Bug 1574372 - Add API to test stream converters to find out their output type. r=bzbarsky

We don't want to run stream conversion in the parent (since a lot of them require access to the document), so this instead adds a way to find out what their output type will be.

Differential Revision: https://phabricator.services.mozilla.com/D56134

--HG--
extra : moz-landing-system : lando

browser/extensions/pdfjs/content/PdfStreamConverter.jsm

@@ -1008,6 +1008,10 @@ PdfStreamConverter.prototype = {
     this.listener = aListener;
   },
 
+  getConvertedType(aFromType) {
+    return "text/html";
+  },
+
   // nsIStreamListener::onDataAvailable
   onDataAvailable(aRequest, aInputStream, aOffset, aCount) {
     if (!this.dataListener) {

devtools/client/jsonview/converter-child.js

@@ -75,6 +75,9 @@ Converter.prototype = {
   asyncConvertData: function(fromType, toType, listener, ctx) {
     this.listener = listener;
   },
+  getConvertedType: function(fromType) {
+    return "text/html";
+  },
 
   onDataAvailable: function(request, inputStream, offset, count) {
     // Decode and insert data.

modules/libjar/zipwriter/nsDeflateConverter.cpp

@@ -91,6 +91,12 @@ NS_IMETHODIMP nsDeflateConverter::AsyncConvertData(const char* aFromType,
   return rv;
 }
 
+NS_IMETHODIMP
+nsDeflateConverter::GetConvertedType(const nsACString& aFromType,
+                                     nsACString& aToType) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
 NS_IMETHODIMP nsDeflateConverter::OnDataAvailable(nsIRequest* aRequest,
                                                   nsIInputStream* aInputStream,
                                                   uint64_t aOffset,

netwerk/streamconv/converters/mozTXTToHTMLConv.cpp

@@ -1217,6 +1217,12 @@ mozTXTToHTMLConv::AsyncConvertData(const char* aFromType, const char* aToType,
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
+NS_IMETHODIMP
+mozTXTToHTMLConv::GetConvertedType(const nsACString& aFromType,
+                                   nsACString& aToType) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
 NS_IMETHODIMP
 mozTXTToHTMLConv::OnDataAvailable(nsIRequest* request, nsIInputStream* inStr,
                                   uint64_t sourceOffset, uint32_t count) {

netwerk/streamconv/converters/nsFTPDirListingConv.cpp

@@ -70,6 +70,12 @@ nsFTPDirListingConv::AsyncConvertData(const char* aFromType,
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsFTPDirListingConv::GetConvertedType(const nsACString& aFromType,
+                                      nsACString& aToType) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
 // nsIStreamListener implementation
 NS_IMETHODIMP
 nsFTPDirListingConv::OnDataAvailable(nsIRequest* request, nsIInputStream* inStr,

netwerk/streamconv/converters/nsHTTPCompressConv.cpp

@@ -115,6 +115,12 @@ nsHTTPCompressConv::AsyncConvertData(const char* aFromType, const char* aToType,
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsHTTPCompressConv::GetConvertedType(const nsACString& aFromType,
+                                     nsACString& aToType) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
 NS_IMETHODIMP
 nsHTTPCompressConv::OnStartRequest(nsIRequest* request) {
   LOG(("nsHttpCompresssConv %p onstart\n", this));

netwerk/streamconv/converters/nsIndexedToHTML.cpp

@@ -90,6 +90,12 @@ nsIndexedToHTML::AsyncConvertData(const char* aFromType, const char* aToType,
   return Init(aListener);
 }
 
+NS_IMETHODIMP
+nsIndexedToHTML::GetConvertedType(const nsACString& aFromType,
+                                  nsACString& aToType) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
 NS_IMETHODIMP
 nsIndexedToHTML::OnStartRequest(nsIRequest* request) {
   nsCString buffer;

netwerk/streamconv/converters/nsMultiMixedConv.cpp

@@ -406,6 +406,12 @@ nsMultiMixedConv::AsyncConvertData(const char* aFromType, const char* aToType,
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsMultiMixedConv::GetConvertedType(const nsACString& aFromType,
+                                   nsACString& aToType) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
 // nsIRequestObserver implementation
 NS_IMETHODIMP
 nsMultiMixedConv::OnStartRequest(nsIRequest* request) {

netwerk/streamconv/converters/nsUnknownDecoder.cpp

@@ -143,6 +143,12 @@ nsUnknownDecoder::AsyncConvertData(const char* aFromType, const char* aToType,
   return (aListener) ? NS_OK : NS_ERROR_FAILURE;
 }
 
+NS_IMETHODIMP
+nsUnknownDecoder::GetConvertedType(const nsACString& aFromType,
+                                   nsACString& aToType) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
 // ----
 //
 // nsIStreamListener methods...

netwerk/streamconv/nsIStreamConverter.idl

@@ -93,6 +93,15 @@ interface nsIStreamConverter : nsIStreamListener {
                           in string aToType,
                           in nsIStreamListener aListener,
                           in nsISupports aCtxt);
+
+    /**
+     * Returns the content type that the stream listener passed to asyncConvertData will
+     * see on the channel if the conversion is being done from aFromType to * /*.
+     *
+     * @throws if the converter does not support conversion to * /* or if it doesn't know
+     *         the type in advance.
+     */
+    ACString getConvertedType(in ACString aFromType);
 };
 
 %{C++

netwerk/streamconv/nsIStreamConverterService.idl

@@ -34,6 +34,14 @@ interface nsIStreamConverterService : nsISupports {
      */
     boolean canConvert(in string aFromType, in string aToType);
 
+    /**
+     * Returns the content type that will be returned from a converter
+     * created with aFromType and  * /*.
+     * Can fail if no converters support this conversion, or if the
+     * output type isn't known in advance.
+     */
+    ACString convertedType(in ACString aFromType);
+
     /**
      * <b>SYNCHRONOUS VERSION</b>
      * Converts a stream of one type, to a stream of another type.

netwerk/streamconv/nsStreamConverterService.cpp

@@ -352,6 +352,25 @@ nsStreamConverterService::CanConvert(const char* aFromType, const char* aToType,
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsStreamConverterService::ConvertedType(const nsACString& aFromType,
+                                        nsACString& aOutToType) {
+  // first determine whether we can even handle this conversion
+  // build a CONTRACTID
+  nsAutoCString contractID;
+  contractID.AssignLiteral(NS_ISTREAMCONVERTER_KEY "?from=");
+  contractID.Append(aFromType);
+  contractID.AppendLiteral("&to=*/*");
+  const char* cContractID = contractID.get();
+
+  nsresult rv;
+  nsCOMPtr<nsIStreamConverter> converter(do_CreateInstance(cContractID, &rv));
+  if (NS_SUCCEEDED(rv)) {
+    return converter->GetConvertedType(aFromType, aOutToType);
+  }
+  return rv;
+}
+
 NS_IMETHODIMP
 nsStreamConverterService::Convert(nsIInputStream* aFromStream,
                                   const char* aFromType, const char* aToType,