netwerk/streamconv/src/nsStreamConverterService.cpp

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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   4  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   5  *
   6  * The contents of this file are subject to the Mozilla Public License Version
   7  * 1.1 (the "License"); you may not use this file except in compliance with
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  16  * The Original Code is mozilla.org code.
  17  *
  18  * The Initial Developer of the Original Code is
  19  * Netscape Communications Corporation.
  20  * Portions created by the Initial Developer are Copyright (C) 1998
  21  * the Initial Developer. All Rights Reserved.
  22  *
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  26  * either the GNU General Public License Version 2 or later (the "GPL"), or
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  28  * in which case the provisions of the GPL or the LGPL are applicable instead
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  37  * ***** END LICENSE BLOCK *****
  38  *
  39  *
  40  * This Original Code has been modified by IBM Corporation.
  41  * Modifications made by IBM described herein are
  42  * Copyright (c) International Business Machines
  43  * Corporation, 2000
  44  *
  45  * Modifications to Mozilla code or documentation
  46  * identified per MPL Section 3.3
  47  *
  48  * Date         Modified by     Description of modification
  49  * 03/27/2000   IBM Corp.       Added PR_CALLBACK for Optlink
  50  *                               use in OS2
  51  */
  52
  53 #include "nsStreamConverterService.h"
  54 #include "nsIServiceManager.h"
  55 #include "nsIComponentManager.h"
  56 #include "nsIComponentRegistrar.h"
  57 #include "nsString.h"
  58 #include "nsReadableUtils.h"
  59 #include "nsIAtom.h"
  60 #include "nsDeque.h"
  61 #include "nsIInputStream.h"
  62 #include "nsIOutputStream.h"
  63 #include "nsIStreamConverter.h"
  64 #include "nsICategoryManager.h"
  65 #include "nsXPCOM.h"
  66 #include "nsISupportsPrimitives.h"
  67 #include "nsXPIDLString.h"
  68
  69 ////////////////////////////////////////////////////////////
  70 // nsISupports methods
  71 NS_IMPL_ISUPPORTS1(nsStreamConverterService, nsIStreamConverterService)
  72
  73
  74 ////////////////////////////////////////////////////////////
  75 // nsIStreamConverterService methods
  76
  77 ////////////////////////////////////////////////////////////
  78 // nsStreamConverterService methods
  79 nsStreamConverterService::nsStreamConverterService() : mAdjacencyList(nsnull) {
  80 }
  81
  82 nsStreamConverterService::~nsStreamConverterService() {
  83     NS_ASSERTION(mAdjacencyList, "init wasn't called, or the retval was ignored");
  84     delete mAdjacencyList;
  85 }
  86
  87 // Delete all the entries in the adjacency list
  88 static PRBool DeleteAdjacencyEntry(nsHashKey *aKey, void *aData, void* closure) {
  89     SCTableData *entry = (SCTableData*)aData;
  90     NS_ASSERTION(entry->key && entry->data.edges, "malformed adjacency list entry");
  91     delete entry->key;
  92     delete entry->data.edges;
  93     delete entry;
  94     return PR_TRUE;
  95 }
  96
  97 nsresult
  98 nsStreamConverterService::Init() {
  99     mAdjacencyList = new nsObjectHashtable(nsnull, nsnull,
 100                                            DeleteAdjacencyEntry, nsnull);
 101     if (!mAdjacencyList) return NS_ERROR_OUT_OF_MEMORY;
 102     return NS_OK;
 103 }
 104
 105 // Builds the graph represented as an adjacency list (and built up in
 106 // memory using an nsObjectHashtable and nsISupportsArray combination).
 107 //
 108 // :BuildGraph() consults the category manager for all stream converter
 109 // CONTRACTIDS then fills the adjacency list with edges.
 110 // An edge in this case is comprised of a FROM and TO MIME type combination.
 111 //
 112 // CONTRACTID format:
 113 // @mozilla.org/streamconv;1?from=text/html&to=text/plain
 114 // XXX curently we only handle a single from and to combo, we should repeat the
 115 // XXX registration process for any series of from-to combos.
 116 // XXX can use nsTokenizer for this.
 117 //
 118
 119 nsresult
 120 nsStreamConverterService::BuildGraph() {
 121
 122     nsresult rv;
 123
 124     nsCOMPtr<nsICategoryManager> catmgr(do_GetService(NS_CATEGORYMANAGER_CONTRACTID, &rv));
 125     if (NS_FAILED(rv)) return rv;
 126
 127     nsCOMPtr<nsISimpleEnumerator> entries;
 128     rv = catmgr->EnumerateCategory(NS_ISTREAMCONVERTER_KEY, getter_AddRefs(entries));
 129     if (NS_FAILED(rv)) return rv;
 130
 131     // go through each entry to build the graph
 132     nsCOMPtr<nsISupportsCString> entry;
 133     rv = entries->GetNext(getter_AddRefs(entry));
 134     while (NS_SUCCEEDED(rv)) {
 135
 136         // get the entry string
 137         nsCAutoString entryString;
 138         rv = entry->GetData(entryString);
 139         if (NS_FAILED(rv)) return rv;
 140
 141         // cobble the entry string w/ the converter key to produce a full contractID.
 142         nsCAutoString contractID(NS_ISTREAMCONVERTER_KEY);
 143         contractID.Append(entryString);
 144
 145         // now we've got the CONTRACTID, let's parse it up.
 146         rv = AddAdjacency(contractID.get());
 147         if (NS_FAILED(rv)) return rv;
 148
 149         rv = entries->GetNext(getter_AddRefs(entry));
 150     }
 151
 152     return NS_OK;
 153 }
 154
 155
 156 // XXX currently you can not add the same adjacency (i.e. you can't have multiple
 157 // XXX stream converters registering to handle the same from-to combination. It's
 158 // XXX not programatically prohibited, it's just that results are un-predictable
 159 // XXX right now.
 160 nsresult
 161 nsStreamConverterService::AddAdjacency(const char *aContractID) {
 162     nsresult rv;
 163     // first parse out the FROM and TO MIME-types.
 164
 165     nsCAutoString fromStr, toStr;
 166     rv = ParseFromTo(aContractID, fromStr, toStr);
 167     if (NS_FAILED(rv)) return rv;
 168
 169     // Each MIME-type is a vertex in the graph, so first lets make sure
 170     // each MIME-type is represented as a key in our hashtable.
 171
 172     nsCStringKey fromKey(fromStr);
 173     SCTableData *fromEdges = (SCTableData*)mAdjacencyList->Get(&fromKey);
 174     if (!fromEdges) {
 175         // There is no fromStr vertex, create one.
 176
 177         nsCStringKey *newFromKey = new nsCStringKey(ToNewCString(fromStr), fromStr.Length(), nsCStringKey::OWN);
 178         if (!newFromKey) return NS_ERROR_OUT_OF_MEMORY;
 179
 180         SCTableData *data = new SCTableData(newFromKey);
 181         if (!data) {
 182             delete newFromKey;
 183             return NS_ERROR_OUT_OF_MEMORY;
 184         }
 185
 186         nsCOMArray<nsIAtom>* edgeArray = new nsCOMArray<nsIAtom>;
 187         if (!edgeArray) {
 188             delete newFromKey;
 189             data->key = nsnull;
 190             delete data;
 191             return NS_ERROR_OUT_OF_MEMORY;
 192         }
 193         data->data.edges = edgeArray;
 194
 195         mAdjacencyList->Put(newFromKey, data);
 196         fromEdges = data;
 197     }
 198
 199     nsCStringKey toKey(toStr);
 200     if (!mAdjacencyList->Get(&toKey)) {
 201         // There is no toStr vertex, create one.
 202         nsCStringKey *newToKey = new nsCStringKey(ToNewCString(toStr), toStr.Length(), nsCStringKey::OWN);
 203         if (!newToKey) return NS_ERROR_OUT_OF_MEMORY;
 204
 205         SCTableData *data = new SCTableData(newToKey);
 206         if (!data) {
 207             delete newToKey;
 208             return NS_ERROR_OUT_OF_MEMORY;
 209         }
 210
 211         nsCOMArray<nsIAtom>* edgeArray = new nsCOMArray<nsIAtom>;
 212         if (!edgeArray) {
 213             delete newToKey;
 214             data->key = nsnull;
 215             delete data;
 216             return NS_ERROR_OUT_OF_MEMORY;
 217         }
 218         data->data.edges = edgeArray;
 219         mAdjacencyList->Put(newToKey, data);
 220     }
 221
 222     // Now we know the FROM and TO types are represented as keys in the hashtable.
 223     // Let's "connect" the verticies, making an edge.
 224
 225     nsCOMPtr<nsIAtom> vertex = do_GetAtom(toStr.get());
 226     if (!vertex) return NS_ERROR_OUT_OF_MEMORY;
 227
 228     NS_ASSERTION(fromEdges, "something wrong in adjacency list construction");
 229     if (!fromEdges)
 230         return NS_ERROR_FAILURE;
 231
 232     nsCOMArray<nsIAtom> *adjacencyList = fromEdges->data.edges;
 233     return adjacencyList->AppendObject(vertex) ? NS_OK : NS_ERROR_FAILURE;
 234 }
 235
 236 nsresult
 237 nsStreamConverterService::ParseFromTo(const char *aContractID, nsCString &aFromRes, nsCString &aToRes) {
 238
 239     nsCAutoString ContractIDStr(aContractID);
 240
 241     PRInt32 fromLoc = ContractIDStr.Find("from=");
 242     PRInt32 toLoc   = ContractIDStr.Find("to=");
 243     if (-1 == fromLoc || -1 == toLoc ) return NS_ERROR_FAILURE;
 244
 245     fromLoc = fromLoc + 5;
 246     toLoc = toLoc + 3;
 247
 248     nsCAutoString fromStr, toStr;
 249
 250     ContractIDStr.Mid(fromStr, fromLoc, toLoc - 4 - fromLoc);
 251     ContractIDStr.Mid(toStr, toLoc, ContractIDStr.Length() - toLoc);
 252
 253     aFromRes.Assign(fromStr);
 254     aToRes.Assign(toStr);
 255
 256     return NS_OK;
 257 }
 258
 259 // nsObjectHashtable enumerator functions.
 260
 261 // Initializes the BFS state table.
 262 static PRBool InitBFSTable(nsHashKey *aKey, void *aData, void* closure) {
 263     NS_ASSERTION((SCTableData*)aData, "no data in the table enumeration");
 264
 265     nsHashtable *BFSTable = (nsHashtable*)closure;
 266     if (!BFSTable) return PR_FALSE;
 267
 268     BFSState *state = new BFSState;
 269     if (!state) return PR_FALSE;
 270
 271     state->color = white;
 272     state->distance = -1;
 273     state->predecessor = nsnull;
 274
 275     SCTableData *data = new SCTableData(static_cast<nsCStringKey*>(aKey));
 276     if (!data) {
 277         delete state;
 278         return PR_FALSE;
 279     }
 280     data->data.state = state;
 281
 282     BFSTable->Put(aKey, data);
 283     return PR_TRUE;
 284 }
 285
 286 // cleans up the BFS state table
 287 static PRBool DeleteBFSEntry(nsHashKey *aKey, void *aData, void *closure) {
 288     SCTableData *data = (SCTableData*)aData;
 289     BFSState *state = data->data.state;
 290     delete state;
 291     data->key = nsnull;
 292     delete data;
 293     return PR_TRUE;
 294 }
 295
 296 class CStreamConvDeallocator : public nsDequeFunctor {
 297 public:
 298     virtual void* operator()(void* anObject) {
 299         nsCStringKey *key = (nsCStringKey*)anObject;
 300         delete key;
 301         return 0;
 302     }
 303 };
 304
 305 // walks the graph using a breadth-first-search algorithm which generates a discovered
 306 // verticies tree. This tree is then walked up (from destination vertex, to origin vertex)
 307 // and each link in the chain is added to an nsStringArray. A direct lookup for the given
 308 // CONTRACTID should be made prior to calling this method in an attempt to find a direct
 309 // converter rather than walking the graph.
 310 nsresult
 311 nsStreamConverterService::FindConverter(const char *aContractID, nsCStringArray **aEdgeList) {
 312     nsresult rv;
 313     if (!aEdgeList) return NS_ERROR_NULL_POINTER;
 314     *aEdgeList = nsnull;
 315
 316     // walk the graph in search of the appropriate converter.
 317
 318     PRInt32 vertexCount = mAdjacencyList->Count();
 319     if (0 >= vertexCount) return NS_ERROR_FAILURE;
 320
 321     // Create a corresponding color table for each vertex in the graph.
 322     nsObjectHashtable lBFSTable(nsnull, nsnull, DeleteBFSEntry, nsnull);
 323     mAdjacencyList->Enumerate(InitBFSTable, &lBFSTable);
 324
 325     NS_ASSERTION(lBFSTable.Count() == vertexCount, "strmconv BFS table init problem");
 326
 327     // This is our source vertex; our starting point.
 328     nsCAutoString fromC, toC;
 329     rv = ParseFromTo(aContractID, fromC, toC);
 330     if (NS_FAILED(rv)) return rv;
 331
 332     nsCStringKey *source = new nsCStringKey(fromC.get());
 333     if (!source) return NS_ERROR_OUT_OF_MEMORY;
 334
 335     SCTableData *data = (SCTableData*)lBFSTable.Get(source);
 336     if (!data) {
 337         delete source;
 338         return NS_ERROR_FAILURE;
 339     }
 340
 341     BFSState *state = data->data.state;
 342
 343     state->color = gray;
 344     state->distance = 0;
 345     CStreamConvDeallocator *dtorFunc = new CStreamConvDeallocator();
 346     if (!dtorFunc) {
 347         delete source;
 348         return NS_ERROR_OUT_OF_MEMORY;
 349     }
 350
 351     nsDeque grayQ(dtorFunc);
 352
 353     // Now generate the shortest path tree.
 354     grayQ.Push(source);
 355     while (0 < grayQ.GetSize()) {
 356         nsCStringKey *currentHead = (nsCStringKey*)grayQ.PeekFront();
 357         SCTableData *data2 = (SCTableData*)mAdjacencyList->Get(currentHead);
 358         if (!data2) return NS_ERROR_FAILURE;
 359
 360         nsCOMArray<nsIAtom> *edges = data2->data.edges;
 361         NS_ASSERTION(edges, "something went wrong with BFS strmconv algorithm");
 362         if (!edges) return NS_ERROR_FAILURE;
 363
 364         // Get the state of the current head to calculate the distance of each
 365         // reachable vertex in the loop.
 366         data2 = (SCTableData*)lBFSTable.Get(currentHead);
 367         if (!data2) return NS_ERROR_FAILURE;
 368
 369         BFSState *headVertexState = data2->data.state;
 370         NS_ASSERTION(headVertexState, "problem with the BFS strmconv algorithm");
 371         if (!headVertexState) return NS_ERROR_FAILURE;
 372
 373         PRInt32 edgeCount = edges->Count();
 374
 375         for (PRInt32 i = 0; i < edgeCount; i++) {
 376             nsIAtom* curVertexAtom = edges->ObjectAt(i);
 377             nsAutoString curVertexStr;
 378             curVertexAtom->ToString(curVertexStr);
 379             nsCStringKey *curVertex = new nsCStringKey(ToNewCString(curVertexStr),
 380                                         curVertexStr.Length(), nsCStringKey::OWN);
 381             if (!curVertex) return NS_ERROR_OUT_OF_MEMORY;
 382
 383             SCTableData *data3 = (SCTableData*)lBFSTable.Get(curVertex);
 384             if (!data3) {
 385                 delete curVertex;
 386                 return NS_ERROR_FAILURE;
 387             }
 388             BFSState *curVertexState = data3->data.state;
 389             NS_ASSERTION(curVertexState, "something went wrong with the BFS strmconv algorithm");
 390             if (!curVertexState) return NS_ERROR_FAILURE;
 391
 392             if (white == curVertexState->color) {
 393                 curVertexState->color = gray;
 394                 curVertexState->distance = headVertexState->distance + 1;
 395                 curVertexState->predecessor = (nsCStringKey*)currentHead->Clone();
 396                 if (!curVertexState->predecessor) {
 397                     delete curVertex;
 398                     return NS_ERROR_OUT_OF_MEMORY;
 399                 }
 400                 grayQ.Push(curVertex);
 401             } else {
 402                 delete curVertex; // if this vertex has already been discovered, we don't want
 403                                   // to leak it. (non-discovered vertex's get cleaned up when
 404                                   // they're popped).
 405             }
 406         }
 407         headVertexState->color = black;
 408         nsCStringKey *cur = (nsCStringKey*)grayQ.PopFront();
 409         delete cur;
 410         cur = nsnull;
 411     }
 412     // The shortest path (if any) has been generated and is represetned by the chain of
 413     // BFSState->predecessor keys. Start at the bottom and work our way up.
 414
 415     // first parse out the FROM and TO MIME-types being registered.
 416
 417     nsCAutoString fromStr, toStr;
 418     rv = ParseFromTo(aContractID, fromStr, toStr);
 419     if (NS_FAILED(rv)) return rv;
 420
 421     // get the root CONTRACTID
 422     nsCAutoString ContractIDPrefix(NS_ISTREAMCONVERTER_KEY);
 423     nsCStringArray *shortestPath = new nsCStringArray();
 424     if (!shortestPath) return NS_ERROR_OUT_OF_MEMORY;
 425
 426     nsCStringKey toMIMEType(toStr);
 427     data = (SCTableData*)lBFSTable.Get(&toMIMEType);
 428     if (!data) {
 429         // If this vertex isn't in the BFSTable, then no-one has registered for it,
 430         // therefore we can't do the conversion.
 431         delete shortestPath;
 432         return NS_ERROR_FAILURE;
 433     }
 434
 435     while (data) {
 436         BFSState *curState = data->data.state;
 437
 438         nsCStringKey *key = data->key;
 439
 440         if (fromStr.Equals(key->GetString())) {
 441             // found it. We're done here.
 442             *aEdgeList = shortestPath;
 443             return NS_OK;
 444         }
 445
 446         // reconstruct the CONTRACTID.
 447         // Get the predecessor.
 448         if (!curState->predecessor) break; // no predecessor
 449         SCTableData *predecessorData = (SCTableData*)lBFSTable.Get(curState->predecessor);
 450
 451         if (!predecessorData) break; // no predecessor, chain doesn't exist.
 452
 453         // build out the CONTRACTID.
 454         nsCAutoString newContractID(ContractIDPrefix);
 455         newContractID.AppendLiteral("?from=");
 456
 457         nsCStringKey *predecessorKey = predecessorData->key;
 458         newContractID.Append(predecessorKey->GetString());
 459
 460         newContractID.AppendLiteral("&to=");
 461         newContractID.Append(key->GetString());
 462
 463         // Add this CONTRACTID to the chain.
 464         rv = shortestPath->AppendCString(newContractID) ? NS_OK : NS_ERROR_FAILURE;  // XXX this method incorrectly returns a bool
 465         NS_ASSERTION(NS_SUCCEEDED(rv), "AppendElement failed");
 466
 467         // move up the tree.
 468         data = predecessorData;
 469     }
 470     delete shortestPath;
 471     return NS_ERROR_FAILURE; // couldn't find a stream converter or chain.
 472 }
 473
 474
 475 /////////////////////////////////////////////////////
 476 // nsIStreamConverterService methods
 477 NS_IMETHODIMP
 478 nsStreamConverterService::CanConvert(const char* aFromType,
 479                                      const char* aToType,
 480                                      PRBool* _retval) {
 481     nsCOMPtr<nsIComponentRegistrar> reg;
 482     nsresult rv = NS_GetComponentRegistrar(getter_AddRefs(reg));
 483     if (NS_FAILED(rv))
 484         return rv;
 485
 486     nsCAutoString contractID;
 487     contractID.AssignLiteral(NS_ISTREAMCONVERTER_KEY "?from=");
 488     contractID.Append(aFromType);
 489     contractID.AppendLiteral("&to=");
 490     contractID.Append(aToType);
 491
 492     // See if we have a direct match
 493     rv = reg->IsContractIDRegistered(contractID.get(), _retval);
 494     if (NS_FAILED(rv))
 495         return rv;
 496     if (*_retval)
 497         return NS_OK;
 498
 499     // Otherwise try the graph.
 500     rv = BuildGraph();
 501     if (NS_FAILED(rv))
 502         return rv;
 503
 504     nsCStringArray *converterChain = nsnull;
 505     rv = FindConverter(contractID.get(), &converterChain);
 506     *_retval = NS_SUCCEEDED(rv);
 507
 508     delete converterChain;
 509     return NS_OK;
 510 }
 511
 512 NS_IMETHODIMP
 513 nsStreamConverterService::Convert(nsIInputStream *aFromStream,
 514                                   const char *aFromType,
 515                                   const char *aToType,
 516                                   nsISupports *aContext,
 517                                   nsIInputStream **_retval) {
 518     if (!aFromStream || !aFromType || !aToType || !_retval) return NS_ERROR_NULL_POINTER;
 519     nsresult rv;
 520
 521     // first determine whether we can even handle this conversion
 522     // build a CONTRACTID
 523     nsCAutoString contractID;
 524     contractID.AssignLiteral(NS_ISTREAMCONVERTER_KEY "?from=");
 525     contractID.Append(aFromType);
 526     contractID.AppendLiteral("&to=");
 527     contractID.Append(aToType);
 528     const char *cContractID = contractID.get();
 529
 530     nsCOMPtr<nsIStreamConverter> converter(do_CreateInstance(cContractID, &rv));
 531     if (NS_FAILED(rv)) {
 532         // couldn't go direct, let's try walking the graph of converters.
 533         rv = BuildGraph();
 534         if (NS_FAILED(rv)) return rv;
 535
 536         nsCStringArray *converterChain = nsnull;
 537
 538         rv = FindConverter(cContractID, &converterChain);
 539         if (NS_FAILED(rv)) {
 540             // can't make this conversion.
 541             // XXX should have a more descriptive error code.
 542             return NS_ERROR_FAILURE;
 543         }
 544
 545         PRInt32 edgeCount = converterChain->Count();
 546         NS_ASSERTION(edgeCount > 0, "findConverter should have failed");
 547
 548
 549         // convert the stream using each edge of the graph as a step.
 550         // this is our stream conversion traversal.
 551         nsCOMPtr<nsIInputStream> dataToConvert = aFromStream;
 552         nsCOMPtr<nsIInputStream> convertedData;
 553
 554         for (PRInt32 i = edgeCount-1; i >= 0; i--) {
 555             nsCString *contractIDStr = converterChain->CStringAt(i);
 556             if (!contractIDStr) {
 557                 delete converterChain;
 558                 return NS_ERROR_FAILURE;
 559             }
 560             const char *lContractID = contractIDStr->get();
 561
 562             converter = do_CreateInstance(lContractID, &rv);
 563
 564             if (NS_FAILED(rv)) {
 565                 delete converterChain;
 566                 return rv;
 567             }
 568
 569             nsCAutoString fromStr, toStr;
 570             rv = ParseFromTo(lContractID, fromStr, toStr);
 571             if (NS_FAILED(rv)) {
 572                 delete converterChain;
 573                 return rv;
 574             }
 575
 576             rv = converter->Convert(dataToConvert, fromStr.get(), toStr.get(), aContext, getter_AddRefs(convertedData));
 577             dataToConvert = convertedData;
 578             if (NS_FAILED(rv)) {
 579                 delete converterChain;
 580                 return rv;
 581             }
 582         }
 583
 584         delete converterChain;
 585         *_retval = convertedData;
 586         NS_ADDREF(*_retval);
 587
 588     } else {
 589         // we're going direct.
 590         rv = converter->Convert(aFromStream, aFromType, aToType, aContext, _retval);
 591     }
 592
 593     return rv;
 594 }
 595
 596
 597 NS_IMETHODIMP
 598 nsStreamConverterService::AsyncConvertData(const char *aFromType,
 599                                            const char *aToType,
 600                                            nsIStreamListener *aListener,
 601                                            nsISupports *aContext,
 602                                            nsIStreamListener **_retval) {
 603     if (!aFromType || !aToType || !aListener || !_retval) return NS_ERROR_NULL_POINTER;
 604
 605     nsresult rv;
 606
 607     // first determine whether we can even handle this conversion
 608     // build a CONTRACTID
 609     nsCAutoString contractID;
 610     contractID.AssignLiteral(NS_ISTREAMCONVERTER_KEY "?from=");
 611     contractID.Append(aFromType);
 612     contractID.AppendLiteral("&to=");
 613     contractID.Append(aToType);
 614     const char *cContractID = contractID.get();
 615
 616     nsCOMPtr<nsIStreamConverter> listener(do_CreateInstance(cContractID, &rv));
 617     if (NS_FAILED(rv)) {
 618         // couldn't go direct, let's try walking the graph of converters.
 619         rv = BuildGraph();
 620         if (NS_FAILED(rv)) return rv;
 621
 622         nsCStringArray *converterChain = nsnull;
 623
 624         rv = FindConverter(cContractID, &converterChain);
 625         if (NS_FAILED(rv)) {
 626             // can't make this conversion.
 627             // XXX should have a more descriptive error code.
 628             return NS_ERROR_FAILURE;
 629         }
 630
 631         // aListener is the listener that wants the final, converted, data.
 632         // we initialize finalListener w/ aListener so it gets put at the
 633         // tail end of the chain, which in the loop below, means the *first*
 634         // converter created.
 635         nsCOMPtr<nsIStreamListener> finalListener = aListener;
 636
 637         // convert the stream using each edge of the graph as a step.
 638         // this is our stream conversion traversal.
 639         PRInt32 edgeCount = converterChain->Count();
 640         NS_ASSERTION(edgeCount > 0, "findConverter should have failed");
 641         for (int i = 0; i < edgeCount; i++) {
 642             nsCString *contractIDStr = converterChain->CStringAt(i);
 643             if (!contractIDStr) {
 644                 delete converterChain;
 645                 return NS_ERROR_FAILURE;
 646             }
 647             const char *lContractID = contractIDStr->get();
 648
 649             // create the converter for this from/to pair
 650             nsCOMPtr<nsIStreamConverter> converter(do_CreateInstance(lContractID));
 651             NS_ASSERTION(converter, "graph construction problem, built a contractid that wasn't registered");
 652
 653             nsCAutoString fromStr, toStr;
 654             rv = ParseFromTo(lContractID, fromStr, toStr);
 655             if (NS_FAILED(rv)) {
 656                 delete converterChain;
 657                 return rv;
 658             }
 659
 660             // connect the converter w/ the listener that should get the converted data.
 661             rv = converter->AsyncConvertData(fromStr.get(), toStr.get(), finalListener, aContext);
 662             if (NS_FAILED(rv)) {
 663                 delete converterChain;
 664                 return rv;
 665             }
 666
 667             nsCOMPtr<nsIStreamListener> chainListener(do_QueryInterface(converter, &rv));
 668             if (NS_FAILED(rv)) {
 669                 delete converterChain;
 670                 return rv;
 671             }
 672
 673             // the last iteration of this loop will result in finalListener
 674             // pointing to the converter that "starts" the conversion chain.
 675             // this converter's "from" type is the original "from" type. Prior
 676             // to the last iteration, finalListener will continuously be wedged
 677             // into the next listener in the chain, then be updated.
 678             finalListener = chainListener;
 679         }
 680         delete converterChain;
 681         // return the first listener in the chain.
 682         *_retval = finalListener;
 683         NS_ADDREF(*_retval);
 684
 685     } else {
 686         // we're going direct.
 687         *_retval = listener;
 688         NS_ADDREF(*_retval);
 689
 690         rv = listener->AsyncConvertData(aFromType, aToType, aListener, aContext);
 691     }
 692
 693     return rv;
 694
 695 }
 696
 697 nsresult
 698 NS_NewStreamConv(nsStreamConverterService** aStreamConv)
 699 {
 700     NS_PRECONDITION(aStreamConv != nsnull, "null ptr");
 701     if (!aStreamConv) return NS_ERROR_NULL_POINTER;
 702
 703     *aStreamConv = new nsStreamConverterService();
 704     if (!*aStreamConv) return NS_ERROR_OUT_OF_MEMORY;
 705
 706     NS_ADDREF(*aStreamConv);
 707     nsresult rv = (*aStreamConv)->Init();
 708     if (NS_FAILED(rv))
 709         NS_RELEASE(*aStreamConv);
 710
 711     return rv;
 712 }