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- // walkFiles starts a goroutine to walk the directory tree at root and send the
- // path of each regular file on the string channel. It sends the result of the
- // walk on the error channel. If done is closed, walkFiles abandons its work.
- func walkFiles(done <-chan struct{}, root string) (<-chan string, <-chan error) {
- paths := make(chan string)
- errc := make(chan error, 1)
- go func() { // HL
- // Close the paths channel after Walk returns.
- defer close(paths) // HL
- // No select needed for this send, since errc is buffered.
- errc <- filepath.Walk(root, func(path string, info os.FileInfo, err error) error { // HL
- if err != nil {
- return err
- }
- if !info.Mode().IsRegular() {
- return nil
- }
- select {
- case paths <- path: // HL
- case <-done: // HL
- return errors.New("walk canceled")
- }
- return nil
- })
- }()
- return paths, errc
- }
- // A result is the product of reading and summing a file using MD5.
- type result struct {
- path string
- sum [md5.Size]byte
- err error
- }
- // digester reads path names from paths and sends digests of the corresponding
- // files on c until either paths or done is closed.
- func digester(done <-chan struct{}, paths <-chan string, c chan<- result) {
- for path := range paths { // HLpaths
- data, err := ioutil.ReadFile(path)
- select {
- case c <- result{path, md5.Sum(data), err}:
- case <-done:
- return
- }
- }
- }
- // MD5All reads all the files in the file tree rooted at root and returns a map
- // from file path to the MD5 sum of the file's contents. If the directory walk
- // fails or any read operation fails, MD5All returns an error. In that case,
- // MD5All does not wait for inflight read operations to complete.
- 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) // HLc
- var wg sync.WaitGroup
- const numDigesters = 20
- wg.Add(numDigesters)
- for i := 0; i < numDigesters; i++ {
- go func() {
- digester(done, paths, c) // HLc
- wg.Done()
- }()
- }
- go func() {
- wg.Wait()
- close(c) // HLc
- }()
- // End of pipeline. OMIT
- 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 { // HLerrc
- 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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