clash/common/picker/picker.go
2020-04-16 18:31:40 +08:00

80 lines
1.8 KiB
Go

package picker
import (
"context"
"sync"
"time"
)
// Picker provides synchronization, and Context cancelation
// for groups of goroutines working on subtasks of a common task.
// Inspired by errGroup
type Picker struct {
ctx context.Context
cancel func()
wg sync.WaitGroup
once sync.Once
errOnce sync.Once
result interface{}
err error
}
func newPicker(ctx context.Context, cancel func()) *Picker {
return &Picker{
ctx: ctx,
cancel: cancel,
}
}
// WithContext returns a new Picker and an associated Context derived from ctx.
// and cancel when first element return.
func WithContext(ctx context.Context) (*Picker, context.Context) {
ctx, cancel := context.WithCancel(ctx)
return newPicker(ctx, cancel), ctx
}
// WithTimeout returns a new Picker and an associated Context derived from ctx with timeout.
func WithTimeout(ctx context.Context, timeout time.Duration) (*Picker, context.Context) {
ctx, cancel := context.WithTimeout(ctx, timeout)
return newPicker(ctx, cancel), ctx
}
// Wait blocks until all function calls from the Go method have returned,
// then returns the first nil error result (if any) from them.
func (p *Picker) Wait() interface{} {
p.wg.Wait()
if p.cancel != nil {
p.cancel()
}
return p.result
}
// Error return the first error (if all success return nil)
func (p *Picker) Error() error {
return p.err
}
// Go calls the given function in a new goroutine.
// The first call to return a nil error cancels the group; its result will be returned by Wait.
func (p *Picker) Go(f func() (interface{}, error)) {
p.wg.Add(1)
go func() {
defer p.wg.Done()
if ret, err := f(); err == nil {
p.once.Do(func() {
p.result = ret
if p.cancel != nil {
p.cancel()
}
})
} else {
p.errOnce.Do(func() {
p.err = err
})
}
}()
}