"encoding/binary"
 	"fmt"
 	"io"
+	"os"
 	"strconv"
 )
 
@@ -18,7 +19,7 @@ type ID3v11Tags struct {
 	Genre    string
 }
 
-// Retrieves ID3v1.1 field values of provided io.ReadSeeker (usually a file)
+// Retrieves ID3v1.1 field values of provided io.ReadSeeker
 func GetID3v11Tags(rs io.ReadSeeker) (*ID3v11Tags, error) {
 	// set reader to the last 128 bytes
 	_, err := rs.Seek(-int64(ID3V1SIZE), io.SeekEnd)
@@ -106,7 +107,7 @@ func GetID3v11Tags(rs io.ReadSeeker) (*ID3v11Tags, error) {
 }
 
 // Writes given ID3v1.1 tags to dst
-func WriteID3v11Tags(dst io.WriteSeeker, tags ID3v11Tags) error {
+func WriteID3v11Tags(dst io.WriteSeeker, tags *ID3v11Tags) error {
 	dst.Seek(0, io.SeekEnd)
 
 	// TAG
@@ -175,3 +176,45 @@ func WriteID3v11Tags(dst io.WriteSeeker, tags ID3v11Tags) error {
 
 	return nil
 }
+
+// Checks for existing ID3v1.1 tag in file, if present - removes it and replaces with provided tags
+func WriteID3v11ToFile(f *os.File, tags *ID3v11Tags) error {
+	defer f.Close()
+
+	// check for existing ID3v1.1 tag
+	f.Seek(-int64(ID3V1SIZE), io.SeekEnd)
+
+	tag, err := read(f, 3)
+	if err != nil {
+		return err
+	}
+
+	if !bytes.Equal(tag, []byte("TAG")) {
+		// no existing tag, just write given tags
+		err = WriteID3v11Tags(f, tags)
+		if err != nil {
+			return err
+		}
+		return nil
+	}
+
+	// does contain ID3v1.1 tag. Removing it
+	fStats, err := f.Stat()
+	if err != nil {
+		return err
+	}
+
+	err = f.Truncate(fStats.Size() - int64(ID3V1SIZE))
+	if err != nil {
+		return nil
+	}
+
+	// writing new tags
+	err = WriteID3v11Tags(f, tags)
+	if err != nil {
+		return err
+	}
+
+	return nil
+
+}

id3v11_test.go

@@ -6,8 +6,18 @@ import (
 	"testing"
 )
 
+var TESTV11TAGS = &ID3v11Tags{
+	SongName: "testsong",
+	Artist:   "testartist",
+	Album:    "testalbum",
+	Year:     727,
+	Comment:  "testcomment",
+	Track:    5,
+	Genre:    "Blues",
+}
+
 func TestGetID3v11Tags(t *testing.T) {
-	testfile, err := os.Open("./testData/testread.mp3")
+	testfile, err := os.Open("./testData/testreadv1.mp3")
 	if err != nil {
 		t.Errorf("could not open file for testing: %s", err)
 	}
@@ -27,23 +37,15 @@ func TestGetID3v11Tags(t *testing.T) {
 }
 
 func TestWriteID3v11Tags(t *testing.T) {
-	os.Remove("./testData/testwrite.mp3")
+	os.Remove("./testData/testwritev1.mp3")
 
-	f, err := os.Create("./testData/testwrite.mp3")
+	f, err := os.Create("./testData/testwritev1.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",
-	}
+	tags := TESTV11TAGS
 
 	err = WriteID3v11Tags(f, tags)
 	if err != nil {
@@ -67,3 +69,17 @@ func TestWriteID3v11Tags(t *testing.T) {
 		t.Errorf("WriteID3v11Tags failed: expected %d; got %d", 5, readTags.Track)
 	}
 }
+
+func TestWriteID3v11ToFile(t *testing.T) {
+	f, err := os.Open("./testData/testwritev1.mp3")
+	if err != nil {
+		t.Errorf("%s", err)
+	}
+
+	tags := TESTV11TAGS
+
+	err = WriteID3v11ToFile(f, tags)
+	if err != nil {
+		t.Errorf("WriteID3v1ToFile failed: %s", err)
+	}
+}