github.com/camlistore/go4@v0.0.0-20200104003542-c7e774b10ea0/syncutil/group.go (about)

     1  /*
     2  Copyright 2013 Google Inc.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8       http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package syncutil
    18  
    19  import "sync"
    20  
    21  // A Group is like a sync.WaitGroup and coordinates doing
    22  // multiple things at once. Its zero value is ready to use.
    23  type Group struct {
    24  	wg   sync.WaitGroup
    25  	mu   sync.Mutex // guards errs
    26  	errs []error
    27  }
    28  
    29  // Go runs fn in its own goroutine, but does not wait for it to complete.
    30  // Call Err or Errs to wait for all the goroutines to complete.
    31  func (g *Group) Go(fn func() error) {
    32  	g.wg.Add(1)
    33  	go func() {
    34  		defer g.wg.Done()
    35  		err := fn()
    36  		if err != nil {
    37  			g.mu.Lock()
    38  			defer g.mu.Unlock()
    39  			g.errs = append(g.errs, err)
    40  		}
    41  	}()
    42  }
    43  
    44  // Wait waits for all the previous calls to Go to complete.
    45  func (g *Group) Wait() {
    46  	g.wg.Wait()
    47  }
    48  
    49  // Err waits for all previous calls to Go to complete and returns the
    50  // first non-nil error, or nil.
    51  func (g *Group) Err() error {
    52  	g.wg.Wait()
    53  	if len(g.errs) > 0 {
    54  		return g.errs[0]
    55  	}
    56  	return nil
    57  }
    58  
    59  // Errs waits for all previous calls to Go to complete and returns
    60  // all non-nil errors.
    61  func (g *Group) Errs() []error {
    62  	g.wg.Wait()
    63  	return g.errs
    64  }