DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Header

Mercurial (2b8c9e2f1f28)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=4 sw=4 et tw=80:
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsRDFXMLSerializer.h"

#include "nsAtom.h"
#include "nsIOutputStream.h"
#include "nsIRDFService.h"
#include "nsIRDFContainerUtils.h"
#include "nsIServiceManager.h"
#include "nsString.h"
#include "nsTArray.h"
#include "rdf.h"
#include "rdfutil.h"
#include "mozilla/Attributes.h"

#include "rdfIDataSource.h"

int32_t nsRDFXMLSerializer::gRefCnt = 0;
nsIRDFContainerUtils* nsRDFXMLSerializer::gRDFC;
nsIRDFResource* nsRDFXMLSerializer::kRDF_instanceOf;
nsIRDFResource* nsRDFXMLSerializer::kRDF_type;
nsIRDFResource* nsRDFXMLSerializer::kRDF_nextVal;
nsIRDFResource* nsRDFXMLSerializer::kRDF_Bag;
nsIRDFResource* nsRDFXMLSerializer::kRDF_Seq;
nsIRDFResource* nsRDFXMLSerializer::kRDF_Alt;

static const char kRDFDescriptionOpen[]      = "  <RDF:Description";
static const char kIDAttr[]                  = " RDF:ID=\"";
static const char kAboutAttr[]               = " RDF:about=\"";
static const char kRDFDescriptionClose[]     = "  </RDF:Description>\n";
static const char kRDFResource1[] = " RDF:resource=\"";
static const char kRDFResource2[] = "\"/>\n";
static const char kRDFParseTypeInteger[] = " NC:parseType=\"Integer\">";
static const char kRDFParseTypeDate[] = " NC:parseType=\"Date\">";
static const char kRDFUnknown[] = "><!-- unknown node type -->";

nsresult
nsRDFXMLSerializer::Create(nsISupports* aOuter, REFNSIID aIID, void** aResult)
{
    if (aOuter)
        return NS_ERROR_NO_AGGREGATION;

    nsCOMPtr<nsIRDFXMLSerializer> result = new nsRDFXMLSerializer();
    if (! result)
        return NS_ERROR_OUT_OF_MEMORY;
    // The serializer object is here, addref gRefCnt so that the
    // destructor can safely release it.
    gRefCnt++;

    nsresult rv;
    rv = result->QueryInterface(aIID, aResult);

    if (NS_FAILED(rv)) return rv;

    if (gRefCnt == 1) do {
        nsCOMPtr<nsIRDFService> rdf = do_GetService("@mozilla.org/rdf/rdf-service;1", &rv);
        if (NS_FAILED(rv)) break;

        rv = rdf->GetResource(NS_LITERAL_CSTRING(RDF_NAMESPACE_URI "instanceOf"),
                              &kRDF_instanceOf);
        if (NS_FAILED(rv)) break;

        rv = rdf->GetResource(NS_LITERAL_CSTRING(RDF_NAMESPACE_URI "type"),
                              &kRDF_type);
        if (NS_FAILED(rv)) break;

        rv = rdf->GetResource(NS_LITERAL_CSTRING(RDF_NAMESPACE_URI "nextVal"),
                              &kRDF_nextVal);
        if (NS_FAILED(rv)) break;

        rv = rdf->GetResource(NS_LITERAL_CSTRING(RDF_NAMESPACE_URI "Bag"),
                              &kRDF_Bag);
        if (NS_FAILED(rv)) break;

        rv = rdf->GetResource(NS_LITERAL_CSTRING(RDF_NAMESPACE_URI "Seq"),
                              &kRDF_Seq);
        if (NS_FAILED(rv)) break;

        rv = rdf->GetResource(NS_LITERAL_CSTRING(RDF_NAMESPACE_URI "Alt"),
                              &kRDF_Alt);
        if (NS_FAILED(rv)) break;

        rv = CallGetService("@mozilla.org/rdf/container-utils;1", &gRDFC);
        if (NS_FAILED(rv)) break;
    } while (0);

    return rv;
}

nsRDFXMLSerializer::nsRDFXMLSerializer()
{
}

nsRDFXMLSerializer::~nsRDFXMLSerializer()
{
    if (--gRefCnt == 0) {
        NS_IF_RELEASE(kRDF_Bag);
        NS_IF_RELEASE(kRDF_Seq);
        NS_IF_RELEASE(kRDF_Alt);
        NS_IF_RELEASE(kRDF_instanceOf);
        NS_IF_RELEASE(kRDF_type);
        NS_IF_RELEASE(kRDF_nextVal);
        NS_IF_RELEASE(gRDFC);
    }
}

NS_IMPL_ISUPPORTS(nsRDFXMLSerializer, nsIRDFXMLSerializer, nsIRDFXMLSource)

NS_IMETHODIMP
nsRDFXMLSerializer::Init(nsIRDFDataSource* aDataSource)
{
    if (! aDataSource)
        return NS_ERROR_NULL_POINTER;

    mDataSource = aDataSource;
    mDataSource->GetURI(mBaseURLSpec);

    // Add the ``RDF'' prefix, by default.
    RefPtr<nsAtom> prefix;

    prefix = NS_Atomize("RDF");
    AddNameSpace(prefix, NS_LITERAL_STRING("http://www.w3.org/1999/02/22-rdf-syntax-ns#"));

    prefix = NS_Atomize("NC");
    AddNameSpace(prefix, NS_LITERAL_STRING("http://home.netscape.com/NC-rdf#"));

    mPrefixID = 0;

    return NS_OK;
}

NS_IMETHODIMP
nsRDFXMLSerializer::AddNameSpace(nsAtom* aPrefix, const nsAString& aURI)
{
    RefPtr<nsAtom> prefix = aPrefix;
    if (!prefix) {
        // Make up a prefix, we don't want default namespaces, so
        // that we can use QNames for elements and attributes alike.
        prefix = EnsureNewPrefix();
    }
    mNameSpaces.Put(aURI, prefix);
    return NS_OK;
}

static nsresult
rdf_BlockingWrite(nsIOutputStream* stream, const char* buf, uint32_t size)
{
    uint32_t written = 0;
    uint32_t remaining = size;
    while (remaining > 0) {
        nsresult rv;
        uint32_t cb;

        if (NS_FAILED(rv = stream->Write(buf + written, remaining, &cb)))
            return rv;

        written += cb;
        remaining -= cb;
    }
    return NS_OK;
}

static nsresult
rdf_BlockingWrite(nsIOutputStream* stream, const nsACString& s)
{
    return rdf_BlockingWrite(stream, s.BeginReading(), s.Length());
}

static nsresult
rdf_BlockingWrite(nsIOutputStream* stream, const nsAString& s)
{
    NS_ConvertUTF16toUTF8 utf8(s);
    return rdf_BlockingWrite(stream, utf8.get(), utf8.Length());
}

already_AddRefed<nsAtom>
nsRDFXMLSerializer::EnsureNewPrefix()
{
    nsAutoString qname;
    RefPtr<nsAtom> prefix;
    bool isNewPrefix;
    do {
        isNewPrefix = true;
        qname.AssignLiteral("NS");
        qname.AppendInt(++mPrefixID, 10);
        prefix = NS_Atomize(qname);
        nsNameSpaceMap::const_iterator iter = mNameSpaces.first();
        while (iter != mNameSpaces.last() && isNewPrefix) {
            isNewPrefix = (iter->mPrefix != prefix);
            ++iter;
        }
    } while (!isNewPrefix);
    return prefix.forget();
}

// This converts a property resource (like
// "http://www.w3.org/TR/WD-rdf-syntax#Description") into a QName
// ("RDF:Description"), and registers the namespace, if it's made up.

nsresult
nsRDFXMLSerializer::RegisterQName(nsIRDFResource* aResource)
{
    nsAutoCString uri, qname;
    aResource->GetValueUTF8(uri);

    nsNameSpaceMap::const_iterator iter = mNameSpaces.GetNameSpaceOf(uri);
    if (iter != mNameSpaces.last()) {
        NS_ENSURE_TRUE(iter->mPrefix, NS_ERROR_UNEXPECTED);
        iter->mPrefix->ToUTF8String(qname);
        qname.Append(':');
        qname += StringTail(uri, uri.Length() - iter->mURI.Length());
        mQNames.Put(aResource, qname);
        return NS_OK;
    }

    // Okay, so we don't have it in our map. Try to make one up. This
    // is very bogus.
    int32_t i = uri.RFindChar('#'); // first try a '#'
    if (i == -1) {
        i = uri.RFindChar('/');
        if (i == -1) {
            // Okay, just punt and assume there is _no_ namespace on
            // this thing...
            mQNames.Put(aResource, uri);
            return NS_OK;
        }
    }

    // Take whatever is to the right of the '#' or '/' and call it the
    // local name, make up a prefix.
    RefPtr<nsAtom> prefix = EnsureNewPrefix();
    mNameSpaces.Put(StringHead(uri, i+1), prefix);
    prefix->ToUTF8String(qname);
    qname.Append(':');
    qname += StringTail(uri, uri.Length() - (i + 1));

    mQNames.Put(aResource, qname);
    return NS_OK;
}

nsresult
nsRDFXMLSerializer::GetQName(nsIRDFResource* aResource, nsCString& aQName)
{
    return mQNames.Get(aResource, &aQName) ? NS_OK : NS_ERROR_UNEXPECTED;
}

bool
nsRDFXMLSerializer::IsContainerProperty(nsIRDFResource* aProperty)
{
    // Return `true' if the property is an internal property related
    // to being a container.
    if (aProperty == kRDF_instanceOf)
        return true;

    if (aProperty == kRDF_nextVal)
        return true;

    bool isOrdinal = false;
    gRDFC->IsOrdinalProperty(aProperty, &isOrdinal);
    if (isOrdinal)
        return true;

    return false;
}


// convert '&', '<', and '>' into "&amp;", "&lt;", and "&gt", respectively.
static const char amp[] = "&amp;";
static const char lt[] = "&lt;";
static const char gt[] = "&gt;";
static const char quot[] = "&quot;";

static void
rdf_EscapeAmpersandsAndAngleBrackets(nsCString& s)
{
    uint32_t newLength, origLength;
    newLength = origLength = s.Length();

    // Compute the length of the result string.
    const char* start = s.BeginReading();
    const char* end = s.EndReading();
    const char* c = start;
    while (c != end) {
        switch (*c) {
        case '&' :
            newLength += sizeof(amp) - 2;
            break;
        case '<':
        case '>':
            newLength += sizeof(gt) - 2;
            break;
        default:
            break;
        }
        ++c;
    }
    if (newLength == origLength) {
        // nothing to escape
        return;
    }

    // escape the chars from the end back to the front.
    s.SetLength(newLength);

    // Buffer might have changed, get the pointers again
    start = s.BeginReading(); // begin of string
    c = start + origLength - 1; // last char in original string
    char* w = s.EndWriting() - 1; // last char in grown buffer
    while (c >= start) {
        switch (*c) {
        case '&' :
            w -= 4;
            nsCharTraits<char>::copy(w, amp, sizeof(amp) - 1);
            break;
        case '<':
            w -= 3;
            nsCharTraits<char>::copy(w, lt, sizeof(lt) - 1);
            break;
        case '>':
            w -= 3;
            nsCharTraits<char>::copy(w, gt, sizeof(gt) - 1);
            break;
        default:
            *w = *c;
        }
        --w;
        --c;
    }
}

// convert '"' to "&quot;"
static void
rdf_EscapeQuotes(nsCString& s)
{
    int32_t i = 0;
    while ((i = s.FindChar('"', i)) != -1) {
        s.Replace(i, 1, quot, sizeof(quot) - 1);
        i += sizeof(quot) - 2;
    }
}

static void
rdf_EscapeAttributeValue(nsCString& s)
{
    rdf_EscapeAmpersandsAndAngleBrackets(s);
    rdf_EscapeQuotes(s);
}


nsresult
nsRDFXMLSerializer::SerializeInlineAssertion(nsIOutputStream* aStream,
                                             nsIRDFResource* aResource,
                                             nsIRDFResource* aProperty,
                                             nsIRDFLiteral* aValue)
{
    nsresult rv;
    nsCString qname;
    rv = GetQName(aProperty, qname);
    NS_ENSURE_SUCCESS(rv, rv);

    rv = rdf_BlockingWrite(aStream,
                           NS_LITERAL_CSTRING("\n                   "));
    if (NS_FAILED(rv)) return rv;

    const char16_t* value;
    aValue->GetValueConst(&value);
    NS_ConvertUTF16toUTF8 s(value);

    rdf_EscapeAttributeValue(s);

    rv = rdf_BlockingWrite(aStream, qname);
    if (NS_FAILED(rv)) return rv;
    rv = rdf_BlockingWrite(aStream, "=\"", 2);
    if (NS_FAILED(rv)) return rv;
    s.Append('"');
    return rdf_BlockingWrite(aStream, s);
}

nsresult
nsRDFXMLSerializer::SerializeChildAssertion(nsIOutputStream* aStream,
                                            nsIRDFResource* aResource,
                                            nsIRDFResource* aProperty,
                                            nsIRDFNode* aValue)
{
    nsCString qname;
    nsresult rv = GetQName(aProperty, qname);
    NS_ENSURE_SUCCESS(rv, rv);

    rv = rdf_BlockingWrite(aStream, "    <", 5);
    if (NS_FAILED(rv)) return rv;
    rv = rdf_BlockingWrite(aStream, qname);
    if (NS_FAILED(rv)) return rv;

    nsCOMPtr<nsIRDFResource> resource;
    nsCOMPtr<nsIRDFLiteral> literal;
    nsCOMPtr<nsIRDFInt> number;
    nsCOMPtr<nsIRDFDate> date;

    if ((resource = do_QueryInterface(aValue)) != nullptr) {
        nsAutoCString uri;
        resource->GetValueUTF8(uri);

        rdf_MakeRelativeRef(mBaseURLSpec, uri);
        rdf_EscapeAttributeValue(uri);

        rv = rdf_BlockingWrite(aStream, kRDFResource1,
                               sizeof(kRDFResource1) - 1);
        if (NS_FAILED(rv)) return rv;
        rv = rdf_BlockingWrite(aStream, uri);
        if (NS_FAILED(rv)) return rv;
        rv = rdf_BlockingWrite(aStream, kRDFResource2,
                               sizeof(kRDFResource2) - 1);
        if (NS_FAILED(rv)) return rv;

        goto no_close_tag;
    }
    else if ((literal = do_QueryInterface(aValue)) != nullptr) {
        const char16_t *value;
        literal->GetValueConst(&value);
        NS_ConvertUTF16toUTF8 s(value);

        rdf_EscapeAmpersandsAndAngleBrackets(s);

        rv = rdf_BlockingWrite(aStream, ">", 1);
        if (NS_FAILED(rv)) return rv;
        rv = rdf_BlockingWrite(aStream, s);
        if (NS_FAILED(rv)) return rv;
    }
    else if ((number = do_QueryInterface(aValue)) != nullptr) {
        int32_t value;
        number->GetValue(&value);

        nsAutoCString n;
        n.AppendInt(value);

        rv = rdf_BlockingWrite(aStream, kRDFParseTypeInteger,
                               sizeof(kRDFParseTypeInteger) - 1);
        if (NS_FAILED(rv)) return rv;
        rv = rdf_BlockingWrite(aStream, n);
        if (NS_FAILED(rv)) return rv;
    }
    else if ((date = do_QueryInterface(aValue)) != nullptr) {
        PRTime value;
        date->GetValue(&value);

        nsAutoCString s;
        rdf_FormatDate(value, s);

        rv = rdf_BlockingWrite(aStream, kRDFParseTypeDate,
                               sizeof(kRDFParseTypeDate) - 1);
        if (NS_FAILED(rv)) return rv;
        rv = rdf_BlockingWrite(aStream, s);
        if (NS_FAILED(rv)) return rv;
    }
    else {
        // XXX it doesn't support nsIRDFResource _or_ nsIRDFLiteral???
        // We should serialize nsIRDFInt, nsIRDFDate, etc...
        NS_WARNING("unknown RDF node type");

        rv = rdf_BlockingWrite(aStream, kRDFUnknown, sizeof(kRDFUnknown) - 1);
        if (NS_FAILED(rv)) return rv;
    }

    rv = rdf_BlockingWrite(aStream, "</", 2);
    if (NS_FAILED(rv)) return rv;
    rv = rdf_BlockingWrite(aStream, qname);
    if (NS_FAILED(rv)) return rv;
    return rdf_BlockingWrite(aStream, ">\n", 2);

 no_close_tag:
    return NS_OK;
}

nsresult
nsRDFXMLSerializer::SerializeProperty(nsIOutputStream* aStream,
                                      nsIRDFResource* aResource,
                                      nsIRDFResource* aProperty,
                                      bool aInline,
                                      int32_t* aSkipped)
{
    nsresult rv = NS_OK;

    int32_t skipped = 0;

    nsCOMPtr<nsISimpleEnumerator> assertions;
    mDataSource->GetTargets(aResource, aProperty, true, getter_AddRefs(assertions));
    if (! assertions)
        return NS_ERROR_FAILURE;

    // Serializing the assertion inline is ok as long as the property has
    // only one target value, and it is a literal that doesn't include line
    // breaks.
    bool needsChild = false;

    while (1) {
        bool hasMore = false;
        assertions->HasMoreElements(&hasMore);
        if (! hasMore)
            break;

        nsCOMPtr<nsISupports> isupports;
        assertions->GetNext(getter_AddRefs(isupports));
        nsCOMPtr<nsIRDFLiteral> literal = do_QueryInterface(isupports);
        needsChild |= (!literal);

        if (!needsChild) {
            assertions->HasMoreElements(&needsChild);
            if (!needsChild) {
                const char16_t* literalVal = nullptr;
                literal->GetValueConst(&literalVal);
                if (literalVal) {
                    for (; *literalVal; literalVal++) {
                        if (*literalVal == char16_t('\n') ||
                            *literalVal == char16_t('\r')) {
                            needsChild = true;
                            break;
                        }
                    }
                }
            }
        }

        if (aInline && !needsChild) {
            rv = SerializeInlineAssertion(aStream, aResource, aProperty, literal);
        }
        else if (!aInline && needsChild) {
            nsCOMPtr<nsIRDFNode> value = do_QueryInterface(isupports);
            rv = SerializeChildAssertion(aStream, aResource, aProperty, value);
        }
        else {
            ++skipped;
            rv = NS_OK;
        }

        if (NS_FAILED(rv))
            break;
    }

    *aSkipped += skipped;
    return rv;
}


nsresult
nsRDFXMLSerializer::SerializeDescription(nsIOutputStream* aStream,
                                         nsIRDFResource* aResource)
{
    nsresult rv;

    bool isTypedNode = false;
    nsCString typeQName;

    nsCOMPtr<nsIRDFNode> typeNode;
    mDataSource->GetTarget(aResource, kRDF_type, true, getter_AddRefs(typeNode));
    if (typeNode) {
        nsCOMPtr<nsIRDFResource> type = do_QueryInterface(typeNode, &rv);
        if (type) {
            // Try to get a namespace prefix.  If none is available,
            // just treat the description as if it weren't a typed node
            // after all and emit rdf:type as a normal property.  This
            // seems preferable to using a bogus (invented) prefix.
            isTypedNode = NS_SUCCEEDED(GetQName(type, typeQName));
        }
    }

    nsAutoCString uri;
    rv = aResource->GetValueUTF8(uri);
    if (NS_FAILED(rv)) return rv;

    rdf_MakeRelativeRef(mBaseURLSpec, uri);
    rdf_EscapeAttributeValue(uri);

    // Emit an open tag and the subject
    if (isTypedNode) {
        rv = rdf_BlockingWrite(aStream, NS_LITERAL_STRING("  <"));
        if (NS_FAILED(rv)) return rv;
        // Watch out for the default namespace!
        rv = rdf_BlockingWrite(aStream, typeQName);
        if (NS_FAILED(rv)) return rv;
    }
    else {
        rv = rdf_BlockingWrite(aStream, kRDFDescriptionOpen,
                               sizeof(kRDFDescriptionOpen) - 1);
        if (NS_FAILED(rv)) return rv;
    }
    if (uri[0] == char16_t('#')) {
        uri.Cut(0, 1);
        rv = rdf_BlockingWrite(aStream, kIDAttr, sizeof(kIDAttr) - 1);
    }
    else {
        rv = rdf_BlockingWrite(aStream, kAboutAttr, sizeof(kAboutAttr) - 1);
    }
    if (NS_FAILED(rv)) return rv;

    uri.Append('"');
    rv = rdf_BlockingWrite(aStream, uri);
    if (NS_FAILED(rv)) return rv;

    // Any value that's a literal we can write out as an inline
    // attribute on the RDF:Description
    AutoTArray<nsIRDFResource*, 8> visited;
    int32_t skipped = 0;

    nsCOMPtr<nsISimpleEnumerator> arcs;
    mDataSource->ArcLabelsOut(aResource, getter_AddRefs(arcs));

    if (arcs) {
        // Don't re-serialize rdf:type later on
        if (isTypedNode)
            visited.AppendElement(kRDF_type);

        while (1) {
            bool hasMore = false;
            arcs->HasMoreElements(&hasMore);
            if (! hasMore)
                break;

            nsCOMPtr<nsISupports> isupports;
            arcs->GetNext(getter_AddRefs(isupports));

            nsCOMPtr<nsIRDFResource> property = do_QueryInterface(isupports);
            if (! property)
                continue;

            // Ignore properties that pertain to containers; we may be
            // called from SerializeContainer() if the container resource
            // has been assigned non-container properties.
            if (IsContainerProperty(property))
                continue;

            // Only serialize values for the property once.
            if (visited.Contains(property.get()))
                continue;

            visited.AppendElement(property.get());

            SerializeProperty(aStream, aResource, property, true, &skipped);
        }
    }

    if (skipped) {
        // Close the RDF:Description tag.
        rv = rdf_BlockingWrite(aStream, NS_LITERAL_CSTRING(">\n"));
        if (NS_FAILED(rv)) return rv;

        // Now write out resources (which might have their own
        // substructure) as children.
        mDataSource->ArcLabelsOut(aResource, getter_AddRefs(arcs));

        if (arcs) {
            // Forget that we've visited anything
            visited.Clear();
            // ... except for rdf:type
            if (isTypedNode)
                visited.AppendElement(kRDF_type);

            while (1) {
                bool hasMore = false;
                arcs->HasMoreElements(&hasMore);
                if (! hasMore)
                    break;

                nsCOMPtr<nsISupports> isupports;
                arcs->GetNext(getter_AddRefs(isupports));

                nsCOMPtr<nsIRDFResource> property = do_QueryInterface(isupports);
                if (! property)
                    continue;

                // Ignore properties that pertain to containers; we may be
                // called from SerializeContainer() if the container
                // resource has been assigned non-container properties.
                if (IsContainerProperty(property))
                    continue;

                // have we already seen this property?  If so, don't write it
                // out again; serialize property will write each instance.
                if (visited.Contains(property.get()))
                    continue;

                visited.AppendElement(property.get());

                SerializeProperty(aStream, aResource, property, false, &skipped);
            }
        }

        // Emit a proper close-tag.
        if (isTypedNode) {
            rv = rdf_BlockingWrite(aStream,  NS_LITERAL_CSTRING("  </"));
            if (NS_FAILED(rv)) return rv;
            // Watch out for the default namespace!
            rdf_BlockingWrite(aStream, typeQName);
            if (NS_FAILED(rv)) return rv;
            rdf_BlockingWrite(aStream, ">\n", 2);
            if (NS_FAILED(rv)) return rv;
        }
        else {
            rv = rdf_BlockingWrite(aStream, kRDFDescriptionClose,
                                   sizeof(kRDFDescriptionClose) - 1);
            if (NS_FAILED(rv)) return rv;
        }
    }
    else {
        // If we saw _no_ child properties, then we can don't need a
        // close-tag.
        rv = rdf_BlockingWrite(aStream, NS_LITERAL_CSTRING(" />\n"));
        if (NS_FAILED(rv)) return rv;
    }

    return NS_OK;
}

nsresult
nsRDFXMLSerializer::SerializeMember(nsIOutputStream* aStream,
                                      nsIRDFResource* aContainer,
                                      nsIRDFNode* aMember)
{
    // If it's a resource, then output a "<RDF:li RDF:resource=... />"
    // tag, because we'll be dumping the resource separately. (We
    // iterate thru all the resources in the datasource,
    // remember?) Otherwise, output the literal value.

    nsCOMPtr<nsIRDFResource> resource;
    nsCOMPtr<nsIRDFLiteral> literal;
    nsCOMPtr<nsIRDFInt> number;
    nsCOMPtr<nsIRDFDate> date;

static const char kRDFLIOpen[] = "    <RDF:li";
    nsresult rv = rdf_BlockingWrite(aStream, kRDFLIOpen,
                                    sizeof(kRDFLIOpen) - 1);
    if (NS_FAILED(rv)) return rv;

    if ((resource = do_QueryInterface(aMember)) != nullptr) {
        nsAutoCString uri;
        resource->GetValueUTF8(uri);

        rdf_MakeRelativeRef(mBaseURLSpec, uri);
        rdf_EscapeAttributeValue(uri);

        rv = rdf_BlockingWrite(aStream, kRDFResource1,
                               sizeof(kRDFResource1) - 1);
        if (NS_FAILED(rv)) return rv;
        rv = rdf_BlockingWrite(aStream, uri);
        if (NS_FAILED(rv)) return rv;
        rv = rdf_BlockingWrite(aStream, kRDFResource2,
                               sizeof(kRDFResource2) - 1);
        if (NS_FAILED(rv)) return rv;

        goto no_close_tag;
    }
    else if ((literal = do_QueryInterface(aMember)) != nullptr) {
        const char16_t *value;
        literal->GetValueConst(&value);
static const char kRDFLIOpenGT[] = ">";
        // close the '<RDF:LI' before adding the literal
        rv = rdf_BlockingWrite(aStream, kRDFLIOpenGT,
                               sizeof(kRDFLIOpenGT) - 1);
        if (NS_FAILED(rv)) return rv;

        NS_ConvertUTF16toUTF8 s(value);
        rdf_EscapeAmpersandsAndAngleBrackets(s);

        rv = rdf_BlockingWrite(aStream, s);
        if (NS_FAILED(rv)) return rv;
    }
    else if ((number = do_QueryInterface(aMember)) != nullptr) {
        int32_t value;
        number->GetValue(&value);

        nsAutoCString n;
        n.AppendInt(value);

        rv = rdf_BlockingWrite(aStream, kRDFParseTypeInteger,
                               sizeof(kRDFParseTypeInteger) - 1);
        if (NS_FAILED(rv)) return rv;
        rv = rdf_BlockingWrite(aStream, n);
        if (NS_FAILED(rv)) return rv;
    }
    else if ((date = do_QueryInterface(aMember)) != nullptr) {
        PRTime value;
        date->GetValue(&value);

        nsAutoCString s;
        rdf_FormatDate(value, s);

        rv = rdf_BlockingWrite(aStream, kRDFParseTypeDate,
                               sizeof(kRDFParseTypeDate) - 1);
        if (NS_FAILED(rv)) return rv;
        rv = rdf_BlockingWrite(aStream, s);
        if (NS_FAILED(rv)) return rv;
    }
    else {
        // XXX it doesn't support nsIRDFResource _or_ nsIRDFLiteral???
        // We should serialize nsIRDFInt, nsIRDFDate, etc...
        NS_WARNING("unknown RDF node type");

        rv = rdf_BlockingWrite(aStream, kRDFUnknown, sizeof(kRDFUnknown) - 1);
        if (NS_FAILED(rv)) return rv;
    }

    {
static const char kRDFLIClose[] = "</RDF:li>\n";
        rv = rdf_BlockingWrite(aStream, kRDFLIClose, sizeof(kRDFLIClose) - 1);
        if (NS_FAILED(rv)) return rv;
    }

 no_close_tag:
    return NS_OK;
}


nsresult
nsRDFXMLSerializer::SerializeContainer(nsIOutputStream* aStream,
                                         nsIRDFResource* aContainer)
{
    nsresult rv;
    nsAutoCString tag;

    // Decide if it's a sequence, bag, or alternation, and print the
    // appropriate tag-open sequence

    if (IsA(mDataSource, aContainer, kRDF_Bag)) {
        tag.AssignLiteral("RDF:Bag");
    }
    else if (IsA(mDataSource, aContainer, kRDF_Seq)) {
        tag.AssignLiteral("RDF:Seq");
    }
    else if (IsA(mDataSource, aContainer, kRDF_Alt)) {
        tag.AssignLiteral("RDF:Alt");
    }
    else {
        NS_ASSERTION(false, "huh? this is _not_ a container.");
        return NS_ERROR_UNEXPECTED;
    }

    rv = rdf_BlockingWrite(aStream, "  <", 3);
    if (NS_FAILED(rv)) return rv;
    rv = rdf_BlockingWrite(aStream, tag);
    if (NS_FAILED(rv)) return rv;


    // Unfortunately, we always need to print out the identity of the
    // resource, even if was constructed "anonymously". We need to do
    // this because we never really know who else might be referring
    // to it...

    nsAutoCString uri;
    if (NS_SUCCEEDED(aContainer->GetValueUTF8(uri))) {
        rdf_MakeRelativeRef(mBaseURLSpec, uri);

        rdf_EscapeAttributeValue(uri);

        if (uri.First() == '#') {
            // Okay, it's actually identified as an element in the
            // current document, not trying to decorate some absolute
            // URI. We can use the 'ID=' attribute...

            uri.Cut(0, 1); // chop the '#'
            rv = rdf_BlockingWrite(aStream, kIDAttr, sizeof(kIDAttr) - 1);
            if (NS_FAILED(rv)) return rv;
        }
        else {
            // We need to cheat and spit out an illegal 'about=' on
            // the sequence.
            rv = rdf_BlockingWrite(aStream, kAboutAttr,
                                   sizeof(kAboutAttr) - 1);
            if (NS_FAILED(rv)) return rv;
        }

        rv = rdf_BlockingWrite(aStream, uri);
        if (NS_FAILED(rv)) return rv;
        rv = rdf_BlockingWrite(aStream, "\"", 1);
        if (NS_FAILED(rv)) return rv;
    }

    rv = rdf_BlockingWrite(aStream, ">\n", 2);
    if (NS_FAILED(rv)) return rv;

    // First iterate through each of the ordinal elements (the RDF/XML
    // syntax doesn't allow us to place properties on RDF container
    // elements).
    nsCOMPtr<nsISimpleEnumerator> elements;
    rv = NS_NewContainerEnumerator(mDataSource, aContainer, getter_AddRefs(elements));

    if (NS_SUCCEEDED(rv)) {
        while (1) {
            bool hasMore;
            rv = elements->HasMoreElements(&hasMore);
            if (NS_FAILED(rv)) break;

            if (! hasMore)
                break;

            nsCOMPtr<nsISupports> isupports;
            elements->GetNext(getter_AddRefs(isupports));

            nsCOMPtr<nsIRDFNode> element = do_QueryInterface(isupports);
            NS_ASSERTION(element != nullptr, "not an nsIRDFNode");
            if (! element)
                continue;

            SerializeMember(aStream, aContainer, element);
        }
    }

    // close the container tag
    rv = rdf_BlockingWrite(aStream, "  </", 4);
    if (NS_FAILED(rv)) return rv;
    tag.Append(">\n", 2);
    rv = rdf_BlockingWrite(aStream, tag);
    if (NS_FAILED(rv)) return rv;

    // Now, we iterate through _all_ of the arcs, in case someone has
    // applied properties to the bag itself. These'll be placed in a
    // separate RDF:Description element.
    nsCOMPtr<nsISimpleEnumerator> arcs;
    mDataSource->ArcLabelsOut(aContainer, getter_AddRefs(arcs));

    bool wroteDescription = false;
    while (! wroteDescription) {
        bool hasMore = false;
        rv = arcs->HasMoreElements(&hasMore);
        if (NS_FAILED(rv)) break;

        if (! hasMore)
            break;

        nsIRDFResource* property;
        rv = arcs->GetNext((nsISupports**) &property);
        if (NS_FAILED(rv)) break;

        // If it's a membership property, then output a "LI"
        // tag. Otherwise, output a property.
        if (! IsContainerProperty(property)) {
            rv = SerializeDescription(aStream, aContainer);
            wroteDescription = true;
        }

        NS_RELEASE(property);
        if (NS_FAILED(rv))
            break;
    }

    return NS_OK;
}


nsresult
nsRDFXMLSerializer::SerializePrologue(nsIOutputStream* aStream)
{
static const char kXMLVersion[] = "<?xml version=\"1.0\"?>\n";

    nsresult rv;
    rv = rdf_BlockingWrite(aStream, kXMLVersion, sizeof(kXMLVersion) - 1);
    if (NS_FAILED(rv)) return rv;

    // global name space declarations
    rv = rdf_BlockingWrite(aStream, NS_LITERAL_CSTRING("<RDF:RDF "));
    if (NS_FAILED(rv)) return rv;

    nsNameSpaceMap::const_iterator first = mNameSpaces.first();
    nsNameSpaceMap::const_iterator last = mNameSpaces.last();
    for (nsNameSpaceMap::const_iterator entry = first; entry != last; ++entry) {
        if (entry != first) {
            rv = rdf_BlockingWrite(aStream, NS_LITERAL_CSTRING("\n         "));
            if (NS_FAILED(rv)) return rv;
        }
        rv = rdf_BlockingWrite(aStream, NS_LITERAL_CSTRING("xmlns"));
        if (NS_FAILED(rv)) return rv;

        if (entry->mPrefix) {
            rv = rdf_BlockingWrite(aStream, NS_LITERAL_CSTRING(":"));
            if (NS_FAILED(rv)) return rv;
            nsAutoCString prefix;
            entry->mPrefix->ToUTF8String(prefix);
            rv = rdf_BlockingWrite(aStream, prefix);
            if (NS_FAILED(rv)) return rv;
        }

        rv = rdf_BlockingWrite(aStream, NS_LITERAL_CSTRING("=\""));
        if (NS_FAILED(rv)) return rv;
        nsAutoCString uri(entry->mURI);
        rdf_EscapeAttributeValue(uri);
        rv = rdf_BlockingWrite(aStream, uri);
        if (NS_FAILED(rv)) return rv;
        rv = rdf_BlockingWrite(aStream, NS_LITERAL_CSTRING("\""));
        if (NS_FAILED(rv)) return rv;
    }

    return rdf_BlockingWrite(aStream, NS_LITERAL_CSTRING(">\n"));
}


nsresult
nsRDFXMLSerializer::SerializeEpilogue(nsIOutputStream* aStream)
{
    return rdf_BlockingWrite(aStream, NS_LITERAL_CSTRING("</RDF:RDF>\n"));
}

class QNameCollector final : public rdfITripleVisitor {
public:
    NS_DECL_ISUPPORTS
    NS_DECL_RDFITRIPLEVISITOR
    explicit QNameCollector(nsRDFXMLSerializer* aParent)
        : mParent(aParent){}
private:
    ~QNameCollector() {}
    nsRDFXMLSerializer* mParent;
};

NS_IMPL_ISUPPORTS(QNameCollector, rdfITripleVisitor)
nsresult
QNameCollector::Visit(nsIRDFNode* aSubject, nsIRDFResource* aPredicate,
                      nsIRDFNode* aObject, bool aTruthValue)
{
    if (aPredicate == nsRDFXMLSerializer::kRDF_type) {
        // try to get a type QName for aObject, should be a resource
        nsCOMPtr<nsIRDFResource> resType = do_QueryInterface(aObject);
        if (!resType) {
            // ignore error
            return NS_OK;
        }
        if (mParent->mQNames.Get(resType, nullptr)) {
            return NS_OK;
        }
        mParent->RegisterQName(resType);
        return NS_OK;
    }

    if (mParent->mQNames.Get(aPredicate, nullptr)) {
        return NS_OK;
    }
    if (aPredicate == nsRDFXMLSerializer::kRDF_instanceOf ||
        aPredicate == nsRDFXMLSerializer::kRDF_nextVal)
        return NS_OK;
    bool isOrdinal = false;
    nsRDFXMLSerializer::gRDFC->IsOrdinalProperty(aPredicate, &isOrdinal);
    if (isOrdinal)
        return NS_OK;

    mParent->RegisterQName(aPredicate);

    return NS_OK;
}

nsresult
nsRDFXMLSerializer::CollectNamespaces()
{
    // Iterate over all Triples to get namespaces for subject resource types
    // and Predicates and cache all the QNames we want to use.
    nsCOMPtr<rdfITripleVisitor> collector =
        new QNameCollector(this);
    nsCOMPtr<rdfIDataSource> ds = do_QueryInterface(mDataSource); // XXX API
    NS_ENSURE_TRUE(collector && ds, NS_ERROR_FAILURE);
    return ds->VisitAllTriples(collector);
}

//----------------------------------------------------------------------

NS_IMETHODIMP
nsRDFXMLSerializer::Serialize(nsIOutputStream* aStream)
{
    nsresult rv;

    rv = CollectNamespaces();
    if (NS_FAILED(rv)) return rv;

    nsCOMPtr<nsISimpleEnumerator> resources;
    rv = mDataSource->GetAllResources(getter_AddRefs(resources));
    if (NS_FAILED(rv)) return rv;

    rv = SerializePrologue(aStream);
    if (NS_FAILED(rv))
        return rv;

    while (1) {
        bool hasMore = false;
        resources->HasMoreElements(&hasMore);
        if (! hasMore)
            break;

        nsCOMPtr<nsISupports> isupports;
        resources->GetNext(getter_AddRefs(isupports));

        nsCOMPtr<nsIRDFResource> resource = do_QueryInterface(isupports);
        if (! resource)
            continue;

        if (IsA(mDataSource, resource, kRDF_Bag) ||
            IsA(mDataSource, resource, kRDF_Seq) ||
            IsA(mDataSource, resource, kRDF_Alt)) {
            rv = SerializeContainer(aStream, resource);
        }
        else {
            rv = SerializeDescription(aStream, resource);
        }

        if (NS_FAILED(rv))
            break;
    }

    rv = SerializeEpilogue(aStream);

    return rv;
}


bool
nsRDFXMLSerializer::IsA(nsIRDFDataSource* aDataSource, nsIRDFResource* aResource, nsIRDFResource* aType)
{
    nsresult rv;

    bool result;
    rv = aDataSource->HasAssertion(aResource, kRDF_instanceOf, aType, true, &result);
    if (NS_FAILED(rv)) return false;

    return result;
}