starknet_os_runner: class provider

crates/starknet_os_runner/Cargo.toml

@@ -9,6 +9,7 @@ description = "Runs transactions through the Starknet OS and returns Cairo PIE a
 [dependencies]
 blockifier.workspace = true
 blockifier_reexecution.workspace = true
+cairo-lang-starknet-classes.workspace = true
 indexmap.workspace = true
 starknet-rust.workspace = true
 starknet-rust-core.workspace = true

crates/starknet_os_runner/src/classes_provider.rs

@@ -0,0 +1,26 @@
+use std::collections::{BTreeMap, HashSet};
+
+use cairo_lang_starknet_classes::casm_contract_class::CasmContractClass;
+use starknet_api::core::{ClassHash, CompiledClassHash};
+use starknet_api::deprecated_contract_class::ContractClass;
+
+use crate::errors::ClassesProviderError;
+
+/// The classes required for a Starknet OS run.
+/// Matches the fields in `StarknetOsInput` and `OsBlockInput`.
+pub struct ClassesInput {
+    /// Deprecated (Cairo 0) contract classes.
+    /// Maps ClassHash to the contract class definition.
+    pub deprecated_compiled_classes: BTreeMap<ClassHash, ContractClass>,
+    /// Cairo 1+ contract classes (CASM).
+    /// Maps CompiledClassHash to the CASM contract class definition.
+    pub compiled_classes: BTreeMap<CompiledClassHash, CasmContractClass>,
+}
+
+pub trait ClassesProvider {
+    /// Fetches all classes required for the OS run based on the executed class hashes.
+    fn get_classes(
+        &self,
+        executed_class_hashes: HashSet<ClassHash>,
+    ) -> Result<ClassesInput, ClassesProviderError>;
+}

crates/starknet_os_runner/src/errors.rs

@@ -26,3 +26,9 @@ pub enum ProofProviderError {
     #[error("Invalid RPC proof response: {0}")]
     InvalidProofResponse(String),
 }
+
+#[derive(Debug, Error)]
+pub enum ClassesProviderError {
+    #[error("Failed to get classes: {0}")]
+    GetClassesError(String),
+}

crates/starknet_os_runner/src/lib.rs

@@ -1,3 +1,4 @@
+pub mod classes_provider;
 pub mod errors;
 pub mod storage_proofs;
 pub mod virtual_block_executor;