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dwelling-radio/internal/radio/listeners.go

73 lines
1.7 KiB
Go

package radio
import (
"encoding/json"
"errors"
"fmt"
"math"
"sync"
)
// ListenerCounter stores the current and peak numbers of listeners.
type ListenerCounter struct {
mut sync.Mutex
current, peak int
}
// NewListenerCounter returns a new ListenerCounter struct instance.
func NewListenerCounter() *ListenerCounter {
return &ListenerCounter{}
}
// Current returns a number of current listeners.
func (l *ListenerCounter) Current() int {
l.mut.Lock()
defer l.mut.Unlock()
return l.current
}
// Current returns a number of peak listeners.
func (l *ListenerCounter) Peak() int {
l.mut.Lock()
defer l.mut.Unlock()
return l.peak
}
// Inc increments by 1 a current number of listeners and updates a peak number.
func (l *ListenerCounter) Inc() int {
l.mut.Lock()
defer l.mut.Unlock()
if l.current == math.MaxInt {
// We panic here because if this will ever happen, then something's going certainly wrong.
panic(fmt.Sprint("a current number of listeners exceeded MaxInt which is", math.MaxInt))
}
l.current++
if l.current > l.peak {
l.peak = l.current
}
return l.current
}
// Dec decrements by 1 a current number of listeners. An error will occur if
// a resulting number is less than 0.
func (l *ListenerCounter) Dec() (int, error) {
l.mut.Lock()
defer l.mut.Unlock()
if l.current == 0 {
return l.current, errors.New("an attempt to decrement a number of current listeners down to less than 0")
}
l.current--
return l.current, nil
}
func (l *ListenerCounter) MarshalJSON() ([]byte, error) {
l.mut.Lock()
defer l.mut.Unlock()
return json.Marshal(&struct {
Current int `json:"current"`
Peak int `json:"peak"`
}{
Current: l.current,
Peak: l.peak})
}