summaryrefslogtreecommitdiff
path: root/src/t_list.c
blob: 232cb5c52aa2c8d5b971a68c7c282be5ce6a5264 (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
/*
 * Copyright (c) 2009-2012, Salvatore Sanfilippo <antirez at gmail dot com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   * Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *   * Neither the name of Redis nor the names of its contributors may be used
 *     to endorse or promote products derived from this software without
 *     specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "redis.h"

/*-----------------------------------------------------------------------------
 * List API
 *----------------------------------------------------------------------------*/

/* The function pushes an element to the specified list object 'subject',
 * at head or tail position as specified by 'where'.
 *
 * There is no need for the caller to increment the refcount of 'value' as
 * the function takes care of it if needed. */
void listTypePush(robj *subject, robj *value, int where) {
    if (subject->encoding == REDIS_ENCODING_QUICKLIST) {
        int pos = (where == REDIS_HEAD) ? QUICKLIST_HEAD : QUICKLIST_TAIL;
        value = getDecodedObject(value);
        size_t len = sdslen(value->ptr);
        quicklistPush(subject->ptr, value->ptr, len, pos);
        decrRefCount(value);
    } else {
        redisPanic("Unknown list encoding");
    }
}

void *listPopSaver(unsigned char *data, unsigned int sz) {
    return createStringObject((char*)data,sz);
}

robj *listTypePop(robj *subject, int where) {
    long long vlong;
    robj *value = NULL;

    int ql_where = where == REDIS_HEAD ? QUICKLIST_HEAD : QUICKLIST_TAIL;
    if (subject->encoding == REDIS_ENCODING_QUICKLIST) {
        if (quicklistPopCustom(subject->ptr, ql_where, (unsigned char **)&value,
                               NULL, &vlong, listPopSaver)) {
            if (!value)
                value = createStringObjectFromLongLong(vlong);
        }
    } else {
        redisPanic("Unknown list encoding");
    }
    return value;
}

unsigned long listTypeLength(robj *subject) {
    if (subject->encoding == REDIS_ENCODING_QUICKLIST) {
        return quicklistCount(subject->ptr);
    } else {
        redisPanic("Unknown list encoding");
    }
}

/* Initialize an iterator at the specified index. */
listTypeIterator *listTypeInitIterator(robj *subject, long index,
                                       unsigned char direction) {
    listTypeIterator *li = zmalloc(sizeof(listTypeIterator));
    li->subject = subject;
    li->encoding = subject->encoding;
    li->direction = direction;
    li->iter = NULL;
    /* REDIS_HEAD means start at TAIL and move *towards* head.
     * REDIS_TAIL means start at HEAD and move *towards tail. */
    int iter_direction =
        direction == REDIS_HEAD ? AL_START_TAIL : AL_START_HEAD;
    if (li->encoding == REDIS_ENCODING_QUICKLIST) {
        li->iter = quicklistGetIteratorAtIdx(li->subject->ptr,
                                             iter_direction, index);
    } else {
        redisPanic("Unknown list encoding");
    }
    return li;
}

/* Clean up the iterator. */
void listTypeReleaseIterator(listTypeIterator *li) {
    zfree(li->iter);
    zfree(li);
}

/* Stores pointer to current the entry in the provided entry structure
 * and advances the position of the iterator. Returns 1 when the current
 * entry is in fact an entry, 0 otherwise. */
int listTypeNext(listTypeIterator *li, listTypeEntry *entry) {
    /* Protect from converting when iterating */
    redisAssert(li->subject->encoding == li->encoding);

    entry->li = li;
    if (li->encoding == REDIS_ENCODING_QUICKLIST) {
        return quicklistNext(li->iter, &entry->entry);
    } else {
        redisPanic("Unknown list encoding");
    }
    return 0;
}

/* Return entry or NULL at the current position of the iterator. */
robj *listTypeGet(listTypeEntry *entry) {
    robj *value = NULL;
    if (entry->li->encoding == REDIS_ENCODING_QUICKLIST) {
        if (entry->entry.value) {
            value = createStringObject((char *)entry->entry.value,
                                       entry->entry.sz);
        } else {
            value = createStringObjectFromLongLong(entry->entry.longval);
        }
    } else {
        redisPanic("Unknown list encoding");
    }
    return value;
}

void listTypeInsert(listTypeEntry *entry, robj *value, int where) {
    if (entry->li->encoding == REDIS_ENCODING_QUICKLIST) {
        value = getDecodedObject(value);
        sds str = value->ptr;
        size_t len = sdslen(str);
        if (where == REDIS_TAIL) {
            quicklistInsertAfter((quicklist *)entry->entry.quicklist,
                                 &entry->entry, str, len);
        } else if (where == REDIS_HEAD) {
            quicklistInsertBefore((quicklist *)entry->entry.quicklist,
                                  &entry->entry, str, len);
        }
        decrRefCount(value);
    } else {
        redisPanic("Unknown list encoding");
    }
}

/* Compare the given object with the entry at the current position. */
int listTypeEqual(listTypeEntry *entry, robj *o) {
    if (entry->li->encoding == REDIS_ENCODING_QUICKLIST) {
        redisAssertWithInfo(NULL,o,sdsEncodedObject(o));
        return quicklistCompare(entry->entry.zi,o->ptr,sdslen(o->ptr));
    } else {
        redisPanic("Unknown list encoding");
    }
}

/* Delete the element pointed to. */
void listTypeDelete(listTypeIterator *iter, listTypeEntry *entry) {
    if (entry->li->encoding == REDIS_ENCODING_QUICKLIST) {
        quicklistDelEntry(iter->iter, &entry->entry);
    } else {
        redisPanic("Unknown list encoding");
    }
}

/* Create a quicklist from a single ziplist */
void listTypeConvert(robj *subject, int enc) {
    redisAssertWithInfo(NULL,subject,subject->type==REDIS_LIST);
    redisAssertWithInfo(NULL,subject,subject->encoding==REDIS_ENCODING_ZIPLIST);

    if (enc == REDIS_ENCODING_QUICKLIST) {
        size_t zlen = server.list_max_ziplist_size;
        int depth = server.list_compress_depth;
        subject->ptr = quicklistCreateFromZiplist(zlen, depth, subject->ptr);
        subject->encoding = REDIS_ENCODING_QUICKLIST;
    } else {
        redisPanic("Unsupported list conversion");
    }
}

/*-----------------------------------------------------------------------------
 * List Commands
 *----------------------------------------------------------------------------*/

void pushGenericCommand(redisClient *c, int where) {
    int j, waiting = 0, pushed = 0;
    robj *lobj = lookupKeyWrite(c->db,c->argv[1]);

    if (lobj && lobj->type != REDIS_LIST) {
        addReply(c,shared.wrongtypeerr);
        return;
    }

    for (j = 2; j < c->argc; j++) {
        c->argv[j] = tryObjectEncoding(c->argv[j]);
        if (!lobj) {
            lobj = createQuicklistObject();
            quicklistSetOptions(lobj->ptr, server.list_max_ziplist_size,
                                server.list_compress_depth);
            dbAdd(c->db,c->argv[1],lobj);
        }
        listTypePush(lobj,c->argv[j],where);
        pushed++;
    }
    addReplyLongLong(c, waiting + (lobj ? listTypeLength(lobj) : 0));
    if (pushed) {
        char *event = (where == REDIS_HEAD) ? "lpush" : "rpush";

        signalModifiedKey(c->db,c->argv[1]);
        notifyKeyspaceEvent(REDIS_NOTIFY_LIST,event,c->argv[1],c->db->id);
    }
    server.dirty += pushed;
}

void lpushCommand(redisClient *c) {
    pushGenericCommand(c,REDIS_HEAD);
}

void rpushCommand(redisClient *c) {
    pushGenericCommand(c,REDIS_TAIL);
}

void pushxGenericCommand(redisClient *c, robj *refval, robj *val, int where) {
    robj *subject;
    listTypeIterator *iter;
    listTypeEntry entry;
    int inserted = 0;

    if ((subject = lookupKeyWriteOrReply(c,c->argv[1],shared.czero)) == NULL ||
        checkType(c,subject,REDIS_LIST)) return;

    if (refval != NULL) {
        /* Seek refval from head to tail */
        iter = listTypeInitIterator(subject,0,REDIS_TAIL);
        while (listTypeNext(iter,&entry)) {
            if (listTypeEqual(&entry,refval)) {
                listTypeInsert(&entry,val,where);
                inserted = 1;
                break;
            }
        }
        listTypeReleaseIterator(iter);

        if (inserted) {
            signalModifiedKey(c->db,c->argv[1]);
            notifyKeyspaceEvent(REDIS_NOTIFY_LIST,"linsert",
                                c->argv[1],c->db->id);
            server.dirty++;
        } else {
            /* Notify client of a failed insert */
            addReply(c,shared.cnegone);
            return;
        }
    } else {
        char *event = (where == REDIS_HEAD) ? "lpush" : "rpush";

        listTypePush(subject,val,where);
        signalModifiedKey(c->db,c->argv[1]);
        notifyKeyspaceEvent(REDIS_NOTIFY_LIST,event,c->argv[1],c->db->id);
        server.dirty++;
    }

    addReplyLongLong(c,listTypeLength(subject));
}

void lpushxCommand(redisClient *c) {
    c->argv[2] = tryObjectEncoding(c->argv[2]);
    pushxGenericCommand(c,NULL,c->argv[2],REDIS_HEAD);
}

void rpushxCommand(redisClient *c) {
    c->argv[2] = tryObjectEncoding(c->argv[2]);
    pushxGenericCommand(c,NULL,c->argv[2],REDIS_TAIL);
}

void linsertCommand(redisClient *c) {
    c->argv[4] = tryObjectEncoding(c->argv[4]);
    if (strcasecmp(c->argv[2]->ptr,"after") == 0) {
        pushxGenericCommand(c,c->argv[3],c->argv[4],REDIS_TAIL);
    } else if (strcasecmp(c->argv[2]->ptr,"before") == 0) {
        pushxGenericCommand(c,c->argv[3],c->argv[4],REDIS_HEAD);
    } else {
        addReply(c,shared.syntaxerr);
    }
}

void llenCommand(redisClient *c) {
    robj *o = lookupKeyReadOrReply(c,c->argv[1],shared.czero);
    if (o == NULL || checkType(c,o,REDIS_LIST)) return;
    addReplyLongLong(c,listTypeLength(o));
}

void lindexCommand(redisClient *c) {
    robj *o = lookupKeyReadOrReply(c,c->argv[1],shared.nullbulk);
    if (o == NULL || checkType(c,o,REDIS_LIST)) return;
    long index;
    robj *value = NULL;

    if ((getLongFromObjectOrReply(c, c->argv[2], &index, NULL) != REDIS_OK))
        return;

    if (o->encoding == REDIS_ENCODING_QUICKLIST) {
        quicklistEntry entry;
        if (quicklistIndex(o->ptr, index, &entry)) {
            if (entry.value) {
                value = createStringObject((char*)entry.value,entry.sz);
            } else {
                value = createStringObjectFromLongLong(entry.longval);
            }
            addReplyBulk(c,value);
            decrRefCount(value);
        } else {
            addReply(c,shared.nullbulk);
        }
    } else {
        redisPanic("Unknown list encoding");
    }
}

void lsetCommand(redisClient *c) {
    robj *o = lookupKeyWriteOrReply(c,c->argv[1],shared.nokeyerr);
    if (o == NULL || checkType(c,o,REDIS_LIST)) return;
    long index;
    robj *value = c->argv[3];

    if ((getLongFromObjectOrReply(c, c->argv[2], &index, NULL) != REDIS_OK))
        return;

    if (o->encoding == REDIS_ENCODING_QUICKLIST) {
        quicklist *ql = o->ptr;
        int replaced = quicklistReplaceAtIndex(ql, index,
                                               value->ptr, sdslen(value->ptr));
        if (!replaced) {
            addReply(c,shared.outofrangeerr);
        } else {
            addReply(c,shared.ok);
            signalModifiedKey(c->db,c->argv[1]);
            notifyKeyspaceEvent(REDIS_NOTIFY_LIST,"lset",c->argv[1],c->db->id);
            server.dirty++;
        }
    } else {
        redisPanic("Unknown list encoding");
    }
}

void popGenericCommand(redisClient *c, int where) {
    robj *o = lookupKeyWriteOrReply(c,c->argv[1],shared.nullbulk);
    if (o == NULL || checkType(c,o,REDIS_LIST)) return;

    robj *value = listTypePop(o,where);
    if (value == NULL) {
        addReply(c,shared.nullbulk);
    } else {
        char *event = (where == REDIS_HEAD) ? "lpop" : "rpop";

        addReplyBulk(c,value);
        decrRefCount(value);
        notifyKeyspaceEvent(REDIS_NOTIFY_LIST,event,c->argv[1],c->db->id);
        if (listTypeLength(o) == 0) {
            notifyKeyspaceEvent(REDIS_NOTIFY_GENERIC,"del",
                                c->argv[1],c->db->id);
            dbDelete(c->db,c->argv[1]);
        }
        signalModifiedKey(c->db,c->argv[1]);
        server.dirty++;
    }
}

void lpopCommand(redisClient *c) {
    popGenericCommand(c,REDIS_HEAD);
}

void rpopCommand(redisClient *c) {
    popGenericCommand(c,REDIS_TAIL);
}

void lrangeCommand(redisClient *c) {
    robj *o;
    long start, end, llen, rangelen;

    if ((getLongFromObjectOrReply(c, c->argv[2], &start, NULL) != REDIS_OK) ||
        (getLongFromObjectOrReply(c, c->argv[3], &end, NULL) != REDIS_OK)) return;

    if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.emptymultibulk)) == NULL
         || checkType(c,o,REDIS_LIST)) return;
    llen = listTypeLength(o);

    /* convert negative indexes */
    if (start < 0) start = llen+start;
    if (end < 0) end = llen+end;
    if (start < 0) start = 0;

    /* Invariant: start >= 0, so this test will be true when end < 0.
     * The range is empty when start > end or start >= length. */
    if (start > end || start >= llen) {
        addReply(c,shared.emptymultibulk);
        return;
    }
    if (end >= llen) end = llen-1;
    rangelen = (end-start)+1;

    /* Return the result in form of a multi-bulk reply */
    addReplyMultiBulkLen(c,rangelen);
    if (o->encoding == REDIS_ENCODING_QUICKLIST) {
        listTypeIterator *iter = listTypeInitIterator(o, start, REDIS_TAIL);

        while(rangelen--) {
            listTypeEntry entry;
            listTypeNext(iter, &entry);
            quicklistEntry *qe = &entry.entry;
            if (qe->value) {
                addReplyBulkCBuffer(c,qe->value,qe->sz);
            } else {
                addReplyBulkLongLong(c,qe->longval);
            }
        }
        listTypeReleaseIterator(iter);
    } else {
        redisPanic("List encoding is not QUICKLIST!");
    }
}

void ltrimCommand(redisClient *c) {
    robj *o;
    long start, end, llen, ltrim, rtrim;

    if ((getLongFromObjectOrReply(c, c->argv[2], &start, NULL) != REDIS_OK) ||
        (getLongFromObjectOrReply(c, c->argv[3], &end, NULL) != REDIS_OK)) return;

    if ((o = lookupKeyWriteOrReply(c,c->argv[1],shared.ok)) == NULL ||
        checkType(c,o,REDIS_LIST)) return;
    llen = listTypeLength(o);

    /* convert negative indexes */
    if (start < 0) start = llen+start;
    if (end < 0) end = llen+end;
    if (start < 0) start = 0;

    /* Invariant: start >= 0, so this test will be true when end < 0.
     * The range is empty when start > end or start >= length. */
    if (start > end || start >= llen) {
        /* Out of range start or start > end result in empty list */
        ltrim = llen;
        rtrim = 0;
    } else {
        if (end >= llen) end = llen-1;
        ltrim = start;
        rtrim = llen-end-1;
    }

    /* Remove list elements to perform the trim */
    if (o->encoding == REDIS_ENCODING_QUICKLIST) {
        quicklistDelRange(o->ptr,0,ltrim);
        quicklistDelRange(o->ptr,-rtrim,rtrim);
    } else {
        redisPanic("Unknown list encoding");
    }

    notifyKeyspaceEvent(REDIS_NOTIFY_LIST,"ltrim",c->argv[1],c->db->id);
    if (listTypeLength(o) == 0) {
        dbDelete(c->db,c->argv[1]);
        notifyKeyspaceEvent(REDIS_NOTIFY_GENERIC,"del",c->argv[1],c->db->id);
    }
    signalModifiedKey(c->db,c->argv[1]);
    server.dirty++;
    addReply(c,shared.ok);
}

void lremCommand(redisClient *c) {
    robj *subject, *obj;
    obj = c->argv[3];
    long toremove;
    long removed = 0;

    if ((getLongFromObjectOrReply(c, c->argv[2], &toremove, NULL) != REDIS_OK))
        return;

    subject = lookupKeyWriteOrReply(c,c->argv[1],shared.czero);
    if (subject == NULL || checkType(c,subject,REDIS_LIST)) return;

    listTypeIterator *li;
    if (toremove < 0) {
        toremove = -toremove;
        li = listTypeInitIterator(subject,-1,REDIS_HEAD);
    } else {
        li = listTypeInitIterator(subject,0,REDIS_TAIL);
    }

    listTypeEntry entry;
    while (listTypeNext(li,&entry)) {
        if (listTypeEqual(&entry,obj)) {
            listTypeDelete(li, &entry);
            server.dirty++;
            removed++;
            if (toremove && removed == toremove) break;
        }
    }
    listTypeReleaseIterator(li);

    if (listTypeLength(subject) == 0) {
        dbDelete(c->db,c->argv[1]);
    }

    addReplyLongLong(c,removed);
    if (removed) signalModifiedKey(c->db,c->argv[1]);
}

/* This is the semantic of this command:
 *  RPOPLPUSH srclist dstlist:
 *    IF LLEN(srclist) > 0
 *      element = RPOP srclist
 *      LPUSH dstlist element
 *      RETURN element
 *    ELSE
 *      RETURN nil
 *    END
 *  END
 *
 * The idea is to be able to get an element from a list in a reliable way
 * since the element is not just returned but pushed against another list
 * as well. This command was originally proposed by Ezra Zygmuntowicz.
 */

void rpoplpushHandlePush(redisClient *c, robj *dstkey, robj *dstobj, robj *value) {
    /* Create the list if the key does not exist */
    if (!dstobj) {
        dstobj = createQuicklistObject();
        quicklistSetOptions(dstobj->ptr, server.list_max_ziplist_size,
                            server.list_compress_depth);
        dbAdd(c->db,dstkey,dstobj);
    }
    signalModifiedKey(c->db,dstkey);
    listTypePush(dstobj,value,REDIS_HEAD);
    notifyKeyspaceEvent(REDIS_NOTIFY_LIST,"lpush",dstkey,c->db->id);
    /* Always send the pushed value to the client. */
    addReplyBulk(c,value);
}

void rpoplpushCommand(redisClient *c) {
    robj *sobj, *value;
    if ((sobj = lookupKeyWriteOrReply(c,c->argv[1],shared.nullbulk)) == NULL ||
        checkType(c,sobj,REDIS_LIST)) return;

    if (listTypeLength(sobj) == 0) {
        /* This may only happen after loading very old RDB files. Recent
         * versions of Redis delete keys of empty lists. */
        addReply(c,shared.nullbulk);
    } else {
        robj *dobj = lookupKeyWrite(c->db,c->argv[2]);
        robj *touchedkey = c->argv[1];

        if (dobj && checkType(c,dobj,REDIS_LIST)) return;
        value = listTypePop(sobj,REDIS_TAIL);
        /* We saved touched key, and protect it, since rpoplpushHandlePush
         * may change the client command argument vector (it does not
         * currently). */
        incrRefCount(touchedkey);
        rpoplpushHandlePush(c,c->argv[2],dobj,value);

        /* listTypePop returns an object with its refcount incremented */
        decrRefCount(value);

        /* Delete the source list when it is empty */
        notifyKeyspaceEvent(REDIS_NOTIFY_LIST,"rpop",touchedkey,c->db->id);
        if (listTypeLength(sobj) == 0) {
            dbDelete(c->db,touchedkey);
            notifyKeyspaceEvent(REDIS_NOTIFY_GENERIC,"del",
                                touchedkey,c->db->id);
        }
        signalModifiedKey(c->db,touchedkey);
        decrRefCount(touchedkey);
        server.dirty++;
    }
}

/*-----------------------------------------------------------------------------
 * Blocking POP operations
 *----------------------------------------------------------------------------*/

/* This is how the current blocking POP works, we use BLPOP as example:
 * - If the user calls BLPOP and the key exists and contains a non empty list
 *   then LPOP is called instead. So BLPOP is semantically the same as LPOP
 *   if blocking is not required.
 * - If instead BLPOP is called and the key does not exists or the list is
 *   empty we need to block. In order to do so we remove the notification for
 *   new data to read in the client socket (so that we'll not serve new
 *   requests if the blocking request is not served). Also we put the client
 *   in a dictionary (db->blocking_keys) mapping keys to a list of clients
 *   blocking for this keys.
 * - If a PUSH operation against a key with blocked clients waiting is
 *   performed, we mark this key as "ready", and after the current command,
 *   MULTI/EXEC block, or script, is executed, we serve all the clients waiting
 *   for this list, from the one that blocked first, to the last, accordingly
 *   to the number of elements we have in the ready list.
 */

/* Set a client in blocking mode for the specified key, with the specified
 * timeout */
void blockForKeys(redisClient *c, robj **keys, int numkeys, mstime_t timeout, robj *target) {
    dictEntry *de;
    list *l;
    int j;

    c->bpop.timeout = timeout;
    c->bpop.target = target;

    if (target != NULL) incrRefCount(target);

    for (j = 0; j < numkeys; j++) {
        /* If the key already exists in the dict ignore it. */
        if (dictAdd(c->bpop.keys,keys[j],NULL) != DICT_OK) continue;
        incrRefCount(keys[j]);

        /* And in the other "side", to map keys -> clients */
        de = dictFind(c->db->blocking_keys,keys[j]);
        if (de == NULL) {
            int retval;

            /* For every key we take a list of clients blocked for it */
            l = listCreate();
            retval = dictAdd(c->db->blocking_keys,keys[j],l);
            incrRefCount(keys[j]);
            redisAssertWithInfo(c,keys[j],retval == DICT_OK);
        } else {
            l = dictGetVal(de);
        }
        listAddNodeTail(l,c);
    }
    blockClient(c,REDIS_BLOCKED_LIST);
}

/* Unblock a client that's waiting in a blocking operation such as BLPOP.
 * You should never call this function directly, but unblockClient() instead. */
void unblockClientWaitingData(redisClient *c) {
    dictEntry *de;
    dictIterator *di;
    list *l;

    redisAssertWithInfo(c,NULL,dictSize(c->bpop.keys) != 0);
    di = dictGetIterator(c->bpop.keys);
    /* The client may wait for multiple keys, so unblock it for every key. */
    while((de = dictNext(di)) != NULL) {
        robj *key = dictGetKey(de);

        /* Remove this client from the list of clients waiting for this key. */
        l = dictFetchValue(c->db->blocking_keys,key);
        redisAssertWithInfo(c,key,l != NULL);
        listDelNode(l,listSearchKey(l,c));
        /* If the list is empty we need to remove it to avoid wasting memory */
        if (listLength(l) == 0)
            dictDelete(c->db->blocking_keys,key);
    }
    dictReleaseIterator(di);

    /* Cleanup the client structure */
    dictEmpty(c->bpop.keys,NULL);
    if (c->bpop.target) {
        decrRefCount(c->bpop.target);
        c->bpop.target = NULL;
    }
}

/* If the specified key has clients blocked waiting for list pushes, this
 * function will put the key reference into the server.ready_keys list.
 * Note that db->ready_keys is a hash table that allows us to avoid putting
 * the same key again and again in the list in case of multiple pushes
 * made by a script or in the context of MULTI/EXEC.
 *
 * The list will be finally processed by handleClientsBlockedOnLists() */
void signalListAsReady(redisDb *db, robj *key) {
    readyList *rl;

    /* No clients blocking for this key? No need to queue it. */
    if (dictFind(db->blocking_keys,key) == NULL) return;

    /* Key was already signaled? No need to queue it again. */
    if (dictFind(db->ready_keys,key) != NULL) return;

    /* Ok, we need to queue this key into server.ready_keys. */
    rl = zmalloc(sizeof(*rl));
    rl->key = key;
    rl->db = db;
    incrRefCount(key);
    listAddNodeTail(server.ready_keys,rl);

    /* We also add the key in the db->ready_keys dictionary in order
     * to avoid adding it multiple times into a list with a simple O(1)
     * check. */
    incrRefCount(key);
    redisAssert(dictAdd(db->ready_keys,key,NULL) == DICT_OK);
}

/* This is a helper function for handleClientsBlockedOnLists(). It's work
 * is to serve a specific client (receiver) that is blocked on 'key'
 * in the context of the specified 'db', doing the following:
 *
 * 1) Provide the client with the 'value' element.
 * 2) If the dstkey is not NULL (we are serving a BRPOPLPUSH) also push the
 *    'value' element on the destination list (the LPUSH side of the command).
 * 3) Propagate the resulting BRPOP, BLPOP and additional LPUSH if any into
 *    the AOF and replication channel.
 *
 * The argument 'where' is REDIS_TAIL or REDIS_HEAD, and indicates if the
 * 'value' element was popped fron the head (BLPOP) or tail (BRPOP) so that
 * we can propagate the command properly.
 *
 * The function returns REDIS_OK if we are able to serve the client, otherwise
 * REDIS_ERR is returned to signal the caller that the list POP operation
 * should be undone as the client was not served: This only happens for
 * BRPOPLPUSH that fails to push the value to the destination key as it is
 * of the wrong type. */
int serveClientBlockedOnList(redisClient *receiver, robj *key, robj *dstkey, redisDb *db, robj *value, int where)
{
    robj *argv[3];

    if (dstkey == NULL) {
        /* Propagate the [LR]POP operation. */
        argv[0] = (where == REDIS_HEAD) ? shared.lpop :
                                          shared.rpop;
        argv[1] = key;
        propagate((where == REDIS_HEAD) ?
            server.lpopCommand : server.rpopCommand,
            db->id,argv,2,REDIS_PROPAGATE_AOF|REDIS_PROPAGATE_REPL);

        /* BRPOP/BLPOP */
        addReplyMultiBulkLen(receiver,2);
        addReplyBulk(receiver,key);
        addReplyBulk(receiver,value);
    } else {
        /* BRPOPLPUSH */
        robj *dstobj =
            lookupKeyWrite(receiver->db,dstkey);
        if (!(dstobj &&
             checkType(receiver,dstobj,REDIS_LIST)))
        {
            /* Propagate the RPOP operation. */
            argv[0] = shared.rpop;
            argv[1] = key;
            propagate(server.rpopCommand,
                db->id,argv,2,
                REDIS_PROPAGATE_AOF|
                REDIS_PROPAGATE_REPL);
            rpoplpushHandlePush(receiver,dstkey,dstobj,
                value);
            /* Propagate the LPUSH operation. */
            argv[0] = shared.lpush;
            argv[1] = dstkey;
            argv[2] = value;
            propagate(server.lpushCommand,
                db->id,argv,3,
                REDIS_PROPAGATE_AOF|
                REDIS_PROPAGATE_REPL);
        } else {
            /* BRPOPLPUSH failed because of wrong
             * destination type. */
            return REDIS_ERR;
        }
    }
    return REDIS_OK;
}

/* This function should be called by Redis every time a single command,
 * a MULTI/EXEC block, or a Lua script, terminated its execution after
 * being called by a client.
 *
 * All the keys with at least one client blocked that received at least
 * one new element via some PUSH operation are accumulated into
 * the server.ready_keys list. This function will run the list and will
 * serve clients accordingly. Note that the function will iterate again and
 * again as a result of serving BRPOPLPUSH we can have new blocking clients
 * to serve because of the PUSH side of BRPOPLPUSH. */
void handleClientsBlockedOnLists(void) {
    while(listLength(server.ready_keys) != 0) {
        list *l;

        /* Point server.ready_keys to a fresh list and save the current one
         * locally. This way as we run the old list we are free to call
         * signalListAsReady() that may push new elements in server.ready_keys
         * when handling clients blocked into BRPOPLPUSH. */
        l = server.ready_keys;
        server.ready_keys = listCreate();

        while(listLength(l) != 0) {
            listNode *ln = listFirst(l);
            readyList *rl = ln->value;

            /* First of all remove this key from db->ready_keys so that
             * we can safely call signalListAsReady() against this key. */
            dictDelete(rl->db->ready_keys,rl->key);

            /* If the key exists and it's a list, serve blocked clients
             * with data. */
            robj *o = lookupKeyWrite(rl->db,rl->key);
            if (o != NULL && o->type == REDIS_LIST) {
                dictEntry *de;

                /* We serve clients in the same order they blocked for
                 * this key, from the first blocked to the last. */
                de = dictFind(rl->db->blocking_keys,rl->key);
                if (de) {
                    list *clients = dictGetVal(de);
                    int numclients = listLength(clients);

                    while(numclients--) {
                        listNode *clientnode = listFirst(clients);
                        redisClient *receiver = clientnode->value;
                        robj *dstkey = receiver->bpop.target;
                        int where = (receiver->lastcmd &&
                                     receiver->lastcmd->proc == blpopCommand) ?
                                    REDIS_HEAD : REDIS_TAIL;
                        robj *value = listTypePop(o,where);

                        if (value) {
                            /* Protect receiver->bpop.target, that will be
                             * freed by the next unblockClient()
                             * call. */
                            if (dstkey) incrRefCount(dstkey);
                            unblockClient(receiver);

                            if (serveClientBlockedOnList(receiver,
                                rl->key,dstkey,rl->db,value,
                                where) == REDIS_ERR)
                            {
                                /* If we failed serving the client we need
                                 * to also undo the POP operation. */
                                    listTypePush(o,value,where);
                            }

                            if (dstkey) decrRefCount(dstkey);
                            decrRefCount(value);
                        } else {
                            break;
                        }
                    }
                }

                if (listTypeLength(o) == 0) {
                    dbDelete(rl->db,rl->key);
                }
                /* We don't call signalModifiedKey() as it was already called
                 * when an element was pushed on the list. */
            }

            /* Free this item. */
            decrRefCount(rl->key);
            zfree(rl);
            listDelNode(l,ln);
        }
        listRelease(l); /* We have the new list on place at this point. */
    }
}

/* Blocking RPOP/LPOP */
void blockingPopGenericCommand(redisClient *c, int where) {
    robj *o;
    mstime_t timeout;
    int j;

    if (getTimeoutFromObjectOrReply(c,c->argv[c->argc-1],&timeout,UNIT_SECONDS)
        != REDIS_OK) return;

    for (j = 1; j < c->argc-1; j++) {
        o = lookupKeyWrite(c->db,c->argv[j]);
        if (o != NULL) {
            if (o->type != REDIS_LIST) {
                addReply(c,shared.wrongtypeerr);
                return;
            } else {
                if (listTypeLength(o) != 0) {
                    /* Non empty list, this is like a non normal [LR]POP. */
                    char *event = (where == REDIS_HEAD) ? "lpop" : "rpop";
                    robj *value = listTypePop(o,where);
                    redisAssert(value != NULL);

                    addReplyMultiBulkLen(c,2);
                    addReplyBulk(c,c->argv[j]);
                    addReplyBulk(c,value);
                    decrRefCount(value);
                    notifyKeyspaceEvent(REDIS_NOTIFY_LIST,event,
                                        c->argv[j],c->db->id);
                    if (listTypeLength(o) == 0) {
                        dbDelete(c->db,c->argv[j]);
                        notifyKeyspaceEvent(REDIS_NOTIFY_GENERIC,"del",
                                            c->argv[j],c->db->id);
                    }
                    signalModifiedKey(c->db,c->argv[j]);
                    server.dirty++;

                    /* Replicate it as an [LR]POP instead of B[LR]POP. */
                    rewriteClientCommandVector(c,2,
                        (where == REDIS_HEAD) ? shared.lpop : shared.rpop,
                        c->argv[j]);
                    return;
                }
            }
        }
    }

    /* If we are inside a MULTI/EXEC and the list is empty the only thing
     * we can do is treating it as a timeout (even with timeout 0). */
    if (c->flags & REDIS_MULTI) {
        addReply(c,shared.nullmultibulk);
        return;
    }

    /* If the list is empty or the key does not exists we must block */
    blockForKeys(c, c->argv + 1, c->argc - 2, timeout, NULL);
}

void blpopCommand(redisClient *c) {
    blockingPopGenericCommand(c,REDIS_HEAD);
}

void brpopCommand(redisClient *c) {
    blockingPopGenericCommand(c,REDIS_TAIL);
}

void brpoplpushCommand(redisClient *c) {
    mstime_t timeout;

    if (getTimeoutFromObjectOrReply(c,c->argv[3],&timeout,UNIT_SECONDS)
        != REDIS_OK) return;

    robj *key = lookupKeyWrite(c->db, c->argv[1]);

    if (key == NULL) {
        if (c->flags & REDIS_MULTI) {
            /* Blocking against an empty list in a multi state
             * returns immediately. */
            addReply(c, shared.nullbulk);
        } else {
            /* The list is empty and the client blocks. */
            blockForKeys(c, c->argv + 1, 1, timeout, c->argv[2]);
        }
    } else {
        if (key->type != REDIS_LIST) {
            addReply(c, shared.wrongtypeerr);
        } else {
            /* The list exists and has elements, so
             * the regular rpoplpushCommand is executed. */
            redisAssertWithInfo(c,key,listTypeLength(key) > 0);
            rpoplpushCommand(c);
        }
    }
}