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     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         redisAssert(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     int index = atoi(c->argv[2]->ptr);
 385     robj *value = NULL;
 386
 387     if (o->encoding == REDIS_ENCODING_ZIPLIST) {
 388         unsigned char *p;
 389         unsigned char *vstr;
 390         unsigned int vlen;
 391         long long vlong;
 392         p = ziplistIndex(o->ptr,index);
 393         if (ziplistGet(p,&vstr,&vlen,&vlong)) {
 394             if (vstr) {
 395                 value = createStringObject((char*)vstr,vlen);
 396             } else {
 397                 value = createStringObjectFromLongLong(vlong);
 398             }
 399             addReplyBulk(c,value);
 400             decrRefCount(value);
 401         } else {
 402             addReply(c,shared.nullbulk);
 403         }
 404     } else if (o->encoding == REDIS_ENCODING_LINKEDLIST) {
 405         listNode *ln = listIndex(o->ptr,index);
 406         if (ln != NULL) {
 407             value = listNodeValue(ln);
 408             addReplyBulk(c,value);
 409         } else {
 410             addReply(c,shared.nullbulk);
 411         }
 412     } else {
 413         redisPanic("Unknown list encoding");
 414     }
 415 }
 416
 417 void lsetCommand(redisClient *c) {
 418     robj *o = lookupKeyWriteOrReply(c,c->argv[1],shared.nokeyerr);
 419     if (o == NULL || checkType(c,o,REDIS_LIST)) return;
 420     int index = atoi(c->argv[2]->ptr);
 421     robj *value = (c->argv[3] = tryObjectEncoding(c->argv[3]));
 422
 423     listTypeTryConversion(o,value);
 424     if (o->encoding == REDIS_ENCODING_ZIPLIST) {
 425         unsigned char *p, *zl = o->ptr;
 426         p = ziplistIndex(zl,index);
 427         if (p == NULL) {
 428             addReply(c,shared.outofrangeerr);
 429         } else {
 430             o->ptr = ziplistDelete(o->ptr,&p);
 431             value = getDecodedObject(value);
 432             o->ptr = ziplistInsert(o->ptr,p,value->ptr,sdslen(value->ptr));
 433             decrRefCount(value);
 434             addReply(c,shared.ok);
 435             signalModifiedKey(c->db,c->argv[1]);
 436             server.dirty++;
 437         }
 438     } else if (o->encoding == REDIS_ENCODING_LINKEDLIST) {
 439         listNode *ln = listIndex(o->ptr,index);
 440         if (ln == NULL) {
 441             addReply(c,shared.outofrangeerr);
 442         } else {
 443             decrRefCount((robj*)listNodeValue(ln));
 444             listNodeValue(ln) = value;
 445             incrRefCount(value);
 446             addReply(c,shared.ok);
 447             signalModifiedKey(c->db,c->argv[1]);
 448             server.dirty++;
 449         }
 450     } else {
 451         redisPanic("Unknown list encoding");
 452     }
 453 }
 454
 455 void popGenericCommand(redisClient *c, int where) {
 456     robj *o = lookupKeyWriteOrReply(c,c->argv[1],shared.nullbulk);
 457     if (o == NULL || checkType(c,o,REDIS_LIST)) return;
 458
 459     robj *value = listTypePop(o,where);
 460     if (value == NULL) {
 461         addReply(c,shared.nullbulk);
 462     } else {
 463         addReplyBulk(c,value);
 464         decrRefCount(value);
 465         if (listTypeLength(o) == 0) dbDelete(c->db,c->argv[1]);
 466         signalModifiedKey(c->db,c->argv[1]);
 467         server.dirty++;
 468     }
 469 }
 470
 471 void lpopCommand(redisClient *c) {
 472     popGenericCommand(c,REDIS_HEAD);
 473 }
 474
 475 void rpopCommand(redisClient *c) {
 476     popGenericCommand(c,REDIS_TAIL);
 477 }
 478
 479 void lrangeCommand(redisClient *c) {
 480     robj *o;
 481     int start = atoi(c->argv[2]->ptr);
 482     int end = atoi(c->argv[3]->ptr);
 483     int llen;
 484     int rangelen;
 485
 486     if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.emptymultibulk)) == NULL
 487          || checkType(c,o,REDIS_LIST)) return;
 488     llen = listTypeLength(o);
 489
 490     /* convert negative indexes */
 491     if (start < 0) start = llen+start;
 492     if (end < 0) end = llen+end;
 493     if (start < 0) start = 0;
 494
 495     /* Invariant: start >= 0, so this test will be true when end < 0.
 496      * The range is empty when start > end or start >= length. */
 497     if (start > end || start >= llen) {
 498         addReply(c,shared.emptymultibulk);
 499         return;
 500     }
 501     if (end >= llen) end = llen-1;
 502     rangelen = (end-start)+1;
 503
 504     /* Return the result in form of a multi-bulk reply */
 505     addReplyMultiBulkLen(c,rangelen);
 506     if (o->encoding == REDIS_ENCODING_ZIPLIST) {
 507         unsigned char *p = ziplistIndex(o->ptr,start);
 508         unsigned char *vstr;
 509         unsigned int vlen;
 510         long long vlong;
 511
 512         while(rangelen--) {
 513             ziplistGet(p,&vstr,&vlen,&vlong);
 514             if (vstr) {
 515                 addReplyBulkCBuffer(c,vstr,vlen);
 516             } else {
 517                 addReplyBulkLongLong(c,vlong);
 518             }
 519             p = ziplistNext(o->ptr,p);
 520         }
 521     } else if (o->encoding == REDIS_ENCODING_LINKEDLIST) {
 522         listNode *ln = listIndex(o->ptr,start);
 523
 524         while(rangelen--) {
 525             addReplyBulk(c,ln->value);
 526             ln = ln->next;
 527         }
 528     } else {
 529         redisPanic("List encoding is not LINKEDLIST nor ZIPLIST!");
 530     }
 531 }
 532
 533 void ltrimCommand(redisClient *c) {
 534     robj *o;
 535     int start = atoi(c->argv[2]->ptr);
 536     int end = atoi(c->argv[3]->ptr);
 537     int llen;
 538     int j, ltrim, rtrim;
 539     list *list;
 540     listNode *ln;
 541
 542     if ((o = lookupKeyWriteOrReply(c,c->argv[1],shared.ok)) == NULL ||
 543         checkType(c,o,REDIS_LIST)) return;
 544     llen = listTypeLength(o);
 545
 546     /* convert negative indexes */
 547     if (start < 0) start = llen+start;
 548     if (end < 0) end = llen+end;
 549     if (start < 0) start = 0;
 550
 551     /* Invariant: start >= 0, so this test will be true when end < 0.
 552      * The range is empty when start > end or start >= length. */
 553     if (start > end || start >= llen) {
 554         /* Out of range start or start > end result in empty list */
 555         ltrim = llen;
 556         rtrim = 0;
 557     } else {
 558         if (end >= llen) end = llen-1;
 559         ltrim = start;
 560         rtrim = llen-end-1;
 561     }
 562
 563     /* Remove list elements to perform the trim */
 564     if (o->encoding == REDIS_ENCODING_ZIPLIST) {
 565         o->ptr = ziplistDeleteRange(o->ptr,0,ltrim);
 566         o->ptr = ziplistDeleteRange(o->ptr,-rtrim,rtrim);
 567     } else if (o->encoding == REDIS_ENCODING_LINKEDLIST) {
 568         list = o->ptr;
 569         for (j = 0; j < ltrim; j++) {
 570             ln = listFirst(list);
 571             listDelNode(list,ln);
 572         }
 573         for (j = 0; j < rtrim; j++) {
 574             ln = listLast(list);
 575             listDelNode(list,ln);
 576         }
 577     } else {
 578         redisPanic("Unknown list encoding");
 579     }
 580     if (listTypeLength(o) == 0) dbDelete(c->db,c->argv[1]);
 581     signalModifiedKey(c->db,c->argv[1]);
 582     server.dirty++;
 583     addReply(c,shared.ok);
 584 }
 585
 586 void lremCommand(redisClient *c) {
 587     robj *subject, *obj;
 588     obj = c->argv[3] = tryObjectEncoding(c->argv[3]);
 589     int toremove = atoi(c->argv[2]->ptr);
 590     int removed = 0;
 591     listTypeEntry entry;
 592
 593     subject = lookupKeyWriteOrReply(c,c->argv[1],shared.czero);
 594     if (subject == NULL || checkType(c,subject,REDIS_LIST)) return;
 595
 596     /* Make sure obj is raw when we're dealing with a ziplist */
 597     if (subject->encoding == REDIS_ENCODING_ZIPLIST)
 598         obj = getDecodedObject(obj);
 599
 600     listTypeIterator *li;
 601     if (toremove < 0) {
 602         toremove = -toremove;
 603         li = listTypeInitIterator(subject,-1,REDIS_HEAD);
 604     } else {
 605         li = listTypeInitIterator(subject,0,REDIS_TAIL);
 606     }
 607
 608     while (listTypeNext(li,&entry)) {
 609         if (listTypeEqual(&entry,obj)) {
 610             listTypeDelete(&entry);
 611             server.dirty++;
 612             removed++;
 613             if (toremove && removed == toremove) break;
 614         }
 615     }
 616     listTypeReleaseIterator(li);
 617
 618     /* Clean up raw encoded object */
 619     if (subject->encoding == REDIS_ENCODING_ZIPLIST)
 620         decrRefCount(obj);
 621
 622     if (listTypeLength(subject) == 0) dbDelete(c->db,c->argv[1]);
 623     addReplyLongLong(c,removed);
 624     if (removed) signalModifiedKey(c->db,c->argv[1]);
 625 }
 626
 627 /* This is the semantic of this command:
 628  *  RPOPLPUSH srclist dstlist:
 629  *    IF LLEN(srclist) > 0
 630  *      element = RPOP srclist
 631  *      LPUSH dstlist element
 632  *      RETURN element
 633  *    ELSE
 634  *      RETURN nil
 635  *    END
 636  *  END
 637  *
 638  * The idea is to be able to get an element from a list in a reliable way
 639  * since the element is not just returned but pushed against another list
 640  * as well. This command was originally proposed by Ezra Zygmuntowicz.
 641  */
 642
 643 void rpoplpushHandlePush(redisClient *c, robj *dstkey, robj *dstobj, robj *value) {
 644     if (!handleClientsWaitingListPush(c,dstkey,value)) {
 645         /* Create the list if the key does not exist */
 646         if (!dstobj) {
 647             dstobj = createZiplistObject();
 648             dbAdd(c->db,dstkey,dstobj);
 649         } else {
 650             signalModifiedKey(c->db,dstkey);
 651             server.dirty++;
 652         }
 653         listTypePush(dstobj,value,REDIS_HEAD);
 654     }
 655
 656     /* Always send the pushed value to the client. */
 657     addReplyBulk(c,value);
 658 }
 659
 660 void rpoplpushCommand(redisClient *c) {
 661     robj *sobj, *value;
 662     if ((sobj = lookupKeyWriteOrReply(c,c->argv[1],shared.nullbulk)) == NULL ||
 663         checkType(c,sobj,REDIS_LIST)) return;
 664
 665     if (listTypeLength(sobj) == 0) {
 666         addReply(c,shared.nullbulk);
 667     } else {
 668         robj *dobj = lookupKeyWrite(c->db,c->argv[2]);
 669         if (dobj && checkType(c,dobj,REDIS_LIST)) return;
 670         value = listTypePop(sobj,REDIS_TAIL);
 671         rpoplpushHandlePush(c,c->argv[2],dobj,value);
 672
 673         /* listTypePop returns an object with its refcount incremented */
 674         decrRefCount(value);
 675
 676         /* Delete the source list when it is empty */
 677         if (listTypeLength(sobj) == 0) dbDelete(c->db,c->argv[1]);
 678         signalModifiedKey(c->db,c->argv[1]);
 679         server.dirty++;
 680     }
 681 }
 682
 683 /*-----------------------------------------------------------------------------
 684  * Blocking POP operations
 685  *----------------------------------------------------------------------------*/
 686
 687 /* Currently Redis blocking operations support is limited to list POP ops,
 688  * so the current implementation is not fully generic, but it is also not
 689  * completely specific so it will not require a rewrite to support new
 690  * kind of blocking operations in the future.
 691  *
 692  * Still it's important to note that list blocking operations can be already
 693  * used as a notification mechanism in order to implement other blocking
 694  * operations at application level, so there must be a very strong evidence
 695  * of usefulness and generality before new blocking operations are implemented.
 696  *
 697  * This is how the current blocking POP works, we use BLPOP as example:
 698  * - If the user calls BLPOP and the key exists and contains a non empty list
 699  *   then LPOP is called instead. So BLPOP is semantically the same as LPOP
 700  *   if there is not to block.
 701  * - If instead BLPOP is called and the key does not exists or the list is
 702  *   empty we need to block. In order to do so we remove the notification for
 703  *   new data to read in the client socket (so that we'll not serve new
 704  *   requests if the blocking request is not served). Also we put the client
 705  *   in a dictionary (db->blocking_keys) mapping keys to a list of clients
 706  *   blocking for this keys.
 707  * - If a PUSH operation against a key with blocked clients waiting is
 708  *   performed, we serve the first in the list: basically instead to push
 709  *   the new element inside the list we return it to the (first / oldest)
 710  *   blocking client, unblock the client, and remove it form the list.
 711  *
 712  * The above comment and the source code should be enough in order to understand
 713  * the implementation and modify / fix it later.
 714  */
 715
 716 /* Set a client in blocking mode for the specified key, with the specified
 717  * timeout */
 718 void blockForKeys(redisClient *c, robj **keys, int numkeys, time_t timeout, robj *target) {
 719     dictEntry *de;
 720     list *l;
 721     int j;
 722
 723     c->bpop.keys = zmalloc(sizeof(robj*)*numkeys);
 724     c->bpop.count = numkeys;
 725     c->bpop.timeout = timeout;
 726     c->bpop.target = target;
 727
 728     if (target != NULL) {
 729         incrRefCount(target);
 730     }
 731
 732     for (j = 0; j < numkeys; j++) {
 733         /* Add the key in the client structure, to map clients -> keys */
 734         c->bpop.keys[j] = keys[j];
 735         incrRefCount(keys[j]);
 736
 737         /* And in the other "side", to map keys -> clients */
 738         de = dictFind(c->db->blocking_keys,keys[j]);
 739         if (de == NULL) {
 740             int retval;
 741
 742             /* For every key we take a list of clients blocked for it */
 743             l = listCreate();
 744             retval = dictAdd(c->db->blocking_keys,keys[j],l);
 745             incrRefCount(keys[j]);
 746             redisAssert(retval == DICT_OK);
 747         } else {
 748             l = dictGetEntryVal(de);
 749         }
 750         listAddNodeTail(l,c);
 751     }
 752     /* Mark the client as a blocked client */
 753     c->flags |= REDIS_BLOCKED;
 754     server.bpop_blocked_clients++;
 755 }
 756
 757 /* Unblock a client that's waiting in a blocking operation such as BLPOP */
 758 void unblockClientWaitingData(redisClient *c) {
 759     dictEntry *de;
 760     list *l;
 761     int j;
 762
 763     redisAssert(c->bpop.keys != NULL);
 764     /* The client may wait for multiple keys, so unblock it for every key. */
 765     for (j = 0; j < c->bpop.count; j++) {
 766         /* Remove this client from the list of clients waiting for this key. */
 767         de = dictFind(c->db->blocking_keys,c->bpop.keys[j]);
 768         redisAssert(de != NULL);
 769         l = dictGetEntryVal(de);
 770         listDelNode(l,listSearchKey(l,c));
 771         /* If the list is empty we need to remove it to avoid wasting memory */
 772         if (listLength(l) == 0)
 773             dictDelete(c->db->blocking_keys,c->bpop.keys[j]);
 774         decrRefCount(c->bpop.keys[j]);
 775     }
 776
 777     /* Cleanup the client structure */
 778     zfree(c->bpop.keys);
 779     c->bpop.keys = NULL;
 780     c->bpop.target = NULL;
 781     c->flags &= ~REDIS_BLOCKED;
 782     c->flags |= REDIS_UNBLOCKED;
 783     server.bpop_blocked_clients--;
 784     listAddNodeTail(server.unblocked_clients,c);
 785 }
 786
 787 /* This should be called from any function PUSHing into lists.
 788  * 'c' is the "pushing client", 'key' is the key it is pushing data against,
 789  * 'ele' is the element pushed.
 790  *
 791  * If the function returns 0 there was no client waiting for a list push
 792  * against this key.
 793  *
 794  * If the function returns 1 there was a client waiting for a list push
 795  * against this key, the element was passed to this client thus it's not
 796  * needed to actually add it to the list and the caller should return asap. */
 797 int handleClientsWaitingListPush(redisClient *c, robj *key, robj *ele) {
 798     struct dictEntry *de;
 799     redisClient *receiver;
 800     int numclients;
 801     list *clients;
 802     listNode *ln;
 803     robj *dstkey, *dstobj;
 804
 805     de = dictFind(c->db->blocking_keys,key);
 806     if (de == NULL) return 0;
 807     clients = dictGetEntryVal(de);
 808     numclients = listLength(clients);
 809
 810     /* Try to handle the push as long as there are clients waiting for a push.
 811      * Note that "numclients" is used because the list of clients waiting for a
 812      * push on "key" is deleted by unblockClient() when empty.
 813      *
 814      * This loop will have more than 1 iteration when there is a BRPOPLPUSH
 815      * that cannot push the target list because it does not contain a list. If
 816      * this happens, it simply tries the next client waiting for a push. */
 817     while (numclients--) {
 818         ln = listFirst(clients);
 819         redisAssert(ln != NULL);
 820         receiver = ln->value;
 821         dstkey = receiver->bpop.target;
 822
 823         /* This should remove the first element of the "clients" list. */
 824         unblockClientWaitingData(receiver);
 825         redisAssert(ln != listFirst(clients));
 826
 827         if (dstkey == NULL) {
 828             /* BRPOP/BLPOP */
 829             addReplyMultiBulkLen(receiver,2);
 830             addReplyBulk(receiver,key);
 831             addReplyBulk(receiver,ele);
 832             return 1;
 833         } else {
 834             /* BRPOPLPUSH, note that receiver->db is always equal to c->db. */
 835             dstobj = lookupKeyWrite(receiver->db,dstkey);
 836             if (dstobj && checkType(receiver,dstobj,REDIS_LIST)) {
 837                 decrRefCount(dstkey);
 838             } else {
 839                 rpoplpushHandlePush(receiver,dstkey,dstobj,ele);
 840                 decrRefCount(dstkey);
 841                 return 1;
 842             }
 843         }
 844     }
 845
 846     return 0;
 847 }
 848
 849 int getTimeoutFromObjectOrReply(redisClient *c, robj *object, time_t *timeout) {
 850     long tval;
 851
 852     if (getLongFromObjectOrReply(c,object,&tval,
 853         "timeout is not an integer or out of range") != REDIS_OK)
 854         return REDIS_ERR;
 855
 856     if (tval < 0) {
 857         addReplyError(c,"timeout is negative");
 858         return REDIS_ERR;
 859     }
 860
 861     if (tval > 0) tval += time(NULL);
 862     *timeout = tval;
 863
 864     return REDIS_OK;
 865 }
 866
 867 /* Blocking RPOP/LPOP */
 868 void blockingPopGenericCommand(redisClient *c, int where) {
 869     robj *o;
 870     time_t timeout;
 871     int j;
 872
 873     if (getTimeoutFromObjectOrReply(c,c->argv[c->argc-1],&timeout) != REDIS_OK)
 874         return;
 875
 876     for (j = 1; j < c->argc-1; j++) {
 877         o = lookupKeyWrite(c->db,c->argv[j]);
 878         if (o != NULL) {
 879             if (o->type != REDIS_LIST) {
 880                 addReply(c,shared.wrongtypeerr);
 881                 return;
 882             } else {
 883                 if (listTypeLength(o) != 0) {
 884                     /* If the list contains elements fall back to the usual
 885                      * non-blocking POP operation */
 886                     robj *argv[2], **orig_argv;
 887                     int orig_argc;
 888
 889                     /* We need to alter the command arguments before to call
 890                      * popGenericCommand() as the command takes a single key. */
 891                     orig_argv = c->argv;
 892                     orig_argc = c->argc;
 893                     argv[1] = c->argv[j];
 894                     c->argv = argv;
 895                     c->argc = 2;
 896
 897                     /* Also the return value is different, we need to output
 898                      * the multi bulk reply header and the key name. The
 899                      * "real" command will add the last element (the value)
 900                      * for us. If this souds like an hack to you it's just
 901                      * because it is... */
 902                     addReplyMultiBulkLen(c,2);
 903                     addReplyBulk(c,argv[1]);
 904
 905                     popGenericCommand(c,where);
 906
 907                     /* Fix the client structure with the original stuff */
 908                     c->argv = orig_argv;
 909                     c->argc = orig_argc;
 910
 911                     return;
 912                 }
 913             }
 914         }
 915     }
 916
 917     /* If we are inside a MULTI/EXEC and the list is empty the only thing
 918      * we can do is treating it as a timeout (even with timeout 0). */
 919     if (c->flags & REDIS_MULTI) {
 920         addReply(c,shared.nullmultibulk);
 921         return;
 922     }
 923
 924     /* If the list is empty or the key does not exists we must block */
 925     blockForKeys(c, c->argv + 1, c->argc - 2, timeout, NULL);
 926 }
 927
 928 void blpopCommand(redisClient *c) {
 929     blockingPopGenericCommand(c,REDIS_HEAD);
 930 }
 931
 932 void brpopCommand(redisClient *c) {
 933     blockingPopGenericCommand(c,REDIS_TAIL);
 934 }
 935
 936 void brpoplpushCommand(redisClient *c) {
 937     time_t timeout;
 938
 939     if (getTimeoutFromObjectOrReply(c,c->argv[3],&timeout) != REDIS_OK)
 940         return;
 941
 942     robj *key = lookupKeyWrite(c->db, c->argv[1]);
 943
 944     if (key == NULL) {
 945         if (c->flags & REDIS_MULTI) {
 946
 947             /* Blocking against an empty list in a multi state
 948              * returns immediately. */
 949             addReply(c, shared.nullbulk);
 950         } else {
 951             /* The list is empty and the client blocks. */
 952             blockForKeys(c, c->argv + 1, 1, timeout, c->argv[2]);
 953         }
 954     } else {
 955         if (key->type != REDIS_LIST) {
 956             addReply(c, shared.wrongtypeerr);
 957         } else {
 958
 959             /* The list exists and has elements, so
 960              * the regular rpoplpushCommand is executed. */
 961             redisAssert(listTypeLength(key) > 0);
 962             rpoplpushCommand(c);
 963         }
 964     }
 965 }