1
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forked from um/cli
cli/algo/ximalaya/x2m_crypto.go

35 lines
808 B
Go

package ximalaya
import (
_ "embed"
"encoding/binary"
)
const x2mHeaderSize = 1024
var x2mKey = [...]byte{'x', 'm', 'l', 'y'}
var x2mScrambleTable = [x2mHeaderSize]uint16{}
//go:embed x2m_scramble_table.bin
var x2mScrambleTableBytes []byte
func init() {
if len(x2mScrambleTableBytes) != 2*x2mHeaderSize {
panic("invalid x2m scramble table")
}
for i := range x2mScrambleTable {
x2mScrambleTable[i] = binary.LittleEndian.Uint16(x2mScrambleTableBytes[i*2:])
}
}
// decryptX2MHeader decrypts the header of ximalaya .x2m file.
// make sure input src is 1024(x2mHeaderSize) bytes long.
func decryptX2MHeader(src []byte) []byte {
dst := make([]byte, len(src))
for dstIdx := range src {
srcIdx := x2mScrambleTable[dstIdx]
dst[dstIdx] = src[srcIdx] ^ x2mKey[dstIdx%len(x2mKey)]
}
return dst
}