65 lines
1.6 KiB
Go
65 lines
1.6 KiB
Go
package kgm
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import (
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"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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)
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var (
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vprHeader = []byte{
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0x05, 0x28, 0xBC, 0x96, 0xE9, 0xE4, 0x5A, 0x43,
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0x91, 0xAA, 0xBD, 0xD0, 0x7A, 0xF5, 0x36, 0x31,
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}
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kgmHeader = []byte{
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0x7C, 0xD5, 0x32, 0xEB, 0x86, 0x02, 0x7F, 0x4B,
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0xA8, 0xAF, 0xA6, 0x8E, 0x0F, 0xFF, 0x99, 0x14,
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}
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ErrKgmMagicHeader = errors.New("kgm magic header not matched")
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)
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// Header is the header of a KGM file.
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type Header struct {
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MagicHeader []byte // 0x00-0x0f: magic header
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AudioOffset uint32 // 0x10-0x13: offset of audio data
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CryptoVersion uint32 // 0x14-0x17: crypto version
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CryptoSlot uint32 // 0x18-0x1b: crypto key slot
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CryptoTestData []byte // 0x1c-0x2b: crypto test data
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CryptoKey []byte // 0x2c-0x3b: crypto key
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}
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func (h *Header) FromFile(rd io.ReadSeeker) error {
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if _, err := rd.Seek(0, io.SeekStart); err != nil {
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return fmt.Errorf("kgm seek start: %w", err)
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}
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buf := make([]byte, 0x3c)
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if _, err := io.ReadFull(rd, buf); err != nil {
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return fmt.Errorf("kgm read header: %w", err)
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}
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return h.FromBytes(buf)
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}
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func (h *Header) FromBytes(buf []byte) error {
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if len(buf) < 0x3c {
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return errors.New("invalid kgm header length")
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}
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h.MagicHeader = buf[:0x10]
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if !bytes.Equal(kgmHeader, h.MagicHeader) && !bytes.Equal(vprHeader, h.MagicHeader) {
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return ErrKgmMagicHeader
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}
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h.AudioOffset = binary.LittleEndian.Uint32(buf[0x10:0x14])
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h.CryptoVersion = binary.LittleEndian.Uint32(buf[0x14:0x18])
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h.CryptoSlot = binary.LittleEndian.Uint32(buf[0x18:0x1c])
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h.CryptoTestData = buf[0x1c:0x2c]
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h.CryptoKey = buf[0x2c:0x3c]
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return nil
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}
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