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Goでのパイプラインとキャンセル http://qiita.com/sudix/items/f95ef0e5bbd0cd3d4378
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| // Goでのパイプラインとキャンセル http://qiita.com/sudix/items/f95ef0e5bbd0cd3d4378 | |
| package main | |
| import ( | |
| "crypto/md5" | |
| "errors" | |
| "fmt" | |
| "io/ioutil" | |
| "os" | |
| "path/filepath" | |
| "sort" | |
| "sync" | |
| ) | |
| type result struct { | |
| path string | |
| sum [md5.Size]byte | |
| err error | |
| } | |
| func walkFiles(done <-chan struct{}, root string) (<-chan string, <-chan error) { | |
| paths := make(chan string) | |
| errc := make(chan error, 1) | |
| go func() { | |
| // Close the paths channel after Walk returns. | |
| defer close(paths) | |
| // No select needed for this send, since errc is buffered. | |
| errc <- filepath.Walk(root, func(path string, info os.FileInfo, err error) error { | |
| if err != nil { | |
| return err | |
| } | |
| if info.IsDir() { | |
| return nil | |
| } | |
| select { | |
| case paths <- path: | |
| case <-done: | |
| return errors.New("walk canceled") | |
| } | |
| return nil | |
| }) | |
| }() | |
| return paths, errc | |
| } | |
| func digester(done <-chan struct{}, paths <-chan string, c chan<- result) { | |
| for path := range paths { | |
| data, err := ioutil.ReadFile(path) | |
| select { | |
| case c <- result{path, md5.Sum(data), err}: | |
| case <-done: | |
| return | |
| } | |
| } | |
| } | |
| func MD5All(root string) (map[string][md5.Size]byte, error) { | |
| // MD5All closes the done channel when it returns; it may do so before | |
| // receiving all the values from c and errc. | |
| done := make(chan struct{}) | |
| defer close(done) | |
| paths, errc := walkFiles(done, root) | |
| // Start a fixed number of goroutines to read and digest files. | |
| c := make(chan result) | |
| var wg sync.WaitGroup | |
| const numDigesters = 20 | |
| wg.Add(numDigesters) | |
| for i := 0; i < numDigesters; i++ { | |
| go func() { | |
| digester(done, paths, c) | |
| wg.Done() | |
| }() | |
| } | |
| go func() { | |
| wg.Wait() | |
| close(c) | |
| }() | |
| m := make(map[string][md5.Size]byte) | |
| for r := range c { | |
| if r.err != nil { | |
| return nil, r.err | |
| } | |
| m[r.path] = r.sum | |
| } | |
| // Check whether the Walk failed. | |
| if err := <-errc; err != nil { | |
| return nil, err | |
| } | |
| return m, nil | |
| } | |
| func main() { | |
| // Calculate the MD5 sum of all files under the specified directory, | |
| // then print the results sorted by path name. | |
| m, err := MD5All(os.Args[1]) | |
| if err != nil { | |
| fmt.Println(err) | |
| return | |
| } | |
| var paths []string | |
| for path := range m { | |
| paths = append(paths, path) | |
| } | |
| sort.Strings(paths) | |
| for _, path := range paths { | |
| fmt.Printf("%x %s\n", m[path], path) | |
| } | |
| } |
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http://qiita.com/sudix/items/f95ef0e5bbd0cd3d4378