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Forked from kylelemons/gotour-69.go
Created August 20, 2013 09:54
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package main
import (
"os"
"fmt"
)
type Fetcher interface {
// Fetch returns the body of URL and
// a slice of URLs found on that page.
Fetch(url string) (body string, urls []string, err os.Error)
}
// Crawl uses fetcher to recursively crawl
// pages starting with url, to a maximum of depth.
func Crawl(url string, depth int, fetcher Fetcher) {
type moreUrls struct{
depth int
urls []string
}
more := make(chan moreUrls)
getPage := func(url string, depth int) {
body, urls, err := fetcher.Fetch(url)
if err != nil {
fmt.Println(err)
} else {
fmt.Printf("found[%d:%s] %q\n", depth, url, body)
}
more <- moreUrls{depth+1, urls}
}
outstanding := 1
go getPage(url, 0)
visited := map[string]bool{url:true}
for outstanding > 0 {
next := <-more
outstanding--
if next.depth > depth {
continue
}
for _, url := range next.urls {
if _, seen := visited[url]; seen {
continue
}
visited[url] = true
outstanding++
go getPage(url, next.depth)
}
}
}
func main() {
Crawl("http://golang.org/", 4, fetcher)
}
// fakeFetcher is Fetcher that returns canned results.
type fakeFetcher map[string]*fakeResult
type fakeResult struct {
body string
urls []string
}
func (f *fakeFetcher) Fetch(url string) (string, []string, os.Error) {
if res, ok := (*f)[url]; ok {
return res.body, res.urls, nil
}
return "", nil, fmt.Errorf("not found: %s", url)
}
// fetcher is a populated fakeFetcher.
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/",
},
},
}
found[0:http://golang.org/] "The Go Programming Language"
found[1:http://golang.org/pkg/] "Packages"
not found: http://golang.org/cmd/
found[2:http://golang.org/pkg/fmt/] "Package fmt"
found[2:http://golang.org/pkg/os/] "Package os"
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