Use u32 sizes in serialization of vote payloads

u64 is overkill, the computations will become impractical
before the number of voters or votes approaches 1^32.

chain-impl-mockchain/src/vote/payload.rs

@@ -72,12 +72,10 @@ impl Payload {
                 encrypted_vote,
                 proof,
             } => {
-                let size = encrypted_vote.len();
-                let mut bb = bb.u64(size as u64);
-                for ct in encrypted_vote.iter() {
+                let bb = bb.iter32(encrypted_vote, |bb, ct| {
                     let buffer = ct.to_bytes();
-                    bb = bb.bytes(&buffer);
-                }
+                    bb.bytes(&buffer)
+                });
                 proof.serialize_in(bb)
             }
         }
@@ -92,7 +90,7 @@ impl Payload {
         match t {
             PayloadType::Public => buf.get_u8().map(Choice::new).map(Self::public),
             PayloadType::Private => {
-                let len: usize = buf.get_u64()? as usize;
+                let len: usize = buf.get_u32()? as usize;
                 let mut cypher_texts: Vec<Ciphertext> = Vec::new();
                 for _ in 0..len {
                     let ct_buf = buf.get_slice(CIPHERTEXT_BYTES_LEN)?;

chain-vote/src/lib.rs

@@ -103,11 +103,7 @@ pub struct TallyResult {
 
 impl TallyDecryptShare {
     pub fn serialize_in(&self, bb: ByteBuilder<Self>) -> ByteBuilder<Self> {
-        let mut bb = bb.u64(self.r1s.len() as u64);
-        for e in &self.r1s {
-            bb = bb.bytes(&e.to_bytes())
-        }
-        bb
+        bb.iter32(&self.r1s, |bb, e| bb.bytes(&e.to_bytes()))
     }
 
     pub fn serialize(&self) -> ByteArray<Self> {