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, int 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         redisAssert(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     redisAssert(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     robj *lobj = lookupKeyWrite(c->db,c->argv[1]);
 263     c->argv[2] = tryObjectEncoding(c->argv[2]);
 264     if (lobj == NULL) {
 265         if (handleClientsWaitingListPush(c,c->argv[1],c->argv[2])) {
 266             addReply(c,shared.cone);
 267             return;
 268         }
 269         lobj = createZiplistObject();
 270         dbAdd(c->db,c->argv[1],lobj);
 271     } else {
 272         if (lobj->type != REDIS_LIST) {
 273             addReply(c,shared.wrongtypeerr);
 274             return;
 275         }
 276         if (handleClientsWaitingListPush(c,c->argv[1],c->argv[2])) {
 277             touchWatchedKey(c->db,c->argv[1]);
 278             addReply(c,shared.cone);
 279             return;
 280         }
 281     }
 282     listTypePush(lobj,c->argv[2],where);
 283     addReplyLongLong(c,listTypeLength(lobj));
 284     touchWatchedKey(c->db,c->argv[1]);
 285     server.dirty++;
 286 }
 287
 288 void lpushCommand(redisClient *c) {
 289     pushGenericCommand(c,REDIS_HEAD);
 290 }
 291
 292 void rpushCommand(redisClient *c) {
 293     pushGenericCommand(c,REDIS_TAIL);
 294 }
 295
 296 void pushxGenericCommand(redisClient *c, robj *refval, robj *val, int where) {
 297     robj *subject;
 298     listTypeIterator *iter;
 299     listTypeEntry entry;
 300     int inserted = 0;
 301
 302     if ((subject = lookupKeyReadOrReply(c,c->argv[1],shared.czero)) == NULL ||
 303         checkType(c,subject,REDIS_LIST)) return;
 304
 305     if (refval != NULL) {
 306         /* Note: we expect refval to be string-encoded because it is *not* the
 307          * last argument of the multi-bulk LINSERT. */
 308         redisAssert(refval->encoding == REDIS_ENCODING_RAW);
 309
 310         /* We're not sure if this value can be inserted yet, but we cannot
 311          * convert the list inside the iterator. We don't want to loop over
 312          * the list twice (once to see if the value can be inserted and once
 313          * to do the actual insert), so we assume this value can be inserted
 314          * and convert the ziplist to a regular list if necessary. */
 315         listTypeTryConversion(subject,val);
 316
 317         /* Seek refval from head to tail */
 318         iter = listTypeInitIterator(subject,0,REDIS_TAIL);
 319         while (listTypeNext(iter,&entry)) {
 320             if (listTypeEqual(&entry,refval)) {
 321                 listTypeInsert(&entry,val,where);
 322                 inserted = 1;
 323                 break;
 324             }
 325         }
 326         listTypeReleaseIterator(iter);
 327
 328         if (inserted) {
 329             /* Check if the length exceeds the ziplist length threshold. */
 330             if (subject->encoding == REDIS_ENCODING_ZIPLIST &&
 331                 ziplistLen(subject->ptr) > server.list_max_ziplist_entries)
 332                     listTypeConvert(subject,REDIS_ENCODING_LINKEDLIST);
 333             touchWatchedKey(c->db,c->argv[1]);
 334             server.dirty++;
 335         } else {
 336             /* Notify client of a failed insert */
 337             addReply(c,shared.cnegone);
 338             return;
 339         }
 340     } else {
 341         listTypePush(subject,val,where);
 342         touchWatchedKey(c->db,c->argv[1]);
 343         server.dirty++;
 344     }
 345
 346     addReplyLongLong(c,listTypeLength(subject));
 347 }
 348
 349 void lpushxCommand(redisClient *c) {
 350     c->argv[2] = tryObjectEncoding(c->argv[2]);
 351     pushxGenericCommand(c,NULL,c->argv[2],REDIS_HEAD);
 352 }
 353
 354 void rpushxCommand(redisClient *c) {
 355     c->argv[2] = tryObjectEncoding(c->argv[2]);
 356     pushxGenericCommand(c,NULL,c->argv[2],REDIS_TAIL);
 357 }
 358
 359 void linsertCommand(redisClient *c) {
 360     c->argv[4] = tryObjectEncoding(c->argv[4]);
 361     if (strcasecmp(c->argv[2]->ptr,"after") == 0) {
 362         pushxGenericCommand(c,c->argv[3],c->argv[4],REDIS_TAIL);
 363     } else if (strcasecmp(c->argv[2]->ptr,"before") == 0) {
 364         pushxGenericCommand(c,c->argv[3],c->argv[4],REDIS_HEAD);
 365     } else {
 366         addReply(c,shared.syntaxerr);
 367     }
 368 }
 369
 370 void llenCommand(redisClient *c) {
 371     robj *o = lookupKeyReadOrReply(c,c->argv[1],shared.czero);
 372     if (o == NULL || checkType(c,o,REDIS_LIST)) return;
 373     addReplyLongLong(c,listTypeLength(o));
 374 }
 375
 376 void lindexCommand(redisClient *c) {
 377     robj *o = lookupKeyReadOrReply(c,c->argv[1],shared.nullbulk);
 378     if (o == NULL || checkType(c,o,REDIS_LIST)) return;
 379     int index = atoi(c->argv[2]->ptr);
 380     robj *value = NULL;
 381
 382     if (o->encoding == REDIS_ENCODING_ZIPLIST) {
 383         unsigned char *p;
 384         unsigned char *vstr;
 385         unsigned int vlen;
 386         long long vlong;
 387         p = ziplistIndex(o->ptr,index);
 388         if (ziplistGet(p,&vstr,&vlen,&vlong)) {
 389             if (vstr) {
 390                 value = createStringObject((char*)vstr,vlen);
 391             } else {
 392                 value = createStringObjectFromLongLong(vlong);
 393             }
 394             addReplyBulk(c,value);
 395             decrRefCount(value);
 396         } else {
 397             addReply(c,shared.nullbulk);
 398         }
 399     } else if (o->encoding == REDIS_ENCODING_LINKEDLIST) {
 400         listNode *ln = listIndex(o->ptr,index);
 401         if (ln != NULL) {
 402             value = listNodeValue(ln);
 403             addReplyBulk(c,value);
 404         } else {
 405             addReply(c,shared.nullbulk);
 406         }
 407     } else {
 408         redisPanic("Unknown list encoding");
 409     }
 410 }
 411
 412 void lsetCommand(redisClient *c) {
 413     robj *o = lookupKeyWriteOrReply(c,c->argv[1],shared.nokeyerr);
 414     if (o == NULL || checkType(c,o,REDIS_LIST)) return;
 415     int index = atoi(c->argv[2]->ptr);
 416     robj *value = (c->argv[3] = tryObjectEncoding(c->argv[3]));
 417
 418     listTypeTryConversion(o,value);
 419     if (o->encoding == REDIS_ENCODING_ZIPLIST) {
 420         unsigned char *p, *zl = o->ptr;
 421         p = ziplistIndex(zl,index);
 422         if (p == NULL) {
 423             addReply(c,shared.outofrangeerr);
 424         } else {
 425             o->ptr = ziplistDelete(o->ptr,&p);
 426             value = getDecodedObject(value);
 427             o->ptr = ziplistInsert(o->ptr,p,value->ptr,sdslen(value->ptr));
 428             decrRefCount(value);
 429             addReply(c,shared.ok);
 430             touchWatchedKey(c->db,c->argv[1]);
 431             server.dirty++;
 432         }
 433     } else if (o->encoding == REDIS_ENCODING_LINKEDLIST) {
 434         listNode *ln = listIndex(o->ptr,index);
 435         if (ln == NULL) {
 436             addReply(c,shared.outofrangeerr);
 437         } else {
 438             decrRefCount((robj*)listNodeValue(ln));
 439             listNodeValue(ln) = value;
 440             incrRefCount(value);
 441             addReply(c,shared.ok);
 442             touchWatchedKey(c->db,c->argv[1]);
 443             server.dirty++;
 444         }
 445     } else {
 446         redisPanic("Unknown list encoding");
 447     }
 448 }
 449
 450 void popGenericCommand(redisClient *c, int where) {
 451     robj *o = lookupKeyWriteOrReply(c,c->argv[1],shared.nullbulk);
 452     if (o == NULL || checkType(c,o,REDIS_LIST)) return;
 453
 454     robj *value = listTypePop(o,where);
 455     if (value == NULL) {
 456         addReply(c,shared.nullbulk);
 457     } else {
 458         addReplyBulk(c,value);
 459         decrRefCount(value);
 460         if (listTypeLength(o) == 0) dbDelete(c->db,c->argv[1]);
 461         touchWatchedKey(c->db,c->argv[1]);
 462         server.dirty++;
 463     }
 464 }
 465
 466 void lpopCommand(redisClient *c) {
 467     popGenericCommand(c,REDIS_HEAD);
 468 }
 469
 470 void rpopCommand(redisClient *c) {
 471     popGenericCommand(c,REDIS_TAIL);
 472 }
 473
 474 void lrangeCommand(redisClient *c) {
 475     robj *o;
 476     int start = atoi(c->argv[2]->ptr);
 477     int end = atoi(c->argv[3]->ptr);
 478     int llen;
 479     int rangelen;
 480
 481     if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.emptymultibulk)) == NULL
 482          || checkType(c,o,REDIS_LIST)) return;
 483     llen = listTypeLength(o);
 484
 485     /* convert negative indexes */
 486     if (start < 0) start = llen+start;
 487     if (end < 0) end = llen+end;
 488     if (start < 0) start = 0;
 489
 490     /* Invariant: start >= 0, so this test will be true when end < 0.
 491      * The range is empty when start > end or start >= length. */
 492     if (start > end || start >= llen) {
 493         addReply(c,shared.emptymultibulk);
 494         return;
 495     }
 496     if (end >= llen) end = llen-1;
 497     rangelen = (end-start)+1;
 498
 499     /* Return the result in form of a multi-bulk reply */
 500     addReplyMultiBulkLen(c,rangelen);
 501     if (o->encoding == REDIS_ENCODING_ZIPLIST) {
 502         unsigned char *p = ziplistIndex(o->ptr,start);
 503         unsigned char *vstr;
 504         unsigned int vlen;
 505         long long vlong;
 506
 507         while(rangelen--) {
 508             ziplistGet(p,&vstr,&vlen,&vlong);
 509             if (vstr) {
 510                 addReplyBulkCBuffer(c,vstr,vlen);
 511             } else {
 512                 addReplyBulkLongLong(c,vlong);
 513             }
 514             p = ziplistNext(o->ptr,p);
 515         }
 516     } else if (o->encoding == REDIS_ENCODING_LINKEDLIST) {
 517         listNode *ln = listIndex(o->ptr,start);
 518
 519         while(rangelen--) {
 520             addReplyBulk(c,ln->value);
 521             ln = ln->next;
 522         }
 523     } else {
 524         redisPanic("List encoding is not LINKEDLIST nor ZIPLIST!");
 525     }
 526 }
 527
 528 void ltrimCommand(redisClient *c) {
 529     robj *o;
 530     int start = atoi(c->argv[2]->ptr);
 531     int end = atoi(c->argv[3]->ptr);
 532     int llen;
 533     int j, ltrim, rtrim;
 534     list *list;
 535     listNode *ln;
 536
 537     if ((o = lookupKeyWriteOrReply(c,c->argv[1],shared.ok)) == NULL ||
 538         checkType(c,o,REDIS_LIST)) return;
 539     llen = listTypeLength(o);
 540
 541     /* convert negative indexes */
 542     if (start < 0) start = llen+start;
 543     if (end < 0) end = llen+end;
 544     if (start < 0) start = 0;
 545
 546     /* Invariant: start >= 0, so this test will be true when end < 0.
 547      * The range is empty when start > end or start >= length. */
 548     if (start > end || start >= llen) {
 549         /* Out of range start or start > end result in empty list */
 550         ltrim = llen;
 551         rtrim = 0;
 552     } else {
 553         if (end >= llen) end = llen-1;
 554         ltrim = start;
 555         rtrim = llen-end-1;
 556     }
 557
 558     /* Remove list elements to perform the trim */
 559     if (o->encoding == REDIS_ENCODING_ZIPLIST) {
 560         o->ptr = ziplistDeleteRange(o->ptr,0,ltrim);
 561         o->ptr = ziplistDeleteRange(o->ptr,-rtrim,rtrim);
 562     } else if (o->encoding == REDIS_ENCODING_LINKEDLIST) {
 563         list = o->ptr;
 564         for (j = 0; j < ltrim; j++) {
 565             ln = listFirst(list);
 566             listDelNode(list,ln);
 567         }
 568         for (j = 0; j < rtrim; j++) {
 569             ln = listLast(list);
 570             listDelNode(list,ln);
 571         }
 572     } else {
 573         redisPanic("Unknown list encoding");
 574     }
 575     if (listTypeLength(o) == 0) dbDelete(c->db,c->argv[1]);
 576     touchWatchedKey(c->db,c->argv[1]);
 577     server.dirty++;
 578     addReply(c,shared.ok);
 579 }
 580
 581 void lremCommand(redisClient *c) {
 582     robj *subject, *obj;
 583     obj = c->argv[3] = tryObjectEncoding(c->argv[3]);
 584     int toremove = atoi(c->argv[2]->ptr);
 585     int removed = 0;
 586     listTypeEntry entry;
 587
 588     subject = lookupKeyWriteOrReply(c,c->argv[1],shared.czero);
 589     if (subject == NULL || checkType(c,subject,REDIS_LIST)) return;
 590
 591     /* Make sure obj is raw when we're dealing with a ziplist */
 592     if (subject->encoding == REDIS_ENCODING_ZIPLIST)
 593         obj = getDecodedObject(obj);
 594
 595     listTypeIterator *li;
 596     if (toremove < 0) {
 597         toremove = -toremove;
 598         li = listTypeInitIterator(subject,-1,REDIS_HEAD);
 599     } else {
 600         li = listTypeInitIterator(subject,0,REDIS_TAIL);
 601     }
 602
 603     while (listTypeNext(li,&entry)) {
 604         if (listTypeEqual(&entry,obj)) {
 605             listTypeDelete(&entry);
 606             server.dirty++;
 607             removed++;
 608             if (toremove && removed == toremove) break;
 609         }
 610     }
 611     listTypeReleaseIterator(li);
 612
 613     /* Clean up raw encoded object */
 614     if (subject->encoding == REDIS_ENCODING_ZIPLIST)
 615         decrRefCount(obj);
 616
 617     if (listTypeLength(subject) == 0) dbDelete(c->db,c->argv[1]);
 618     addReplyLongLong(c,removed);
 619     if (removed) touchWatchedKey(c->db,c->argv[1]);
 620 }
 621
 622 /* This is the semantic of this command:
 623  *  RPOPLPUSH srclist dstlist:
 624  *   IF LLEN(srclist) > 0
 625  *     element = RPOP srclist
 626  *     LPUSH dstlist element
 627  *     RETURN element
 628  *   ELSE
 629  *     RETURN nil
 630  *   END
 631  *  END
 632  *
 633  * The idea is to be able to get an element from a list in a reliable way
 634  * since the element is not just returned but pushed against another list
 635  * as well. This command was originally proposed by Ezra Zygmuntowicz.
 636  */
 637 void rpoplpushcommand(redisClient *c) {
 638     robj *sobj, *value;
 639     if ((sobj = lookupKeyWriteOrReply(c,c->argv[1],shared.nullbulk)) == NULL ||
 640         checkType(c,sobj,REDIS_LIST)) return;
 641
 642     if (listTypeLength(sobj) == 0) {
 643         addReply(c,shared.nullbulk);
 644     } else {
 645         robj *dobj = lookupKeyWrite(c->db,c->argv[2]);
 646         if (dobj && checkType(c,dobj,REDIS_LIST)) return;
 647         value = listTypePop(sobj,REDIS_TAIL);
 648
 649         /* Add the element to the target list (unless it's directly
 650          * passed to some BLPOP-ing client */
 651         if (!handleClientsWaitingListPush(c,c->argv[2],value)) {
 652             /* Create the list if the key does not exist */
 653             if (!dobj) {
 654                 dobj = createZiplistObject();
 655                 dbAdd(c->db,c->argv[2],dobj);
 656             }
 657             listTypePush(dobj,value,REDIS_HEAD);
 658         }
 659
 660         /* Send the element to the client as reply as well */
 661         addReplyBulk(c,value);
 662
 663         /* listTypePop returns an object with its refcount incremented */
 664         decrRefCount(value);
 665
 666         /* Delete the source list when it is empty */
 667         if (listTypeLength(sobj) == 0) dbDelete(c->db,c->argv[1]);
 668         touchWatchedKey(c->db,c->argv[1]);
 669         server.dirty++;
 670     }
 671 }
 672
 673 /*-----------------------------------------------------------------------------
 674  * Blocking POP operations
 675  *----------------------------------------------------------------------------*/
 676
 677 /* Currently Redis blocking operations support is limited to list POP ops,
 678  * so the current implementation is not fully generic, but it is also not
 679  * completely specific so it will not require a rewrite to support new
 680  * kind of blocking operations in the future.
 681  *
 682  * Still it's important to note that list blocking operations can be already
 683  * used as a notification mechanism in order to implement other blocking
 684  * operations at application level, so there must be a very strong evidence
 685  * of usefulness and generality before new blocking operations are implemented.
 686  *
 687  * This is how the current blocking POP works, we use BLPOP as example:
 688  * - If the user calls BLPOP and the key exists and contains a non empty list
 689  *   then LPOP is called instead. So BLPOP is semantically the same as LPOP
 690  *   if there is not to block.
 691  * - If instead BLPOP is called and the key does not exists or the list is
 692  *   empty we need to block. In order to do so we remove the notification for
 693  *   new data to read in the client socket (so that we'll not serve new
 694  *   requests if the blocking request is not served). Also we put the client
 695  *   in a dictionary (db->blocking_keys) mapping keys to a list of clients
 696  *   blocking for this keys.
 697  * - If a PUSH operation against a key with blocked clients waiting is
 698  *   performed, we serve the first in the list: basically instead to push
 699  *   the new element inside the list we return it to the (first / oldest)
 700  *   blocking client, unblock the client, and remove it form the list.
 701  *
 702  * The above comment and the source code should be enough in order to understand
 703  * the implementation and modify / fix it later.
 704  */
 705
 706 /* Set a client in blocking mode for the specified key, with the specified
 707  * timeout */
 708 void blockForKeys(redisClient *c, robj **keys, int numkeys, time_t timeout) {
 709     dictEntry *de;
 710     list *l;
 711     int j;
 712
 713     c->blocking_keys = zmalloc(sizeof(robj*)*numkeys);
 714     c->blocking_keys_num = numkeys;
 715     c->blockingto = timeout;
 716     for (j = 0; j < numkeys; j++) {
 717         /* Add the key in the client structure, to map clients -> keys */
 718         c->blocking_keys[j] = keys[j];
 719         incrRefCount(keys[j]);
 720
 721         /* And in the other "side", to map keys -> clients */
 722         de = dictFind(c->db->blocking_keys,keys[j]);
 723         if (de == NULL) {
 724             int retval;
 725
 726             /* For every key we take a list of clients blocked for it */
 727             l = listCreate();
 728             retval = dictAdd(c->db->blocking_keys,keys[j],l);
 729             incrRefCount(keys[j]);
 730             redisAssert(retval == DICT_OK);
 731         } else {
 732             l = dictGetEntryVal(de);
 733         }
 734         listAddNodeTail(l,c);
 735     }
 736     /* Mark the client as a blocked client */
 737     c->flags |= REDIS_BLOCKED;
 738     server.blpop_blocked_clients++;
 739 }
 740
 741 /* Unblock a client that's waiting in a blocking operation such as BLPOP */
 742 void unblockClientWaitingData(redisClient *c) {
 743     dictEntry *de;
 744     list *l;
 745     int j;
 746
 747     redisAssert(c->blocking_keys != NULL);
 748     /* The client may wait for multiple keys, so unblock it for every key. */
 749     for (j = 0; j < c->blocking_keys_num; j++) {
 750         /* Remove this client from the list of clients waiting for this key. */
 751         de = dictFind(c->db->blocking_keys,c->blocking_keys[j]);
 752         redisAssert(de != NULL);
 753         l = dictGetEntryVal(de);
 754         listDelNode(l,listSearchKey(l,c));
 755         /* If the list is empty we need to remove it to avoid wasting memory */
 756         if (listLength(l) == 0)
 757             dictDelete(c->db->blocking_keys,c->blocking_keys[j]);
 758         decrRefCount(c->blocking_keys[j]);
 759     }
 760     /* Cleanup the client structure */
 761     zfree(c->blocking_keys);
 762     c->blocking_keys = NULL;
 763     c->flags &= (~REDIS_BLOCKED);
 764     server.blpop_blocked_clients--;
 765     /* We want to process data if there is some command waiting
 766      * in the input buffer. Note that this is safe even if
 767      * unblockClientWaitingData() gets called from freeClient() because
 768      * freeClient() will be smart enough to call this function
 769      * *after* c->querybuf was set to NULL. */
 770     if (c->querybuf && sdslen(c->querybuf) > 0) processInputBuffer(c);
 771 }
 772
 773 /* This should be called from any function PUSHing into lists.
 774  * 'c' is the "pushing client", 'key' is the key it is pushing data against,
 775  * 'ele' is the element pushed.
 776  *
 777  * If the function returns 0 there was no client waiting for a list push
 778  * against this key.
 779  *
 780  * If the function returns 1 there was a client waiting for a list push
 781  * against this key, the element was passed to this client thus it's not
 782  * needed to actually add it to the list and the caller should return asap. */
 783 int handleClientsWaitingListPush(redisClient *c, robj *key, robj *ele) {
 784     struct dictEntry *de;
 785     redisClient *receiver;
 786     list *l;
 787     listNode *ln;
 788
 789     de = dictFind(c->db->blocking_keys,key);
 790     if (de == NULL) return 0;
 791     l = dictGetEntryVal(de);
 792     ln = listFirst(l);
 793     redisAssert(ln != NULL);
 794     receiver = ln->value;
 795
 796     addReplyMultiBulkLen(receiver,2);
 797     addReplyBulk(receiver,key);
 798     addReplyBulk(receiver,ele);
 799     unblockClientWaitingData(receiver);
 800     return 1;
 801 }
 802
 803 /* Blocking RPOP/LPOP */
 804 void blockingPopGenericCommand(redisClient *c, int where) {
 805     robj *o;
 806     long long lltimeout;
 807     time_t timeout;
 808     int j;
 809
 810     /* Make sure timeout is an integer value */
 811     if (getLongLongFromObjectOrReply(c,c->argv[c->argc-1],&lltimeout,
 812             "timeout is not an integer") != REDIS_OK) return;
 813
 814     /* Make sure the timeout is not negative */
 815     if (lltimeout < 0) {
 816         addReplyError(c,"timeout is negative");
 817         return;
 818     }
 819
 820     for (j = 1; j < c->argc-1; j++) {
 821         o = lookupKeyWrite(c->db,c->argv[j]);
 822         if (o != NULL) {
 823             if (o->type != REDIS_LIST) {
 824                 addReply(c,shared.wrongtypeerr);
 825                 return;
 826             } else {
 827                 if (listTypeLength(o) != 0) {
 828                     /* If the list contains elements fall back to the usual
 829                      * non-blocking POP operation */
 830                     robj *argv[2], **orig_argv;
 831                     int orig_argc;
 832
 833                     /* We need to alter the command arguments before to call
 834                      * popGenericCommand() as the command takes a single key. */
 835                     orig_argv = c->argv;
 836                     orig_argc = c->argc;
 837                     argv[1] = c->argv[j];
 838                     c->argv = argv;
 839                     c->argc = 2;
 840
 841                     /* Also the return value is different, we need to output
 842                      * the multi bulk reply header and the key name. The
 843                      * "real" command will add the last element (the value)
 844                      * for us. If this souds like an hack to you it's just
 845                      * because it is... */
 846                     addReplyMultiBulkLen(c,2);
 847                     addReplyBulk(c,argv[1]);
 848                     popGenericCommand(c,where);
 849
 850                     /* Fix the client structure with the original stuff */
 851                     c->argv = orig_argv;
 852                     c->argc = orig_argc;
 853                     return;
 854                 }
 855             }
 856         }
 857     }
 858
 859     /* If we are inside a MULTI/EXEC and the list is empty the only thing
 860      * we can do is treating it as a timeout (even with timeout 0). */
 861     if (c->flags & REDIS_MULTI) {
 862         addReply(c,shared.nullmultibulk);
 863         return;
 864     }
 865
 866     /* If the list is empty or the key does not exists we must block */
 867     timeout = lltimeout;
 868     if (timeout > 0) timeout += time(NULL);
 869     blockForKeys(c,c->argv+1,c->argc-2,timeout);
 870 }
 871
 872 void blpopCommand(redisClient *c) {
 873     blockingPopGenericCommand(c,REDIS_HEAD);
 874 }
 875
 876 void brpopCommand(redisClient *c) {
 877     blockingPopGenericCommand(c,REDIS_TAIL);
 878 }