You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
105 lines
2.4 KiB
105 lines
2.4 KiB
package util |
|
|
|
import ( |
|
"fmt" |
|
"strconv" |
|
"strings" |
|
|
|
euni "golang.org/x/text/encoding/unicode" |
|
) |
|
|
|
// got the logic from: https://github.com/bogem/id3v2 , thank you very much. |
|
|
|
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 |
|
} |
|
return integer, nil |
|
} |
|
|
|
// Decodes given integer bytes into integer, ignores the first bit |
|
// of every given byte in binary form |
|
func BytesToIntIgnoreFirstBit(gBytes []byte) uint32 { |
|
var integer uint32 = 0 |
|
for _, b := range gBytes { |
|
integer = integer << 7 |
|
integer = integer | uint32(b) |
|
} |
|
|
|
return integer |
|
} |
|
|
|
// The exact opposite of what `BytesToIntIgnoreFirstBit` does |
|
func IntToBytesFirstBitZeroed(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 |
|
bytes = append(bytes, byte(shifted)) |
|
} |
|
|
|
return bytes |
|
} |
|
|
|
// Converts given bytes into string, ignoring the first 31 non-printable ASCII characters. |
|
// (LOSSY, if given bytes contain some nasty ones) |
|
func ToStringLossy(gBytes []byte) string { |
|
var runes []rune |
|
for _, b := range gBytes { |
|
if b <= 31 { |
|
continue |
|
} |
|
runes = append(runes, rune(b)) |
|
} |
|
|
|
return strings.ToValidUTF8(string(runes), "") |
|
} |
|
|
|
// Decodes the given frame`s contents |
|
func DecodeText(fContents []byte) string { |
|
textEncoding := fContents[0] // the first byte is the encoding |
|
|
|
switch textEncoding { |
|
case 0: |
|
// ISO-8859-1 |
|
return ToStringLossy(fContents[1:]) |
|
case 1: |
|
// UTF-16 with BOM |
|
encoding := euni.UTF16(euni.BigEndian, euni.ExpectBOM) |
|
decoder := encoding.NewDecoder() |
|
|
|
decodedBytes := make([]byte, len(fContents)*2) |
|
_, _, err := decoder.Transform(decodedBytes, fContents[1:], true) |
|
if err != nil { |
|
return "" |
|
} |
|
|
|
return string(decodedBytes) |
|
|
|
case 2: |
|
// UTF-16 |
|
encoding := euni.UTF16(euni.BigEndian, euni.IgnoreBOM) |
|
decoder := encoding.NewDecoder() |
|
|
|
decodedBytes := make([]byte, len(fContents)*2) |
|
_, _, err := decoder.Transform(decodedBytes, fContents[1:], true) |
|
if err != nil { |
|
return "" |
|
} |
|
|
|
return string(decodedBytes) |
|
|
|
case 3: |
|
// UTF-8 |
|
return ToStringLossy(fContents[1:]) |
|
} |
|
|
|
return "" |
|
}
|
|
|