/
frame.go
85 lines (76 loc) · 1.56 KB
/
frame.go
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package id3v2
import (
"fmt"
"io"
)
type Frame struct {
FrameId string
Size uint64
StatusFlags FrameStatusFlags
FormatFlags FrameFormatFlags
Payload []byte
}
type FrameStatusFlags struct {
TagAlterPreservation bool
FileAlterPreservation bool
ReadOnly bool
}
type FrameFormatFlags struct {
GroupingIdentity bool
Compression bool
Encryption bool
Unsynchronisation bool
DataLengthIndicator bool
}
// 4
func (f *Frame) Read(r io.Reader) error {
buf := make([]byte, 4)
err := readBytes(buf, r, 4)
if err != nil {
return err
}
f.FrameId = string(buf)
err = readBytes(buf, r, 4)
if err != nil {
return err
}
f.Size = toUint64(buf)
if f.Size == 0 {
return fmt.Errorf("Empty frame")
}
err = f.readFlags(r)
if err != nil {
return err
}
f.Payload = make([]byte, f.Size)
err = readBytes(f.Payload, r, len(f.Payload))
if err != nil {
return err
}
return nil
}
// 4.1
func (f *Frame) readFlags(r io.Reader) error {
buf := make([]byte, 2)
err := readBytes(buf, r, 2)
if err != nil {
return err
}
f.StatusFlags.read(buf[0])
f.FormatFlags.read(buf[1])
return nil
}
// 4.1.1
func (f *FrameStatusFlags) read(b byte) {
f.TagAlterPreservation = (b & (1 << 6)) != 0
f.FileAlterPreservation = (b & (1 << 5)) != 0
f.ReadOnly = (b & 1 << 4) != 0
}
// 4.1.2
func (f *FrameFormatFlags) read(b byte) {
f.GroupingIdentity = (b & (1 << 6)) != 0
f.Compression = (b & (1 << 3)) != 0
f.Encryption = (b & (1 << 2)) != 0
f.Unsynchronisation = (b & (1 << 1)) != 0
f.DataLengthIndicator = (b & (1 << 0)) != 0
}