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94 lines
2.6 KiB
Go
94 lines
2.6 KiB
Go
package qmc
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import (
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bytes "bytes"
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"encoding/binary"
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"errors"
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"fmt"
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"io"
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"strings"
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)
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type MusicExTagV1 struct {
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SongID uint32 // Song ID
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Unknown1 uint32 // unused & unknown
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Unknown2 uint32 // unused & unknown
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MediaID string // Media ID
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MediaFileName string // real file name
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Unknown3 uint32 // unused; uninitialized memory?
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// 16 byte at the end of tag.
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// TagSize should be respected when parsing.
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TagSize uint32 // 19.57: fixed value: 0xC0
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TagVersion uint32 // 19.57: fixed value: 0x01
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TagMagic []byte // fixed value "musicex\0" (8 bytes)
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}
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func NewMusicExTag(f io.ReadSeeker) (*MusicExTagV1, error) {
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_, err := f.Seek(-16, io.SeekEnd)
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if err != nil {
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return nil, fmt.Errorf("musicex seek error: %w", err)
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}
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buffer := make([]byte, 16)
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bytesRead, err := f.Read(buffer)
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if err != nil {
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return nil, fmt.Errorf("get musicex error: %w", err)
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}
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if bytesRead != 16 {
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return nil, fmt.Errorf("MusicExV1: read %d bytes (expected %d)", bytesRead, 16)
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}
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tag := &MusicExTagV1{
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TagSize: binary.LittleEndian.Uint32(buffer[0x00:0x04]),
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TagVersion: binary.LittleEndian.Uint32(buffer[0x04:0x08]),
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TagMagic: buffer[0x04:0x0C],
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}
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if !bytes.Equal(tag.TagMagic, []byte("musicex\x00")) {
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return nil, errors.New("MusicEx magic mismatch")
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}
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if tag.TagVersion != 1 {
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return nil, errors.New(fmt.Sprintf("unsupported musicex tag version. expecting 1, got %d", tag.TagVersion))
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}
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if tag.TagSize < 0xC0 {
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return nil, errors.New(fmt.Sprintf("unsupported musicex tag size. expecting at least 0xC0, got 0x%02x", tag.TagSize))
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}
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buffer = make([]byte, tag.TagSize)
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bytesRead, err = f.Read(buffer)
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if err != nil {
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return nil, err
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}
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if uint32(bytesRead) != tag.TagSize {
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return nil, fmt.Errorf("MusicExV1: read %d bytes (expected %d)", bytesRead, tag.TagSize)
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}
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tag.SongID = binary.LittleEndian.Uint32(buffer[0x00:0x04])
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tag.Unknown1 = binary.LittleEndian.Uint32(buffer[0x04:0x08])
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tag.Unknown2 = binary.LittleEndian.Uint32(buffer[0x08:0x0C])
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tag.MediaID = readUnicodeTagName(buffer[0x0C:], 30*2)
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tag.MediaFileName = readUnicodeTagName(buffer[0x48:], 50*2)
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tag.Unknown3 = binary.LittleEndian.Uint32(buffer[0xAC:0xB0])
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return tag, nil
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}
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// readUnicodeTagName reads a buffer to maxLen.
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// reconstruct text by skipping alternate char (ascii chars encoded in UTF-16-LE),
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// until finding a zero or reaching maxLen.
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func readUnicodeTagName(buffer []byte, maxLen int) string {
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builder := strings.Builder{}
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for i := 0; i < maxLen; i += 2 {
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chr := buffer[i]
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if chr != 0 {
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builder.WriteByte(chr)
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} else {
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break
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}
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}
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return builder.String()
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}
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