# Errors

> UStore for C

`#include <ustore/types.h>`

## ustore_status_t

What went wrong, in one vocabulary shared by every engine and binding.

```c
enum ustore_status_t
```

Shared statuses carry USearch's numbers, leaving 3, 4, 5, 11 and 13 unused, and UStore's own start at 18. Statuses fall into five categories: resources, input, state, interruptions and defects. Any verb that allocates, binds a device or touches a file may also return a resources status; any verb taking a progress callback may return an interruption. A verb's own block lists only what its contract adds.

- `ustore_status_success_k` = `0`: The call succeeded; `message` carries nothing.
- `ustore_status_deferred_k` = `1`: A deferred call that has not finished; the one status that is never final.
- `ustore_status_out_of_memory_k` = `2`: An allocation could not be satisfied.
- `ustore_status_read_only_k` = `6`: The call would change a database opened read-only, as [`ustore_database_view_rocksdb`](https://www.unum.cloud/docs/ustore/c/quickstart.md#ustore_database_view_rocksdb) opens one.
- `ustore_status_io_k` = `7`: A file or directory could not be opened, read, written, or closed.
- `ustore_status_device_k` = `8`: A device could not be selected, or its memory could not be claimed, or the call's executor, database and arena belong to different residencies or devices.
- `ustore_status_malformed_k` = `9`: Stored or supplied data could not be decoded, like a corrupted file, an invalid document, or raw NVMe data directories listed in another order than the database was created with.
- `ustore_status_internal_k` = `10`: The engine failed in a way no other status names, which points at a defect.
- `ustore_status_uninitialized_k` = `12`: The call needs a database or transaction that was never opened.
- `ustore_status_contended_k` = `14`: The call was refused rather than waited for: its executor's deferred table is full, its arena or its transaction serves another call, or it drains or blocks from a callback its own executor runs.
- `ustore_status_cancelled_k` = `15`: A progress callback stopped the call, which unwound and published nothing.
- `ustore_status_unsupported_k` = `16`: The engine or build does not implement what the call asks for, like io_uring on a kernel without it.
- `ustore_status_invalid_argument_k` = `17`: An argument is null, contradicts another one, or carries a choice the call does not accept, like a collection of another modality, a name reserved for a system collection, or a batch of strings in an unknown layout.
- `ustore_status_not_found_k` = `18`: A collection, a directory, or a document a modification needs does not exist, while a read marks a missing key with an unset presence bit instead.
- `ustore_status_already_exists_k` = `19`: A collection name or a document the call creates is already taken, or the first slot of a raw medium an NVMe database opens belongs to something else.
- `ustore_status_write_conflict_k` = `20`: A concurrent writer changed a key this transaction wrote; retry the transaction.
- `ustore_status_read_conflict_k` = `21`: A concurrent writer changed a key this transaction read; retry the transaction.
- `ustore_status_phantom_conflict_k` = `22`: A concurrent writer inserted into a range this transaction scanned; retry the transaction.
- `ustore_status_capacity_exhausted_k` = `23`: A hard design ceiling was reached.

Spellings: ```
char const * ustore_status_name(ustore_status_t status);
```

```
ustore_status_t ustore_status_from_name(ustore_bytes_view_t name);
```