⚫Now can read ID3v2 header ⚫

README.md

@@ -3,7 +3,10 @@
 
 ---
 
-# Under construction !
+# //////////////////////////////////////
+# //(ᗜˬᗜ)~⭐//Under construction//(ᗜ‸ᗜ)//
+# //////////////////////////////////////
+
 
 ---
 

id3v10.go

@@ -71,7 +71,7 @@ func GetID3v1Tags(rs io.ReadSeeker) (*ID3v1Tags, error) {
 	if err != nil {
 		return nil, err
 	}
-	genreInt, err := binary.ReadVarint(bytes.NewBuffer(genreByte))
+	genreInt, err := bytesToInt(genreByte)
 	if err != nil {
 		return nil, err
 	}

id3v11.go

@@ -77,7 +77,7 @@ func GetID3v11Tags(rs io.ReadSeeker) (*ID3v11Tags, error) {
 		return nil, err
 	}
 
-	track, err := binary.ReadVarint(bytes.NewBuffer(trackByte))
+	track, err := bytesToInt(trackByte)
 	if err != nil {
 		return nil, err
 	}
@@ -86,7 +86,7 @@ func GetID3v11Tags(rs io.ReadSeeker) (*ID3v11Tags, error) {
 	if err != nil {
 		return nil, err
 	}
-	genreInt, err := binary.ReadVarint(bytes.NewBuffer(genreByte))
+	genreInt, err := bytesToInt(genreByte)
 	if err != nil {
 		return nil, err
 	}
@@ -218,5 +218,4 @@ func (tags *ID3v11Tags) WriteToFile(f *os.File) error {
 	}
 
 	return nil
-
 }

id3v20.go

@@ -8,15 +8,19 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"strconv"
 )
 
+// ID3v2.x header structure
 type Header struct {
 	Identifier       string
-	Version    int
+	Version          string
-	Flags      int
+	Unsynchronisated bool
+	Compressed       bool
 	Size             int64
 }
 
+// Reads and structuralises ID3v2 header
 func GetHeader(rs io.ReadSeeker) (*Header, error) {
 	var header Header
 
@@ -28,11 +32,69 @@ func GetHeader(rs io.ReadSeeker) (*Header, error) {
 	}
 	// check if ID3v2 is used
 	if !bytes.Equal([]byte(ID3v2IDENTIFIER), identifier) {
-		return nil, fmt.Errorf("does not use ID3v2")
+		return nil, fmt.Errorf("no ID3v2 identifier found")
 	}
-	////
-
 	header.Identifier = string(identifier)
 
+	// version
+	majorVersionByte, err := read(rs, 1)
+	if err != nil {
+		return nil, err
+	}
+	revisionNumberByte, err := read(rs, 1)
+	if err != nil {
+		return nil, err
+	}
+
+	majorVersion, err := bytesToInt(majorVersionByte)
+	if err != nil {
+		return nil, err
+	}
+	revisionNumber, err := bytesToInt(revisionNumberByte)
+	if err != nil {
+		return nil, err
+	}
+	header.Version = fmt.Sprintf("%d%d", -majorVersion, revisionNumber)
+
+	// flags
+	flags, err := read(rs, 1)
+	if err != nil {
+		return nil, err
+	}
+	bits := fmt.Sprintf("%08b", flags) // 1 byte is 8 bits
+	if bits[0] == 1 {
+		header.Unsynchronisated = true
+	} else {
+		header.Unsynchronisated = false
+	}
+	if bits[1] == 1 {
+		header.Compressed = true
+	} else {
+		header.Compressed = false
+	}
+
+	// size
+	sizeBytes, err := read(rs, 4)
+	if err != nil {
+		return nil, err
+	}
+
+	// represent each byte in size as binary and get rid from the first useless bit,
+	// then concatenate filtered parts
+	var filteredSizeStr string
+	for _, b := range sizeBytes {
+		// the first bit is always 0, so filter it out
+		filteredPart := fmt.Sprintf("%08b", b)[1:] // byte is 8 bits
+		filteredSizeStr += filteredPart
+	}
+
+	// converting filtered binary size into usable int64
+	size, err := strconv.ParseInt(filteredSizeStr, 2, 64)
+	if err != nil {
+		return nil, err
+	}
+
+	header.Size = int64(size)
+
 	return &header, nil
 }

id3v20_test.go

@@ -0,0 +1,34 @@
+package id3ed
+
+import (
+	"os"
+	"testing"
+)
+
+func TestGetHeader(t *testing.T) {
+	f, err := os.Open("./testData/testreadv2.mp3")
+	if err != nil {
+		t.Errorf("%s", err)
+	}
+
+	header, err := GetHeader(f)
+	if err != nil {
+		t.Errorf("GetHeader failed: %s", err)
+	}
+
+	if header.Identifier != "ID3" {
+		t.Errorf("GetHeader failed: expected identifier %s; got %s", "ID3", header.Identifier)
+	}
+
+	if header.Compressed != false {
+		t.Errorf("GetHeader failed: expected flag %v; got %v", false, header.Compressed)
+	}
+
+	if header.Unsynchronisated != false {
+		t.Errorf("GetHeader failed: expected flag %v; got %v", false, header.Unsynchronisated)
+	}
+
+	if header.Size != 1138 {
+		t.Errorf("GetHeader failed: expected size %v; got %v", 1138, header.Size)
+	}
+}

metadata.go

@@ -1,15 +0,0 @@
-package id3ed
-
-import (
-	"io"
-	"os"
-)
-
-// I`m still a bit confused about interfaces,
-// I`ll look into them and try to figure out
-// how to use them properly
-type Metadata interface {
-	Read(io.ReadSeeker) error
-	Write(io.WriteSeeker) error
-	WriteToFile(*os.File) error
-}

util.go

@@ -2,6 +2,7 @@ package id3ed
 
 import (
 	"bytes"
+	"encoding/binary"
 	"fmt"
 	"io"
 )
@@ -76,3 +77,14 @@ func getKey(mp map[int]string, givenValue string) int {
 	}
 	return -1
 }
+
+// Decodes given integer bytes into integer
+func bytesToInt(gBytes []byte) (int64, error) {
+	buff := bytes.NewBuffer(gBytes)
+	integer, err := binary.ReadVarint(buff)
+	if err != nil {
+		return 0, err
+	}
+	buff = nil
+	return integer, nil
+}