src/t_list.c

   1 #include "redis.h"
   2
   3 /*-----------------------------------------------------------------------------
   4  * List API
   5  *----------------------------------------------------------------------------*/
   6
   7 /* Check the argument length to see if it requires us to convert the ziplist
   8  * to a real list. Only check raw-encoded objects because integer encoded
   9  * objects are never too long. */
  10 void listTypeTryConversion(robj *subject, robj *value) {
  11     if (subject->encoding != REDIS_ENCODING_ZIPLIST) return;
  12     if (value->encoding == REDIS_ENCODING_RAW &&
  13         sdslen(value->ptr) > server.list_max_ziplist_value)
  14             listTypeConvert(subject,REDIS_ENCODING_LINKEDLIST);
  15 }
  16
  17 void listTypePush(robj *subject, robj *value, int where) {
  18     /* Check if we need to convert the ziplist */
  19     listTypeTryConversion(subject,value);
  20     if (subject->encoding == REDIS_ENCODING_ZIPLIST &&
  21         ziplistLen(subject->ptr) >= server.list_max_ziplist_entries)
  22             listTypeConvert(subject,REDIS_ENCODING_LINKEDLIST);
  23
  24     if (subject->encoding == REDIS_ENCODING_ZIPLIST) {
  25         int pos = (where == REDIS_HEAD) ? ZIPLIST_HEAD : ZIPLIST_TAIL;
  26         value = getDecodedObject(value);
  27         subject->ptr = ziplistPush(subject->ptr,value->ptr,sdslen(value->ptr),pos);
  28         decrRefCount(value);
  29     } else if (subject->encoding == REDIS_ENCODING_LINKEDLIST) {
  30         if (where == REDIS_HEAD) {
  31             listAddNodeHead(subject->ptr,value);
  32         } else {
  33             listAddNodeTail(subject->ptr,value);
  34         }
  35         incrRefCount(value);
  36     } else {
  37         redisPanic("Unknown list encoding");
  38     }
  39 }
  40
  41 robj *listTypePop(robj *subject, int where) {
  42     robj *value = NULL;
  43     if (subject->encoding == REDIS_ENCODING_ZIPLIST) {
  44         unsigned char *p;
  45         unsigned char *vstr;
  46         unsigned int vlen;
  47         long long vlong;
  48         int pos = (where == REDIS_HEAD) ? 0 : -1;
  49         p = ziplistIndex(subject->ptr,pos);
  50         if (ziplistGet(p,&vstr,&vlen,&vlong)) {
  51             if (vstr) {
  52                 value = createStringObject((char*)vstr,vlen);
  53             } else {
  54                 value = createStringObjectFromLongLong(vlong);
  55             }
  56             /* We only need to delete an element when it exists */
  57             subject->ptr = ziplistDelete(subject->ptr,&p);
  58         }
  59     } else if (subject->encoding == REDIS_ENCODING_LINKEDLIST) {
  60         list *list = subject->ptr;
  61         listNode *ln;
  62         if (where == REDIS_HEAD) {
  63             ln = listFirst(list);
  64         } else {
  65             ln = listLast(list);
  66         }
  67         if (ln != NULL) {
  68             value = listNodeValue(ln);
  69             incrRefCount(value);
  70             listDelNode(list,ln);
  71         }
  72     } else {
  73         redisPanic("Unknown list encoding");
  74     }
  75     return value;
  76 }
  77
  78 unsigned long listTypeLength(robj *subject) {
  79     if (subject->encoding == REDIS_ENCODING_ZIPLIST) {
  80         return ziplistLen(subject->ptr);
  81     } else if (subject->encoding == REDIS_ENCODING_LINKEDLIST) {
  82         return listLength((list*)subject->ptr);
  83     } else {
  84         redisPanic("Unknown list encoding");
  85     }
  86 }
  87
  88 /* Initialize an iterator at the specified index. */
  89 listTypeIterator *listTypeInitIterator(robj *subject, long index, unsigned char direction) {
  90     listTypeIterator *li = zmalloc(sizeof(listTypeIterator));
  91     li->subject = subject;
  92     li->encoding = subject->encoding;
  93     li->direction = direction;
  94     if (li->encoding == REDIS_ENCODING_ZIPLIST) {
  95         li->zi = ziplistIndex(subject->ptr,index);
  96     } else if (li->encoding == REDIS_ENCODING_LINKEDLIST) {
  97         li->ln = listIndex(subject->ptr,index);
  98     } else {
  99         redisPanic("Unknown list encoding");
 100     }
 101     return li;
 102 }
 103
 104 /* Clean up the iterator. */
 105 void listTypeReleaseIterator(listTypeIterator *li) {
 106     zfree(li);
 107 }
 108
 109 /* Stores pointer to current the entry in the provided entry structure
 110  * and advances the position of the iterator. Returns 1 when the current
 111  * entry is in fact an entry, 0 otherwise. */
 112 int listTypeNext(listTypeIterator *li, listTypeEntry *entry) {
 113     /* Protect from converting when iterating */
 114     redisAssert(li->subject->encoding == li->encoding);
 115
 116     entry->li = li;
 117     if (li->encoding == REDIS_ENCODING_ZIPLIST) {
 118         entry->zi = li->zi;
 119         if (entry->zi != NULL) {
 120             if (li->direction == REDIS_TAIL)
 121                 li->zi = ziplistNext(li->subject->ptr,li->zi);
 122             else
 123                 li->zi = ziplistPrev(li->subject->ptr,li->zi);
 124             return 1;
 125         }
 126     } else if (li->encoding == REDIS_ENCODING_LINKEDLIST) {
 127         entry->ln = li->ln;
 128         if (entry->ln != NULL) {
 129             if (li->direction == REDIS_TAIL)
 130                 li->ln = li->ln->next;
 131             else
 132                 li->ln = li->ln->prev;
 133             return 1;
 134         }
 135     } else {
 136         redisPanic("Unknown list encoding");
 137     }
 138     return 0;
 139 }
 140
 141 /* Return entry or NULL at the current position of the iterator. */
 142 robj *listTypeGet(listTypeEntry *entry) {
 143     listTypeIterator *li = entry->li;
 144     robj *value = NULL;
 145     if (li->encoding == REDIS_ENCODING_ZIPLIST) {
 146         unsigned char *vstr;
 147         unsigned int vlen;
 148         long long vlong;
 149         redisAssert(entry->zi != NULL);
 150         if (ziplistGet(entry->zi,&vstr,&vlen,&vlong)) {
 151             if (vstr) {
 152                 value = createStringObject((char*)vstr,vlen);
 153             } else {
 154                 value = createStringObjectFromLongLong(vlong);
 155             }
 156         }
 157     } else if (li->encoding == REDIS_ENCODING_LINKEDLIST) {
 158         redisAssert(entry->ln != NULL);
 159         value = listNodeValue(entry->ln);
 160         incrRefCount(value);
 161     } else {
 162         redisPanic("Unknown list encoding");
 163     }
 164     return value;
 165 }
 166
 167 void listTypeInsert(listTypeEntry *entry, robj *value, int where) {
 168     robj *subject = entry->li->subject;
 169     if (entry->li->encoding == REDIS_ENCODING_ZIPLIST) {
 170         value = getDecodedObject(value);
 171         if (where == REDIS_TAIL) {
 172             unsigned char *next = ziplistNext(subject->ptr,entry->zi);
 173
 174             /* When we insert after the current element, but the current element
 175              * is the tail of the list, we need to do a push. */
 176             if (next == NULL) {
 177                 subject->ptr = ziplistPush(subject->ptr,value->ptr,sdslen(value->ptr),REDIS_TAIL);
 178             } else {
 179                 subject->ptr = ziplistInsert(subject->ptr,next,value->ptr,sdslen(value->ptr));
 180             }
 181         } else {
 182             subject->ptr = ziplistInsert(subject->ptr,entry->zi,value->ptr,sdslen(value->ptr));
 183         }
 184         decrRefCount(value);
 185     } else if (entry->li->encoding == REDIS_ENCODING_LINKEDLIST) {
 186         if (where == REDIS_TAIL) {
 187             listInsertNode(subject->ptr,entry->ln,value,AL_START_TAIL);
 188         } else {
 189             listInsertNode(subject->ptr,entry->ln,value,AL_START_HEAD);
 190         }
 191         incrRefCount(value);
 192     } else {
 193         redisPanic("Unknown list encoding");
 194     }
 195 }
 196
 197 /* Compare the given object with the entry at the current position. */
 198 int listTypeEqual(listTypeEntry *entry, robj *o) {
 199     listTypeIterator *li = entry->li;
 200     if (li->encoding == REDIS_ENCODING_ZIPLIST) {
 201         redisAssertWithInfo(NULL,o,o->encoding == REDIS_ENCODING_RAW);
 202         return ziplistCompare(entry->zi,o->ptr,sdslen(o->ptr));
 203     } else if (li->encoding == REDIS_ENCODING_LINKEDLIST) {
 204         return equalStringObjects(o,listNodeValue(entry->ln));
 205     } else {
 206         redisPanic("Unknown list encoding");
 207     }
 208 }
 209
 210 /* Delete the element pointed to. */
 211 void listTypeDelete(listTypeEntry *entry) {
 212     listTypeIterator *li = entry->li;
 213     if (li->encoding == REDIS_ENCODING_ZIPLIST) {
 214         unsigned char *p = entry->zi;
 215         li->subject->ptr = ziplistDelete(li->subject->ptr,&p);
 216
 217         /* Update position of the iterator depending on the direction */
 218         if (li->direction == REDIS_TAIL)
 219             li->zi = p;
 220         else
 221             li->zi = ziplistPrev(li->subject->ptr,p);
 222     } else if (entry->li->encoding == REDIS_ENCODING_LINKEDLIST) {
 223         listNode *next;
 224         if (li->direction == REDIS_TAIL)
 225             next = entry->ln->next;
 226         else
 227             next = entry->ln->prev;
 228         listDelNode(li->subject->ptr,entry->ln);
 229         li->ln = next;
 230     } else {
 231         redisPanic("Unknown list encoding");
 232     }
 233 }
 234
 235 void listTypeConvert(robj *subject, int enc) {
 236     listTypeIterator *li;
 237     listTypeEntry entry;
 238     redisAssertWithInfo(NULL,subject,subject->type == REDIS_LIST);
 239
 240     if (enc == REDIS_ENCODING_LINKEDLIST) {
 241         list *l = listCreate();
 242         listSetFreeMethod(l,decrRefCount);
 243
 244         /* listTypeGet returns a robj with incremented refcount */
 245         li = listTypeInitIterator(subject,0,REDIS_TAIL);
 246         while (listTypeNext(li,&entry)) listAddNodeTail(l,listTypeGet(&entry));
 247         listTypeReleaseIterator(li);
 248
 249         subject->encoding = REDIS_ENCODING_LINKEDLIST;
 250         zfree(subject->ptr);
 251         subject->ptr = l;
 252     } else {
 253         redisPanic("Unsupported list conversion");
 254     }
 255 }
 256
 257 /*-----------------------------------------------------------------------------
 258  * List Commands
 259  *----------------------------------------------------------------------------*/
 260
 261 void pushGenericCommand(redisClient *c, int where) {
 262     int j, addlen = 0, pushed = 0;
 263     robj *lobj = lookupKeyWrite(c->db,c->argv[1]);
 264     int may_have_waiting_clients = (lobj == NULL);
 265
 266     if (lobj && lobj->type != REDIS_LIST) {
 267         addReply(c,shared.wrongtypeerr);
 268         return;
 269     }
 270
 271     for (j = 2; j < c->argc; j++) {
 272         c->argv[j] = tryObjectEncoding(c->argv[j]);
 273         if (may_have_waiting_clients) {
 274             if (handleClientsWaitingListPush(c,c->argv[1],c->argv[j])) {
 275                 addlen++;
 276                 continue;
 277             } else {
 278                 may_have_waiting_clients = 0;
 279             }
 280         }
 281         if (!lobj) {
 282             lobj = createZiplistObject();
 283             dbAdd(c->db,c->argv[1],lobj);
 284         }
 285         listTypePush(lobj,c->argv[j],where);
 286         pushed++;
 287     }
 288     addReplyLongLong(c,addlen + (lobj ? listTypeLength(lobj) : 0));
 289     if (pushed) signalModifiedKey(c->db,c->argv[1]);
 290     server.dirty += pushed;
 291 }
 292
 293 void lpushCommand(redisClient *c) {
 294     pushGenericCommand(c,REDIS_HEAD);
 295 }
 296
 297 void rpushCommand(redisClient *c) {
 298     pushGenericCommand(c,REDIS_TAIL);
 299 }
 300
 301 void pushxGenericCommand(redisClient *c, robj *refval, robj *val, int where) {
 302     robj *subject;
 303     listTypeIterator *iter;
 304     listTypeEntry entry;
 305     int inserted = 0;
 306
 307     if ((subject = lookupKeyReadOrReply(c,c->argv[1],shared.czero)) == NULL ||
 308         checkType(c,subject,REDIS_LIST)) return;
 309
 310     if (refval != NULL) {
 311         /* Note: we expect refval to be string-encoded because it is *not* the
 312          * last argument of the multi-bulk LINSERT. */
 313         redisAssertWithInfo(c,refval,refval->encoding == REDIS_ENCODING_RAW);
 314
 315         /* We're not sure if this value can be inserted yet, but we cannot
 316          * convert the list inside the iterator. We don't want to loop over
 317          * the list twice (once to see if the value can be inserted and once
 318          * to do the actual insert), so we assume this value can be inserted
 319          * and convert the ziplist to a regular list if necessary. */
 320         listTypeTryConversion(subject,val);
 321
 322         /* Seek refval from head to tail */
 323         iter = listTypeInitIterator(subject,0,REDIS_TAIL);
 324         while (listTypeNext(iter,&entry)) {
 325             if (listTypeEqual(&entry,refval)) {
 326                 listTypeInsert(&entry,val,where);
 327                 inserted = 1;
 328                 break;
 329             }
 330         }
 331         listTypeReleaseIterator(iter);
 332
 333         if (inserted) {
 334             /* Check if the length exceeds the ziplist length threshold. */
 335             if (subject->encoding == REDIS_ENCODING_ZIPLIST &&
 336                 ziplistLen(subject->ptr) > server.list_max_ziplist_entries)
 337                     listTypeConvert(subject,REDIS_ENCODING_LINKEDLIST);
 338             signalModifiedKey(c->db,c->argv[1]);
 339             server.dirty++;
 340         } else {
 341             /* Notify client of a failed insert */
 342             addReply(c,shared.cnegone);
 343             return;
 344         }
 345     } else {
 346         listTypePush(subject,val,where);
 347         signalModifiedKey(c->db,c->argv[1]);
 348         server.dirty++;
 349     }
 350
 351     addReplyLongLong(c,listTypeLength(subject));
 352 }
 353
 354 void lpushxCommand(redisClient *c) {
 355     c->argv[2] = tryObjectEncoding(c->argv[2]);
 356     pushxGenericCommand(c,NULL,c->argv[2],REDIS_HEAD);
 357 }
 358
 359 void rpushxCommand(redisClient *c) {
 360     c->argv[2] = tryObjectEncoding(c->argv[2]);
 361     pushxGenericCommand(c,NULL,c->argv[2],REDIS_TAIL);
 362 }
 363
 364 void linsertCommand(redisClient *c) {
 365     c->argv[4] = tryObjectEncoding(c->argv[4]);
 366     if (strcasecmp(c->argv[2]->ptr,"after") == 0) {
 367         pushxGenericCommand(c,c->argv[3],c->argv[4],REDIS_TAIL);
 368     } else if (strcasecmp(c->argv[2]->ptr,"before") == 0) {
 369         pushxGenericCommand(c,c->argv[3],c->argv[4],REDIS_HEAD);
 370     } else {
 371         addReply(c,shared.syntaxerr);
 372     }
 373 }
 374
 375 void llenCommand(redisClient *c) {
 376     robj *o = lookupKeyReadOrReply(c,c->argv[1],shared.czero);
 377     if (o == NULL || checkType(c,o,REDIS_LIST)) return;
 378     addReplyLongLong(c,listTypeLength(o));
 379 }
 380
 381 void lindexCommand(redisClient *c) {
 382     robj *o = lookupKeyReadOrReply(c,c->argv[1],shared.nullbulk);
 383     if (o == NULL || checkType(c,o,REDIS_LIST)) return;
 384     long index;
 385     robj *value = NULL;
 386
 387     if ((getLongFromObjectOrReply(c, c->argv[2], &index, NULL) != REDIS_OK))
 388         return;
 389
 390     if (o->encoding == REDIS_ENCODING_ZIPLIST) {
 391         unsigned char *p;
 392         unsigned char *vstr;
 393         unsigned int vlen;
 394         long long vlong;
 395         p = ziplistIndex(o->ptr,index);
 396         if (ziplistGet(p,&vstr,&vlen,&vlong)) {
 397             if (vstr) {
 398                 value = createStringObject((char*)vstr,vlen);
 399             } else {
 400                 value = createStringObjectFromLongLong(vlong);
 401             }
 402             addReplyBulk(c,value);
 403             decrRefCount(value);
 404         } else {
 405             addReply(c,shared.nullbulk);
 406         }
 407     } else if (o->encoding == REDIS_ENCODING_LINKEDLIST) {
 408         listNode *ln = listIndex(o->ptr,index);
 409         if (ln != NULL) {
 410             value = listNodeValue(ln);
 411             addReplyBulk(c,value);
 412         } else {
 413             addReply(c,shared.nullbulk);
 414         }
 415     } else {
 416         redisPanic("Unknown list encoding");
 417     }
 418 }
 419
 420 void lsetCommand(redisClient *c) {
 421     robj *o = lookupKeyWriteOrReply(c,c->argv[1],shared.nokeyerr);
 422     if (o == NULL || checkType(c,o,REDIS_LIST)) return;
 423     long index;
 424     robj *value = (c->argv[3] = tryObjectEncoding(c->argv[3]));
 425
 426     if ((getLongFromObjectOrReply(c, c->argv[2], &index, NULL) != REDIS_OK))
 427         return;
 428
 429     listTypeTryConversion(o,value);
 430     if (o->encoding == REDIS_ENCODING_ZIPLIST) {
 431         unsigned char *p, *zl = o->ptr;
 432         p = ziplistIndex(zl,index);
 433         if (p == NULL) {
 434             addReply(c,shared.outofrangeerr);
 435         } else {
 436             o->ptr = ziplistDelete(o->ptr,&p);
 437             value = getDecodedObject(value);
 438             o->ptr = ziplistInsert(o->ptr,p,value->ptr,sdslen(value->ptr));
 439             decrRefCount(value);
 440             addReply(c,shared.ok);
 441             signalModifiedKey(c->db,c->argv[1]);
 442             server.dirty++;
 443         }
 444     } else if (o->encoding == REDIS_ENCODING_LINKEDLIST) {
 445         listNode *ln = listIndex(o->ptr,index);
 446         if (ln == NULL) {
 447             addReply(c,shared.outofrangeerr);
 448         } else {
 449             decrRefCount((robj*)listNodeValue(ln));
 450             listNodeValue(ln) = value;
 451             incrRefCount(value);
 452             addReply(c,shared.ok);
 453             signalModifiedKey(c->db,c->argv[1]);
 454             server.dirty++;
 455         }
 456     } else {
 457         redisPanic("Unknown list encoding");
 458     }
 459 }
 460
 461 void popGenericCommand(redisClient *c, int where) {
 462     robj *o = lookupKeyWriteOrReply(c,c->argv[1],shared.nullbulk);
 463     if (o == NULL || checkType(c,o,REDIS_LIST)) return;
 464
 465     robj *value = listTypePop(o,where);
 466     if (value == NULL) {
 467         addReply(c,shared.nullbulk);
 468     } else {
 469         addReplyBulk(c,value);
 470         decrRefCount(value);
 471         if (listTypeLength(o) == 0) dbDelete(c->db,c->argv[1]);
 472         signalModifiedKey(c->db,c->argv[1]);
 473         server.dirty++;
 474     }
 475 }
 476
 477 void lpopCommand(redisClient *c) {
 478     popGenericCommand(c,REDIS_HEAD);
 479 }
 480
 481 void rpopCommand(redisClient *c) {
 482     popGenericCommand(c,REDIS_TAIL);
 483 }
 484
 485 void lrangeCommand(redisClient *c) {
 486     robj *o;
 487     long start, end, llen, rangelen;
 488
 489     if ((getLongFromObjectOrReply(c, c->argv[2], &start, NULL) != REDIS_OK) ||
 490         (getLongFromObjectOrReply(c, c->argv[3], &end, NULL) != REDIS_OK)) return;
 491
 492     if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.emptymultibulk)) == NULL
 493          || checkType(c,o,REDIS_LIST)) return;
 494     llen = listTypeLength(o);
 495
 496     /* convert negative indexes */
 497     if (start < 0) start = llen+start;
 498     if (end < 0) end = llen+end;
 499     if (start < 0) start = 0;
 500
 501     /* Invariant: start >= 0, so this test will be true when end < 0.
 502      * The range is empty when start > end or start >= length. */
 503     if (start > end || start >= llen) {
 504         addReply(c,shared.emptymultibulk);
 505         return;
 506     }
 507     if (end >= llen) end = llen-1;
 508     rangelen = (end-start)+1;
 509
 510     /* Return the result in form of a multi-bulk reply */
 511     addReplyMultiBulkLen(c,rangelen);
 512     if (o->encoding == REDIS_ENCODING_ZIPLIST) {
 513         unsigned char *p = ziplistIndex(o->ptr,start);
 514         unsigned char *vstr;
 515         unsigned int vlen;
 516         long long vlong;
 517
 518         while(rangelen--) {
 519             ziplistGet(p,&vstr,&vlen,&vlong);
 520             if (vstr) {
 521                 addReplyBulkCBuffer(c,vstr,vlen);
 522             } else {
 523                 addReplyBulkLongLong(c,vlong);
 524             }
 525             p = ziplistNext(o->ptr,p);
 526         }
 527     } else if (o->encoding == REDIS_ENCODING_LINKEDLIST) {
 528         listNode *ln;
 529
 530         /* If we are nearest to the end of the list, reach the element
 531          * starting from tail and going backward, as it is faster. */
 532         if (start > llen/2) start -= llen;
 533         ln = listIndex(o->ptr,start);
 534
 535         while(rangelen--) {
 536             addReplyBulk(c,ln->value);
 537             ln = ln->next;
 538         }
 539     } else {
 540         redisPanic("List encoding is not LINKEDLIST nor ZIPLIST!");
 541     }
 542 }
 543
 544 void ltrimCommand(redisClient *c) {
 545     robj *o;
 546     long start, end, llen, j, ltrim, rtrim;
 547     list *list;
 548     listNode *ln;
 549
 550     if ((getLongFromObjectOrReply(c, c->argv[2], &start, NULL) != REDIS_OK) ||
 551         (getLongFromObjectOrReply(c, c->argv[3], &end, NULL) != REDIS_OK)) return;
 552
 553     if ((o = lookupKeyWriteOrReply(c,c->argv[1],shared.ok)) == NULL ||
 554         checkType(c,o,REDIS_LIST)) return;
 555     llen = listTypeLength(o);
 556
 557     /* convert negative indexes */
 558     if (start < 0) start = llen+start;
 559     if (end < 0) end = llen+end;
 560     if (start < 0) start = 0;
 561
 562     /* Invariant: start >= 0, so this test will be true when end < 0.
 563      * The range is empty when start > end or start >= length. */
 564     if (start > end || start >= llen) {
 565         /* Out of range start or start > end result in empty list */
 566         ltrim = llen;
 567         rtrim = 0;
 568     } else {
 569         if (end >= llen) end = llen-1;
 570         ltrim = start;
 571         rtrim = llen-end-1;
 572     }
 573
 574     /* Remove list elements to perform the trim */
 575     if (o->encoding == REDIS_ENCODING_ZIPLIST) {
 576         o->ptr = ziplistDeleteRange(o->ptr,0,ltrim);
 577         o->ptr = ziplistDeleteRange(o->ptr,-rtrim,rtrim);
 578     } else if (o->encoding == REDIS_ENCODING_LINKEDLIST) {
 579         list = o->ptr;
 580         for (j = 0; j < ltrim; j++) {
 581             ln = listFirst(list);
 582             listDelNode(list,ln);
 583         }
 584         for (j = 0; j < rtrim; j++) {
 585             ln = listLast(list);
 586             listDelNode(list,ln);
 587         }
 588     } else {
 589         redisPanic("Unknown list encoding");
 590     }
 591     if (listTypeLength(o) == 0) dbDelete(c->db,c->argv[1]);
 592     signalModifiedKey(c->db,c->argv[1]);
 593     server.dirty++;
 594     addReply(c,shared.ok);
 595 }
 596
 597 void lremCommand(redisClient *c) {
 598     robj *subject, *obj;
 599     obj = c->argv[3] = tryObjectEncoding(c->argv[3]);
 600     long toremove;
 601     long removed = 0;
 602     listTypeEntry entry;
 603
 604     if ((getLongFromObjectOrReply(c, c->argv[2], &toremove, NULL) != REDIS_OK))
 605         return;
 606
 607     subject = lookupKeyWriteOrReply(c,c->argv[1],shared.czero);
 608     if (subject == NULL || checkType(c,subject,REDIS_LIST)) return;
 609
 610     /* Make sure obj is raw when we're dealing with a ziplist */
 611     if (subject->encoding == REDIS_ENCODING_ZIPLIST)
 612         obj = getDecodedObject(obj);
 613
 614     listTypeIterator *li;
 615     if (toremove < 0) {
 616         toremove = -toremove;
 617         li = listTypeInitIterator(subject,-1,REDIS_HEAD);
 618     } else {
 619         li = listTypeInitIterator(subject,0,REDIS_TAIL);
 620     }
 621
 622     while (listTypeNext(li,&entry)) {
 623         if (listTypeEqual(&entry,obj)) {
 624             listTypeDelete(&entry);
 625             server.dirty++;
 626             removed++;
 627             if (toremove && removed == toremove) break;
 628         }
 629     }
 630     listTypeReleaseIterator(li);
 631
 632     /* Clean up raw encoded object */
 633     if (subject->encoding == REDIS_ENCODING_ZIPLIST)
 634         decrRefCount(obj);
 635
 636     if (listTypeLength(subject) == 0) dbDelete(c->db,c->argv[1]);
 637     addReplyLongLong(c,removed);
 638     if (removed) signalModifiedKey(c->db,c->argv[1]);
 639 }
 640
 641 /* This is the semantic of this command:
 642  *  RPOPLPUSH srclist dstlist:
 643  *    IF LLEN(srclist) > 0
 644  *      element = RPOP srclist
 645  *      LPUSH dstlist element
 646  *      RETURN element
 647  *    ELSE
 648  *      RETURN nil
 649  *    END
 650  *  END
 651  *
 652  * The idea is to be able to get an element from a list in a reliable way
 653  * since the element is not just returned but pushed against another list
 654  * as well. This command was originally proposed by Ezra Zygmuntowicz.
 655  */
 656
 657 void rpoplpushHandlePush(redisClient *origclient, redisClient *c, robj *dstkey, robj *dstobj, robj *value) {
 658     robj *aux;
 659
 660     if (!handleClientsWaitingListPush(origclient,dstkey,value)) {
 661         /* Create the list if the key does not exist */
 662         if (!dstobj) {
 663             dstobj = createZiplistObject();
 664             dbAdd(c->db,dstkey,dstobj);
 665         } else {
 666             signalModifiedKey(c->db,dstkey);
 667         }
 668         listTypePush(dstobj,value,REDIS_HEAD);
 669         /* If we are pushing as a result of LPUSH against a key
 670          * watched by BRPOPLPUSH, we need to rewrite the command vector
 671          * as an LPUSH.
 672          *
 673          * If this is called directly by RPOPLPUSH (either directly
 674          * or via a BRPOPLPUSH where the popped list exists)
 675          * we should replicate the RPOPLPUSH command itself. */
 676         if (c != origclient) {
 677             aux = createStringObject("LPUSH",5);
 678             rewriteClientCommandVector(origclient,3,aux,dstkey,value);
 679             decrRefCount(aux);
 680         } else {
 681             /* Make sure to always use RPOPLPUSH in the replication / AOF,
 682              * even if the original command was BRPOPLPUSH. */
 683             aux = createStringObject("RPOPLPUSH",9);
 684             rewriteClientCommandVector(origclient,3,aux,c->argv[1],c->argv[2]);
 685             decrRefCount(aux);
 686         }
 687         server.dirty++;
 688     }
 689
 690     /* Always send the pushed value to the client. */
 691     addReplyBulk(c,value);
 692 }
 693
 694 void rpoplpushCommand(redisClient *c) {
 695     robj *sobj, *value;
 696     if ((sobj = lookupKeyWriteOrReply(c,c->argv[1],shared.nullbulk)) == NULL ||
 697         checkType(c,sobj,REDIS_LIST)) return;
 698
 699     if (listTypeLength(sobj) == 0) {
 700         addReply(c,shared.nullbulk);
 701     } else {
 702         robj *dobj = lookupKeyWrite(c->db,c->argv[2]);
 703         robj *touchedkey = c->argv[1];
 704
 705         if (dobj && checkType(c,dobj,REDIS_LIST)) return;
 706         value = listTypePop(sobj,REDIS_TAIL);
 707         /* We saved touched key, and protect it, since rpoplpushHandlePush
 708          * may change the client command argument vector. */
 709         incrRefCount(touchedkey);
 710         rpoplpushHandlePush(c,c,c->argv[2],dobj,value);
 711
 712         /* listTypePop returns an object with its refcount incremented */
 713         decrRefCount(value);
 714
 715         /* Delete the source list when it is empty */
 716         if (listTypeLength(sobj) == 0) dbDelete(c->db,touchedkey);
 717         signalModifiedKey(c->db,touchedkey);
 718         decrRefCount(touchedkey);
 719         server.dirty++;
 720     }
 721 }
 722
 723 /*-----------------------------------------------------------------------------
 724  * Blocking POP operations
 725  *----------------------------------------------------------------------------*/
 726
 727 /* Currently Redis blocking operations support is limited to list POP ops,
 728  * so the current implementation is not fully generic, but it is also not
 729  * completely specific so it will not require a rewrite to support new
 730  * kind of blocking operations in the future.
 731  *
 732  * Still it's important to note that list blocking operations can be already
 733  * used as a notification mechanism in order to implement other blocking
 734  * operations at application level, so there must be a very strong evidence
 735  * of usefulness and generality before new blocking operations are implemented.
 736  *
 737  * This is how the current blocking POP works, we use BLPOP as example:
 738  * - If the user calls BLPOP and the key exists and contains a non empty list
 739  *   then LPOP is called instead. So BLPOP is semantically the same as LPOP
 740  *   if there is not to block.
 741  * - If instead BLPOP is called and the key does not exists or the list is
 742  *   empty we need to block. In order to do so we remove the notification for
 743  *   new data to read in the client socket (so that we'll not serve new
 744  *   requests if the blocking request is not served). Also we put the client
 745  *   in a dictionary (db->blocking_keys) mapping keys to a list of clients
 746  *   blocking for this keys.
 747  * - If a PUSH operation against a key with blocked clients waiting is
 748  *   performed, we serve the first in the list: basically instead to push
 749  *   the new element inside the list we return it to the (first / oldest)
 750  *   blocking client, unblock the client, and remove it form the list.
 751  *
 752  * The above comment and the source code should be enough in order to understand
 753  * the implementation and modify / fix it later.
 754  */
 755
 756 /* Set a client in blocking mode for the specified key, with the specified
 757  * timeout */
 758 void blockForKeys(redisClient *c, robj **keys, int numkeys, time_t timeout, robj *target) {
 759     dictEntry *de;
 760     list *l;
 761     int j;
 762
 763     c->bpop.keys = zmalloc(sizeof(robj*)*numkeys);
 764     c->bpop.count = numkeys;
 765     c->bpop.timeout = timeout;
 766     c->bpop.target = target;
 767
 768     if (target != NULL) {
 769         incrRefCount(target);
 770     }
 771
 772     for (j = 0; j < numkeys; j++) {
 773         /* Add the key in the client structure, to map clients -> keys */
 774         c->bpop.keys[j] = keys[j];
 775         incrRefCount(keys[j]);
 776
 777         /* And in the other "side", to map keys -> clients */
 778         de = dictFind(c->db->blocking_keys,keys[j]);
 779         if (de == NULL) {
 780             int retval;
 781
 782             /* For every key we take a list of clients blocked for it */
 783             l = listCreate();
 784             retval = dictAdd(c->db->blocking_keys,keys[j],l);
 785             incrRefCount(keys[j]);
 786             redisAssertWithInfo(c,keys[j],retval == DICT_OK);
 787         } else {
 788             l = dictGetVal(de);
 789         }
 790         listAddNodeTail(l,c);
 791     }
 792     /* Mark the client as a blocked client */
 793     c->flags |= REDIS_BLOCKED;
 794     server.bpop_blocked_clients++;
 795 }
 796
 797 /* Unblock a client that's waiting in a blocking operation such as BLPOP */
 798 void unblockClientWaitingData(redisClient *c) {
 799     dictEntry *de;
 800     list *l;
 801     int j;
 802
 803     redisAssertWithInfo(c,NULL,c->bpop.keys != NULL);
 804     /* The client may wait for multiple keys, so unblock it for every key. */
 805     for (j = 0; j < c->bpop.count; j++) {
 806         /* Remove this client from the list of clients waiting for this key. */
 807         de = dictFind(c->db->blocking_keys,c->bpop.keys[j]);
 808         redisAssertWithInfo(c,c->bpop.keys[j],de != NULL);
 809         l = dictGetVal(de);
 810         listDelNode(l,listSearchKey(l,c));
 811         /* If the list is empty we need to remove it to avoid wasting memory */
 812         if (listLength(l) == 0)
 813             dictDelete(c->db->blocking_keys,c->bpop.keys[j]);
 814         decrRefCount(c->bpop.keys[j]);
 815     }
 816
 817     /* Cleanup the client structure */
 818     zfree(c->bpop.keys);
 819     c->bpop.keys = NULL;
 820     if (c->bpop.target) decrRefCount(c->bpop.target);
 821     c->bpop.target = NULL;
 822     c->flags &= ~REDIS_BLOCKED;
 823     c->flags |= REDIS_UNBLOCKED;
 824     server.bpop_blocked_clients--;
 825     listAddNodeTail(server.unblocked_clients,c);
 826 }
 827
 828 /* This should be called from any function PUSHing into lists.
 829  * 'c' is the "pushing client", 'key' is the key it is pushing data against,
 830  * 'ele' is the element pushed.
 831  *
 832  * If the function returns 0 there was no client waiting for a list push
 833  * against this key.
 834  *
 835  * If the function returns 1 there was a client waiting for a list push
 836  * against this key, the element was passed to this client thus it's not
 837  * needed to actually add it to the list and the caller should return asap. */
 838 int handleClientsWaitingListPush(redisClient *c, robj *key, robj *ele) {
 839     struct dictEntry *de;
 840     redisClient *receiver;
 841     int numclients;
 842     list *clients;
 843     listNode *ln;
 844     robj *dstkey, *dstobj;
 845
 846     de = dictFind(c->db->blocking_keys,key);
 847     if (de == NULL) return 0;
 848     clients = dictGetVal(de);
 849     numclients = listLength(clients);
 850
 851     /* Try to handle the push as long as there are clients waiting for a push.
 852      * Note that "numclients" is used because the list of clients waiting for a
 853      * push on "key" is deleted by unblockClient() when empty.
 854      *
 855      * This loop will have more than 1 iteration when there is a BRPOPLPUSH
 856      * that cannot push the target list because it does not contain a list. If
 857      * this happens, it simply tries the next client waiting for a push. */
 858     while (numclients--) {
 859         ln = listFirst(clients);
 860         redisAssertWithInfo(c,key,ln != NULL);
 861         receiver = ln->value;
 862         dstkey = receiver->bpop.target;
 863
 864         /* Protect receiver->bpop.target, that will be freed by
 865          * the next unblockClientWaitingData() call. */
 866         if (dstkey) incrRefCount(dstkey);
 867
 868         /* This should remove the first element of the "clients" list. */
 869         unblockClientWaitingData(receiver);
 870
 871         if (dstkey == NULL) {
 872             /* BRPOP/BLPOP */
 873             addReplyMultiBulkLen(receiver,2);
 874             addReplyBulk(receiver,key);
 875             addReplyBulk(receiver,ele);
 876             return 1; /* Serve just the first client as in B[RL]POP semantics */
 877         } else {
 878             /* BRPOPLPUSH, note that receiver->db is always equal to c->db. */
 879             dstobj = lookupKeyWrite(receiver->db,dstkey);
 880             if (!(dstobj && checkType(receiver,dstobj,REDIS_LIST))) {
 881                 rpoplpushHandlePush(c,receiver,dstkey,dstobj,ele);
 882                 decrRefCount(dstkey);
 883                 return 1;
 884             }
 885             decrRefCount(dstkey);
 886         }
 887     }
 888
 889     return 0;
 890 }
 891
 892 int getTimeoutFromObjectOrReply(redisClient *c, robj *object, time_t *timeout) {
 893     long tval;
 894
 895     if (getLongFromObjectOrReply(c,object,&tval,
 896         "timeout is not an integer or out of range") != REDIS_OK)
 897         return REDIS_ERR;
 898
 899     if (tval < 0) {
 900         addReplyError(c,"timeout is negative");
 901         return REDIS_ERR;
 902     }
 903
 904     if (tval > 0) tval += time(NULL);
 905     *timeout = tval;
 906
 907     return REDIS_OK;
 908 }
 909
 910 /* Blocking RPOP/LPOP */
 911 void blockingPopGenericCommand(redisClient *c, int where) {
 912     robj *o;
 913     time_t timeout;
 914     int j;
 915
 916     if (getTimeoutFromObjectOrReply(c,c->argv[c->argc-1],&timeout) != REDIS_OK)
 917         return;
 918
 919     for (j = 1; j < c->argc-1; j++) {
 920         o = lookupKeyWrite(c->db,c->argv[j]);
 921         if (o != NULL) {
 922             if (o->type != REDIS_LIST) {
 923                 addReply(c,shared.wrongtypeerr);
 924                 return;
 925             } else {
 926                 if (listTypeLength(o) != 0) {
 927                     /* If the list contains elements fall back to the usual
 928                      * non-blocking POP operation */
 929                     struct redisCommand *orig_cmd;
 930                     robj *argv[2], **orig_argv;
 931                     int orig_argc;
 932
 933                     /* We need to alter the command arguments before to call
 934                      * popGenericCommand() as the command takes a single key. */
 935                     orig_argv = c->argv;
 936                     orig_argc = c->argc;
 937                     orig_cmd = c->cmd;
 938                     argv[1] = c->argv[j];
 939                     c->argv = argv;
 940                     c->argc = 2;
 941
 942                     /* Also the return value is different, we need to output
 943                      * the multi bulk reply header and the key name. The
 944                      * "real" command will add the last element (the value)
 945                      * for us. If this souds like an hack to you it's just
 946                      * because it is... */
 947                     addReplyMultiBulkLen(c,2);
 948                     addReplyBulk(c,argv[1]);
 949
 950                     popGenericCommand(c,where);
 951
 952                     /* Fix the client structure with the original stuff */
 953                     c->argv = orig_argv;
 954                     c->argc = orig_argc;
 955                     c->cmd = orig_cmd;
 956
 957                     return;
 958                 }
 959             }
 960         }
 961     }
 962
 963     /* If we are inside a MULTI/EXEC and the list is empty the only thing
 964      * we can do is treating it as a timeout (even with timeout 0). */
 965     if (c->flags & REDIS_MULTI) {
 966         addReply(c,shared.nullmultibulk);
 967         return;
 968     }
 969
 970     /* If the list is empty or the key does not exists we must block */
 971     blockForKeys(c, c->argv + 1, c->argc - 2, timeout, NULL);
 972 }
 973
 974 void blpopCommand(redisClient *c) {
 975     blockingPopGenericCommand(c,REDIS_HEAD);
 976 }
 977
 978 void brpopCommand(redisClient *c) {
 979     blockingPopGenericCommand(c,REDIS_TAIL);
 980 }
 981
 982 void brpoplpushCommand(redisClient *c) {
 983     time_t timeout;
 984
 985     if (getTimeoutFromObjectOrReply(c,c->argv[3],&timeout) != REDIS_OK)
 986         return;
 987
 988     robj *key = lookupKeyWrite(c->db, c->argv[1]);
 989
 990     if (key == NULL) {
 991         if (c->flags & REDIS_MULTI) {
 992
 993             /* Blocking against an empty list in a multi state
 994              * returns immediately. */
 995             addReply(c, shared.nullbulk);
 996         } else {
 997             /* The list is empty and the client blocks. */
 998             blockForKeys(c, c->argv + 1, 1, timeout, c->argv[2]);
 999         }
1000     } else {
1001         if (key->type != REDIS_LIST) {
1002             addReply(c, shared.wrongtypeerr);
1003         } else {
1004
1005             /* The list exists and has elements, so
1006              * the regular rpoplpushCommand is executed. */
1007             redisAssertWithInfo(c,key,listTypeLength(key) > 0);
1008             rpoplpushCommand(c);
1009         }
1010     }
1011 }