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/
md5all.go
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/
md5all.go
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package main
import (
"context"
"crypto/md5"
"fmt"
"io/ioutil"
"log"
"os"
"path/filepath"
"golang.org/x/sync/errgroup"
)
// 一个多阶段的pipeline.使用有限的goroutine计算每个文件的md5值.
func main() {
m, err := MD5All(context.Background(), ".")
if err != nil {
log.Fatal(err)
}
for k, sum := range m {
fmt.Printf("%s:\t%x\n", k, sum)
}
}
type result struct {
path string
sum [md5.Size]byte
}
// 遍历根目录下所有的文件和子文件夹,计算它们的md5的值.
func MD5All(ctx context.Context, root string) (map[string][md5.Size]byte, error) {
g, ctx := errgroup.WithContext(ctx)
paths := make(chan string) // 文件路径channel
g.Go(func() error {
defer close(paths)
return filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
if err != nil {
return err
}
if !info.Mode().IsRegular() {
return nil
}
select {
case paths <- path:
case <-ctx.Done():
return ctx.Err()
}
return nil
})
})
// 启动20个goroutine执行计算md5的任务,计算的文件由上一阶段的文件遍历子任务生成.
c := make(chan result)
const numDigesters = 20
for i := 0; i < numDigesters; i++ {
g.Go(func() error {
for path := range paths {
data, err := ioutil.ReadFile(path)
if err != nil {
return err
}
select {
case c <- result{path, md5.Sum(data)}:
case <-ctx.Done():
return ctx.Err()
}
}
return nil
})
}
go func() {
g.Wait()
close(c)
}()
m := make(map[string][md5.Size]byte)
for r := range c { // 将md5结果从chan中读取到map中
m[r.path] = r.sum
}
// 等待所有的任务完成
if err := g.Wait(); err != nil {
return nil, err
}
return m, nil
}