netwerk/streamconv/nsIStreamConverter.idl

   1 /* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #include "nsIThreadRetargetableStreamListener.idl"
   7
   8 interface nsIChannel;
   9 interface nsIInputStream;
  10
  11 /**
  12  * nsIStreamConverter provides an interface to implement when you have code
  13  * that converts data from one type to another.
  14  *
  15  * Suppose you had code that converted plain text into HTML. You could implement
  16  * this interface to allow everyone else to use your conversion logic using a
  17  * standard api.
  18  * <p>
  19  * <b>STREAM CONVERTER USERS</b>
  20  *
  21  * There are currently two ways to use a stream converter:
  22  * <ol>
  23  * <li> <b>SYNCHRONOUS</b> Stream to Stream
  24  *    You can supply the service with a stream of type X
  25  *    and it will convert it to your desired output type and return
  26  *    a converted (blocking) stream to you.</li>
  27  *
  28  * <li> <b>ASYNCHRONOUS</b> nsIStreamListener to nsIStreamListener
  29  *    You can supply data directly to the converter by calling it's
  30  *    nsIStreamListener::OnDataAvailable() method. It will then
  31  *    convert that data from type X to your desired output type and
  32  *    return converted data to you via the nsIStreamListener you passed
  33  *    in by calling its OnDataAvailable() method.</li>
  34  * </ol>
  35  * <p>
  36  *
  37  * <b>STREAM CONVERTER SUPPLIERS</b>
  38  *
  39  * Registering a stream converter:
  40  * Stream converter registration is a two step process. First of all the stream
  41  * converter implementation must register itself with the component manager using
  42  * a contractid in the format below. Second, the stream converter must add the contractid
  43  * to the registry.
  44  *
  45  * Stream converter contractid format (the stream converter root key is defined in this
  46  * file):
  47  *
  48  * <pre>@mozilla.org/streamconv;1?from=FROM_MIME_TYPE&to=TO_MIME_TYPE</pre>
  49  *
  50  * @author Jud Valeski
  51  * @see nsIStreamConverterService
  52  */
  53
  54 [scriptable, uuid(0b6e2c69-5cf5-48b0-9dfd-c95950e2cc7b)]
  55 interface nsIStreamConverter : nsIThreadRetargetableStreamListener {
  56
  57     /**
  58      * <b>SYNCRONOUS VERSION</b>
  59      * Converts a stream of one type, to a stream of another type.
  60      *
  61      * Use this method when you have a stream you want to convert.
  62      *
  63      * @param aFromStream   The stream representing the original/raw data.
  64      * @param aFromType     The MIME type of aFromStream.
  65      * @param aToType       The MIME type of the returned stream.
  66      * @param aCtxt         Either an opaque context, or a converter specific context
  67      *                      (implementation specific).
  68      * @return              The converted stream. NOTE: The returned stream may not
  69      *                      already be converted. An efficient stream converter
  70      *                      implementation will converter data on demand rather than
  71      *                      buffering the converted data until it is used.
  72      */
  73     nsIInputStream convert(in nsIInputStream aFromStream,
  74                            in string aFromType,
  75                            in string aToType,
  76                            in nsISupports aCtxt);
  77
  78     /**
  79      * <b>ASYNCRONOUS VERSION</b>
  80      * Converts data arriving via the converter's nsIStreamListener::OnDataAvailable()
  81      * method from one type to another, pushing the converted data out to the caller
  82      * via aListener::OnDataAvailable().
  83      *
  84      * Use this method when you want to proxy (and convert) nsIStreamListener callbacks
  85      * asynchronously.
  86      *
  87      * @param aFromType     The MIME type of the original/raw data.
  88      * @param aToType       The MIME type of the converted data.
  89      * @param aListener     The listener who receives the converted data.
  90      * @param aCtxt         Either an opaque context, or a converter specific context
  91      *                      (implementation specific).
  92      */
  93     void asyncConvertData(in string aFromType,
  94                           in string aToType,
  95                           in nsIStreamListener aListener,
  96                           in nsISupports aCtxt);
  97
  98     /**
  99      * This is called after the request has installed the stream converter as its listener
 100      * giving the stream converter the option to request retargetting of onDataAvailable.
 101      */
 102     void maybeRetarget(in nsIRequest request);
 103
 104     /**
 105      * Returns the content type that the stream listener passed to asyncConvertData will
 106      * see on the channel if the conversion is being done from aFromType to * /*.
 107      *
 108      * @param aFromType     The type of the content prior to conversion.
 109      * @param aChannel      The channel that we'd like to convert. May be null.
 110      *
 111      * @throws if the converter does not support conversion to * /* or if it doesn't know
 112      *         the type in advance.
 113      */
 114     ACString getConvertedType(in ACString aFromType, in nsIChannel aChannel);
 115 };
 116
 117 %{C++
 118 #define NS_ISTREAMCONVERTER_KEY         "@mozilla.org/streamconv;1"
 119 %}