Merge pull request #313 from Chia-Network/optimize-parse-vec

optimize Vec<T>::parse(), for Streamable

chia-bls/src/secret_key.rs

@@ -76,13 +76,13 @@ fn to_lamport_pk(ikm: [u8; 32], idx: u32) -> [u8; 32] {
     let mut hasher = Sha256::new();
     hasher.update(lamport0);
     hasher.update(lamport1);
-    hasher.finalize().try_into().unwrap()
+    hasher.finalize().into()
 }
 
 fn sha256(bytes: &[u8]) -> [u8; 32] {
     let mut hasher = Sha256::new();
     hasher.update(bytes);
-    hasher.finalize().try_into().unwrap()
+    hasher.finalize().into()
 }
 
 pub fn is_all_zero(buf: &[u8]) -> bool {

chia-protocol/src/bytes.rs

@@ -366,7 +366,7 @@ impl<const N: usize> FromJsonDict for BytesImpl<N> {
                 N
             )));
         }
-        Ok((&buf).try_into()?)
+        Ok((&buf).into())
     }
 }
 

chia-tools/src/bin/fast-forward-spend.rs

@@ -36,8 +36,7 @@ fn main() {
     let new_parents_parent: Bytes32 = hex::decode(args.new_parents_parent)
         .expect("invalid hex")
         .as_slice()
-        .try_into()
-        .expect("parent_id");
+        .into();
 
     let mut a = Allocator::new_limited(500000000, 62500000, 62500000);
     let puzzle = spend.puzzle_reveal.to_clvm(&mut a).expect("to_clvm");

chia-traits/src/streamable.rs

@@ -115,9 +115,12 @@ impl<T: Streamable> Streamable for Vec<T> {
     fn parse(input: &mut Cursor<&[u8]>) -> Result<Self> {
         let len = u32::parse(input)?;
 
-        // TODO: pre-allocate capacity, but we'd need safe-guards for overflow
-        // attacks
-        let mut ret = Vec::<T>::new();
+        let mut ret = if std::mem::size_of::<T>() == 0 {
+            Vec::<T>::new()
+        } else {
+            let limit = 2 * 1024 * 1024 / std::mem::size_of::<T>();
+            Vec::<T>::with_capacity(std::cmp::min(limit, len as usize))
+        };
         for _ in 0..len {
             ret.push(T::parse(input)?);
         }
@@ -172,6 +175,16 @@ impl Streamable for bool {
     }
 }
 
+impl Streamable for () {
+    fn update_digest(&self, _digest: &mut Sha256) {}
+    fn stream(&self, _out: &mut Vec<u8>) -> Result<()> {
+        Ok(())
+    }
+    fn parse(_input: &mut Cursor<&[u8]>) -> Result<Self> {
+        Ok(())
+    }
+}
+
 impl<T: Streamable> Streamable for Option<T> {
     fn update_digest(&self, digest: &mut Sha256) {
         match self {
@@ -356,6 +369,12 @@ fn test_parse_list_list_3() {
     from_bytes::<Vec<Vec<u32>>>(buf, vec![vec![0x01020304], vec![0x01030307], vec![0x402]]);
 }
 
+#[test]
+fn test_parse_list_empty() {
+    let buf: &[u8] = &[0, 0, 0, 3];
+    from_bytes::<Vec<()>>(buf, vec![(), (), ()]);
+}
+
 #[test]
 fn test_parse_long_list() {
     let buf: &[u8] = &[0xff, 0xff, 0xff, 0xff, 0, 0, 0];
@@ -665,6 +684,12 @@ fn test_stream_list() {
     );
 }
 
+#[test]
+fn test_stream_list_of_empty() {
+    let out = stream(&vec![(), (), ()]);
+    assert_eq!(&out, &[0, 0, 0, 3]);
+}
+
 #[test]
 fn test_stream_list_list() {
     let out = stream(&vec![