src/scripting.c

   1 #include "redis.h"
   2 #include "sha1.h"
   3 #include "rand.h"
   4
   5 #include <lua.h>
   6 #include <lauxlib.h>
   7 #include <lualib.h>
   8 #include <ctype.h>
   9 #include <math.h>
  10
  11 char *redisProtocolToLuaType_Int(lua_State *lua, char *reply);
  12 char *redisProtocolToLuaType_Bulk(lua_State *lua, char *reply);
  13 char *redisProtocolToLuaType_Status(lua_State *lua, char *reply);
  14 char *redisProtocolToLuaType_Error(lua_State *lua, char *reply);
  15 char *redisProtocolToLuaType_MultiBulk(lua_State *lua, char *reply);
  16 int redis_math_random (lua_State *L);
  17 int redis_math_randomseed (lua_State *L);
  18
  19 /* Take a Redis reply in the Redis protocol format and convert it into a
  20  * Lua type. Thanks to this function, and the introduction of not connected
  21  * clients, it is trvial to implement the redis() lua function.
  22  *
  23  * Basically we take the arguments, execute the Redis command in the context
  24  * of a non connected client, then take the generated reply and convert it
  25  * into a suitable Lua type. With this trick the scripting feature does not
  26  * need the introduction of a full Redis internals API. Basically the script
  27  * is like a normal client that bypasses all the slow I/O paths.
  28  *
  29  * Note: in this function we do not do any sanity check as the reply is
  30  * generated by Redis directly. This allows use to go faster.
  31  * The reply string can be altered during the parsing as it is discared
  32  * after the conversion is completed.
  33  *
  34  * Errors are returned as a table with a single 'err' field set to the
  35  * error string.
  36  */
  37
  38 char *redisProtocolToLuaType(lua_State *lua, char* reply) {
  39     char *p = reply;
  40
  41     switch(*p) {
  42     case ':':
  43         p = redisProtocolToLuaType_Int(lua,reply);
  44         break;
  45     case '$':
  46         p = redisProtocolToLuaType_Bulk(lua,reply);
  47         break;
  48     case '+':
  49         p = redisProtocolToLuaType_Status(lua,reply);
  50         break;
  51     case '-':
  52         p = redisProtocolToLuaType_Error(lua,reply);
  53         break;
  54     case '*':
  55         p = redisProtocolToLuaType_MultiBulk(lua,reply);
  56         break;
  57     }
  58     return p;
  59 }
  60
  61 char *redisProtocolToLuaType_Int(lua_State *lua, char *reply) {
  62     char *p = strchr(reply+1,'\r');
  63     long long value;
  64
  65     string2ll(reply+1,p-reply-1,&value);
  66     lua_pushnumber(lua,(lua_Number)value);
  67     return p+2;
  68 }
  69
  70 char *redisProtocolToLuaType_Bulk(lua_State *lua, char *reply) {
  71     char *p = strchr(reply+1,'\r');
  72     long long bulklen;
  73
  74     string2ll(reply+1,p-reply-1,&bulklen);
  75     if (bulklen == -1) {
  76         lua_pushboolean(lua,0);
  77         return p+2;
  78     } else {
  79         lua_pushlstring(lua,p+2,bulklen);
  80         return p+2+bulklen+2;
  81     }
  82 }
  83
  84 char *redisProtocolToLuaType_Status(lua_State *lua, char *reply) {
  85     char *p = strchr(reply+1,'\r');
  86
  87     lua_newtable(lua);
  88     lua_pushstring(lua,"ok");
  89     lua_pushlstring(lua,reply+1,p-reply-1);
  90     lua_settable(lua,-3);
  91     return p+2;
  92 }
  93
  94 char *redisProtocolToLuaType_Error(lua_State *lua, char *reply) {
  95     char *p = strchr(reply+1,'\r');
  96
  97     lua_newtable(lua);
  98     lua_pushstring(lua,"err");
  99     lua_pushlstring(lua,reply+1,p-reply-1);
 100     lua_settable(lua,-3);
 101     return p+2;
 102 }
 103
 104 char *redisProtocolToLuaType_MultiBulk(lua_State *lua, char *reply) {
 105     char *p = strchr(reply+1,'\r');
 106     long long mbulklen;
 107     int j = 0;
 108
 109     string2ll(reply+1,p-reply-1,&mbulklen);
 110     p += 2;
 111     if (mbulklen == -1) {
 112         lua_pushboolean(lua,0);
 113         return p;
 114     }
 115     lua_newtable(lua);
 116     for (j = 0; j < mbulklen; j++) {
 117         lua_pushnumber(lua,j+1);
 118         p = redisProtocolToLuaType(lua,p);
 119         lua_settable(lua,-3);
 120     }
 121     return p;
 122 }
 123
 124 void luaPushError(lua_State *lua, char *error) {
 125     lua_newtable(lua);
 126     lua_pushstring(lua,"err");
 127     lua_pushstring(lua, error);
 128     lua_settable(lua,-3);
 129 }
 130
 131 int luaRedisCommand(lua_State *lua) {
 132     int j, argc = lua_gettop(lua);
 133     struct redisCommand *cmd;
 134     robj **argv;
 135     redisClient *c = server.lua_client;
 136     sds reply;
 137
 138     /* Build the arguments vector */
 139     argv = zmalloc(sizeof(robj*)*argc);
 140     for (j = 0; j < argc; j++) {
 141         if (!lua_isstring(lua,j+1)) break;
 142         argv[j] = createStringObject((char*)lua_tostring(lua,j+1),
 143                                      lua_strlen(lua,j+1));
 144     }
 145
 146     /* Check if one of the arguments passed by the Lua script
 147      * is not a string or an integer (lua_isstring() return true for
 148      * integers as well). */
 149     if (j != argc) {
 150         j--;
 151         while (j >= 0) {
 152             decrRefCount(argv[j]);
 153             j--;
 154         }
 155         zfree(argv);
 156         luaPushError(lua,
 157             "Lua redis() command arguments must be strings or integers");
 158         return 1;
 159     }
 160
 161     /* Setup our fake client for command execution */
 162     c->argv = argv;
 163     c->argc = argc;
 164
 165     /* Command lookup */
 166     cmd = lookupCommand(argv[0]->ptr);
 167     if (!cmd || ((cmd->arity > 0 && cmd->arity != argc) ||
 168                    (argc < -cmd->arity)))
 169     {
 170         if (cmd)
 171             luaPushError(lua,
 172                 "Wrong number of args calling Redis command From Lua script");
 173         else
 174             luaPushError(lua,"Unknown Redis command called from Lua script");
 175         goto cleanup;
 176     }
 177
 178     if (cmd->flags & REDIS_CMD_NOSCRIPT) {
 179         luaPushError(lua, "This Redis command is not allowed from scripts");
 180         goto cleanup;
 181     }
 182
 183     if (cmd->flags & REDIS_CMD_WRITE && server.lua_random_dirty) {
 184         luaPushError(lua,
 185             "Write commands not allowed after non deterministic commands");
 186         goto cleanup;
 187     }
 188
 189     if (cmd->flags & REDIS_CMD_RANDOM) server.lua_random_dirty = 1;
 190
 191     /* Run the command */
 192     cmd->proc(c);
 193
 194     /* Convert the result of the Redis command into a suitable Lua type.
 195      * The first thing we need is to create a single string from the client
 196      * output buffers. */
 197     reply = sdsempty();
 198     if (c->bufpos) {
 199         reply = sdscatlen(reply,c->buf,c->bufpos);
 200         c->bufpos = 0;
 201     }
 202     while(listLength(c->reply)) {
 203         robj *o = listNodeValue(listFirst(c->reply));
 204
 205         reply = sdscatlen(reply,o->ptr,sdslen(o->ptr));
 206         listDelNode(c->reply,listFirst(c->reply));
 207     }
 208     redisProtocolToLuaType(lua,reply);
 209     sdsfree(reply);
 210
 211 cleanup:
 212     /* Clean up. Command code may have changed argv/argc so we use the
 213      * argv/argc of the client instead of the local variables. */
 214     for (j = 0; j < c->argc; j++)
 215         decrRefCount(c->argv[j]);
 216     zfree(c->argv);
 217
 218     return 1;
 219 }
 220
 221 int luaLogCommand(lua_State *lua) {
 222     int j, argc = lua_gettop(lua);
 223     int level;
 224     sds log;
 225
 226     if (argc < 2) {
 227         luaPushError(lua, "redis.log() requires two arguments or more.");
 228         return 1;
 229     } else if (!lua_isnumber(lua,-argc)) {
 230         luaPushError(lua, "First argument must be a number (log level).");
 231         return 1;
 232     }
 233     level = lua_tonumber(lua,-argc);
 234     if (level < REDIS_DEBUG || level > REDIS_WARNING) {
 235         luaPushError(lua, "Invalid debug level.");
 236         return 1;
 237     }
 238
 239     /* Glue together all the arguments */
 240     log = sdsempty();
 241     for (j = 1; j < argc; j++) {
 242         size_t len;
 243         char *s;
 244
 245         s = (char*)lua_tolstring(lua,(-argc)+j,&len);
 246         if (s) {
 247             if (j != 1) log = sdscatlen(log," ",1);
 248             log = sdscatlen(log,s,len);
 249         }
 250     }
 251     redisLogRaw(level,log);
 252     sdsfree(log);
 253     return 0;
 254 }
 255
 256 void luaMaskCountHook(lua_State *lua, lua_Debug *ar) {
 257     long long elapsed;
 258     REDIS_NOTUSED(ar);
 259
 260     elapsed = (ustime()/1000) - server.lua_time_start;
 261     if (elapsed >= server.lua_time_limit) {
 262         redisLog(REDIS_NOTICE,"Lua script aborted for max execution time after %lld milliseconds of running time.",elapsed);
 263         lua_pushstring(lua,"Script aborted for max execution time.");
 264         lua_error(lua);
 265     }
 266 }
 267
 268 void luaLoadLib(lua_State *lua, const char *libname, lua_CFunction luafunc) {
 269   lua_pushcfunction(lua, luafunc);
 270   lua_pushstring(lua, libname);
 271   lua_call(lua, 1, 0);
 272 }
 273
 274 LUALIB_API int (luaopen_cjson) (lua_State *L);
 275
 276 void luaLoadLibraries(lua_State *lua) {
 277     luaLoadLib(lua, "", luaopen_base);
 278     luaLoadLib(lua, LUA_TABLIBNAME, luaopen_table);
 279     luaLoadLib(lua, LUA_STRLIBNAME, luaopen_string);
 280     luaLoadLib(lua, LUA_MATHLIBNAME, luaopen_math);
 281     luaLoadLib(lua, LUA_DBLIBNAME, luaopen_debug);
 282     luaLoadLib(lua, "cjson", luaopen_cjson);
 283
 284 #if 0 /* Stuff that we don't load currently, for sandboxing concerns. */
 285     luaLoadLib(lua, LUA_LOADLIBNAME, luaopen_package);
 286     luaLoadLib(lua, LUA_OSLIBNAME, luaopen_os);
 287 #endif
 288 }
 289
 290 void scriptingInit(void) {
 291     lua_State *lua = lua_open();
 292     luaLoadLibraries(lua);
 293
 294     /* Initialize a dictionary we use to map SHAs to scripts.
 295      * This is useful for replication, as we need to replicate EVALSHA
 296      * as EVAL, so we need to remember the associated script. */
 297     server.lua_scripts = dictCreate(&dbDictType,NULL);
 298
 299     /* Register the redis commands table and fields */
 300     lua_newtable(lua);
 301
 302     /* redis.call */
 303     lua_pushstring(lua,"call");
 304     lua_pushcfunction(lua,luaRedisCommand);
 305     lua_settable(lua,-3);
 306
 307     /* redis.log and log levels. */
 308     lua_pushstring(lua,"log");
 309     lua_pushcfunction(lua,luaLogCommand);
 310     lua_settable(lua,-3);
 311
 312     lua_pushstring(lua,"LOG_DEBUG");
 313     lua_pushnumber(lua,REDIS_DEBUG);
 314     lua_settable(lua,-3);
 315
 316     lua_pushstring(lua,"LOG_VERBOSE");
 317     lua_pushnumber(lua,REDIS_VERBOSE);
 318     lua_settable(lua,-3);
 319
 320     lua_pushstring(lua,"LOG_NOTICE");
 321     lua_pushnumber(lua,REDIS_NOTICE);
 322     lua_settable(lua,-3);
 323
 324     lua_pushstring(lua,"LOG_WARNING");
 325     lua_pushnumber(lua,REDIS_WARNING);
 326     lua_settable(lua,-3);
 327
 328     /* Finally set the table as 'redis' global var. */
 329     lua_setglobal(lua,"redis");
 330
 331     /* Replace math.random and math.randomseed with our implementations. */
 332     lua_getglobal(lua,"math");
 333
 334     lua_pushstring(lua,"random");
 335     lua_pushcfunction(lua,redis_math_random);
 336     lua_settable(lua,-3);
 337
 338     lua_pushstring(lua,"randomseed");
 339     lua_pushcfunction(lua,redis_math_randomseed);
 340     lua_settable(lua,-3);
 341
 342     lua_setglobal(lua,"math");
 343
 344     /* Create the (non connected) client that we use to execute Redis commands
 345      * inside the Lua interpreter */
 346     server.lua_client = createClient(-1);
 347     server.lua_client->flags |= REDIS_LUA_CLIENT;
 348
 349     server.lua = lua;
 350 }
 351
 352 /* Hash the scripit into a SHA1 digest. We use this as Lua function name.
 353  * Digest should point to a 41 bytes buffer: 40 for SHA1 converted into an
 354  * hexadecimal number, plus 1 byte for null term. */
 355 void hashScript(char *digest, char *script, size_t len) {
 356     SHA1_CTX ctx;
 357     unsigned char hash[20];
 358     char *cset = "0123456789abcdef";
 359     int j;
 360
 361     SHA1Init(&ctx);
 362     SHA1Update(&ctx,(unsigned char*)script,len);
 363     SHA1Final(hash,&ctx);
 364
 365     for (j = 0; j < 20; j++) {
 366         digest[j*2] = cset[((hash[j]&0xF0)>>4)];
 367         digest[j*2+1] = cset[(hash[j]&0xF)];
 368     }
 369     digest[40] = '\0';
 370 }
 371
 372 void luaReplyToRedisReply(redisClient *c, lua_State *lua) {
 373     int t = lua_type(lua,-1);
 374
 375     switch(t) {
 376     case LUA_TSTRING:
 377         addReplyBulkCBuffer(c,(char*)lua_tostring(lua,-1),lua_strlen(lua,-1));
 378         break;
 379     case LUA_TBOOLEAN:
 380         addReply(c,lua_toboolean(lua,-1) ? shared.cone : shared.nullbulk);
 381         break;
 382     case LUA_TNUMBER:
 383         addReplyLongLong(c,(long long)lua_tonumber(lua,-1));
 384         break;
 385     case LUA_TTABLE:
 386         /* We need to check if it is an array, an error, or a status reply.
 387          * Error are returned as a single element table with 'err' field.
 388          * Status replies are returned as single elment table with 'ok' field */
 389         lua_pushstring(lua,"err");
 390         lua_gettable(lua,-2);
 391         t = lua_type(lua,-1);
 392         if (t == LUA_TSTRING) {
 393             sds err = sdsnew(lua_tostring(lua,-1));
 394             sdsmapchars(err,"\r\n","  ",2);
 395             addReplySds(c,sdscatprintf(sdsempty(),"-%s\r\n",err));
 396             sdsfree(err);
 397             lua_pop(lua,2);
 398             return;
 399         }
 400
 401         lua_pop(lua,1);
 402         lua_pushstring(lua,"ok");
 403         lua_gettable(lua,-2);
 404         t = lua_type(lua,-1);
 405         if (t == LUA_TSTRING) {
 406             sds ok = sdsnew(lua_tostring(lua,-1));
 407             sdsmapchars(ok,"\r\n","  ",2);
 408             addReplySds(c,sdscatprintf(sdsempty(),"+%s\r\n",ok));
 409             sdsfree(ok);
 410             lua_pop(lua,1);
 411         } else {
 412             void *replylen = addDeferredMultiBulkLength(c);
 413             int j = 1, mbulklen = 0;
 414
 415             lua_pop(lua,1); /* Discard the 'ok' field value we popped */
 416             while(1) {
 417                 lua_pushnumber(lua,j++);
 418                 lua_gettable(lua,-2);
 419                 t = lua_type(lua,-1);
 420                 if (t == LUA_TNIL) {
 421                     lua_pop(lua,1);
 422                     break;
 423                 }
 424                 luaReplyToRedisReply(c, lua);
 425                 mbulklen++;
 426             }
 427             setDeferredMultiBulkLength(c,replylen,mbulklen);
 428         }
 429         break;
 430     default:
 431         addReply(c,shared.nullbulk);
 432     }
 433     lua_pop(lua,1);
 434 }
 435
 436 /* Set an array of Redis String Objects as a Lua array (table) stored into a
 437  * global variable. */
 438 void luaSetGlobalArray(lua_State *lua, char *var, robj **elev, int elec) {
 439     int j;
 440
 441     lua_newtable(lua);
 442     for (j = 0; j < elec; j++) {
 443         lua_pushlstring(lua,(char*)elev[j]->ptr,sdslen(elev[j]->ptr));
 444         lua_rawseti(lua,-2,j+1);
 445     }
 446     lua_setglobal(lua,var);
 447 }
 448
 449 void evalGenericCommand(redisClient *c, int evalsha) {
 450     lua_State *lua = server.lua;
 451     char funcname[43];
 452     long long numkeys;
 453
 454     /* We want the same PRNG sequence at every call so that our PRNG is
 455      * not affected by external state. */
 456     redisSrand48(0);
 457
 458     /* We set this flag to zero to remember that so far no random command
 459      * was called. This way we can allow the user to call commands like
 460      * SRANDMEMBER or RANDOMKEY from Lua scripts as far as no write command
 461      * is called (otherwise the replication and AOF would end with non
 462      * deterministic sequences).
 463      *
 464      * Thanks to this flag we'll raise an error every time a write command
 465      * is called after a random command was used. */
 466     server.lua_random_dirty = 0;
 467
 468     /* Get the number of arguments that are keys */
 469     if (getLongLongFromObjectOrReply(c,c->argv[2],&numkeys,NULL) != REDIS_OK)
 470         return;
 471     if (numkeys > (c->argc - 3)) {
 472         addReplyError(c,"Number of keys can't be greater than number of args");
 473         return;
 474     }
 475
 476     /* We obtain the script SHA1, then check if this function is already
 477      * defined into the Lua state */
 478     funcname[0] = 'f';
 479     funcname[1] = '_';
 480     if (!evalsha) {
 481         /* Hash the code if this is an EVAL call */
 482         hashScript(funcname+2,c->argv[1]->ptr,sdslen(c->argv[1]->ptr));
 483     } else {
 484         /* We already have the SHA if it is a EVALSHA */
 485         int j;
 486         char *sha = c->argv[1]->ptr;
 487
 488         for (j = 0; j < 40; j++)
 489             funcname[j+2] = tolower(sha[j]);
 490         funcname[42] = '\0';
 491     }
 492
 493     lua_getglobal(lua, funcname);
 494     if (lua_isnil(lua,1)) {
 495         sds funcdef;
 496
 497         /* Function not defined... let's define it if we have the
 498          * body of the funciton. If this is an EVALSHA call we can just
 499          * return an error. */
 500         if (evalsha) {
 501             addReply(c, shared.noscripterr);
 502             lua_pop(lua,1); /* remove the nil from the stack */
 503             return;
 504         }
 505         funcdef = sdsempty();
 506
 507         lua_pop(lua,1); /* remove the nil from the stack */
 508         funcdef = sdscat(funcdef,"function ");
 509         funcdef = sdscatlen(funcdef,funcname,42);
 510         funcdef = sdscatlen(funcdef," ()\n",4);
 511         funcdef = sdscatlen(funcdef,c->argv[1]->ptr,sdslen(c->argv[1]->ptr));
 512         funcdef = sdscatlen(funcdef,"\nend\n",5);
 513         /* printf("Defining:\n%s\n",funcdef); */
 514
 515         if (luaL_loadbuffer(lua,funcdef,sdslen(funcdef),"func definition")) {
 516             addReplyErrorFormat(c,"Error compiling script (new function): %s\n",
 517                 lua_tostring(lua,-1));
 518             lua_pop(lua,1);
 519             sdsfree(funcdef);
 520             return;
 521         }
 522         sdsfree(funcdef);
 523         if (lua_pcall(lua,0,0,0)) {
 524             addReplyErrorFormat(c,"Error running script (new function): %s\n",
 525                 lua_tostring(lua,-1));
 526             lua_pop(lua,1);
 527             return;
 528         }
 529         lua_getglobal(lua, funcname);
 530
 531         /* We also save a SHA1 -> Original script map in a dictionary
 532          * so that we can replicate / write in the AOF all the
 533          * EVALSHA commands as EVAL using the original script. */
 534         {
 535             int retval = dictAdd(server.lua_scripts,
 536                                  sdsnewlen(funcname+2,40),c->argv[1]);
 537             redisAssertWithInfo(c,NULL,retval == DICT_OK);
 538             incrRefCount(c->argv[1]);
 539         }
 540     }
 541
 542     /* Populate the argv and keys table accordingly to the arguments that
 543      * EVAL received. */
 544     luaSetGlobalArray(lua,"KEYS",c->argv+3,numkeys);
 545     luaSetGlobalArray(lua,"ARGV",c->argv+3+numkeys,c->argc-3-numkeys);
 546
 547     /* Select the right DB in the context of the Lua client */
 548     selectDb(server.lua_client,c->db->id);
 549
 550     /* Set an hook in order to be able to stop the script execution if it
 551      * is running for too much time.
 552      * We set the hook only if the time limit is enabled as the hook will
 553      * make the Lua script execution slower. */
 554     if (server.lua_time_limit > 0) {
 555         lua_sethook(lua,luaMaskCountHook,LUA_MASKCOUNT,100000);
 556         server.lua_time_start = ustime()/1000;
 557     } else {
 558         lua_sethook(lua,luaMaskCountHook,0,0);
 559     }
 560
 561     /* At this point whatever this script was never seen before or if it was
 562      * already defined, we can call it. We have zero arguments and expect
 563      * a single return value. */
 564     if (lua_pcall(lua,0,1,0)) {
 565         selectDb(c,server.lua_client->db->id); /* set DB ID from Lua client */
 566         addReplyErrorFormat(c,"Error running script (call to %s): %s\n",
 567             funcname, lua_tostring(lua,-1));
 568         lua_pop(lua,1);
 569         lua_gc(lua,LUA_GCCOLLECT,0);
 570         return;
 571     }
 572     selectDb(c,server.lua_client->db->id); /* set DB ID from Lua client */
 573     luaReplyToRedisReply(c,lua);
 574     lua_gc(lua,LUA_GCSTEP,1);
 575
 576     /* If we have slaves attached we want to replicate this command as
 577      * EVAL instead of EVALSHA. We do this also in the AOF as currently there
 578      * is no easy way to propagate a command in a different way in the AOF
 579      * and in the replication link.
 580      *
 581      * IMPROVEMENT POSSIBLE:
 582      * 1) Replicate this command as EVALSHA in the AOF.
 583      * 2) Remember what slave already received a given script, and replicate
 584      *    the EVALSHA against this slaves when possible.
 585      */
 586     if (evalsha) {
 587         robj *script = dictFetchValue(server.lua_scripts,c->argv[1]->ptr);
 588
 589         redisAssertWithInfo(c,NULL,script != NULL);
 590         rewriteClientCommandArgument(c,0,
 591             resetRefCount(createStringObject("EVAL",4)));
 592         rewriteClientCommandArgument(c,1,script);
 593     }
 594 }
 595
 596 void evalCommand(redisClient *c) {
 597     evalGenericCommand(c,0);
 598 }
 599
 600 void evalShaCommand(redisClient *c) {
 601     if (sdslen(c->argv[1]->ptr) != 40) {
 602         /* We know that a match is not possible if the provided SHA is
 603          * not the right length. So we return an error ASAP, this way
 604          * evalGenericCommand() can be implemented without string length
 605          * sanity check */
 606         addReply(c, shared.noscripterr);
 607         return;
 608     }
 609     evalGenericCommand(c,1);
 610 }
 611
 612 /* We replace math.random() with our implementation that is not affected
 613  * by specific libc random() implementations and will output the same sequence
 614  * (for the same seed) in every arch. */
 615
 616 /* The following implementation is the one shipped with Lua itself but with
 617  * rand() replaced by redisLrand48(). */
 618 int redis_math_random (lua_State *L) {
 619   /* the `%' avoids the (rare) case of r==1, and is needed also because on
 620      some systems (SunOS!) `rand()' may return a value larger than RAND_MAX */
 621   lua_Number r = (lua_Number)(redisLrand48()%REDIS_LRAND48_MAX) /
 622                                 (lua_Number)REDIS_LRAND48_MAX;
 623   switch (lua_gettop(L)) {  /* check number of arguments */
 624     case 0: {  /* no arguments */
 625       lua_pushnumber(L, r);  /* Number between 0 and 1 */
 626       break;
 627     }
 628     case 1: {  /* only upper limit */
 629       int u = luaL_checkint(L, 1);
 630       luaL_argcheck(L, 1<=u, 1, "interval is empty");
 631       lua_pushnumber(L, floor(r*u)+1);  /* int between 1 and `u' */
 632       break;
 633     }
 634     case 2: {  /* lower and upper limits */
 635       int l = luaL_checkint(L, 1);
 636       int u = luaL_checkint(L, 2);
 637       luaL_argcheck(L, l<=u, 2, "interval is empty");
 638       lua_pushnumber(L, floor(r*(u-l+1))+l);  /* int between `l' and `u' */
 639       break;
 640     }
 641     default: return luaL_error(L, "wrong number of arguments");
 642   }
 643   return 1;
 644 }
 645
 646 int redis_math_randomseed (lua_State *L) {
 647   redisSrand48(luaL_checkint(L, 1));
 648   return 0;
 649 }