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|
package main
import (
"fmt"
)
type Fetcher interface {
Fetch(url string) (body string, urls []string, err error)
}
var lockx = make(chan int,1)
func LockFun(f func()) {
lockx<-1
f()
<-lockx
}
var visited map[string]bool = make(map[string]bool)
func Crawl(url string, depth int, fetcher Fetcher, banner chan int) {
if depth <= 0 || visited[url] {
banner<-1
return
}
body, urls, err := fetcher.Fetch(url)
LockFun(func(){
visited[url]=true
})
fmt.Printf("found: %s %q\n", url, body)
if err != nil {
fmt.Println(err)
banner<-1
return
}
subBanner := make(chan int, len(urls))
for _, u := range urls {
go Crawl(u, depth-1, fetcher, subBanner);
}
for i:=0; i < len(urls); i++ {
<-subBanner
}
banner<-1
return
}
func main() {
mainBanner := make(chan int,1)
Crawl("http://golang.org/", 4, fetcher, mainBanner)
<-mainBanner
}
type fakeFetcher map[string]*fakeResult
type fakeResult struct {
body string
urls []string
}
func (f *fakeFetcher) Fetch(url string) (string, []string, error) {
if res, ok := (*f)[url]; ok {
return res.body, res.urls, nil
}
return "", nil, fmt.Errorf("not found: %s", url)
}
var fetcher = &fakeFetcher{
"http://golang.org/": &fakeResult{
"The Go Programming Language",
[]string{
"http://golang.org/pkg/",
"http://golang.org/cmd/",
},
},
"http://golang.org/pkg/": &fakeResult{
"Packages",
[]string{
"http://golang.org/",
"http://golang.org/cmd/",
"http://golang.org/pkg/fmt/",
"http://golang.org/pkg/os/",
},
},
"http://golang.org/pkg/fmt/": &fakeResult{
"Package fmt",
[]string{
"http://golang.org/",
"http://golang.org/pkg/",
},
},
"http://golang.org/pkg/os/": &fakeResult{
"Package os",
[]string{
"http://golang.org/",
"http://golang.org/pkg/",
},
},
}
|
