New crate for compact trie proofs.

Cargo.toml

@@ -8,5 +8,6 @@ members = [
 	"test-support/trie-standardmap",
 	"test-support/trie-bench",
 	"trie-db",
+	"trie-proof",
 	"trie-root"
 ]

trie-db/src/iter_build.rs

@@ -38,7 +38,7 @@ macro_rules! exponential_out {
 type CacheNode<HO> = Option<ChildReference<HO>>;
 
 #[inline(always)]
-fn new_vec_slice_buffer<HO>() -> [CacheNode<HO>; 16] {
+fn new_vec_slice_buffer<HO: Copy>() -> [CacheNode<HO>; 16] {
 	exponential_out!(@3, [None, None])
 }
 
@@ -314,7 +314,7 @@ pub fn trie_visit<T, I, A, B, F>(input: I, callback: &mut F)
 }
 
 /// Visitor trait to implement when using `trie_visit`.
-pub trait ProcessEncodedNode<HO> {
+pub trait ProcessEncodedNode<HO: Copy> {
 	/// Function call with prefix, encoded value and a boolean indicating if the
 	/// node is the root for each node of the trie.
 	///

trie-db/src/triedb.rs

@@ -303,7 +303,7 @@ impl Crumb {
 	}
 }
 
-/// Iterator for going through all values in the trie.
+/// Iterator for going through all values in the trie in pre-order traversal order.
 pub struct TrieDBIterator<'a, L: TrieLayout> {
 	db: &'a TrieDB<'a, L>,
 	trail: Vec<Crumb>,

trie-db/src/triedbmut.rs

@@ -270,7 +270,8 @@ enum Stored<H> {
 }
 
 /// Used to build a collection of child nodes from a collection of `NodeHandle`s
-pub enum ChildReference<HO> { // `HO` is e.g. `H256`, i.e. the output of a `Hasher`
+#[derive(Clone, Copy)]
+pub enum ChildReference<HO: Copy> { // `HO` is e.g. `H256`, i.e. the output of a `Hasher`
 	Hash(HO),
 	Inline(HO, usize), // usize is the length of the node data we store in the `H::Out`
 }

trie-proof/Cargo.toml

@@ -0,0 +1,27 @@
+[package]
+name = "trie-proof"
+version = "0.15.2"
+authors = ["Parity Technologies <admin@parity.io>"]
+description = "Compact proof generation and verification for Merkle-Patricia trie"
+repository = "https://github.com/paritytech/trie"
+license = "Apache-2.0"
+edition = "2018"
+
+[dependencies]
+hash-db = { path = "../hash-db", default-features = false, version = "0.15.2" }
+memory-db = { path = "../memory-db", default-features = false, version = "0.15.2" }
+parity-scale-codec = { version = "1.0.3", features = ["derive"] }
+trie-db = { path = "../trie-db", default-features = false, version = "0.15.2" }
+
+[dev-dependencies]
+keccak-hasher = { path = "../test-support/keccak-hasher", version = "0.15.2" }
+reference-trie = { path = "../test-support/reference-trie", version = "0.15.2" }
+
+[features]
+default = ["std"]
+std = [
+  "hash-db/std",
+  "memory-db/std",
+  "parity-scale-codec/std",
+  "trie-db/std",
+]