story-kit: merge 260_refactor_upgrade_libsqlite3_sys

vendor/rusqlite/examples/owning_statement.rs

@@ -0,0 +1,30 @@
+extern crate rusqlite;
+use rusqlite::{CachedStatement, Connection, Result, Rows};
+use self_cell::{self_cell, MutBorrow};
+
+type CachedStatementRef<'a> = CachedStatement<'a>;
+
+// Caveat: single statement at a time for one connection.
+// But if you need multiple statements, you can still create your own struct
+// with multiple fields (one for each statement).
+self_cell!(
+    struct OwningStatement {
+        owner: MutBorrow<Connection>,
+        #[covariant]
+        dependent: CachedStatementRef,
+    }
+);
+
+fn main() -> Result<()> {
+    let conn = Connection::open_in_memory()?;
+
+    let mut os = OwningStatement::try_new(MutBorrow::new(conn), |s| {
+        s.borrow_mut().prepare_cached("SELECT 1")
+    })?;
+
+    let mut rows = os.with_dependent_mut(|_conn, stmt| -> Result<Rows<'_>> { stmt.query([]) })?;
+    while let Some(row) = rows.next()? {
+        assert_eq!(Ok(1), row.get(0));
+    }
+    Ok(())
+}