feat: PublicImmutable impl

noir-projects/aztec-nr/aztec/src/state_vars/public_immutable.nr

@@ -0,0 +1,46 @@
+use crate::context::{Context};
+use crate::oracle::storage::storage_read;
+use crate::oracle::storage::storage_write;
+use dep::std::option::Option;
+use dep::protocol_types::traits::{Deserialize, Serialize};
+use crate::state_vars::storage::Storage;
+
+// docs:start:public_immutable_struct
+struct PublicImmutable<T> {
+    context: Context,
+    storage_slot: Field,
+}
+// docs:end:public_immutable_struct
+
+impl<T> Storage<T> for PublicImmutable<T> {}
+
+impl<T> PublicImmutable<T> {
+    // docs:start:public_immutable_struct_new
+    pub fn new(
+        // Note: Passing the contexts to new(...) just to have an interface compatible with a Map.
+        context: Context,
+        storage_slot: Field
+    ) -> Self {
+        assert(storage_slot != 0, "Storage slot 0 not allowed. Storage slots must start from 1.");
+        PublicImmutable { context, storage_slot }
+    }
+    // docs:end:public_immutable_struct_new
+
+    // docs:start:public_immutable_struct_write
+    pub fn initialize<T_SERIALIZED_LEN>(self, value: T) where T: Serialize<T_SERIALIZED_LEN> {
+        assert(
+            self.context.private.is_none(), "PublicImmutable initialization only supported in public functions"
+        );
+        let fields = T::serialize(value);
+        storage_write(self.storage_slot, fields);
+    }
+    // docs:end:public_immutable_struct_write
+
+    // docs:start:public_immutable_struct_read
+    pub fn read<T_SERIALIZED_LEN>(self) -> T where T: Deserialize<T_SERIALIZED_LEN> {
+        assert(self.context.private.is_none(), "PublicImmutable reads only supported in public functions");
+        let fields = storage_read(self.storage_slot);
+        T::deserialize(fields)
+    }
+    // docs:end:public_immutable_struct_read
+}