Make AES crypto return the number of bytes written

src/LibHac/Boot/Package1.cs

@@ -300,7 +300,7 @@ public class Package1
         return Result.Success;
     }
 
-    private delegate void Decryptor(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key,
+    private delegate int Decryptor(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key,
         ReadOnlySpan<byte> iv, bool preferDotNetCrypto = false);
 
     private bool TryFindEristaKeyRevision()

src/LibHac/Crypto/Aes.cs

@@ -102,7 +102,7 @@ public static class Aes
         return new AesXtsEncryptor(key1, key2, iv);
     }
 
-    public static void EncryptEcb128(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key,
+    public static int EncryptEcb128(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key,
         bool preferDotNetCrypto = false)
     {
         if (IsAesNiSupported() && !preferDotNetCrypto)
@@ -110,16 +110,15 @@ public static class Aes
             Unsafe.SkipInit(out AesEcbModeNi cipherNi);
 
             cipherNi.Initialize(key, false);
-            cipherNi.Encrypt(input, output);
-            return;
+            return cipherNi.Encrypt(input, output);
         }
 
         ICipher cipher = CreateEcbEncryptor(key, preferDotNetCrypto);
 
-        cipher.Transform(input, output);
+        return cipher.Transform(input, output);
     }
 
-    public static void DecryptEcb128(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key,
+    public static int DecryptEcb128(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key,
         bool preferDotNetCrypto = false)
     {
         if (IsAesNiSupported() && !preferDotNetCrypto)
@@ -127,16 +126,15 @@ public static class Aes
             Unsafe.SkipInit(out AesEcbModeNi cipherNi);
 
             cipherNi.Initialize(key, true);
-            cipherNi.Decrypt(input, output);
-            return;
+            return cipherNi.Decrypt(input, output);
         }
 
         ICipher cipher = CreateEcbDecryptor(key, preferDotNetCrypto);
 
-        cipher.Transform(input, output);
+        return cipher.Transform(input, output);
     }
 
-    public static void EncryptCbc128(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key,
+    public static int EncryptCbc128(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key,
         ReadOnlySpan<byte> iv, bool preferDotNetCrypto = false)
     {
         if (IsAesNiSupported() && !preferDotNetCrypto)
@@ -144,16 +142,15 @@ public static class Aes
             Unsafe.SkipInit(out AesCbcModeNi cipherNi);
 
             cipherNi.Initialize(key, iv, false);
-            cipherNi.Encrypt(input, output);
-            return;
+            return cipherNi.Encrypt(input, output);
         }
 
         ICipher cipher = CreateCbcEncryptor(key, iv, preferDotNetCrypto);
 
-        cipher.Transform(input, output);
+        return cipher.Transform(input, output);
     }
 
-    public static void DecryptCbc128(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key,
+    public static int DecryptCbc128(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key,
         ReadOnlySpan<byte> iv, bool preferDotNetCrypto = false)
     {
         if (IsAesNiSupported() && !preferDotNetCrypto)
@@ -161,16 +158,15 @@ public static class Aes
             Unsafe.SkipInit(out AesCbcModeNi cipherNi);
 
             cipherNi.Initialize(key, iv, true);
-            cipherNi.Decrypt(input, output);
-            return;
+            return cipherNi.Decrypt(input, output);
         }
 
         ICipher cipher = CreateCbcDecryptor(key, iv, preferDotNetCrypto);
 
-        cipher.Transform(input, output);
+        return cipher.Transform(input, output);
     }
 
-    public static void EncryptCtr128(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key,
+    public static int EncryptCtr128(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key,
         ReadOnlySpan<byte> iv, bool preferDotNetCrypto = false)
     {
         if (IsAesNiSupported() && !preferDotNetCrypto)
@@ -178,16 +174,15 @@ public static class Aes
             Unsafe.SkipInit(out AesCtrModeNi cipherNi);
 
             cipherNi.Initialize(key, iv);
-            cipherNi.Transform(input, output);
-            return;
+            return cipherNi.Transform(input, output);
         }
 
         ICipher cipher = CreateCtrEncryptor(key, iv, preferDotNetCrypto);
 
-        cipher.Transform(input, output);
+        return cipher.Transform(input, output);
     }
 
-    public static void DecryptCtr128(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key,
+    public static int DecryptCtr128(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key,
         ReadOnlySpan<byte> iv, bool preferDotNetCrypto = false)
     {
         if (IsAesNiSupported() && !preferDotNetCrypto)
@@ -195,16 +190,15 @@ public static class Aes
             Unsafe.SkipInit(out AesCtrModeNi cipherNi);
 
             cipherNi.Initialize(key, iv);
-            cipherNi.Transform(input, output);
-            return;
+            return cipherNi.Transform(input, output);
         }
 
         ICipher cipher = CreateCtrDecryptor(key, iv, preferDotNetCrypto);
 
-        cipher.Transform(input, output);
+        return cipher.Transform(input, output);
     }
 
-    public static void EncryptXts128(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key1,
+    public static int EncryptXts128(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key1,
         ReadOnlySpan<byte> key2, ReadOnlySpan<byte> iv, bool preferDotNetCrypto = false)
     {
         if (IsAesNiSupported() && !preferDotNetCrypto)
@@ -212,16 +206,15 @@ public static class Aes
             Unsafe.SkipInit(out AesXtsModeNi cipherNi);
 
             cipherNi.Initialize(key1, key2, iv, false);
-            cipherNi.Encrypt(input, output);
-            return;
+            return cipherNi.Encrypt(input, output);
         }
 
         ICipher cipher = CreateXtsEncryptor(key1, key2, iv, preferDotNetCrypto);
 
-        cipher.Transform(input, output);
+        return cipher.Transform(input, output);
     }
 
-    public static void DecryptXts128(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key1,
+    public static int DecryptXts128(ReadOnlySpan<byte> input, Span<byte> output, ReadOnlySpan<byte> key1,
         ReadOnlySpan<byte> key2, ReadOnlySpan<byte> iv, bool preferDotNetCrypto = false)
     {
         if (IsAesNiSupported() && !preferDotNetCrypto)
@@ -229,13 +222,12 @@ public static class Aes
             Unsafe.SkipInit(out AesXtsModeNi cipherNi);
 
             cipherNi.Initialize(key1, key2, iv, true);
-            cipherNi.Decrypt(input, output);
-            return;
+            return cipherNi.Decrypt(input, output);
         }
 
         ICipher cipher = CreateXtsDecryptor(key1, key2, iv, preferDotNetCrypto);
 
-        cipher.Transform(input, output);
+        return cipher.Transform(input, output);
     }
 
     /// <summary>

src/LibHac/Crypto/AesCbcCipher.cs

@@ -13,9 +13,9 @@ public class AesCbcEncryptor : ICipher
         _baseCipher.Initialize(key, iv, false);
     }
 
-    public void Transform(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Transform(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _baseCipher.Encrypt(input, output);
+        return _baseCipher.Encrypt(input, output);
     }
 }
 
@@ -29,8 +29,8 @@ public class AesCbcDecryptor : ICipher
         _baseCipher.Initialize(key, iv, true);
     }
 
-    public void Transform(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Transform(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _baseCipher.Decrypt(input, output);
+        return _baseCipher.Decrypt(input, output);
     }
 }

src/LibHac/Crypto/AesCbcCipherNi.cs

@@ -18,9 +18,9 @@ public class AesCbcEncryptorNi : ICipherWithIv
         _baseCipher.Initialize(key, iv, false);
     }
 
-    public void Transform(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Transform(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _baseCipher.Encrypt(input, output);
+        return _baseCipher.Encrypt(input, output);
     }
 }
 
@@ -36,8 +36,8 @@ public class AesCbcDecryptorNi : ICipherWithIv
         _baseCipher.Initialize(key, iv, true);
     }
 
-    public void Transform(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Transform(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _baseCipher.Decrypt(input, output);
+        return _baseCipher.Decrypt(input, output);
     }
 }

src/LibHac/Crypto/AesCtrCipher.cs

@@ -16,8 +16,8 @@ public class AesCtrCipher : ICipherWithIv
         _baseCipher.Initialize(key, iv);
     }
 
-    public void Transform(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Transform(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _baseCipher.Transform(input, output);
+        return _baseCipher.Transform(input, output);
     }
 }

src/LibHac/Crypto/AesCtrCipherNi.cs

@@ -18,8 +18,8 @@ public class AesCtrCipherNi : ICipherWithIv
         _baseCipher.Initialize(key, iv);
     }
 
-    public void Transform(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Transform(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _baseCipher.Transform(input, output);
+        return _baseCipher.Transform(input, output);
     }
 }

src/LibHac/Crypto/AesEcbCipher.cs

@@ -13,9 +13,9 @@ public class AesEcbEncryptor : ICipher
         _baseCipher.Initialize(key, false);
     }
 
-    public void Transform(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Transform(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _baseCipher.Encrypt(input, output);
+        return _baseCipher.Encrypt(input, output);
     }
 }
 
@@ -29,8 +29,8 @@ public class AesEcbDecryptor : ICipher
         _baseCipher.Initialize(key, true);
     }
 
-    public void Transform(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Transform(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _baseCipher.Decrypt(input, output);
+        return _baseCipher.Decrypt(input, output);
     }
 }

src/LibHac/Crypto/AesEcbCipherNi.cs

@@ -13,9 +13,9 @@ public class AesEcbEncryptorNi : ICipher
         _baseCipher.Initialize(key, false);
     }
 
-    public void Transform(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Transform(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _baseCipher.Encrypt(input, output);
+        return _baseCipher.Encrypt(input, output);
     }
 }
 
@@ -29,8 +29,8 @@ public class AesEcbDecryptorNi : ICipher
         _baseCipher.Initialize(key, true);
     }
 
-    public void Transform(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Transform(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _baseCipher.Decrypt(input, output);
+        return _baseCipher.Decrypt(input, output);
     }
 }

src/LibHac/Crypto/AesXtsCipher.cs

@@ -16,9 +16,9 @@ public class AesXtsEncryptor : ICipherWithIv
         _baseCipher.Initialize(key1, key2, iv, false);
     }
 
-    public void Transform(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Transform(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _baseCipher.Encrypt(input, output);
+        return _baseCipher.Encrypt(input, output);
     }
 }
 
@@ -34,8 +34,8 @@ public class AesXtsDecryptor : ICipherWithIv
         _baseCipher.Initialize(key1, key2, iv, true);
     }
 
-    public void Transform(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Transform(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _baseCipher.Decrypt(input, output);
+        return _baseCipher.Decrypt(input, output);
     }
 }

src/LibHac/Crypto/AesXtsCipherNi.cs

@@ -18,9 +18,9 @@ public class AesXtsEncryptorNi : ICipherWithIv
         _baseCipher.Initialize(key1, key2, iv, false);
     }
 
-    public void Transform(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Transform(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _baseCipher.Encrypt(input, output);
+        return _baseCipher.Encrypt(input, output);
     }
 }
 
@@ -36,8 +36,8 @@ public class AesXtsDecryptorNi : ICipherWithIv
         _baseCipher.Initialize(key1, key2, iv, true);
     }
 
-    public void Transform(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Transform(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _baseCipher.Decrypt(input, output);
+        return _baseCipher.Decrypt(input, output);
     }
 }

src/LibHac/Crypto/ICipher.cs

@@ -5,7 +5,7 @@ namespace LibHac.Crypto;
 
 public interface ICipher
 {
-    void Transform(ReadOnlySpan<byte> input, Span<byte> output);
+    int Transform(ReadOnlySpan<byte> input, Span<byte> output);
 }
 
 public interface ICipherWithIv : ICipher

src/LibHac/Crypto/Impl/AesCbcMode.cs

@@ -13,13 +13,13 @@ public struct AesCbcMode
         _aesCore.Initialize(key, iv, CipherMode.CBC, isDecrypting);
     }
 
-    public void Encrypt(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Encrypt(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _aesCore.Encrypt(input, output);
+        return _aesCore.Encrypt(input, output);
     }
 
-    public void Decrypt(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Decrypt(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _aesCore.Decrypt(input, output);
+        return _aesCore.Decrypt(input, output);
     }
 }

src/LibHac/Crypto/Impl/AesCbcModeNi.cs

@@ -22,7 +22,7 @@ public struct AesCbcModeNi
         Iv = Unsafe.ReadUnaligned<Vector128<byte>>(ref MemoryMarshal.GetReference(iv));
     }
 
-    public void Encrypt(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Encrypt(ReadOnlySpan<byte> input, Span<byte> output)
     {
         int blockCount = Math.Min(input.Length, output.Length) >> 4;
 
@@ -42,9 +42,11 @@ public struct AesCbcModeNi
         }
 
         Iv = iv;
+
+        return Math.Min(input.Length, output.Length) & ~0xF;
     }
 
-    public void Decrypt(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Decrypt(ReadOnlySpan<byte> input, Span<byte> output)
     {
         int remainingBlocks = Math.Min(input.Length, output.Length) >> 4;
 
@@ -104,5 +106,7 @@ public struct AesCbcModeNi
         }
 
         Iv = iv;
+
+        return Math.Min(input.Length, output.Length) & ~0xF;
     }
 }

src/LibHac/Crypto/Impl/AesCore.cs

@@ -31,43 +31,45 @@ public struct AesCore
         _isDecrypting = isDecrypting;
     }
 
-    public void Encrypt(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Encrypt(ReadOnlySpan<byte> input, Span<byte> output)
     {
         Debug.Assert(!_isDecrypting);
-        Transform(input, output);
+        return Transform(input, output);
     }
 
-    public void Decrypt(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Decrypt(ReadOnlySpan<byte> input, Span<byte> output)
     {
         Debug.Assert(_isDecrypting);
-        Transform(input, output);
+        return Transform(input, output);
     }
 
-    public void Encrypt(byte[] input, byte[] output, int length)
+    public int Encrypt(byte[] input, byte[] output, int length)
     {
         Debug.Assert(!_isDecrypting);
-        Transform(input, output, length);
+        return Transform(input, output, length);
     }
 
-    public void Decrypt(byte[] input, byte[] output, int length)
+    public int Decrypt(byte[] input, byte[] output, int length)
     {
         Debug.Assert(_isDecrypting);
-        Transform(input, output, length);
+        return Transform(input, output, length);
     }
 
-    private void Transform(ReadOnlySpan<byte> input, Span<byte> output)
+    private int Transform(ReadOnlySpan<byte> input, Span<byte> output)
     {
         using var rented = new RentedArray<byte>(input.Length);
 
         input.CopyTo(rented.Array);
 
-        Transform(rented.Array, rented.Array, input.Length);
+        int bytesWritten = Transform(rented.Array, rented.Array, input.Length);
 
         rented.Array.CopyTo(output);
+
+        return bytesWritten;
     }
 
-    private void Transform(byte[] input, byte[] output, int length)
+    private int Transform(byte[] input, byte[] output, int length)
     {
-        _transform.TransformBlock(input, 0, length, output, 0);
+        return _transform.TransformBlock(input, 0, length, output, 0);
     }
 }

src/LibHac/Crypto/Impl/AesCoreNi.cs

@@ -98,9 +98,10 @@ public struct AesCoreNi
         return AesNi.DecryptLast(b, keys[0]);
     }
 
-    public readonly void EncryptInterleaved8(ReadOnlySpan<byte> input, Span<byte> output)
+    public readonly int EncryptInterleaved8(ReadOnlySpan<byte> input, Span<byte> output)
     {
         int remainingBlocks = Math.Min(input.Length, output.Length) >> 4;
+        int length = remainingBlocks << 4;
 
         ref Vector128<byte> inBlock = ref Unsafe.As<byte, Vector128<byte>>(ref MemoryMarshal.GetReference(input));
         ref Vector128<byte> outBlock = ref Unsafe.As<byte, Vector128<byte>>(ref MemoryMarshal.GetReference(output));
@@ -138,11 +139,14 @@ public struct AesCoreNi
             outBlock = ref Unsafe.Add(ref outBlock, 1);
             remainingBlocks -= 1;
         }
+
+        return length;
     }
 
-    public readonly void DecryptInterleaved8(ReadOnlySpan<byte> input, Span<byte> output)
+    public readonly int DecryptInterleaved8(ReadOnlySpan<byte> input, Span<byte> output)
     {
         int remainingBlocks = Math.Min(input.Length, output.Length) >> 4;
+        int length = remainingBlocks << 4;
 
         ref Vector128<byte> inBlock = ref Unsafe.As<byte, Vector128<byte>>(ref MemoryMarshal.GetReference(input));
         ref Vector128<byte> outBlock = ref Unsafe.As<byte, Vector128<byte>>(ref MemoryMarshal.GetReference(output));
@@ -180,6 +184,8 @@ public struct AesCoreNi
             outBlock = ref Unsafe.Add(ref outBlock, 1);
             remainingBlocks -= 1;
         }
+
+        return length;
     }
 
     // When inlining this function, RyuJIT will almost make the

src/LibHac/Crypto/Impl/AesCtrMode.cs

@@ -24,7 +24,7 @@ public struct AesCtrMode
         Iv = Unsafe.ReadUnaligned<Buffer16>(ref MemoryMarshal.GetReference(iv));
     }
 
-    public void Transform(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Transform(ReadOnlySpan<byte> input, Span<byte> output)
     {
         int blockCount = BitUtil.DivideUp(input.Length, Aes.BlockSize);
         int length = blockCount * Aes.BlockSize;
@@ -34,6 +34,8 @@ public struct AesCtrMode
 
         _aesCore.Encrypt(counterBuffer.Array, counterBuffer.Array, length);
         Utilities.XorArrays(output, input, counterBuffer.Span);
+
+        return Math.Min(input.Length, output.Length);
     }
 
     private static void FillDecryptedCounter(Span<byte> counter, Span<byte> buffer)

src/LibHac/Crypto/Impl/AesCtrModeNi.cs

@@ -23,9 +23,10 @@ public struct AesCtrModeNi
         Iv = Unsafe.ReadUnaligned<Vector128<byte>>(ref MemoryMarshal.GetReference(iv));
     }
 
-    public void Transform(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Transform(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        int remaining = Math.Min(input.Length, output.Length);
+        int length = Math.Min(input.Length, output.Length);
+        int remaining = length;
         int blockCount = remaining >> 4;
 
         ref Vector128<byte> inBlock = ref Unsafe.As<byte, Vector128<byte>>(ref MemoryMarshal.GetReference(input));
@@ -103,6 +104,8 @@ public struct AesCtrModeNi
         {
             EncryptCtrPartialBlock(input.Slice(blockCount * 0x10), output.Slice(blockCount * 0x10));
         }
+
+        return length;
     }
 
     private void EncryptCtrPartialBlock(ReadOnlySpan<byte> input, Span<byte> output)

src/LibHac/Crypto/Impl/AesEcbMode.cs

@@ -13,13 +13,13 @@ public struct AesEcbMode
         _aesCore.Initialize(key, ReadOnlySpan<byte>.Empty, CipherMode.ECB, isDecrypting);
     }
 
-    public void Encrypt(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Encrypt(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _aesCore.Encrypt(input, output);
+        return _aesCore.Encrypt(input, output);
     }
 
-    public void Decrypt(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Decrypt(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _aesCore.Decrypt(input, output);
+        return _aesCore.Decrypt(input, output);
     }
 }

src/LibHac/Crypto/Impl/AesEcbModeNi.cs

@@ -11,13 +11,13 @@ public struct AesEcbModeNi
         _aesCore.Initialize(key, isDecrypting);
     }
 
-    public void Encrypt(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Encrypt(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _aesCore.EncryptInterleaved8(input, output);
+        return _aesCore.EncryptInterleaved8(input, output);
     }
 
-    public void Decrypt(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Decrypt(ReadOnlySpan<byte> input, Span<byte> output)
     {
-        _aesCore.DecryptInterleaved8(input, output);
+        return _aesCore.DecryptInterleaved8(input, output);
     }
 }

src/LibHac/Crypto/Impl/AesXtsMode.cs

@@ -26,7 +26,7 @@ public struct AesXtsMode
         Iv = Unsafe.ReadUnaligned<Buffer16>(ref MemoryMarshal.GetReference(iv));
     }
 
-    public void Encrypt(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Encrypt(ReadOnlySpan<byte> input, Span<byte> output)
     {
         int length = Math.Min(input.Length, output.Length);
         int blockCount = length >> 4;
@@ -74,9 +74,11 @@ public struct AesXtsMode
             _dataAesCore.Encrypt(tmp, tmp);
             XorBuffer(ref prevOutBlock, ref tmp, ref tweak);
         }
+
+        return length;
     }
 
-    public void Decrypt(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Decrypt(ReadOnlySpan<byte> input, Span<byte> output)
     {
         int length = Math.Min(input.Length, output.Length);
         int blockCount = length >> 4;
@@ -139,6 +141,8 @@ public struct AesXtsMode
             _dataAesCore.Decrypt(tmp, tmp);
             XorBuffer(ref outBlock, ref tmp, ref tweak);
         }
+
+        return length;
     }
 
     private static Buffer16 FillTweakBuffer(Buffer16 initialTweak, Span<Buffer16> tweakBuffer)

src/LibHac/Crypto/Impl/AesXtsModeNi.cs

@@ -25,7 +25,7 @@ public struct AesXtsModeNi
         Iv = Unsafe.ReadUnaligned<Vector128<byte>>(ref MemoryMarshal.GetReference(iv));
     }
 
-    public void Encrypt(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Encrypt(ReadOnlySpan<byte> input, Span<byte> output)
     {
         int length = Math.Min(input.Length, output.Length);
         int remainingBlocks = length >> 4;
@@ -101,9 +101,11 @@ public struct AesXtsModeNi
         {
             EncryptPartialFinalBlock(ref inBlock, ref outBlock, tweak, leftover);
         }
+
+        return length;
     }
 
-    public void Decrypt(ReadOnlySpan<byte> input, Span<byte> output)
+    public int Decrypt(ReadOnlySpan<byte> input, Span<byte> output)
     {
         int length = Math.Min(input.Length, output.Length);
         int remainingBlocks = length >> 4;
@@ -181,6 +183,8 @@ public struct AesXtsModeNi
         {
             DecryptPartialFinalBlock(ref inBlock, ref outBlock, tweak, mask, leftover);
         }
+
+        return length;
     }
 
     // ReSharper disable once RedundantAssignment