epoll_events.go

// Copyright (c) 2019 Andy Pan
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//go:build linux
// +build linux

package netpoll

import "golang.org/x/sys/unix"

// IOEvent is the integer type of I/O events on Linux.
type IOEvent = uint32

const (
	// InitPollEventsCap represents the initial capacity of poller event-list.
	InitPollEventsCap = 128
	// MaxPollEventsCap is the maximum limitation of events that the poller can process.
	MaxPollEventsCap = 1024
	// MinPollEventsCap is the minimum limitation of events that the poller can process.
	MinPollEventsCap = 32
	// MaxAsyncTasksAtOneTime is the maximum amount of asynchronous tasks that the event-loop will process at one time.
	MaxAsyncTasksAtOneTime = 256
	// ErrEvents represents exceptional events that are not read/write, like socket being closed,
	// reading/writing from/to a closed socket, etc.
	ErrEvents = unix.EPOLLERR | unix.EPOLLHUP | unix.EPOLLRDHUP
	// OutEvents combines EPOLLOUT event and some exceptional events.
	OutEvents = ErrEvents | unix.EPOLLOUT
	// InEvents combines EPOLLIN/EPOLLPRI events and some exceptional events.
	InEvents = ErrEvents | unix.EPOLLIN | unix.EPOLLPRI
)

type eventList struct {
	size   int
	events []epollevent
}

func newEventList(size int) *eventList {
	return &eventList{size, make([]epollevent, size)}
}

func (el *eventList) expand() {
	if newSize := el.size << 1; newSize <= MaxPollEventsCap {
		el.size = newSize
		el.events = make([]epollevent, newSize)
	}
}

func (el *eventList) shrink() {
	if newSize := el.size >> 1; newSize >= MinPollEventsCap {
		el.size = newSize
		el.events = make([]epollevent, newSize)
	}
}