enter

pub fn enter(self: *IoUring, to_submit: u32, min_complete: u32, flags: u32) !u32 {
    assert(self.fd >= 0);
    const res = linux.io_uring_enter(self.fd, to_submit, min_complete, flags, null);
    switch (linux.errno(res)) {
        .SUCCESS => {},
        // The kernel was unable to allocate memory or ran out of resources for the request.
        // The application should wait for some completions and try again:
        .AGAIN => return error.SystemResources,
        // The SQE `fd` is invalid, or IOSQE_FIXED_FILE was set but no files were registered:
        .BADF => return error.FileDescriptorInvalid,
        // The file descriptor is valid, but the ring is not in the right state.
        // See io_uring_register(2) for how to enable the ring.
        .BADFD => return error.FileDescriptorInBadState,
        // The application attempted to overcommit the number of requests it can have pending.
        // The application should wait for some completions and try again:
        .BUSY => return error.CompletionQueueOvercommitted,
        // The SQE is invalid, or valid but the ring was setup with IORING_SETUP_IOPOLL:
        .INVAL => return error.SubmissionQueueEntryInvalid,
        // The buffer is outside the process' accessible address space, or IORING_OP_READ_FIXED
        // or IORING_OP_WRITE_FIXED was specified but no buffers were registered, or the range
        // described by `addr` and `len` is not within the buffer registered at `buf_index`:
        .FAULT => return error.BufferInvalid,
        .NXIO => return error.RingShuttingDown,
        // The kernel believes our `self.fd` does not refer to an io_uring instance,
        // or the opcode is valid but not supported by this kernel (more likely):
        .OPNOTSUPP => return error.OpcodeNotSupported,
        // The thread submitting the work is invalid. This may occur if IORING_ENTER_GETEVENTS
        // and IORING_SETUP_DEFER_TASKRUN is set, but the submitting thread is not the thread
        // that initially created or enabled the io_uring associated with fd.
        .EXIST => return error.InvalidThread,
        // The operation was interrupted by a delivery of a signal before it could complete.
        // This can happen while waiting for events with IORING_ENTER_GETEVENTS:
        .INTR => return error.SignalInterrupt,
        else => |errno| return posix.unexpectedErrno(errno),
    }
    return @as(u32, @intCast(res));
}