Implement the history overlay mechanism

miden-crypto/src/lib.rs

@@ -2,7 +2,6 @@
 
 #[macro_use]
 extern crate alloc;
-
 #[cfg(feature = "std")]
 extern crate std;
 
@@ -49,6 +48,20 @@ pub type Map<K, V> = alloc::collections::BTreeMap<K, V>;
 #[cfg(not(feature = "hashmaps"))]
 pub use alloc::collections::btree_map::Entry as MapEntry;
 
+/// An alias for a simple set.
+///
+/// By default, this is an alias for the [`alloc::collections::BTreeSet`]. However, when the
+/// `hashmaps` feature is enabled, this becomes an alias for hashbrown's HashSet.
+#[cfg(feature = "hashmaps")]
+pub type Set<V> = hashbrown::HashSet<V>;
+
+/// An alias for a simple set.
+///
+/// By default, this is an alias for the [`alloc::collections::BTreeSet`]. However, when the
+/// `hashmaps` feature is enabled, this becomes an alias for hashbrown's HashSet.
+#[cfg(not(feature = "hashmaps"))]
+pub type Set<V> = alloc::collections::BTreeSet<V>;
+
 // CONSTANTS
 // ================================================================================================
 

miden-crypto/src/merkle/smt/large_forest/error.rs

@@ -0,0 +1,21 @@
+//! This module contains the error types and helpers for working with errors from the large SMT
+//! forest.
+
+use thiserror::Error;
+
+use crate::merkle::{MerkleError, smt::large_forest::history::error::HistoryError};
+
+/// The errors returned by operations on the large SMT forest.
+///
+/// This type primarily serves to wrap more specific error types from various subsystems into a
+/// generic interface type.
+#[derive(Debug, Error)]
+pub enum LargeSmtForestError {
+    #[error(transparent)]
+    HistoryError(#[from] HistoryError),
+
+    #[error(transparent)]
+    MerkleError(#[from] MerkleError),
+}
+
+pub mod history {}

miden-crypto/src/merkle/smt/large_forest/history/error.rs

@@ -0,0 +1,23 @@
+//! The error type and utility types for working with errors from the SMT history construct.
+use thiserror::Error;
+
+use crate::merkle::smt::large_forest::history::VersionId;
+
+/// The type of errors returned by the history container.
+#[derive(Debug, Error, PartialEq)]
+pub enum HistoryError {
+    /// Raised when a query expects the history to contain at least one entry, but it is empty.
+    #[error("The history was empty")]
+    HistoryEmpty,
+
+    /// Raised when a version is added to the history and is not newer than the previous.
+    #[error("Version {0} is not monotonic with respect to {1}")]
+    NonMonotonicVersions(VersionId, VersionId),
+
+    /// Raised when no version exists in the history for an arbitrary query.
+    #[error("The specified version is too old to be served by the history")]
+    VersionTooOld,
+}
+
+/// The result type for use within the history container.
+pub type Result<T> = core::result::Result<T, HistoryError>;