fileSetLength

fn fileSetLength(userdata: ?*anyopaque, file: File, length: u64) File.SetLengthError!void {
    const ev: *Evented = @ptrCast(@alignCast(userdata));
    var cancel_region: CancelRegion = .init();
    defer cancel_region.deinit();
    while (true) {
        const thread = try cancel_region.awaitIoUring();
        thread.enqueue().* = .{
            .opcode = .FTRUNCATE,
            .flags = 0,
            .ioprio = 0,
            .fd = file.handle,
            .off = length,
            .addr = 0,
            .len = 0,
            .rw_flags = 0,
            .user_data = @intFromPtr(cancel_region.fiber),
            .buf_index = 0,
            .personality = 0,
            .splice_fd_in = 0,
            .addr3 = 0,
            .resv = 0,
        };
        ev.yield(null, .nothing);
        switch (cancel_region.errno()) {
            .SUCCESS => return,
            .INTR, .CANCELED => {},
            .FBIG => return error.FileTooBig,
            .IO => return error.InputOutput,
            .PERM => return error.PermissionDenied,
            .TXTBSY => return error.FileBusy,
            .BADF => |err| return errnoBug(err), // Handle not open for writing.
            .INVAL => return error.NonResizable, // This is returned for /dev/null for example.
            else => |err| return unexpectedErrno(err),
        }
    }
}