◾ Procrastinated really hard on ID3v2 writing support... ◾

util/conversion.go

@@ -1,8 +1,6 @@
 package util
 
 import (
-	"fmt"
-	"strconv"
 	"strings"
 
 	euni "golang.org/x/text/encoding/unicode"
@@ -12,18 +10,19 @@ import (
 
 const first7BitsMask = uint32(254) << 24 // shifting 11111110 to the end of uint32
 
-// Decodes given byte into integer
-func ByteToInt(gByte byte) (int, error) {
-	integer, err := strconv.Atoi(fmt.Sprintf("%d", gByte))
-	if err != nil {
-		return 0, err
+// Converts given bytes into integer
+func BytesToInt(gBytes []byte) uint32 {
+	var integer uint32 = 0
+	for _, b := range gBytes {
+		integer = integer << 8
+		integer = integer | uint32(b)
 	}
-	return integer, nil
+	return integer
 }
 
 // Decodes given integer bytes into integer, ignores the first bit
 // of every given byte in binary form
-func BytesToIntIgnoreFirstBit(gBytes []byte) uint32 {
+func BytesToIntSynchsafe(gBytes []byte) uint32 {
 	var integer uint32 = 0
 	for _, b := range gBytes {
 		integer = integer << 7
@@ -34,14 +33,14 @@ func BytesToIntIgnoreFirstBit(gBytes []byte) uint32 {
 }
 
 // The exact opposite of what `BytesToIntIgnoreFirstBit` does
-func IntToBytesFirstBitZeroed(gInt uint32) []byte {
+func SynchsafeIntToBytes(gInt uint32) []byte {
 	bytes := make([]byte, 32)
 
 	// looping 4 times (32 bits / 8 bits (4 bytes in int32))
 	for i := 0; i < 32; i += 8 {
-		gIntCopy := gInt //ie: 		  11010100 11001011 00100000 10111111
-		first7 := gIntCopy & first7BitsMask
-		shifted := first7 >> 25 //    00000000 00000000 00000000 01101010
+		gIntCopy := gInt                    //11010101 11001011 00100000 10111111
+		first7 := gIntCopy & first7BitsMask //11010100 00000000 00000000 00000000
+		shifted := first7 >> 25             //00000000 00000000 00000000 01101010
 		bytes = append(bytes, byte(shifted))
 	}
 

util/read.go

@@ -6,9 +6,9 @@ import (
 )
 
 // Shortcut function to read n bytes from reader. The general idea peeked from here: https://github.com/dhowden/tag/blob/master/util.go
-func Read(rs io.Reader, n uint64) ([]byte, error) {
+func Read(r io.Reader, n uint64) ([]byte, error) {
 	read := make([]byte, n)
-	_, err := rs.Read(read)
+	_, err := r.Read(read)
 	if err != nil {
 		return nil, fmt.Errorf("could not read from reader: %s", err)
 	}
@@ -18,9 +18,9 @@ func Read(rs io.Reader, n uint64) ([]byte, error) {
 
 // Reads from rs and conversts read []byte into string, ignoring all non-printable or
 // invalid characters.
-func ReadToString(rs io.Reader, n uint64) (string, error) {
+func ReadToString(r io.Reader, n uint64) (string, error) {
 	read := make([]byte, n)
-	_, err := rs.Read(read)
+	_, err := r.Read(read)
 	if err != nil {
 		return "", fmt.Errorf("could not read from reader: %s", err)
 	}

v1/constants.go

@@ -1,8 +1,11 @@
 package v1
 
 const ID3v1IDENTIFIER string = "TAG"
-const ID3v1SIZE int = 128 // bytes
+const ID3v1SIZE int = 128
 const ID3v1INVALIDGENRE int = 255
 
+const ID3v1ENHANCEDIDENTIFIER string = "TAG+"
+const ENHANCEDSIZE int = 227
+
 const V1_0 string = "ID3v1.0"
 const V1_1 string = "ID3v1.1"

v1/errors.go

@@ -0,0 +1,7 @@
+package v1
+
+// Exported ID3v1-specific errors
+
+import "fmt"
+
+var ErrDoesNotUseID3v1 error = fmt.Errorf("does not use ID3v1")

v1/read.go

@@ -9,12 +9,114 @@ import (
 	"github.com/Unbewohnte/id3ed/util"
 )
 
-var ErrDoesNotUseID3v1 error = fmt.Errorf("does not use ID3v1")
+var errDoesNotUseEnhancedID3v1 error = fmt.Errorf("does not use enhanced ID3v1 tag")
 
-// Retrieves ID3v1 field values of provided io.ReadSeeker (usually a file)
+// Checks if enhanced tag is used
+func usesEnhancedTag(rs io.ReadSeeker) bool {
+	_, err := rs.Seek(-int64(ID3v1SIZE+ENHANCEDSIZE), io.SeekEnd)
+	if err != nil {
+		return false
+	}
+	identifier, err := util.Read(rs, 4)
+	if err != nil {
+		return false
+	}
+	if !bytes.Equal(identifier, []byte(ID3v1ENHANCEDIDENTIFIER)) {
+		return false
+	}
+
+	return true
+}
+
+// Tries to read enhanced ID3V1 tag from rs
+func readEnhancedTag(rs io.ReadSeeker) (EnhancedID3v1Tag, error) {
+
+	if !usesEnhancedTag(rs) {
+		return EnhancedID3v1Tag{}, errDoesNotUseEnhancedID3v1
+	}
+
+	var enhanced EnhancedID3v1Tag
+
+	// set reader into the position
+	_, err := rs.Seek(-int64(ID3v1SIZE+ENHANCEDSIZE), io.SeekEnd)
+	if err != nil {
+		return enhanced, fmt.Errorf("could not seek: %s", err)
+	}
+
+	// songname
+	songName, err := util.ReadToString(rs, 60)
+	if err != nil {
+		return EnhancedID3v1Tag{}, err
+	}
+	enhanced.SongName = songName
+
+	artist, err := util.ReadToString(rs, 60)
+	if err != nil {
+		return enhanced, err
+	}
+	enhanced.Artist = artist
+
+	// album
+	album, err := util.ReadToString(rs, 60)
+	if err != nil {
+		return enhanced, err
+	}
+	enhanced.Album = album
+
+	// speed
+	speedByte, err := util.Read(rs, 1)
+	if err != nil {
+		return enhanced, err
+	}
+
+	var speed string
+	switch speedByte[0] {
+	case 0:
+		speed = "Unset"
+	case 1:
+		speed = "Slow"
+	case 2:
+		speed = "Medium"
+	case 3:
+		speed = "Fast"
+	case 4:
+		speed = "Hardcore"
+	}
+	enhanced.Speed = speed
+
+	// genre
+	genre, err := util.ReadToString(rs, 30)
+	if err != nil {
+		return enhanced, err
+	}
+	enhanced.Genre = genre
+
+	// time
+	startTime, err := util.ReadToString(rs, 6)
+	if err != nil {
+		return enhanced, err
+	}
+	enhanced.StartTime = startTime
+
+	endtime, err := util.ReadToString(rs, 6)
+	if err != nil {
+		return enhanced, err
+	}
+	enhanced.EndTime = endtime
+
+	return enhanced, nil
+}
+
+// Retrieves ID3v1 field values from rs.
 func Readv1Tag(rs io.ReadSeeker) (*ID3v1Tag, error) {
 	var tag ID3v1Tag
 
+	// check if uses enhanced tag
+	if usesEnhancedTag(rs) {
+		enhanced, _ := readEnhancedTag(rs)
+		tag.EnhancedTag = enhanced
+	}
+
 	// set reader to the last 128 bytes
 	_, err := rs.Seek(-int64(ID3v1SIZE), io.SeekEnd)
 	if err != nil {
@@ -76,10 +178,8 @@ func Readv1Tag(rs io.ReadSeeker) (*ID3v1Tag, error) {
 	// check if 29th byte is null byte (v1.0 or v1.1)
 	if comment[28] == 0 {
 		// it is v1.1, track number exists
-		track, err = util.ByteToInt(comment[29])
-		if err != nil {
-			return nil, fmt.Errorf("could not get int from byte: %s", err)
-		}
+		track = int(comment[29])
+
 		tag.Track = uint8(track)
 
 		comment = comment[0:28]
@@ -91,10 +191,8 @@ func Readv1Tag(rs io.ReadSeeker) (*ID3v1Tag, error) {
 	if err != nil {
 		return nil, err
 	}
-	genreInt, err := util.ByteToInt(genreByte[0])
-	if err != nil {
-		return nil, fmt.Errorf("cannot convert bytes to int: %s", err)
-	}
+	genreInt := int(genreByte[0])
+
 	genre, exists := id3v1genres[int(genreInt)]
 	if !exists {
 		genre = ""

v1/tag.go

@@ -11,4 +11,17 @@ type ID3v1Tag struct {
 	Comment     string
 	Track       uint8 // basically a byte, but converted to int for convenience
 	Genre       string
+	EnhancedTag EnhancedID3v1Tag
+}
+
+// from https://en.wikipedia.org/wiki/ID3
+
+type EnhancedID3v1Tag struct {
+	SongName  string
+	Artist    string
+	Album     string
+	Speed     string
+	Genre     string
+	StartTime string
+	EndTime   string
 }

v2/errors.go

@@ -0,0 +1,7 @@
+package v2
+
+// Exported ID3v2-specific errors
+
+import "fmt"
+
+var ErrDoesNotUseID3v2 error = fmt.Errorf("does not use ID3v2")

v2/frame.go

@@ -63,7 +63,7 @@ func getFrameHeader(fHeaderbytes []byte, version string) (FrameHeader, error) {
 		}
 		header.ID = string(fHeaderbytes[0:3])
 
-		framesizeBytes := util.BytesToIntIgnoreFirstBit(fHeaderbytes[3:6])
+		framesizeBytes := util.BytesToIntSynchsafe(fHeaderbytes[3:6])
 		header.Size = framesizeBytes
 
 	case V2_3:
@@ -82,7 +82,7 @@ func getFrameHeader(fHeaderbytes []byte, version string) (FrameHeader, error) {
 		// Size
 		framesizeBytes := fHeaderbytes[4:8]
 
-		framesize := util.BytesToIntIgnoreFirstBit(framesizeBytes)
+		framesize := util.BytesToIntSynchsafe(framesizeBytes)
 
 		header.Size = framesize
 

v2/header.go

@@ -8,24 +8,177 @@ import (
 	"github.com/Unbewohnte/id3ed/util"
 )
 
-var ErrDoesNotUseID3v2 error = fmt.Errorf("does not use ID3v2")
-
+// Main header`s flags
 type HeaderFlags struct {
 	Unsynchronisated  bool
+	Compressed        bool
 	HasExtendedHeader bool
 	Experimental      bool
 	FooterPresent     bool
 }
 
-// ID3v2.x header structure
+// ID3v2.x`s main header structure
 type Header struct {
 	Identifier     string
 	Flags          HeaderFlags
 	Version        string
 	Size           uint32
+	ExtendedHeader ExtendedHeader
+}
+
+// extended header`s flags
+type ExtendedHeaderFlags struct {
+	UpdateTag       bool
+	CRCpresent      bool
+	HasRestrictions bool
+	Restrictions    byte // a `lazy` approach :), just for now, maybe...
+}
+
+type ExtendedHeader struct {
+	Size        uint32
+	Flags       ExtendedHeaderFlags
+	PaddingSize uint32
+	CRCdata     []byte
+}
+
+// Reads and structuralises extended header. Must
+// be called AFTER the main header has beeen read (does not seek).
+// ALSO ISN`T TESTED !!!
+func (h *Header) readExtendedHeader(r io.Reader) error {
+	h.ExtendedHeader = ExtendedHeader{}
+	if !h.Flags.HasExtendedHeader {
+		return nil
+	}
+
+	var extended ExtendedHeader
+
+	// extended size
+	extendedSize, err := util.Read(r, 4)
+	if err != nil {
+		return fmt.Errorf("could not read from reader: %s", err)
+	}
+
+	switch h.Version {
+	case V2_3:
+		extended.Size = util.BytesToInt(extendedSize)
+	case V2_4:
+		extended.Size = util.BytesToIntSynchsafe(extendedSize)
+	}
+
+	// extended flags
+	switch h.Version {
+	case V2_3:
+		extendedFlag, err := util.Read(r, 2) // reading flag byte and a null-byte after
+		if err != nil {
+			return fmt.Errorf("could not read from reader: %s", err)
+		}
+		flagbits := fmt.Sprintf("%08b", extendedFlag[0])
+		if flagbits[0] == 1 {
+			extended.Flags.CRCpresent = true
+		} else {
+			extended.Flags.CRCpresent = false
+		}
+
+	case V2_4:
+		// skipping `Number of flag bytes` because it`s always `1`
+		_, err := util.Read(r, 1)
+		if err != nil {
+			return fmt.Errorf("could not read from reader: %s", err)
+		}
+		flagByte, err := util.Read(r, 1)
+		if err != nil {
+			return fmt.Errorf("could not read from reader: %s", err)
+		}
+
+		flagBits := fmt.Sprintf("%08b", flagByte[0])
+		if flagBits[1] == 1 {
+			extended.Flags.UpdateTag = true
+		} else {
+			extended.Flags.UpdateTag = false
+		}
+
+		if flagBits[2] == 1 {
+			extended.Flags.CRCpresent = true
+		} else {
+			extended.Flags.CRCpresent = false
+		}
+
+		if flagBits[3] == 1 {
+			extended.Flags.HasRestrictions = true
+		} else {
+			extended.Flags.HasRestrictions = false
+		}
+	}
+
+	// extracting data given by flags
+	switch h.Version {
+	case V2_3:
+		if extended.Flags.CRCpresent {
+			crcData, err := util.Read(r, 4)
+			if err != nil {
+				return fmt.Errorf("could not read from reader: %s", err)
+			}
+			extended.CRCdata = crcData
+		}
+
+	case V2_4:
+		// `Each flag that is set in the extended header has data attached`
+
+		if extended.Flags.UpdateTag {
+			// skipping null-byte length of `UpdateTag`
+			_, err := util.Read(r, 1)
+			if err != nil {
+				return fmt.Errorf("could not read from reader: %s", err)
+			}
+		}
+
+		if extended.Flags.CRCpresent {
+			crclen, err := util.Read(r, 1)
+			if err != nil {
+				return fmt.Errorf("could not read from reader: %s", err)
+			}
+			crcData, err := util.Read(r, uint64(crclen[0]))
+			if err != nil {
+				return fmt.Errorf("could not read from reader: %s", err)
+			}
+			extended.CRCdata = crcData
+		}
+
+		if extended.Flags.HasRestrictions {
+			// skipping one-byte length of `Restrictions`, because it`s always `1`
+			_, err := util.Read(r, 1)
+			if err != nil {
+				return fmt.Errorf("could not read from reader: %s", err)
+			}
+
+			restrictionsByte, err := util.Read(r, 1)
+			if err != nil {
+				return fmt.Errorf("could not read from reader: %s", err)
+			}
+			// a `lazy` approach :), just for now
+			extended.Flags.Restrictions = restrictionsByte[0]
+		}
+	}
+
+	// extracting other version-dependent header data
+
+	// padding if V2_3
+	if h.Version == V2_3 {
+		paddingSizeBytes, err := util.Read(r, 4)
+		if err != nil {
+			return fmt.Errorf("could not read from reader: %s", err)
+		}
+		paddingSize := util.BytesToInt(paddingSizeBytes)
+		extended.PaddingSize = paddingSize
+	}
+
+	// finally `attaching` parsed extended header to the main *Header
+	h.ExtendedHeader = extended
+
+	return nil
 }
 
-// Reads and structuralises ID3v2 header from given bytes.
+// Reads and structuralises ID3v2 header and if present - extended header.
 // Returns a blank header struct if encountered an error
 func readHeader(rs io.ReadSeeker) (Header, error) {
 	_, err := rs.Seek(0, io.SeekStart)
@@ -49,14 +202,8 @@ func readHeader(rs io.ReadSeeker) (Header, error) {
 	header.Identifier = string(identifier)
 
 	// version
-	majorVersion, err := util.ByteToInt(hBytes[3])
-	if err != nil {
-		return Header{}, err
-	}
-	revisionNumber, err := util.ByteToInt(hBytes[4])
-	if err != nil {
-		return Header{}, err
-	}
+	majorVersion := int(hBytes[3])
+	revisionNumber := int(hBytes[4])
 
 	switch majorVersion {
 	case 2:
@@ -76,6 +223,17 @@ func readHeader(rs io.ReadSeeker) (Header, error) {
 
 	// v3.0 and v4.0 have different amount of flags
 	switch header.Version {
+	case V2_2:
+		if flagBits[0] == 1 {
+			header.Flags.Unsynchronisated = true
+		} else {
+			header.Flags.Unsynchronisated = false
+		}
+		if flagBits[1] == 1 {
+			header.Flags.Compressed = true
+		} else {
+			header.Flags.Compressed = false
+		}
 	case V2_3:
 		if flagBits[0] == 1 {
 			header.Flags.Unsynchronisated = true
@@ -121,9 +279,16 @@ func readHeader(rs io.ReadSeeker) (Header, error) {
 	// size
 	sizeBytes := hBytes[6:]
 
-	size := util.BytesToIntIgnoreFirstBit(sizeBytes)
+	size := util.BytesToIntSynchsafe(sizeBytes)
 
 	header.Size = size
 
+	if header.Flags.HasExtendedHeader {
+		err = header.readExtendedHeader(rs)
+		if err != nil {
+			return header, err
+		}
+	}
+
 	return header, nil
 }