diff --git a/vlib/os/notify/backend_linux.c.v b/vlib/os/notify/backend_linux.c.v index 35847d848f..6b43df1f26 100644 --- a/vlib/os/notify/backend_linux.c.v +++ b/vlib/os/notify/backend_linux.c.v @@ -24,14 +24,15 @@ fn C.epoll_ctl(int, int, int, &C.epoll_event) int fn C.epoll_wait(int, &C.epoll_event, int, int) int +// EpollNotifier provides methods that implement FdNotifier using the +// epoll I/O event notification facility (linux only) [noinit] struct EpollNotifier { epoll_fd int -mut: - num_watching int // heuristic - events []C.epoll_event } +// EpollEvent describes an event that occurred for a file descriptor in +// the watch list [noinit] struct EpollEvent { pub: @@ -39,6 +40,9 @@ pub: kind FdEventType } +// new creates a new EpollNotifier +// The FdNotifier interface is returned to allow OS specific +// implementations without exposing the concrete type pub fn new() ?FdNotifier { fd := C.epoll_create1(0) // 0 indicates default behavior if fd == -1 { @@ -64,6 +68,7 @@ const ( epoll_exclusive = u32(C.EPOLLEXCLUSIVE) ) +// ctl is a helper method for add, modify, and remove fn (mut en EpollNotifier) ctl(fd int, op int, mask u32) ? { event := C.epoll_event{ events: mask @@ -76,45 +81,43 @@ fn (mut en EpollNotifier) ctl(fd int, op int, mask u32) ? { } } +// add adds a file descriptor to the watch list fn (mut en EpollNotifier) add(fd int, events FdEventType, conf ...FdConfigFlags) ? { mask := flags_to_mask(events, ...conf) en.ctl(fd, C.EPOLL_CTL_ADD, mask) ? - en.num_watching++ } +// modify sets an existing entry in the watch list to the provided events and configuration fn (mut en EpollNotifier) modify(fd int, events FdEventType, conf ...FdConfigFlags) ? { mask := flags_to_mask(events, ...conf) en.ctl(fd, C.EPOLL_CTL_MOD, mask) ? } +// remove removes a file descriptor from the watch list fn (mut en EpollNotifier) remove(fd int) ? { en.ctl(fd, C.EPOLL_CTL_DEL, 0) ? - if en.num_watching > 0 { - en.num_watching-- - } } -[direct_array_access] +// wait waits to be notified of events on the watch list, +// returns at most 512 events fn (mut en EpollNotifier) wait(timeout time.Duration) []FdEvent { - if en.events.cap < en.num_watching { - en.events.grow_cap(en.num_watching - en.events.cap) - } - // populate en.events.data with the new events + // arbitrary 512 limit; events will round robin on successive + // waits if the number exceeds this + // NOTE: we use a fixed size array here for stack allocation; this has + // the added bonus of making EpollNotifier thread safe + events := [512]C.epoll_event{} + // populate events with the new events to := match timeout { time.infinite { -1 } else { int(timeout / time.millisecond) } } - count := C.epoll_wait(en.epoll_fd, en.events.data, en.events.cap, to) - - // set len to count - en.events.clear() - unsafe { en.events.grow_len(count) } + count := C.epoll_wait(en.epoll_fd, &events[0], events.len, to) if count > 0 { mut arr := []FdEvent{cap: count} for i := 0; i < count; i++ { - fd := unsafe { en.events[i].data.fd } - kind := event_mask_to_flag(en.events[i].events) + fd := unsafe { events[i].data.fd } + kind := event_mask_to_flag(events[i].events) if kind.is_empty() { // NOTE: tcc only reports the first event for some // reason, leaving subsequent structs in the array as 0 @@ -131,12 +134,16 @@ fn (mut en EpollNotifier) wait(timeout time.Duration) []FdEvent { return [] } +// close closes the EpollNotifier, +// any successive calls to add, modify, remove, and wait should fail fn (mut en EpollNotifier) close() ? { if C.close(en.epoll_fd) == -1 { return error(os.posix_get_error_msg(C.errno)) } } +// event_mask_to_flag is a helper function that converts a bitmask +// returned by epoll_wait to FdEventType fn event_mask_to_flag(mask u32) FdEventType { mut flags := FdEventType{} @@ -162,6 +169,8 @@ fn event_mask_to_flag(mask u32) FdEventType { return flags } +// flags_to_mask is a helper function that converts FdEventType and +// FdConfigFlags to a bitmask used by the C functions fn flags_to_mask(events FdEventType, confs ...FdConfigFlags) u32 { mut mask := u32(0) if events.has(.read) {