chore: more cleanup for indexing_slicing

Author: kantai

stacks-common/src/util/hash.rs

@@ -580,7 +580,7 @@ where
 // borrowed from Andrew Poelstra's rust-bitcoin library
 /// Convert a hexadecimal-encoded string to its corresponding bytes
 pub fn hex_bytes(s: &str) -> Result<Vec<u8>, HexError> {
-    let mut v = vec![];
+    let mut v = Vec::with_capacity(s.len() / 2);
     let mut iter = s.chars().pair();
     // Do the parsing
     iter.by_ref()

stackslib/src/chainstate/stacks/index/bits.rs

@@ -143,14 +143,12 @@ pub fn ptrs_from_bytes<R: Read>(
     let ptr_bytes = bytes
         .get(1..)
         .ok_or_else(|| Error::CorruptionError("Failed to read >1 bytes from bytes array".into()))?;
-
-    for i in 0..num_ptrs {
-        let ptr_slot = ptrs_buf
-            .get_mut(i)
-            .ok_or_else(|| Error::CorruptionError("ptrs_buff smaller than num_ptrs".into()))?;
-        let next_ptr_bytes = ptr_bytes
-            .get(i * TRIEPTR_SIZE..(i + 1) * TRIEPTR_SIZE)
-            .ok_or_else(|| Error::CorruptionError("ptr_bytes malformed".into()))?;
+    // iterate over the read-in bytes in chunks of TRIEPTR_SIZE and store them
+    //   to `ptrs_buf`
+    let reading_ptrs = ptr_bytes
+        .chunks_exact(TRIEPTR_SIZE)
+        .zip(ptrs_buf.iter_mut());
+    for (next_ptr_bytes, ptr_slot) in reading_ptrs {
         *ptr_slot = TriePtr::from_bytes(next_ptr_bytes);
     }
     Ok(*nid)
@@ -171,9 +169,7 @@ pub fn get_node_hash<M, T: ConsensusSerializable<M> + std::fmt::Debug>(
         hasher.update(child_hash.as_ref());
     }
 
-    let mut res = [0u8; 32];
-    res.copy_from_slice(hasher.finalize().as_slice());
-
+    let res = hasher.finalize().into();
     let ret = TrieHash(res);
 
     trace!(
@@ -191,9 +187,7 @@ pub fn get_leaf_hash(node: &TrieLeaf) -> TrieHash {
     node.write_bytes(&mut hasher)
         .expect("IO Failure pushing to hasher.");
 
-    let mut res = [0u8; 32];
-    res.copy_from_slice(hasher.finalize().as_slice());
-
+    let res = hasher.finalize().into();
     let ret = TrieHash(res);
 
     trace!("get_leaf_hash: hash {:?} = {:?} + []", &ret, node);

stackslib/src/chainstate/stacks/index/mod.rs

@@ -121,14 +121,12 @@ macro_rules! impl_clarity_marf_trie_id {
             fn from(m: MARFValue) -> Self {
                 let h = m.0;
                 let mut d = [0u8; 32];
-                d.copy_from_slice(h.get(..32).expect("Failed to convert MARF value: MARFValue did not have 32 bytes"));
-                if let Some(remainder) = h.get(32..) {
-                    for h_i in remainder {
-                        if *h_i != 0 {
-                            panic!(
-                                "Failed to convert MARF value into BHH: data stored after 32nd byte"
-                            );
-                        }
+                d.copy_from_slice(&h[..32]);
+                for x in &h[32..] {
+                    if *x != 0 {
+                        panic!(
+                            "Failed to convert MARF value into BHH: data stored after 32nd byte"
+                        );
                     }
                 }
                 Self(d)
@@ -192,13 +190,11 @@ impl From<MARFValue> for u32 {
         let h = m.0;
         let mut d = [0u8; 4];
 
-        d.copy_from_slice(h.get(..4).expect("FATAL: MARFValue does not have 4 bytes"));
+        d.copy_from_slice(&h[..4]);
 
-        if let Some(remainder) = h.get(4..) {
-            for h_i in remainder {
-                if *h_i != 0 {
-                    panic!("Failed to convert MARF value into u32: data stored after 4th byte");
-                }
+        for h_i in &h[4..] {
+            if *h_i != 0 {
+                panic!("Failed to convert MARF value into u32: data stored after 4th byte");
             }
         }
         u32::from_le_bytes(d)
@@ -220,11 +216,9 @@ impl MARFValue {
 
     /// Construct from a String that encodes a value inserted into the underlying data store
     pub fn from_value(s: &str) -> MARFValue {
-        let mut tmp = [0u8; 32];
-
         let mut hasher = TrieHasher::new();
         hasher.update(s.as_bytes());
-        tmp.copy_from_slice(hasher.finalize().as_slice());
+        let tmp = hasher.finalize().into();
 
         MARFValue::from_value_hash_bytes(&tmp)
     }