[kgm/ncm/kwm] refactor: improve performance for large file
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@ -15,9 +15,8 @@ impl DecipherV2 {
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impl Decipher for DecipherV2 {
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fn decrypt(&self, buffer: &mut [u8], offset: usize) {
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let key_stream = self.key.iter().cycle().skip(offset % self.key.len());
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for (datum, &k) in buffer.iter_mut().zip(key_stream) {
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*datum ^= k;
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for (datum, offset) in buffer.iter_mut().zip(offset..) {
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*datum ^= self.key[offset % self.key.len()];
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}
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}
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}
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@ -25,34 +25,27 @@ impl DecipherV3 {
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Ok(Self { slot_key, file_key })
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}
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fn offset_key(offset: usize) -> u8 {
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let offset_key = (offset as u32).to_ne_bytes();
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offset_key[0] ^ offset_key[1] ^ offset_key[2] ^ offset_key[3]
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}
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}
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impl Decipher for DecipherV3 {
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fn decrypt(&self, buffer: &mut [u8], offset: usize) {
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let slot_key_stream = self
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.slot_key
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.iter()
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.cycle()
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.skip(offset % self.slot_key.len());
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let file_key_stream = self
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.file_key
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.iter()
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.cycle()
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.skip(offset % self.file_key.len());
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for (datum, offset) in buffer.iter_mut().zip(offset..) {
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let offset_key = Self::offset_key(offset);
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let mut offset = offset as u32;
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let key_stream = slot_key_stream.zip(file_key_stream);
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for (datum, (&slot_key, &file_key)) in buffer.iter_mut().zip(key_stream) {
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let offset_key = offset.to_ne_bytes().iter().fold(0, |acc, &x| acc ^ x);
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let file_key = self.file_key[offset % self.file_key.len()];
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let slot_key = self.slot_key[offset % self.slot_key.len()];
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let mut temp = *datum;
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temp ^= file_key;
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temp ^= temp.wrapping_shl(4);
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temp ^= temp << 4;
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temp ^= slot_key;
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temp ^= offset_key;
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*datum = temp;
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offset = offset.wrapping_add(1);
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}
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}
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}
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@ -11,10 +11,8 @@ const KEY: [u8; 0x20] = [
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impl CipherV1 {
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pub fn new(resource_id: u32) -> Self {
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let mut key = KEY;
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for (k, r) in key
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.iter_mut()
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.zip(resource_id.to_string().as_bytes().iter().cycle())
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{
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let resource_id = resource_id.to_string();
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for (k, &r) in key.iter_mut().zip(resource_id.as_bytes().iter().cycle()) {
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*k ^= r;
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}
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@ -26,10 +24,9 @@ impl CipherV1 {
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T: AsMut<[u8]> + ?Sized,
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{
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let data = data.as_mut();
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let key_stream = self.key.iter().cycle().skip(offset % self.key.len());
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for (datum, key) in data.iter_mut().zip(key_stream) {
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*datum ^= *key;
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for (datum, offset) in data.iter_mut().zip(offset..) {
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*datum ^= self.key[offset % self.key.len()];
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}
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}
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}
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@ -182,9 +182,8 @@ impl NCMFile {
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where
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T: AsMut<[u8]> + ?Sized,
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{
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let key_stream = self.audio_rc4_key_stream.iter().cycle().skip(offset & 0xff);
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for (datum, &key) in data.as_mut().iter_mut().zip(key_stream) {
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*datum ^= key;
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for (datum, offset) in data.as_mut().iter_mut().zip(offset..) {
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*datum ^= self.audio_rc4_key_stream[offset % self.audio_rc4_key_stream.len()];
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}
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}
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}
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