Bug 813438 - Part 1: Implement NS_SniffContent; r=bzbarsky

netwerk/base/public/nsNetUtil.h

@@ -79,6 +79,8 @@
 #include "nsIPrivateBrowsingChannel.h"
 #include "mozIApplicationClearPrivateDataParams.h"
 #include "nsIOfflineCacheUpdate.h"
+#include "nsIContentSniffer.h"
+#include "nsCategoryCache.h"
 
 #include <limits>
 
@@ -2154,4 +2156,46 @@ NS_GenerateHostPort(const nsCString& host, int32_t port,
     return NS_OK;
 }
 
+/**
+ * Sniff the content type for a given request or a given buffer.
+ *
+ * aSnifferType can be either NS_CONTENT_SNIFFER_CATEGORY or
+ * NS_DATA_SNIFFER_CATEGORY.  The function returns the sniffed content type
+ * in the aSniffedType argument.  This argument will not be modified if the
+ * content type could not be sniffed.
+ */
+inline void
+NS_SniffContent(const char* aSnifferType, nsIRequest* aRequest,
+                const uint8_t* aData, uint32_t aLength,
+                nsACString& aSniffedType)
+{
+  typedef nsCategoryCache<nsIContentSniffer> ContentSnifferCache;
+  extern NS_HIDDEN_(ContentSnifferCache*) gNetSniffers;
+  extern NS_HIDDEN_(ContentSnifferCache*) gDataSniffers;
+  ContentSnifferCache* cache = nullptr;
+  if (!strcmp(aSnifferType, NS_CONTENT_SNIFFER_CATEGORY)) {
+    if (!gNetSniffers) {
+      gNetSniffers = new ContentSnifferCache(NS_CONTENT_SNIFFER_CATEGORY);
+    }
+    cache = gNetSniffers;
+  } else if (!strcmp(aSnifferType, NS_DATA_SNIFFER_CATEGORY)) {
+    if (!gDataSniffers) {
+      gDataSniffers = new ContentSnifferCache(NS_DATA_SNIFFER_CATEGORY);
+    }
+    cache = gDataSniffers;
+  } else {
+    // Invalid content sniffer type was requested
+    MOZ_ASSERT(false);
+    return;
+  }
+
+  const nsCOMArray<nsIContentSniffer>& sniffers = cache->GetEntries();
+  for (int32_t i = 0; i < sniffers.Count(); ++i) {
+    nsresult rv = sniffers[i]->GetMIMETypeFromContent(aRequest, aData, aLength, aSniffedType);
+    if (NS_SUCCEEDED(rv) && !aSniffedType.IsEmpty()) {
+      break;
+    }
+  }
+}
+
 #endif // !nsNetUtil_h__

netwerk/build/nsNetCID.h

@@ -1027,6 +1027,12 @@
  */
 #define NS_CONTENT_SNIFFER_CATEGORY "net-content-sniffers"
 
+/**
+ * Services in this category can sniff content that is not necessarily loaded
+ * from the network, and they won't be told about each load.
+ */
+#define NS_DATA_SNIFFER_CATEGORY "content-sniffing-services"
+
 /**
  * Must implement nsINSSErrorsService.
  */

netwerk/build/nsNetModule.cpp

@@ -34,6 +34,8 @@
 #include "nsDNSPrefetch.h"
 #include "nsAboutProtocolHandler.h"
 #include "nsXULAppAPI.h"
+#include "nsCategoryCache.h"
+#include "nsIContentSniffer.h"
 
 #include "nsNetCID.h"
 
@@ -45,6 +47,10 @@
 #define BUILD_BINHEX_DECODER 1
 #endif
 
+typedef nsCategoryCache<nsIContentSniffer> ContentSnifferCache;
+NS_HIDDEN_(ContentSnifferCache*) gNetSniffers = nullptr;
+NS_HIDDEN_(ContentSnifferCache*) gDataSniffers = nullptr;
+
 ///////////////////////////////////////////////////////////////////////////////
 
 #include "nsIOService.h"
@@ -643,6 +649,11 @@ static void nsNetShutdown()
     // Release the Websocket Admission Manager
     mozilla::net::WebSocketChannel::Shutdown();
 #endif // NECKO_PROTOCOL_websocket
+
+    delete gNetSniffers;
+    gNetSniffers = nullptr;
+    delete gDataSniffers;
+    gDataSniffers = nullptr;
 }
 
 NS_DEFINE_NAMED_CID(NS_IOSERVICE_CID);

xpcom/glue/nsCategoryCache.h

@@ -59,7 +59,7 @@ class NS_COM_GLUE nsCategoryObserver MOZ_FINAL : public nsIObserver {
  * then get the name of the category.
  */
 template<class T>
-class nsCategoryCache : protected nsCategoryListener {
+class nsCategoryCache MOZ_FINAL : protected nsCategoryListener {
   public:
     explicit nsCategoryCache(const char* aCategory);
     ~nsCategoryCache() { if (mObserver) mObserver->ListenerDied(); }