port: migrated functions for computing trie root from reth to alloy

Cargo.toml

@@ -26,6 +26,7 @@ alloy-primitives = { version = "0.8.5", default-features = false, features = [
 ] }
 alloy-rlp = { version = "0.3.8", default-features = false, features = [
     "derive",
+    "arrayvec",
 ] }
 
 arrayvec = { version = "0.7", default-features = false }

src/lib.rs

@@ -31,6 +31,8 @@ pub mod proof;
 mod mask;
 pub use mask::TrieMask;
 
+pub mod root;
+
 #[doc(hidden)]
 pub use alloy_primitives::map::HashMap;
 

src/root.rs

@@ -0,0 +1,49 @@
+use alloy_primitives::B256;
+use alloy_rlp::Encodable;
+use nybbles::Nibbles;
+use alloc::vec::Vec;
+
+use crate::{HashBuilder, EMPTY_ROOT_HASH};
+
+/// Adjust the index of an item for rlp encoding.
+pub const fn adjust_index_for_rlp(i: usize, len: usize) -> usize {
+    if i > 0x7f {
+        i
+    } else if i == 0x7f || i + 1 == len {
+        0
+    } else {
+        i + 1
+    }
+}
+
+/// Compute a trie root of the collection of rlp encodable items.
+pub fn ordered_trie_root<T: Encodable>(items: &[T]) -> B256 {
+    ordered_trie_root_with_encoder(items, |item, buf| item.encode(buf))
+}
+
+/// Compute a trie root of the collection of items with a custom encoder.
+pub fn ordered_trie_root_with_encoder<T, F>(items: &[T], mut encode: F) -> B256
+where
+    F: FnMut(&T, &mut Vec<u8>),
+{
+    if items.is_empty() {
+        return EMPTY_ROOT_HASH;
+    }
+
+    let mut value_buffer = Vec::new();
+
+    let mut hb = HashBuilder::default();
+    let items_len = items.len();
+    for i in 0..items_len {
+        let index = adjust_index_for_rlp(i, items_len);
+
+        let index_buffer = alloy_rlp::encode_fixed_size(&index);
+
+        value_buffer.clear();
+        encode(&items[index], &mut value_buffer);
+
+        hb.add_leaf(Nibbles::unpack(&index_buffer), &value_buffer);
+    }
+
+    hb.root()
+}