Handle inputs/outputs and nulls correctly.

jni/src/main/java/fr/acinq/secp256k1/Secp256k1CFunctions.java

@@ -264,9 +264,10 @@ public class Secp256k1CFunctions {
      *                this function returns 0. For uniformly random 32-byte arrays the
      *                chance of being invalid is negligible (around 1 in 2^128).
      *
-     * @return output_pubkey: pointer to a public key to store the result. Will be set
-     *                        to an invalid value if this function returns 0. If you
-     *                        do not need it, this arg can be NULL.
+     * @return
+     *      [0] output_pubkey: pointer to a public key to store the result. Will be set to an invalid value if this
+     *              function returns 0. If you do not need it, this arg can be NULL.
+     *      [1] tweak_cache: pointer to a `frost_tweak_cache` struct initialized by `frost_pubkey_tweak`
      */
     public static native byte[][] secp256k1_frost_pubkey_xonly_tweak_add(long ctx, byte[] tweakCache, byte[] tweak32);
 
@@ -348,7 +349,7 @@ public class Secp256k1CFunctions {
      * @param tweak_cache pointer to frost_tweak_cache struct (can be NULL)
      *
      * @return
-     *      pointer to struct to store the partial signature
+     *      partial_sig: pointer to struct to store the partial signature
      *      TODO: [1] secnonce: pointer to the secnonce struct created in frost_nonce_gen that has been never used in a
      *          partial_sign call before
      *
@@ -377,6 +378,7 @@ public class Secp256k1CFunctions {
      *                    `secp256k1_frost_compute_pubshare`
      * @param session pointer to the session that was created with `frost_nonce_process`
      * @param tweakCache pointer to frost_tweak_cache struct (can be NULL)
+     *
      * @return 0 if the arguments are invalid or the partial signature does not verify, 1 otherwise
      */
     public static native int secp256k1_frost_partial_sig_verify(long ctx, byte[] partialSig, byte[] publicNonce, byte[] publicShare, byte[] session, byte[] tweakCache);

jni/src/main/kotlin/fr/acinq/secp256k1/NativeSecp256k1.kt

@@ -130,24 +130,23 @@ public object NativeSecp256k1 : Secp256k1 {
     }
 
     override fun frostSharesGen(
-        pok64: ByteArray,
         seed32: ByteArray,
         threshold: Int,
         totalSigners: Int,
         ids33: Array<ByteArray>
-    ): Pair<Array<ByteArray>, Array<ByteArray>> {
+    ): Triple<Array<ByteArray>, Array<ByteArray>, ByteArray> {
         val result = Secp256k1CFunctions.secp256k1_frost_shares_gen(
             Secp256k1Context.getContext(),
-            pok64,
             seed32,
             threshold,
             totalSigners,
             ids33
         )
 
-        return Pair(
+        return Triple(
             result[0],
-            result[1]
+            result[1],
+            result[2].first() // This is bad code...
         )
     }
 
@@ -217,7 +216,7 @@ public object NativeSecp256k1 : Secp256k1 {
         )
     }
 
-    override fun frostPublicKeyXonlyTweakAdd(tweakCache: ByteArray, tweak32: ByteArray): Pair<ByteArray, ByteArray> {
+    override fun frostPublicKeyXonlyTweakAdd(tweakCache: ByteArray, tweak32: ByteArray): Pair<ByteArray?, ByteArray> {
         val result = Secp256k1CFunctions.secp256k1_frost_pubkey_xonly_tweak_add(
             Secp256k1Context.getContext(),
             tweakCache,
@@ -232,9 +231,9 @@ public object NativeSecp256k1 : Secp256k1 {
 
     override fun frostNonceGen(
         sessionId32: ByteArray,
-        share: ByteArray,
-        msg32: ByteArray,
-        publicKey: ByteArray,
+        share: ByteArray?,
+        msg32: ByteArray?,
+        publicKey: ByteArray?,
         extraInput32: ByteArray?
     ): Pair<ByteArray, ByteArray> {
         val result =  Secp256k1CFunctions.secp256k1_frost_nonce_gen(
@@ -258,7 +257,7 @@ public object NativeSecp256k1 : Secp256k1 {
         publicKey: ByteArray,
         id33: ByteArray,
         ids33: Array<ByteArray>,
-        tweakCache: ByteArray,
+        tweakCache: ByteArray?,
         adaptor: ByteArray?
     ): ByteArray {
         return Secp256k1CFunctions.secp256k1_frost_nonce_process(
@@ -277,7 +276,7 @@ public object NativeSecp256k1 : Secp256k1 {
         secnonce: ByteArray,
         share: ByteArray,
         session: ByteArray,
-        tweakCache: ByteArray
+        tweakCache: ByteArray?
     ): ByteArray {
         return Secp256k1CFunctions.secp256k1_frost_partial_sign(
             Secp256k1Context.getContext(),
@@ -293,7 +292,7 @@ public object NativeSecp256k1 : Secp256k1 {
         publicNonce: ByteArray,
         publicShare: ByteArray,
         session: ByteArray,
-        tweakCache: ByteArray
+        tweakCache: ByteArray?
     ): Int {
         return Secp256k1CFunctions.secp256k1_frost_partial_sig_verify(
             Secp256k1Context.getContext(),