/* fetchPage() - takes a _SpiderWorkItemDataWrapper object that will be cast from an object
* (because the work method of a C# ThreadPool work item has to take a single
* object argument, and be static/void), and fetches the _SpiderPageCandidate
* at the index specified by the _index field in the _SpiderWorkItemDataWrapper
* @o - the object argument to be cast into a _SpiderWorkItemDataWrapper
*/
static void fetchPage(object o)
{
// unpack the _SpiderWorkItemDataWrapper object
_SpiderWorkItemDataWrapper wi = (_SpiderWorkItemDataWrapper)o;
// get our spider object and our candidate_page to process
Spider spider_object = wi.getSpiderObject();
_SpiderPageCandidate candidate_page = wi.getCandidatePage();
List <string> pre_pages = new List <string>();
byte[] buf = new byte[8192];
StringBuilder sb = new StringBuilder();
HttpWebResponse resp = null;
try {
HttpWebRequest req = (HttpWebRequest)WebRequest.Create(candidate_page._candidate_getUrl());
//req.Timeout = 1000;
// sleep for the niceness time of this spider object
spider_object.acquireFetchLock();
resp = (HttpWebResponse)req.GetResponse();
}
catch (Exception e) {
candidate_page._candidate_setError();
spider_object.writeStatus("ERROR: " + e.Message);
spider_object.writeStatus("\tpage - " + candidate_page._candidate_getUrl() + "\n\t\treferred to by:");
List <SpiderLink> curr_refs = candidate_page.getReferredByLinks();
for (int i = 0; i < curr_refs.Count; i++)
{
spider_object.writeStatus("\t\t\t" + curr_refs.ElementAt(i).getReferringUrl());
}
}
if (resp != null)
{
// record the final Url after any redirects from this link
string normalized_final_url = spider_object.normalizeUrl(resp.ResponseUri.ToString(), "");
if (normalized_final_url.Count() < 1)
{
candidate_page._candidate_setError();
spider_object.writeStatus("fetchPage(): candidate page " + candidate_page._candidate_getUrl() +
" redirected to an illegal page.");
}
candidate_page.setUrl(normalized_final_url);
spider_object.writeStatus("thread id: " + Thread.CurrentThread.ManagedThreadId +
", fetchPage(): fetched " + candidate_page._candidate_getUrl() +
"\n\tfetchPage(): normalized final url - " + candidate_page.getUrl());
if (!candidate_page._candidate_isError())
{
// read in the content of the page
Stream resp_stream = resp.GetResponseStream();
string temp_string = null;
int count = 0;
do
{
count = resp_stream.Read(buf, 0, buf.Length);
if (count != 0)
{
temp_string = Encoding.ASCII.GetString(buf, 0, count);
sb.Append(temp_string);
}
}while (count > 0);
// add the source into the candidate page object
candidate_page.setPageContent(sb.ToString());
// parse the page for links
HtmlDocument doc = new HtmlDocument();
doc.LoadHtml(sb.ToString());
var linksOnPage = from lnks in doc.DocumentNode.Descendants()
where lnks.Name == "a" &&
lnks.Attributes["href"] != null &&
lnks.InnerText.Trim().Length > 0
select new {
Url = lnks.Attributes["href"].Value,
};
foreach (var link in linksOnPage)
{
pre_pages.Add(link.Url);
}
;
// parse out the distinct links on this page, removing any duplicates, and marking illegal links as such
List <string> distinct_pre_pages = pre_pages.Distinct().ToList();
for (int m = 0; m < distinct_pre_pages.Count; m++)
{
string new_url = distinct_pre_pages.ElementAt(m);
SpiderLink new_link = new SpiderLink(new_url, spider_object.normalizeUrl(new_url, candidate_page.getUrl()),
candidate_page.getUrl());
if (new_link.getNormalizedUrl().Count() < 1)
{
new_link.setIllegalLink();
}
candidate_page.addLinkingToLink(new_link);
}
// set this candidate page as processed
candidate_page._candidate_setDone();
}
}
// mark this thread as done in _thread_status
spider_object.removeThreadStatus();
}
/* spiderProcess() - master spider process:
*
* PART 1: process the candidate pages that the fetchPage() threads
* crawled after PART 2 of last round, generate a list of new
* links for PART 2 (of this round)
* PART 2: make new fetchPage() threads to crawl the new candidate pages
* found in the links from PART 1
*
*/
static void spiderProcess(object o)
{
// cast our argument back to a Spider object
Spider spider_object = (Spider)o;
// loop spiderProcess() until we're done processing candidate pages
do
{
// wait for all the worker threads to be done before starting each round of spiderProcess()
bool ready = false;
do
{
ready = spider_object.checkWorkerThreads();
} while (!ready);
// all of this is dependent on _master_pages and _candidate_pages, need the spider object locked
lock (spider_object) {
// PART 1: process the candidate pages that were crawled by the worker threads created in
// the last round of spiderProcess()
// list of all the links found in the candidate pages we process
List <SpiderLink> new_links_found = new List <SpiderLink>();
// list of all the candidate page URLs that we add to the master results this round
List <string[]> added_candidate_urls = new List <string[]>();
int candidate_page_count = spider_object._candidate_pages.Count;
// iterative for-loop, don't see a better way to do this really (or why we'd want one)...
for (int i = 0; i < candidate_page_count; i++)
{
bool found = false;
_SpiderPageCandidate current_candidate_page = spider_object.getCandidatePageAtIndex(i);
// make sure this candidate page was crawled by fetchPage(), should be true for every
// candidate page that didn't return a 404 or some error, etc.
if (current_candidate_page._candidate_isDone())
{
// see if this candidate page went to the same final URL as a page that we've already
// added in this round of spiderProcess()
int already_added_candidate_index = added_candidate_urls.FindIndex(delegate(string[] s) {
return(s[0] == current_candidate_page.getUrl());
});
// two tests of whether this candidate page *could* already be in the master results: 1) if this page's
// final URL is in the already-added-list (then it's certainly in the master results), or 2) it was an
// alias candidate (i.e. a redirect to a different final url); otherwise we're guaranteed that this
// candidate page is a new page, and therefore not already in the master results, and all of this
// will be skipped
if (already_added_candidate_index > -1 || current_candidate_page._candidate_isAliasCandidate())
{
int real_page_index = -1;
if (already_added_candidate_index > -1)
{
real_page_index = Int32.Parse(added_candidate_urls.ElementAt(already_added_candidate_index)[1]);
}
else
{
real_page_index = spider_object.findPageIndex(current_candidate_page.getUrl());
}
// was it an existing page after all? if so, add any referring links that have been added to this
// candidate page (i.e. links to its alias address that were found in PART 2 of spiderProcess()
// last time), and add this alias URL to the existing page's list of alias URLs (if it was an alias,
// it's also possible that the link that generated this candidate page was found after a link that
// went to an alias of this page, in which case this one could not be an alias)
if (real_page_index > -1)
{
found = true;
SpiderPage real_page = spider_object.getPageAtIndex(real_page_index);
List <SpiderLink> current_candidate_referred_links = current_candidate_page.getReferredByLinks();
// another iterative for-loop, doesn't need to be improved really afaik?
for (int k = 0; k < current_candidate_referred_links.Count; k++)
{
real_page.addReferredByLink(current_candidate_referred_links.ElementAt(k));
}
if (current_candidate_page._candidate_isAliasCandidate())
{
real_page.addAliasUrl(current_candidate_page._candidate_getUrl());
}
}
}
// this candidate page was a real new page- add it to the master results, add its links to the
// new links found this round, and add it to the list of pages added this round
if (!found)
{
SpiderPage new_page = current_candidate_page._candidate_makeNewSpiderPage();
new_links_found.AddRange(new_page.getLinkingToLinks());
spider_object.addNewPage(new_page);
added_candidate_urls.Add(new string[] { new_page.getUrl(), spider_object.getLastPageIndex().ToString() });
}
// this candidate page is done being processed- remove it from the list
spider_object._candidate_pages.RemoveAt(i);
candidate_page_count--;
i--;
}
}
// PART 2: make new candidate pages from the new links that go to pages we haven't seen before,
// create new fetchPage() worker threads to crawl them
List <_SpiderPageCandidate> new_candidate_pages = new List <_SpiderPageCandidate>();
for (int j = 0; j < new_links_found.Count; j++)
{
SpiderLink current_link = new_links_found.ElementAt(j);
if (current_link.isLegalLink())
{
// see if we've made a new candidate page for this link already
int link_index = -1;
// for-loop being used for search, DEFINITELY can be improved with some
// better data-structure etc.
for (int y = 0; y < new_candidate_pages.Count; y++)
{
if (new_candidate_pages.ElementAt(y)._candidate_getUrl() == current_link.getNormalizedUrl())
{
link_index = y;
break;
}
}
// if we have made a new candidate page already, just add a referred-by link to the
// candidate page we already made
if (link_index > -1)
{
new_candidate_pages.ElementAt(link_index).addReferredByLink(current_link);
}
// otherwise, search the master results to see if we need to create a new candidate
// page or not
else
{
int real_page_index = spider_object.findPageIndex(current_link.getNormalizedUrl());
// if this link's URL exists in the master results already, just add a referred-by link
if (real_page_index > -1)
{
SpiderPage real_page = spider_object.getPageAtIndex(real_page_index);
real_page.addReferredByLink(current_link);
}
// otherwise, make a new candidate page from this link
else
{
new_candidate_pages.Add(new _SpiderPageCandidate(current_link));
}
}
}
}
// create a new fetchPage() worker thread for every new candidate page we made
// iterative for-loop, seems fine...
for (int p = 0; p < new_candidate_pages.Count; p++)
{
spider_object._candidate_pages.Add(new_candidate_pages.ElementAt(p));
spider_object.addThreadStatus();
ThreadPool.QueueUserWorkItem(new WaitCallback(fetchPage),
new _SpiderWorkItemDataWrapper(spider_object, spider_object._candidate_pages.Count - 1));
}
}
}
// loop spiderProcess() until there are either no candidate pages in the list or there are only
// error candidate pages left
while (spider_object._candidate_pages.Count > 0 &&
spider_object._candidate_pages.Any(delegate(_SpiderPageCandidate spc) { return(!spc._candidate_isError()); }));
// we're done spidering now, clear our _thread_status (the 0-index in _thread_status is reserved for
// spiderProcess(), worker threads are indices > 0)
spider_object._thread_status.RemoveAt(0);
}