summaryrefslogtreecommitdiff
path: root/src/mongo/bson/bsonobj.h
blob: 0c24e4cd676789be75849f02e16a3dcc53d2ca5e (plain)
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
/**
 *    Copyright (C) 2018-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the Server Side Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */

#pragma once

#include <bitset>
#include <list>
#include <set>
#include <string>
#include <type_traits>
#include <utility>
#include <vector>

#include "mongo/base/data_type.h"
#include "mongo/base/string_data.h"
#include "mongo/base/string_data_comparator_interface.h"
#include "mongo/bson/bson_comparator_interface_base.h"
#include "mongo/bson/bsonelement.h"
#include "mongo/bson/bsontypes.h"
#include "mongo/bson/oid.h"
#include "mongo/bson/timestamp.h"
#include "mongo/bson/util/builder.h"
#include "mongo/platform/atomic_word.h"
#include "mongo/util/bufreader.h"
#include "mongo/util/shared_buffer.h"
#include "mongo/util/string_map.h"

namespace mongo {

class BSONObjBuilder;
class BSONObjStlIterator;
class ExtendedCanonicalV200Generator;
class ExtendedRelaxedV200Generator;
class LegacyStrictGenerator;

/**
   C++ representation of a "BSON" object -- that is, an extended JSON-style
   object in a binary representation.

   See bsonspec.org.

   Note that BSONObj's have a smart pointer capability built in -- so you can
   pass them around by value.  The reference counts used to implement this
   do not use locking, so copying and destroying BSONObj's are not thread-safe
   operations.

 BSON object format:

 code
 <unsigned totalSize> {<byte BSONType><cstring FieldName><Data>}* EOO

 totalSize includes itself.

 Data:
 Bool:      <byte>
 EOO:       nothing follows
 Undefined: nothing follows
 OID:       an OID object
 NumberDouble: <double>
 NumberInt: <int32>
 NumberDecimal: <dec128>
 String:    <unsigned32 strsizewithnull><cstring>
 Date:      <8bytes>
 Regex:     <cstring regex><cstring options>
 Object:    a nested object, leading with its entire size, which terminates with EOO.
 Array:     same as object
 DBRef:     <strlen> <cstring ns> <oid>
 DBRef:     a database reference: basically a collection name plus an Object ID
 BinData:   <int len> <byte subtype> <byte[len] data>
 Code:      a function (not a closure): same format as String.
 Symbol:    a language symbol (say a python symbol).  same format as String.
 Code With Scope: <total size><String><Object>
 \endcode
 */
class BSONObj {
public:
    struct DefaultSizeTrait {
        constexpr static int MaxSize = BSONObjMaxInternalSize;
    };
    struct LargeSizeTrait {
        constexpr static int MaxSize = BufferMaxSize;
    };

    // Declared in bsonobj_comparator_interface.h.
    class ComparatorInterface;

    /**
     * Operator overloads for relops return a DeferredComparison which can subsequently be evaluated
     * by a BSONObj::ComparatorInterface.
     */
    using DeferredComparison = BSONComparatorInterfaceBase<BSONObj>::DeferredComparison;

    /**
     * Set of rules that dictate the behavior of the comparison APIs.
     */
    using ComparisonRules = BSONComparatorInterfaceBase<BSONObj>::ComparisonRules;
    using ComparisonRulesSet = BSONComparatorInterfaceBase<BSONObj>::ComparisonRulesSet;

    static constexpr char kMinBSONLength = 5;
    static const BSONObj kEmptyObject;

    /**
     * Construct an empty BSONObj -- that is, {}.
     */
    BSONObj() {
        // Little endian ordering here, but that is ok regardless as BSON is spec'd to be
        // little endian external to the system. (i.e. the rest of the implementation of
        // bson, not this part, fails to support big endian)
        _objdata = kEmptyObjectPrototype;
    }

    /**
     * Construct a BSONObj from data in the proper format.
     *  Use this constructor when something else owns bsonData's buffer
     */
    template <typename Traits = DefaultSizeTrait>
    explicit BSONObj(const char* bsonData, Traits t = Traits{}) {
        init<Traits>(bsonData);
    }

    explicit BSONObj(ConstSharedBuffer ownedBuffer)
        : _objdata(ownedBuffer.get() ? ownedBuffer.get() : BSONObj().objdata()),
          _ownedBuffer(std::move(ownedBuffer)) {}

    /**
     * Move construct a BSONObj
     */
    BSONObj(BSONObj&& other) noexcept
        : _objdata(std::move(other._objdata)), _ownedBuffer(std::move(other._ownedBuffer)) {
        other._objdata = BSONObj()._objdata;  // To return to an empty state.
        dassert(!other.isOwned());
    }

    // The explicit move constructor above will inhibit generation of the copy ctor, so
    // explicitly request the default implementation.

    /**
     * Copy construct a BSONObj.
     */
    BSONObj(const BSONObj&) = default;

    /**
     * Provide assignment semantics. We use the value taking form so that we can use copy
     * and swap, and consume both lvalue and rvalue references.
     */
    BSONObj& operator=(BSONObj otherCopy) noexcept {
        this->swap(otherCopy);
        return *this;
    }

    /**
     * Swap this BSONObj with 'other'
     */
    void swap(BSONObj& other) noexcept {
        using std::swap;
        swap(_objdata, other._objdata);
        swap(_ownedBuffer, other._ownedBuffer);
    }

    /**
       A BSONObj can use a buffer it "owns" or one it does not.

       OWNED CASE
       If the BSONObj owns the buffer, the buffer can be shared among several BSONObj's (by
       assignment). In this case the buffer is basically implemented as a shared_ptr.
       Since BSONObj's are typically immutable, this works well.

       UNOWNED CASE
       A BSONObj can also point to BSON data in some other data structure it does not "own" or free
       later. For example, in a memory mapped file.  In this case, it is important the original data
       stays in scope for as long as the BSONObj is in use.  If you think the original data may go
       out of scope, call BSONObj::getOwned() to promote your BSONObj to having its own copy.

       On a BSONObj assignment, if the source is unowned, both the source and dest will have unowned
       pointers to the original buffer after the assignment.

       If you are not sure about ownership but need the buffer to last as long as the BSONObj, call
       getOwned().  getOwned() is a no-op if the buffer is already owned.  If not already owned, a
       malloc and memcpy will result.

       Most ways to create BSONObj's create 'owned' variants.  Unowned versions can be created with:
       (1) specifying true for the ifree parameter in the constructor
       (2) calling BSONObjBuilder::done().  Use BSONObjBuilder::obj() to get an owned copy
       (3) retrieving a subobject retrieves an unowned pointer into the parent BSON object

       @return true if this is in owned mode
    */
    bool isOwned() const {
        return bool(_ownedBuffer);
    }

    /**
     * Share ownership with another object.
     *
     * It is the callers responsibility to ensure that the other object is owned and contains the
     * data this BSONObj is viewing. This can happen if this is a subobject or sibling object
     * contained in a larger buffer.
     */
    BSONObj& shareOwnershipWith(ConstSharedBuffer buffer) & {
        invariant(buffer);
        _ownedBuffer = buffer;
        return *this;
    }
    BSONObj& shareOwnershipWith(const BSONObj& other) & {
        shareOwnershipWith(other.sharedBuffer());
        return *this;
    }
    BSONObj&& shareOwnershipWith(ConstSharedBuffer buffer) && {
        return std::move(shareOwnershipWith(buffer));
    }
    BSONObj&& shareOwnershipWith(const BSONObj& other) && {
        return std::move(shareOwnershipWith(other));
    }

    const ConstSharedBuffer& sharedBuffer() const {
        invariant(isOwned());
        return _ownedBuffer;
    }

    ConstSharedBuffer releaseSharedBuffer() {
        invariant(isOwned());
        BSONObj sink = std::move(*this);  // Leave *this in a valid moved-from state.
        return std::move(sink._ownedBuffer);
    }

    /**
     * If the data buffer is under the control of this BSONObj, return it.
     * Else return an owned copy.
     */
    BSONObj getOwned() const;

    /**
     * Returns an owned copy of the given BSON object.
     */
    static BSONObj getOwned(const BSONObj& obj);

    /**
     * @return a new full (and owned) copy of the object.
     */
    BSONObj copy() const;

    /**
     * If the data buffer is not under the control of this BSONObj, allocate
     * a separate copy and make this object a fully owned one.
     */
    void makeOwned();

    /**
     * @return a new full (and owned) redacted copy of the object.
     */
    BSONObj redact(
        bool onlyEncryptedFields = false,
        std::function<std::string(const BSONElement&)> fieldNameRedactor = nullptr) const;

    /**
     * Readable representation of a BSON object in an extended JSON-style notation.
     * This is an abbreviated representation which might be used for logging.
     */
    enum { maxToStringRecursionDepth = 100 };

    std::string toString(bool redactValues = false) const;
    void toString(StringBuilder& s,
                  bool isArray = false,
                  bool full = false,
                  bool redactValues = false,
                  int depth = 0) const;

    /**
     * Properly formatted JSON string.
     * @param pretty if true we try to add some lf's and indentation
     */
    std::string jsonString(JsonStringFormat format = ExtendedCanonicalV2_0_0,
                           int pretty = 0,
                           bool isArray = false,
                           size_t writeLimit = 0,
                           BSONObj* outTruncationResult = nullptr) const;

    BSONObj jsonStringBuffer(JsonStringFormat format,
                             int pretty,
                             bool isArray,
                             fmt::memory_buffer& buffer,
                             size_t writeLimit = 0) const;

    BSONObj jsonStringGenerator(ExtendedCanonicalV200Generator const& generator,
                                int pretty,
                                bool isArray,
                                fmt::memory_buffer& buffer,
                                size_t writeLimit = 0) const;
    BSONObj jsonStringGenerator(ExtendedRelaxedV200Generator const& generator,
                                int pretty,
                                bool isArray,
                                fmt::memory_buffer& buffer,
                                size_t writeLimit = 0) const;
    BSONObj jsonStringGenerator(LegacyStrictGenerator const& generator,
                                int pretty,
                                bool isArray,
                                fmt::memory_buffer& buffer,
                                size_t writeLimit = 0) const;

    /**
     * Add specific field to the end of the object if it did not exist, otherwise replace it
     * preserving original field order. Returns newly built object. Returns copy of this for empty
     * field.
     */
    BSONObj addField(const BSONElement& field) const;

    /**
     * Merges the specified 'fields' from the 'from' object into the current BSON and returns the
     * merged object. If the 'fields' is not specified, all the fields from the 'from' object are
     * merged.
     *
     * Note that if the original object already has a particular field, then the field will be
     * replaced.
     */
    BSONObj addFields(const BSONObj& from,
                      const boost::optional<StringDataSet>& fields = boost::none) const;

    /**
     * Remove specified field and return a new object with the remaining fields.
     * slowish as builds a full new object
     */
    BSONObj removeField(StringData name) const;

    /**
     * Remove specified fields and return a new object with the remaining fields.
     */
    BSONObj removeFields(const std::set<std::string>& fields) const;
    BSONObj removeFields(const StringDataSet& fields) const;

    /**
     * Returns # of top level fields in the object
     * note: iterates to count the fields
     */
    int nFields() const;

    /**
     * Returns a 'Container' populated with the field names of the object.
     */
    template <class Container>
    Container getFieldNames() const;

    /**
     * Get the field of the specified name. eoo() is true on the returned
     * element if not found.
     */
    BSONElement getField(StringData name) const;

    /**
     * Get several fields at once. This is faster than separate getField() calls as the size of
     * elements iterated can then be calculated only once each.
     * @param n number of fieldNames, and number of elements in the fields array
     * @param fields if a field is found its element is stored in its corresponding position in
     *          this array. if not found the array element is unchanged.
     */
    void getFields(unsigned n, const char** fieldNames, BSONElement* fields) const;

    /**
     * Get several fields at once. This is faster than separate getField() calls as the size of
     * elements iterated can then be calculated only once each.
     */
    template <size_t N>
    void getFields(const std::array<StringData, N>& fieldNames,
                   std::array<BSONElement, N>* fields) const;


    /**
     * Get the field of the specified name. eoo() is true on the returned
     * element if not found.
     */
    BSONElement operator[](StringData field) const {
        return getField(field);
    }

    BSONElement operator[](int field) const {
        StringBuilder ss;
        ss << field;
        std::string s = ss.str();
        return getField(s.c_str());
    }

    /**
     * @return true if field exists
     */
    bool hasField(StringData name) const {
        return !getField(name).eoo();
    }
    /**
     * @return true if field exists
     */
    bool hasElement(StringData name) const {
        return hasField(name);
    }

    /**
     * Looks up the element with the given 'name'. If the element is a string,
     * returns it as a StringData. Otherwise returns an empty StringData.
     */
    StringData getStringField(StringData name) const;

    /**
     * @return subobject of the given name
     */
    BSONObj getObjectField(StringData name) const;

    /**
     * @return INT_MIN if not present - does some type conversions
     */
    int getIntField(StringData name) const;

    /**
     * @return false if not present
     * @see BSONElement::trueValue()
     */
    bool getBoolField(StringData name) const;

    /**
     * @param pattern a BSON obj indicating a set of (un-dotted) field
     * names.  Element values are ignored.
     * @return a BSON obj constructed by taking the elements of this obj
     * that correspond to the fields in pattern. Field names of the
     * returned object are replaced with the empty string. If field in
     * pattern is missing, it is omitted from the returned object.
     *
     * Example: if this = {a : 4 , b : 5 , c : 6})
     *   this.extractFieldsUnDotted({a : 1 , c : 1}) -> {"" : 4 , "" : 6 }
     *   this.extractFieldsUnDotted({b : "blah"}) -> {"" : 5}
     */
    BSONObj extractFieldsUndotted(const BSONObj& pattern) const;
    void extractFieldsUndotted(BSONObjBuilder* b, const BSONObj& pattern) const;

    BSONObj filterFieldsUndotted(const BSONObj& filter, bool inFilter) const;
    void filterFieldsUndotted(BSONObjBuilder* b, const BSONObj& filter, bool inFilter) const;

    BSONElement getFieldUsingIndexNames(StringData fieldName, const BSONObj& indexKey) const;

    /**
     * arrays are bson objects with numeric and increasing field names
     * @return true if field names are numeric and increasing
     */
    bool couldBeArray() const;

    /**
     * @return the raw data of the object
     */
    const char* objdata() const {
        return _objdata;
    }

    /**
     * @return total size of the BSON object in bytes
     */
    int objsize() const {
        return ConstDataView(objdata()).read<LittleEndian<int>>();
    }

    /**
     * performs a cursory check on the object's size only.
     */
    template <typename Traits = DefaultSizeTrait>
    bool isValid() const {
        static_assert(Traits::MaxSize > 0 && Traits::MaxSize <= std::numeric_limits<int>::max(),
                      "BSONObj maximum size must be within possible limits");
        int x = objsize();
        return x > 0 && x <= Traits::MaxSize;
    }

    /**
     * Validates that the element is okay to be stored in a collection.
     * Recursively validates children.
     */
    Status storageValidEmbedded() const;

    /**
     * @return true if object is empty -- i.e.,  {}
     */
    bool isEmpty() const {
        return objsize() <= kMinBSONLength;
    }

    /**
     * Whether this BSONObj is the "empty prototype" special case.
     */
    bool isEmptyPrototype() const {
        return _objdata == kEmptyObjectPrototype;
    }

    /**
     * Alternative output format
     */
    std::string hexDump() const;

    //
    // Comparison API.
    //
    // BSONObj instances can be compared either using woCompare() or via operator overloads. Most
    // callers should prefer operator overloads. Note that the operator overloads return a
    // DeferredComparison, which must be subsequently evaluated by a BSONObj::ComparatorInterface.
    // See bsonobj_comparator_interface.h for details.
    //

    /**
     * Compares two BSON Objects using the rules specified by 'rules', 'comparator' for
     * string comparisons, and 'o' for ascending vs. descending ordering.
     *
     * Returns <0 if 'this' is less than 'obj'.
     *         >0 if 'this' is greater than 'obj'.
     *          0 if 'this' is equal to 'obj'.
     */
    int woCompare(const BSONObj& r,
                  const Ordering& o,
                  ComparisonRulesSet rules = ComparisonRules::kConsiderFieldName,
                  const StringData::ComparatorInterface* comparator = nullptr) const;

    int woCompare(const BSONObj& r,
                  const BSONObj& ordering = BSONObj(),
                  ComparisonRulesSet rules = ComparisonRules::kConsiderFieldName,
                  const StringData::ComparatorInterface* comparator = nullptr) const;

    DeferredComparison operator<(const BSONObj& other) const {
        return DeferredComparison(DeferredComparison::Type::kLT, *this, other);
    }

    DeferredComparison operator<=(const BSONObj& other) const {
        return DeferredComparison(DeferredComparison::Type::kLTE, *this, other);
    }

    DeferredComparison operator>(const BSONObj& other) const {
        return DeferredComparison(DeferredComparison::Type::kGT, *this, other);
    }

    DeferredComparison operator>=(const BSONObj& other) const {
        return DeferredComparison(DeferredComparison::Type::kGTE, *this, other);
    }

    DeferredComparison operator==(const BSONObj& other) const {
        return DeferredComparison(DeferredComparison::Type::kEQ, *this, other);
    }

    DeferredComparison operator!=(const BSONObj& other) const {
        return DeferredComparison(DeferredComparison::Type::kNE, *this, other);
    }

    /**
     * Returns true if 'this' is a prefix of otherObj- in other words if otherObj contains the same
     * field names and field vals in the same order as 'this', plus optionally some additional
     * elements.
     *
     * All comparisons between elements are made using 'eltCmp'.
     */
    bool isPrefixOf(const BSONObj& otherObj, const BSONElement::ComparatorInterface& eltCmp) const;

    /**
     * @param otherObj
     * @return returns true if the list of field names in 'this' is a prefix
     * of the list of field names in otherObj.  Similar to 'isPrefixOf',
     * but ignores the field values and only looks at field names.
     */
    bool isFieldNamePrefixOf(const BSONObj& otherObj) const;

    /**
     * This is "shallow equality" -- ints and doubles won't match.  for a
     * deep equality test use woCompare (which is slower).
     */
    bool binaryEqual(const BSONObj& r) const {
        int os = objsize();
        if (os == r.objsize()) {
            return (os == 0 || memcmp(objdata(), r.objdata(), os) == 0);
        }
        return false;
    }

    /**
     * @return first field of the object
     */
    BSONElement firstElement() const {
        return BSONElement(objdata() + 4);
    }

    /**
     * faster than firstElement().fieldName() - for the first element we can easily find the
     * fieldname without computing the element size.
     */
    const char* firstElementFieldName() const {
        const char* p = objdata() + 4;
        return *p == EOO ? "" : p + 1;
    }

    StringData firstElementFieldNameStringData() const {
        return StringData(firstElementFieldName());
    }

    BSONType firstElementType() const {
        const char* p = objdata() + 4;
        return (BSONType)*p;
    }

    /**
     * Get the _id field from the object.  For good performance drivers should
     * assure that _id is the first element of the object; however, correct operation
     * is assured regardless.
     * @return true if found
     */
    bool getObjectID(BSONElement& e) const;

    /**
     * Return a version of this object where top level elements of types
     * that are not part of the bson wire protocol are replaced with
     * std::string identifier equivalents.
     * TODO Support conversion of element types other than min and max.
     */
    BSONObj clientReadable() const;

    /**
     * Return new object with the field names replaced by those in the
     * passed object.
     */
    BSONObj replaceFieldNames(const BSONObj& obj) const;

    static BSONObj stripFieldNames(const BSONObj& obj);

    bool hasFieldNames() const;

    /**
     * add all elements of the object to the specified vector
     */
    void elems(std::vector<BSONElement>&) const;
    /**
     * add all elements of the object to the specified list
     */
    void elems(std::list<BSONElement>&) const;

    friend class BSONObjIterator;
    friend class BSONObjStlIterator;
    typedef BSONObjStlIterator iterator;
    typedef BSONObjStlIterator const_iterator;

    /**
     * These enable range-based for loops over BSONObjs:
     *
     *      for (BSONElement elem : BSON("a" << 1 << "b" << 2)) {
     *          ... // Do something with elem
     *      }
     *
     * You can also loop over a bson object as-if it were a map<StringData, BSONElement>:
     *
     *      for (auto [fieldName, elem] : BSON("a" << 1 << "b" << 2)) {
     *          ... // Do something with fieldName and elem
     *      }
     */
    iterator begin() const;
    iterator end() const;

    void appendSelfToBufBuilder(BufBuilder& b) const {
        verify(objsize());
        b.appendBuf(objdata(), objsize());
    }

    template <typename T>
    bool coerceVector(std::vector<T>* out) const;

    /// members for Sorter
    struct SorterDeserializeSettings {};  // unused
    void serializeForSorter(BufBuilder& buf) const {
        buf.appendBuf(objdata(), objsize());
    }
    static BSONObj deserializeForSorter(BufReader& buf, const SorterDeserializeSettings&) {
        const int size = buf.peek<LittleEndian<int>>();
        const void* ptr = buf.skip(size);
        return BSONObj(static_cast<const char*>(ptr));
    }
    int memUsageForSorter() const {
        // TODO consider ownedness?
        return sizeof(BSONObj) + objsize();
    }

private:
    static constexpr char kEmptyObjectPrototype[] = {/*size*/ kMinBSONLength, 0, 0, 0, /*eoo*/ 0};

    template <typename Generator>
    BSONObj _jsonStringGenerator(const Generator& g,
                                 int pretty,
                                 bool isArray,
                                 fmt::memory_buffer& buffer,
                                 size_t writeLimit) const;

    void _assertInvalid(int maxSize) const;

    template <typename Traits = DefaultSizeTrait>
    void init(const char* data) {
        _objdata = data;
        if (!isValid<Traits>())
            _assertInvalid(Traits::MaxSize);
    }

    void _validateUnownedSize(int size) const;

    const char* _objdata;
    ConstSharedBuffer _ownedBuffer;
};

MONGO_STATIC_ASSERT(std::is_nothrow_move_constructible_v<BSONObj>);
MONGO_STATIC_ASSERT(std::is_nothrow_move_assignable_v<BSONObj>);

std::ostream& operator<<(std::ostream& s, const BSONObj& o);
std::ostream& operator<<(std::ostream& s, const BSONElement& e);

StringBuilder& operator<<(StringBuilder& s, const BSONObj& o);
StringBuilder& operator<<(StringBuilder& s, const BSONElement& e);

inline void swap(BSONObj& l, BSONObj& r) noexcept {
    l.swap(r);
}

struct BSONArray : BSONObj {
    // Don't add anything other than forwarding constructors!!!
    BSONArray() : BSONObj() {}
    explicit BSONArray(const BSONObj& obj) : BSONObj(obj) {}
};

/**
 * An stl-compatible forward iterator over the elements of a BSONObj.
 *
 * The BSONObj must stay in scope for the duration of the iterator's execution.
 */
class BSONObjStlIterator {
public:
    using iterator_category = std::forward_iterator_tag;
    using difference_type = ptrdiff_t;
    using value_type = BSONElement;
    using pointer = const BSONElement*;
    using reference = const BSONElement&;

    /**
     * All default constructed iterators are equal to each other.
     * They are in a dereferencable state, and return an EOO BSONElement.
     * They must not be incremented.
     */
    BSONObjStlIterator() = default;

    /**
     * Constructs an iterator pointing to the first element in obj or EOO if it is empty.
     */
    explicit BSONObjStlIterator(const BSONObj& obj) : BSONObjStlIterator(obj.firstElement()) {}

    /**
     * Returns an iterator pointing to the EOO element in obj.
     */
    static BSONObjStlIterator endOf(const BSONObj& obj) {
        auto eooElem = BSONElement();
        eooElem.data = (obj.objdata() + obj.objsize() - 1);
        dassert(eooElem.eoo());  // This is checked in the BSONObj constructor.
        return BSONObjStlIterator(eooElem);
    }

    /**
     * pre-increment
     */
    BSONObjStlIterator& operator++() {
        dassert(!_cur.eoo());
        *this = BSONObjStlIterator(BSONElement(_cur.rawdata() + _cur.size()));
        return *this;
    }

    /**
     * post-increment
     */
    BSONObjStlIterator operator++(int) {
        BSONObjStlIterator oldPos = *this;
        ++*this;
        return oldPos;
    }

    const BSONElement& operator*() const {
        return _cur;
    }
    const BSONElement* operator->() const {
        return &_cur;
    }

    friend bool operator==(const BSONObjStlIterator& lhs, const BSONObjStlIterator& rhs) {
        return lhs._cur.rawdata() == rhs._cur.rawdata();
    }
    friend bool operator!=(const BSONObjStlIterator& lhs, const BSONObjStlIterator& rhs) {
        return !(lhs == rhs);
    }

private:
    explicit BSONObjStlIterator(BSONElement elem) : _cur(elem) {}

    BSONElement _cur;
};

/**
 * Non-STL iterator for a BSONObj
 *
 * For simple loops over BSONObj, do this instead: for (auto&& elem : obj) { ... }
 *
 * Note each BSONObj ends with an EOO element: so you will get moreWithEOO() on an empty
 * object, although more() will be false and next().eoo() will be true.
 *
 * The BSONObj must stay in scope for the duration of the iterator's execution.
 */
class BSONObjIterator {
public:
    /**
     * Create an iterator for a BSON object.
     */
    explicit BSONObjIterator(const BSONObj& jso) {
        int sz = jso.objsize();
        if (MONGO_unlikely(sz == 0)) {
            _pos = _theend = nullptr;
            return;
        }
        _pos = jso.objdata() + 4;
        _theend = jso.objdata() + sz - 1;
    }

    BSONObjIterator(const char* start, const char* end) {
        _pos = start + 4;
        _theend = end - 1;
    }

    /**
     * Advance '_pos' by currentElement.size(). The element passed in must be equivalent to the
     * current element '_pos' is at.
     */
    void advance(const BSONElement& currentElement) {
        dassert(BSONElement(_pos).size() == currentElement.size());
        _pos += currentElement.size();
    }

    /**
     * Return true if the current element is equal to 'otherElement'.
     * Do *not* use with moreWithEOO() as the function will return false if the current element and
     * 'otherElement' are EOO.
     */
    bool currentElementBinaryEqual(const BSONElement& otherElement) {
        auto sz = otherElement.size();
        return sz <= (_theend - _pos) && memcmp(otherElement.rawdata(), _pos, sz) == 0;
    }

    /**
     * @return true if more elements exist to be enumerated.
     */
    bool more() const {
        return _pos < _theend;
    }

    /**
     * @return true if more elements exist to be enumerated INCLUDING the EOO element which is
     * always at the end.
     */
    bool moreWithEOO() const {
        return _pos <= _theend;
    }

    BSONElement next() {
        verify(_pos <= _theend);
        BSONElement e(_pos);
        _pos += e.size();
        return e;
    }

    /**
     * pre-increment
     */
    BSONObjIterator& operator++() {
        next();
        return *this;
    }

    /**
     * post-increment
     */
    BSONObjIterator operator++(int) {
        BSONObjIterator oldPos = *this;
        next();
        return oldPos;
    }

    BSONElement operator*() {
        verify(_pos <= _theend);
        return BSONElement(_pos);
    }

    bool operator==(const BSONObjIterator& other) {
        dassert(_theend == other._theend);
        return _pos == other._pos;
    }

    bool operator!=(const BSONObjIterator& other) {
        return !(*this == other);
    }

private:
    const char* _pos;
    const char* _theend;
};

/**
 * Base class implementing ordered iteration through BSONElements.
 */
class BSONIteratorSorted {
    BSONIteratorSorted(const BSONIteratorSorted&) = delete;
    BSONIteratorSorted& operator=(const BSONIteratorSorted&) = delete;

public:
    ~BSONIteratorSorted() {
        verify(_fields);
    }

    bool more() {
        return _cur < _nfields;
    }

    BSONElement next() {
        verify(_fields);
        if (_cur < _nfields) {
            const auto& element = _fields[_cur++];
            return BSONElement(element.fieldName.rawData() - 1,  // Include type byte
                               element.fieldName.size() + 1,     // Add null terminator
                               element.totalSize);
        }

        return BSONElement();
    }

protected:
    class ElementFieldCmp;
    BSONIteratorSorted(const BSONObj& o, const ElementFieldCmp& cmp);

private:
    const int _nfields;
    struct Field {
        StringData fieldName;
        int totalSize;
    };
    const std::unique_ptr<Field[]> _fields;
    int _cur;
};

/**
 * Provides iteration of a BSONObj's BSONElements in lexical field order.
 */
class BSONObjIteratorSorted : public BSONIteratorSorted {
public:
    BSONObjIteratorSorted(const BSONObj& object);
};

/**
 * Provides iteration of a BSONArray's BSONElements in numeric field order.
 * The elements of a bson array should always be numerically ordered by field name, but this
 * implementation re-sorts them anyway.
 */
class BSONArrayIteratorSorted : public BSONIteratorSorted {
public:
    BSONArrayIteratorSorted(const BSONArray& array);
};

inline BSONObj::iterator BSONObj::begin() const {
    return BSONObj::iterator(*this);
}
inline BSONObj::iterator BSONObj::end() const {
    return BSONObj::iterator::endOf(*this);
}

/**
 * Similar to BOOST_FOREACH
 *
 * DEPRECATED: Use range-based for loops now.
 */
#define BSONForEach(elemName, obj) for (BSONElement elemName : (obj))

template <>
struct DataType::Handler<BSONObj> {
    static Status load(BSONObj* bson,
                       const char* ptr,
                       size_t length,
                       size_t* advanced,
                       std::ptrdiff_t debug_offset) noexcept try {
        auto temp = BSONObj(ptr);
        auto len = temp.objsize();
        if (bson) {
            *bson = std::move(temp);
        }
        if (advanced) {
            *advanced = len;
        }
        return Status::OK();
    } catch (const DBException& e) {
        return e.toStatus();
    }

    static Status store(const BSONObj& bson,
                        char* ptr,
                        size_t length,
                        size_t* advanced,
                        std::ptrdiff_t debug_offset) noexcept;

    static BSONObj defaultConstruct() {
        return BSONObj();
    }
};

template <size_t N>
inline void BSONObj::getFields(const std::array<StringData, N>& fieldNames,
                               std::array<BSONElement, N>* fields) const {
    std::bitset<N> foundFields;
    for (auto&& el : *this) {
        auto fieldName = el.fieldNameStringData();
        for (std::size_t i = 0; i < N; ++i) {
            if (!foundFields.test(i) && (fieldNames[i] == fieldName)) {
                (*fields)[i] = std::move(el);
                foundFields.set(i);
                break;
            }
        }
        if (foundFields.all())
            break;
    }
}

template <class Container>
Container BSONObj::getFieldNames() const {
    Container fields;
    for (auto&& elem : *this) {
        if (elem.eoo())
            break;
        fields.insert(elem.fieldName());
    }
    return fields;
}

}  // namespace mongo