async-io-model

Turso uses cooperative yielding with explicit state machines instead of Rust async/await. Functions returning IOResult must be called repeatedly until Done . A Completion tracks a single I/O operation: To wait for multiple I/O operations, use CompletionGroup : CompletionGroup features: Unwraps IOResult , propagates IO variant up the call stack: Yields a single completion: Operations that may yield use explicit state enums: The function loops, matching on state and transitioning: State mutations before yield points cause bugs on re-entry. If something_that_might_yield() returns IO , caller waits for completion, then calls bad_example() again. counter gets incremented twice (or more). Encode progress in state variants: Key files: Re-entrancy bugs often only manifest under specific IO timing. Use: - Aggregates multiple completions into one - Calls callback when all complete (or any errors) - Can nest groups (add a group's completion to another group) - Cancellable via group.cancel() - core/types.rs - IOResult , IOCompletions , return_if_io! , return_and_restore_if_io! - core/io/completions.rs - Completion , CompletionGroup - core/util.rs - io_yield_one! macro - core/state_machine.rs - Generic StateMachine wrapper - core/storage/btree.rs - Many state machine examples - core/storage/pager.rs - CompletionGroup usage examples - Deterministic simulation ( testing/simulator/ ) -...