❖ Improved utils, continued to work on v2 frames ❖

util/etc.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/binary"
 	"fmt"
+	"strconv"
 )
 
 // Returns found key (int) in provided map by value (string);
@@ -27,3 +28,24 @@ func BytesToInt(gBytes []byte) (int64, error) {
 	buff = nil
 	return integer, nil
 }
+
+// Decodes given integer bytes into integer, ignores the first bit
+// of every given byte in binary form
+func BytesToIntIgnoreFirstBit(gBytes []byte) (int64, error) {
+	// represent each byte in size as binary and get rid from the first bit,
+	// then concatenate filtered parts
+	var filteredBits string
+	for _, b := range gBytes {
+		// ignore the first bit
+		filteredPart := fmt.Sprintf("%08b", b)[1:] // byte is 8 bits
+		filteredBits += filteredPart
+	}
+
+	// convert filtered binary into usable int64
+	integer, err := strconv.ParseInt(filteredBits, 2, 64)
+	if err != nil {
+		return -1, err
+	}
+
+	return integer, nil
+}

util/read.go

@@ -18,7 +18,7 @@ func Read(rs io.Reader, n uint64) ([]byte, error) {
 
 // Shortcut function to read n bytes and convert them into string.
 // If encountered zero-byte - converts to string only previously read bytes
-func ReadToString(rs io.Reader, n int) (string, error) {
+func ReadToStringIgnoreNullB(rs io.Reader, n uint64) (string, error) {
 	read := make([]byte, n)
 	_, err := rs.Read(read)
 	if err != nil {
@@ -35,3 +35,14 @@ func ReadToString(rs io.Reader, n int) (string, error) {
 
 	return readString, nil
 }
+
+// Reads from rs and conversts read []byte into string
+func ReadToString(rs io.Reader, n uint64) (string, error) {
+	read := make([]byte, n)
+	_, err := rs.Read(read)
+	if err != nil {
+		return "", fmt.Errorf("could not read from reader: %s", err)
+	}
+
+	return string(read), nil
+}

v1/id3v10.go

@@ -40,22 +40,22 @@ func Getv1Tags(rs io.ReadSeeker) (*ID3v1Tags, error) {
 		return nil, fmt.Errorf("does not use ID3v1: expected %s; got %s", ID3v1IDENTIFIER, tag)
 	}
 
-	songname, err := util.ReadToString(rs, 30)
+	songname, err := util.ReadToStringIgnoreNullB(rs, 30)
 	if err != nil {
 		return nil, err
 	}
 
-	artist, err := util.ReadToString(rs, 30)
+	artist, err := util.ReadToStringIgnoreNullB(rs, 30)
 	if err != nil {
 		return nil, err
 	}
 
-	album, err := util.ReadToString(rs, 30)
+	album, err := util.ReadToStringIgnoreNullB(rs, 30)
 	if err != nil {
 		return nil, err
 	}
 
-	yearStr, err := util.ReadToString(rs, 4)
+	yearStr, err := util.ReadToStringIgnoreNullB(rs, 4)
 	if err != nil {
 		return nil, err
 	}
@@ -64,7 +64,7 @@ func Getv1Tags(rs io.ReadSeeker) (*ID3v1Tags, error) {
 		return nil, fmt.Errorf("could not convert yearbytes into int: %s", err)
 	}
 
-	comment, err := util.ReadToString(rs, 30)
+	comment, err := util.ReadToStringIgnoreNullB(rs, 30)
 	if err != nil {
 		return nil, err
 	}

v1/id3v11.go

@@ -39,22 +39,22 @@ func Getv11Tags(rs io.ReadSeeker) (*ID3v11Tags, error) {
 		return nil, fmt.Errorf("does not use ID3v1: expected %s; got %s", ID3v1IDENTIFIER, tag)
 	}
 
-	songname, err := util.ReadToString(rs, 30)
+	songname, err := util.ReadToStringIgnoreNullB(rs, 30)
 	if err != nil {
 		return nil, err
 	}
 
-	artist, err := util.ReadToString(rs, 30)
+	artist, err := util.ReadToStringIgnoreNullB(rs, 30)
 	if err != nil {
 		return nil, err
 	}
 
-	album, err := util.ReadToString(rs, 30)
+	album, err := util.ReadToStringIgnoreNullB(rs, 30)
 	if err != nil {
 		return nil, err
 	}
 
-	yearStr, err := util.ReadToString(rs, 4)
+	yearStr, err := util.ReadToStringIgnoreNullB(rs, 4)
 	if err != nil {
 		return nil, err
 	}
@@ -63,7 +63,7 @@ func Getv11Tags(rs io.ReadSeeker) (*ID3v11Tags, error) {
 		return nil, fmt.Errorf("could not convert yearbytes into int: %s", err)
 	}
 
-	comment, err := util.ReadToString(rs, 28)
+	comment, err := util.ReadToStringIgnoreNullB(rs, 28)
 	if err != nil {
 		return nil, err
 	}

v2/constants.go

@@ -4,3 +4,5 @@ package v2
 const HEADERIDENTIFIER string = "ID3"
 const HEADERSIZE int = 10           // bytes
 const HEADERMAXSIZE int = 268435456 // bytes (256 MB)
+
+// Version specific constants

v2/frame.go

@@ -11,49 +11,58 @@ import (
 ////////////////////////////////////////////////////////////////////////////
 
 type FrameHeader struct {
-	Identifier string
+	ID        string
 	FrameSize int64
+	Flags     int
 }
 
 type Frame struct {
-	Header   *FrameHeader
+	Header   FrameHeader
 	Contents string
 }
 
-// NOT TESTED !
-func Readv2Frame(rs io.Reader) (*Frame, error) {
-	var frameHeader *FrameHeader
+// NOT TESTED ! Reads v2.3 | v2.4 frame
+func ReadFrame(rs io.Reader) (*Frame, error) {
+	var frameHeader FrameHeader
 	var frame Frame
 
-	identifier, err := util.ReadToString(rs, 3)
+	identifier, err := util.ReadToString(rs, 4)
 	if err != nil {
 		return nil, err
 	}
-	frameHeader.Identifier = identifier
+	frameHeader.ID = identifier
 
-	framesizeBytes, err := util.Read(rs, 3)
+	framesizeBytes, err := util.Read(rs, 4)
 	if err != nil {
 		return nil, err
 	}
 
-	framesize, err := util.BytesToInt(framesizeBytes)
+	framesize, err := util.BytesToIntIgnoreFirstBit(framesizeBytes)
 	if err != nil {
 		return nil, err
 	}
 
 	frameHeader.FrameSize = framesize
 
-	frameContents, err := util.ReadToString(rs, int(framesize))
+	frameFlagsBytes, err := util.Read(rs, 2)
+	if err != nil {
+		return nil, err
+	}
+
+	// STILL NOT IMPLEMENTED FLAG HANDLING  !
+	frameFlags, err := util.BytesToInt(frameFlagsBytes)
+	if err != nil {
+		return nil, err
+	}
+	frameHeader.Flags = int(frameFlags)
+
+	frameContents, err := util.Read(rs, uint64(framesize))
 	if err != nil {
 		return nil, err
 	}
 
 	frame.Header = frameHeader
-	frame.Contents = frameContents
+	frame.Contents = string(frameContents)
 
 	return &frame, nil
 }
-
-// func ReadFrame(rs io.Reader, version string) error {
-// 	return nil
-// }

v2/frame_test.go

@@ -1,16 +1,27 @@
 package v2
 
-// func TestReadFrame(t *testing.T) {
-// 	f, err := os.Open(filepath.Join(TESTDATAPATH, "testreadv2.mp3"))
-// 	if err != nil {
-// 		t.Errorf("%s", err)
-// 	}
+import (
+	"io"
+	"os"
+	"path/filepath"
+	"testing"
+)
 
-// 	// read right after header`s bytes
-// 	f.Seek(int64(HEADERSIZE), io.SeekStart)
+func TestReadFrame(t *testing.T) {
+	f, err := os.Open(filepath.Join(TESTDATAPATH, "testreadv2.mp3"))
+	if err != nil {
+		t.Errorf("%s", err)
+	}
 
-// 	_, err = Readv2Frame(f)
-// 	if err != nil {
-// 		t.Errorf("ReadFrame failed: %s", err)
-// 	}
-// }
+	// read right after header`s bytes
+	f.Seek(int64(HEADERSIZE), io.SeekStart)
+
+	firstFrame, err := ReadFrame(f)
+	if err != nil {
+		t.Errorf("ReadFrame failed: %s", err)
+	}
+
+	if firstFrame.Header.ID != "TRCK" {
+		t.Errorf("ReadFrame failed: expected ID %s; got %s", "TRCK", firstFrame.Header.ID)
+	}
+}

v2/header.go

@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"fmt"
 	"io"
-	"strconv"
 
 	"github.com/Unbewohnte/id3ed/util"
 )
@@ -77,22 +76,12 @@ func GetHeader(rs io.ReadSeeker) (*Header, error) {
 		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)
+	size, err := util.BytesToIntIgnoreFirstBit(sizeBytes)
 	if err != nil {
 		return nil, err
 	}
 
-	header.Size = int64(size)
+	header.Size = size
 
 	return &header, nil
 }