Remove "as", except for floats as needed

Also updates Bulletproofs from C to not be length prefixed, yet rather 
have Rust calculate their length.

Corrects an error in key_gen where self was blamed, instead of the 
faulty participant.

coins/monero/c/wrapper.cpp

@@ -62,10 +62,8 @@ extern "C" {
     std::stringstream ss;
     binary_archive<true> ba(ss);
     ::serialization::serialize(ba, bp);
-    uint8_t* res = (uint8_t*) calloc(2 + ss.str().size(), 1); // malloc would also work
-    memcpy(res + 2, ss.str().data(), ss.str().size());
-    res[0] = ss.str().size() >> 8;
-    res[1] = ss.str().size() & 255;
+    uint8_t* res = (uint8_t*) calloc(ss.str().size(), 1); // malloc would also work
+    memcpy(res, ss.str().data(), ss.str().size());
     return res;
   }
 

coins/monero/src/frost.rs

@@ -44,7 +44,7 @@ impl Curve for Ed25519 {
   }
 
   fn id_len() -> u8 {
-    Self::id().len() as u8
+    u8::try_from(Self::id().len()).unwrap()
   }
 
   fn generator() -> Self::G {

coins/monero/src/ringct/bulletproofs.rs

@@ -41,11 +41,18 @@ impl Bulletproofs {
         fn c_generate_bp(seed: *const u8, len: u8, amounts: *const u64, masks: *const [u8; 32]) -> *const u8;
       }
 
-      let ptr = c_generate_bp(seed.as_ptr(), outputs.len() as u8, amounts.as_ptr(), masks.as_ptr());
-      let len = ((ptr.read() as usize) << 8) + (ptr.add(1).read() as usize);
+      let ptr = c_generate_bp(
+        seed.as_ptr(),
+        u8::try_from(outputs.len()).unwrap(),
+        amounts.as_ptr(),
+        masks.as_ptr()
+      );
+
+      let mut len = 6 * 32;
+      len += (2 * (1 + (usize::from(ptr.add(len).read()) * 32))) + (3 * 32);
       res = Bulletproofs::deserialize(
         // Wrap in a cursor to provide a mutable Reader
-        &mut std::io::Cursor::new(std::slice::from_raw_parts(ptr.add(2), len))
+        &mut std::io::Cursor::new(std::slice::from_raw_parts(ptr, len))
       ).expect("Couldn't deserialize Bulletproofs from Monero");
       free(ptr);
     };
@@ -64,7 +71,7 @@ impl Bulletproofs {
     let mut serialized = Vec::with_capacity((9 + (2 * self.L.len())) * 32);
     self.serialize(&mut serialized).unwrap();
     let commitments: Vec<[u8; 32]> = commitments.iter().map(
-      |commitment| (commitment * Scalar::from(8 as u8).invert()).compress().to_bytes()
+      |commitment| (commitment * Scalar::from(8u8).invert()).compress().to_bytes()
     ).collect();
 
     unsafe {
@@ -79,7 +86,13 @@ impl Bulletproofs {
         ) -> bool;
       }
 
-      c_verify_bp(seed.as_ptr(), serialized.len(), serialized.as_ptr(), commitments.len() as u8, commitments.as_ptr())
+      c_verify_bp(
+        seed.as_ptr(),
+        serialized.len(),
+        serialized.as_ptr(),
+        u8::try_from(commitments.len()).unwrap(),
+        commitments.as_ptr()
+      )
     }
   }
 

coins/monero/src/ringct/clsag/mod.rs

@@ -24,7 +24,7 @@ mod multisig;
 pub use multisig::{ClsagDetails, ClsagMultisig};
 
 lazy_static! {
-  static ref INV_EIGHT: Scalar = Scalar::from(8 as u8).invert();
+  static ref INV_EIGHT: Scalar = Scalar::from(8u8).invert();
 }
 
 #[derive(Clone, Error, Debug)]
@@ -60,8 +60,9 @@ impl ClsagInput {
     if n > u8::MAX.into() {
       Err(ClsagError::InternalError("max ring size in this library is u8 max".to_string()))?;
     }
-    if decoys.i >= (n as u8) {
-      Err(ClsagError::InvalidRingMember(decoys.i, n as u8))?;
+    let n = u8::try_from(n).unwrap();
+    if decoys.i >= n {
+      Err(ClsagError::InvalidRingMember(decoys.i, n))?;
     }
 
     // Validate the commitment matches
@@ -123,13 +124,13 @@ fn core(
   // mu_P with agg_0
   let mu_P = hash_to_scalar(&to_hash);
   // mu_C with agg_1
-  to_hash[AGG_0.len() - 1] = '1' as u8;
+  to_hash[AGG_0.len() - 1] = b'1';
   let mu_C = hash_to_scalar(&to_hash);
 
   // Truncate it for the round transcript, altering the DST as needed
   to_hash.truncate(((2 * n) + 1) * 32);
   for i in 0 .. ROUND.len() {
-    to_hash[PREFIX.len() + i] = ROUND[i] as u8;
+    to_hash[PREFIX.len() + i] = ROUND[i];
   }
   // Unfortunately, it's I D pseudo_out instead of pseudo_out I D, meaning this needs to be
   // truncated just to add it back
@@ -254,7 +255,7 @@ impl Clsag {
         &nonce * &ED25519_BASEPOINT_TABLE,
         nonce * hash_to_point(&inputs[i].2.decoys.ring[usize::from(inputs[i].2.decoys.i)][0])
       );
-      clsag.s[inputs[i].2.decoys.i as usize] = nonce - ((p * inputs[i].0) + c);
+      clsag.s[usize::from(inputs[i].2.decoys.i)] = nonce - ((p * inputs[i].0) + c);
 
       res.push((clsag, pseudo_out));
     }
@@ -341,7 +342,8 @@ impl Clsag {
 
       if c_verify_clsag(
         serialized.len(), serialized.as_ptr(),
-        ring.len() as u8, ring_bytes.as_ptr(),
+        u8::try_from(ring.len()).map_err(|_| ClsagError::InternalError("too large ring".to_string()))?,
+        ring_bytes.as_ptr(),
         I_bytes.as_ptr(), pseudo_out_bytes.as_ptr(), msg.as_ptr()
       ) {
         Ok(())

coins/monero/src/serialize.rs

@@ -7,7 +7,7 @@ pub const VARINT_CONTINUATION_MASK: u8 = 0b1000_0000;
 pub fn write_varint<W: io::Write>(varint: &u64, w: &mut W) -> io::Result<()> {
   let mut varint = *varint;
   while {
-    let mut b = (varint & u64::from(!VARINT_CONTINUATION_MASK)) as u8;
+    let mut b = u8::try_from(varint & u64::from(!VARINT_CONTINUATION_MASK)).unwrap();
     varint >>= 7;
     if varint != 0 {
       b |= VARINT_CONTINUATION_MASK;

coins/monero/src/wallet/send/mod.rs

@@ -237,7 +237,7 @@ impl SignableTransaction {
       PublicKey { point: self.outputs[0].R.compress() }
     ).consensus_encode(&mut extra).unwrap();
     SubField::AdditionalPublickKey(
-      self.outputs[1 .. self.outputs.len()].iter().map(|output| PublicKey { point: output.R.compress() }).collect()
+      self.outputs[1 ..].iter().map(|output| PublicKey { point: output.R.compress() }).collect()
     ).consensus_encode(&mut extra).unwrap();
 
     // Format it for monero-rs