Add 'zcash_history/' from commit 'e2c131fdc308265adcab774e54d4d5804c23b368'

git-subtree-dir: zcash_history
git-subtree-mainline: be0ee9eb82
git-subtree-split: e2c131fdc3

zcash_history/src/lib.rs

@@ -0,0 +1,77 @@
+//! MMR library for Zcash
+//!
+//! To be used in zebra and via FFI bindings in zcashd
+#![warn(missing_docs)]
+
+mod tree;
+mod node_data;
+mod entry;
+
+
+pub use tree::Tree;
+pub use node_data::{NodeData, MAX_NODE_DATA_SIZE};
+pub use entry::{Entry, MAX_ENTRY_SIZE};
+
+/// Crate-level error type
+#[derive(Debug)]
+pub enum Error {
+    /// Entry expected to be presented in the tree view while it was not.
+    ExpectedInMemory(EntryLink),
+    /// Entry expected to be a node (specifying for which link this is not true).
+    ExpectedNode(Option<EntryLink>),
+}
+
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match *self {
+            Self::ExpectedInMemory(l) => write!(f, "Node/leaf expected to be in memory: {}", l),
+            Self::ExpectedNode(None) => write!(f, "Node expected"),
+            Self::ExpectedNode(Some(l)) => write!(f, "Node expected, not leaf: {}", l),
+        }
+    }
+}
+
+/// Reference to to the tree node.
+#[repr(C)]
+#[derive(Clone, Copy, Debug)]
+pub enum EntryLink {
+    /// Reference to the stored (in the array representation) leaf/node.
+    Stored(u32),
+    /// Reference to the generated leaf/node.
+    Generated(u32),
+}
+
+impl std::fmt::Display for EntryLink {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match *self {
+            Self::Stored(v) => write!(f, "stored({})", v),
+            Self::Generated(v) => write!(f, "generated({})", v),
+        }
+    }
+}
+
+/// MMR Node. It is leaf when `left`, `right` are `None` and node when they are not.
+#[repr(C)]
+#[derive(Debug)]
+pub enum EntryKind {
+    /// Leaf entry.
+    Leaf,
+    /// Node entry with children links.
+    Node(EntryLink, EntryLink),
+}
+
+impl Error {
+    /// Entry expected to be a node (specifying for which link this is not true).
+    pub fn link_node_expected(link: EntryLink) -> Self { Self::ExpectedNode(Some(link)) }
+
+    /// Some entry is expected to be node
+    pub fn node_expected() -> Self { Self::ExpectedNode(None) }
+
+    pub (crate) fn augment(self, link: EntryLink) -> Self {
+        match self {
+            Error::ExpectedNode(_) => Error::ExpectedNode(Some(link)),
+            val => val
+        }
+    }
+}
+