Add reverse URL handler for shortening uber URLs

chrome/browser/chrome_content_browser_client.cc

Index: chrome/browser/chrome_content_browser_client.cc
diff --git a/chrome/browser/chrome_content_browser_client.cc b/chrome/browser/chrome_content_browser_client.cc
index 6cd498bc826fc1d16924eeb66143aea99ae9848f..ccdd477b2d2ab9fc6839fd6038860e33124ec419 100644
--- a/chrome/browser/chrome_content_browser_client.cc
+++ b/chrome/browser/chrome_content_browser_client.cc
@@ -160,6 +160,18 @@ const char* kPredefinedAllowedSocketOrigins[] = {
 
 // Handles rewriting Web UI URLs.
 bool HandleWebUI(GURL* url, content::BrowserContext* browser_context) {
+  url_canon::Replacements<char> replacements;
+  replacements.SetHost("chrome", url_parse::Component(0, 6));

[Alexei Svitkine (slow), 2012/08/07 14:59:33]

Nit: Make a const std::string in the local scope and then use its .length() for
the second arg to Component().

+  std::string host = url->host();

[Alexei Svitkine (slow), 2012/08/07 14:59:33]

Nit: Should be const.

+  replacements.SetPath(host.c_str(), url_parse::Component(0, host.length()));
+  GURL chrome_url = url->ReplaceComponents(replacements);

[Alexei Svitkine (slow), 2012/08/07 14:59:33]

Nit: Maybe extract the above block to a separate function for better
readability.

[Cem Kocagil, 2012/08/07 20:56:22]

Good idea. I went further and added two functions: AddUberHost and
RemoveUberHost.

+
+  // Handle valid "chrome://chrome/foo" URLs so the reverse handler will
+  // be called.
+  if (ChromeWebUIControllerFactory::GetInstance()->UseWebUIForURL(
+          browser_context, chrome_url))
+    return true;

[Alexei Svitkine (slow), 2012/08/07 14:59:33]

Add a comment why this doesn't need to set *url even though it returns true.

[Cem Kocagil, 2012/08/07 20:56:22]

The comment right above that block explains why it returns true (so the reverse
handler will be called).

+
   if (!ChromeWebUIControllerFactory::GetInstance()->UseWebUIForURL(
           browser_context, *url))
     return false;
@@ -190,6 +202,35 @@ bool HandleWebUI(GURL* url, content::BrowserContext* browser_context) {
   return true;
 }
 
+// Reverse URL handler for Web UI. Maps "chrome://chrome/foo/" to
+// "chrome://foo/".
+bool HandleWebUIReverse(GURL* url, content::BrowserContext* browser_context) {
+  if (!url->is_valid() || !url->SchemeIs(chrome::kChromeUIScheme) ||
+      url->host() != chrome::kChromeUIUberHost)
+    return false;
+
+  std::string old_path = url->path();

[Alexei Svitkine (slow), 2012/08/07 14:59:33]

Nit: Should be const.

+
+  int separator = old_path.find('/', 1);

[Alexei Svitkine (slow), 2012/08/07 14:59:33]

Nit: Should be const.

+  std::string new_host;
+  std::string new_path;
+  if (separator == std::string::npos) {
+    new_host = old_path.substr(1);

[Alexei Svitkine (slow), 2012/08/07 14:59:33]

What if old_path is an empty string? (Also, does find('/', 1) work in that case?

[Cem Kocagil, 2012/08/07 20:56:22]

It should work when old_path is empty. I checked the C++ spec for the behavior
of string::find where pos >= length and it says it should return npos.

+  } else {
+    new_host = old_path.substr(1, separator - 1);
+    new_path = old_path.substr(separator);
+  }
+
+  url_canon::Replacements<char> replacements;
+  replacements.ClearHost();

[Alexei Svitkine (slow), 2012/08/07 14:59:33]

Is this needed given that you set it immediately after?

+  replacements.SetHost(new_host.c_str(),
+      url_parse::Component(0, new_host.length()));
+  replacements.SetPath(new_path.c_str(),
+      url_parse::Component(0, new_path.length()));
+  *url = url->ReplaceComponents(replacements);
+  return true;
+}
+
 // Used by the GetPrivilegeRequiredByUrl() and GetProcessPrivilege() functions
 // below.  Extension, and isolated apps require different privileges to be
 // granted to their RenderProcessHosts.  This classification allows us to make
@@ -1539,7 +1580,7 @@ void ChromeContentBrowserClient::BrowserURLHandlerCreated(
                           BrowserURLHandler::null_handler());
   // chrome: & friends.
   handler->AddHandlerPair(&HandleWebUI,
-                          BrowserURLHandler::null_handler());
+                          &HandleWebUIReverse);
 }
 
 void ChromeContentBrowserClient::ClearCache(RenderViewHost* rvh) {