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 luaRedisGenericCommand(lua_State *lua, int raise_error) {
 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     if (raise_error && reply[0] != '-') raise_error = 0;
 209     redisProtocolToLuaType(lua,reply);
 210     sdsfree(reply);
 211
 212 cleanup:
 213     /* Clean up. Command code may have changed argv/argc so we use the
 214      * argv/argc of the client instead of the local variables. */
 215     for (j = 0; j < c->argc; j++)
 216         decrRefCount(c->argv[j]);
 217     zfree(c->argv);
 218
 219     if (raise_error) {
 220         /* If we are here we should have an error in the stack, in the
 221          * form of a table with an "err" field. Extract the string to
 222          * return the plain error. */
 223         lua_pushstring(lua,"err");
 224         lua_gettable(lua,-2);
 225         return lua_error(lua);
 226     }
 227     return 1;
 228 }
 229
 230 int luaRedisCallCommand(lua_State *lua) {
 231     return luaRedisGenericCommand(lua,1);
 232 }
 233
 234 int luaRedisPCallCommand(lua_State *lua) {
 235     return luaRedisGenericCommand(lua,0);
 236 }
 237
 238 int luaLogCommand(lua_State *lua) {
 239     int j, argc = lua_gettop(lua);
 240     int level;
 241     sds log;
 242
 243     if (argc < 2) {
 244         luaPushError(lua, "redis.log() requires two arguments or more.");
 245         return 1;
 246     } else if (!lua_isnumber(lua,-argc)) {
 247         luaPushError(lua, "First argument must be a number (log level).");
 248         return 1;
 249     }
 250     level = lua_tonumber(lua,-argc);
 251     if (level < REDIS_DEBUG || level > REDIS_WARNING) {
 252         luaPushError(lua, "Invalid debug level.");
 253         return 1;
 254     }
 255
 256     /* Glue together all the arguments */
 257     log = sdsempty();
 258     for (j = 1; j < argc; j++) {
 259         size_t len;
 260         char *s;
 261
 262         s = (char*)lua_tolstring(lua,(-argc)+j,&len);
 263         if (s) {
 264             if (j != 1) log = sdscatlen(log," ",1);
 265             log = sdscatlen(log,s,len);
 266         }
 267     }
 268     redisLogRaw(level,log);
 269     sdsfree(log);
 270     return 0;
 271 }
 272
 273 void luaMaskCountHook(lua_State *lua, lua_Debug *ar) {
 274     long long elapsed;
 275     REDIS_NOTUSED(ar);
 276
 277     elapsed = (ustime()/1000) - server.lua_time_start;
 278     if (elapsed >= server.lua_time_limit) {
 279         redisLog(REDIS_NOTICE,"Lua script aborted for max execution time after %lld milliseconds of running time.",elapsed);
 280         lua_pushstring(lua,"Script aborted for max execution time.");
 281         lua_error(lua);
 282     }
 283 }
 284
 285 void luaLoadLib(lua_State *lua, const char *libname, lua_CFunction luafunc) {
 286   lua_pushcfunction(lua, luafunc);
 287   lua_pushstring(lua, libname);
 288   lua_call(lua, 1, 0);
 289 }
 290
 291 LUALIB_API int (luaopen_cjson) (lua_State *L);
 292
 293 void luaLoadLibraries(lua_State *lua) {
 294     luaLoadLib(lua, "", luaopen_base);
 295     luaLoadLib(lua, LUA_TABLIBNAME, luaopen_table);
 296     luaLoadLib(lua, LUA_STRLIBNAME, luaopen_string);
 297     luaLoadLib(lua, LUA_MATHLIBNAME, luaopen_math);
 298     luaLoadLib(lua, LUA_DBLIBNAME, luaopen_debug);
 299     luaLoadLib(lua, "cjson", luaopen_cjson);
 300
 301 #if 0 /* Stuff that we don't load currently, for sandboxing concerns. */
 302     luaLoadLib(lua, LUA_LOADLIBNAME, luaopen_package);
 303     luaLoadLib(lua, LUA_OSLIBNAME, luaopen_os);
 304 #endif
 305 }
 306
 307 /* Initialize the scripting environment.
 308  * It is possible to call this function to reset the scripting environment
 309  * assuming that we call scriptingRelease() before.
 310  * See scriptingReset() for more information. */
 311 void scriptingInit(void) {
 312     lua_State *lua = lua_open();
 313     luaLoadLibraries(lua);
 314
 315     /* Initialize a dictionary we use to map SHAs to scripts.
 316      * This is useful for replication, as we need to replicate EVALSHA
 317      * as EVAL, so we need to remember the associated script. */
 318     server.lua_scripts = dictCreate(&dbDictType,NULL);
 319
 320     /* Register the redis commands table and fields */
 321     lua_newtable(lua);
 322
 323     /* redis.call */
 324     lua_pushstring(lua,"call");
 325     lua_pushcfunction(lua,luaRedisCallCommand);
 326     lua_settable(lua,-3);
 327
 328     /* redis.pcall */
 329     lua_pushstring(lua,"pcall");
 330     lua_pushcfunction(lua,luaRedisPCallCommand);
 331     lua_settable(lua,-3);
 332
 333     /* redis.log and log levels. */
 334     lua_pushstring(lua,"log");
 335     lua_pushcfunction(lua,luaLogCommand);
 336     lua_settable(lua,-3);
 337
 338     lua_pushstring(lua,"LOG_DEBUG");
 339     lua_pushnumber(lua,REDIS_DEBUG);
 340     lua_settable(lua,-3);
 341
 342     lua_pushstring(lua,"LOG_VERBOSE");
 343     lua_pushnumber(lua,REDIS_VERBOSE);
 344     lua_settable(lua,-3);
 345
 346     lua_pushstring(lua,"LOG_NOTICE");
 347     lua_pushnumber(lua,REDIS_NOTICE);
 348     lua_settable(lua,-3);
 349
 350     lua_pushstring(lua,"LOG_WARNING");
 351     lua_pushnumber(lua,REDIS_WARNING);
 352     lua_settable(lua,-3);
 353
 354     /* Finally set the table as 'redis' global var. */
 355     lua_setglobal(lua,"redis");
 356
 357     /* Replace math.random and math.randomseed with our implementations. */
 358     lua_getglobal(lua,"math");
 359
 360     lua_pushstring(lua,"random");
 361     lua_pushcfunction(lua,redis_math_random);
 362     lua_settable(lua,-3);
 363
 364     lua_pushstring(lua,"randomseed");
 365     lua_pushcfunction(lua,redis_math_randomseed);
 366     lua_settable(lua,-3);
 367
 368     lua_setglobal(lua,"math");
 369
 370     /* Create the (non connected) client that we use to execute Redis commands
 371      * inside the Lua interpreter.
 372      * Note: there is no need to create it again when this function is called
 373      * by scriptingReset(). */
 374     if (server.lua_client == NULL) {
 375         server.lua_client = createClient(-1);
 376         server.lua_client->flags |= REDIS_LUA_CLIENT;
 377     }
 378
 379     server.lua = lua;
 380 }
 381
 382 /* Release resources related to Lua scripting.
 383  * This function is used in order to reset the scripting environment. */
 384 void scriptingRelease(void) {
 385     dictRelease(server.lua_scripts);
 386     lua_close(server.lua);
 387 }
 388
 389 void scriptingReset(void) {
 390     scriptingRelease();
 391     scriptingInit();
 392 }
 393
 394 /* Hash the scripit into a SHA1 digest. We use this as Lua function name.
 395  * Digest should point to a 41 bytes buffer: 40 for SHA1 converted into an
 396  * hexadecimal number, plus 1 byte for null term. */
 397 void hashScript(char *digest, char *script, size_t len) {
 398     SHA1_CTX ctx;
 399     unsigned char hash[20];
 400     char *cset = "0123456789abcdef";
 401     int j;
 402
 403     SHA1Init(&ctx);
 404     SHA1Update(&ctx,(unsigned char*)script,len);
 405     SHA1Final(hash,&ctx);
 406
 407     for (j = 0; j < 20; j++) {
 408         digest[j*2] = cset[((hash[j]&0xF0)>>4)];
 409         digest[j*2+1] = cset[(hash[j]&0xF)];
 410     }
 411     digest[40] = '\0';
 412 }
 413
 414 void luaReplyToRedisReply(redisClient *c, lua_State *lua) {
 415     int t = lua_type(lua,-1);
 416
 417     switch(t) {
 418     case LUA_TSTRING:
 419         addReplyBulkCBuffer(c,(char*)lua_tostring(lua,-1),lua_strlen(lua,-1));
 420         break;
 421     case LUA_TBOOLEAN:
 422         addReply(c,lua_toboolean(lua,-1) ? shared.cone : shared.nullbulk);
 423         break;
 424     case LUA_TNUMBER:
 425         addReplyLongLong(c,(long long)lua_tonumber(lua,-1));
 426         break;
 427     case LUA_TTABLE:
 428         /* We need to check if it is an array, an error, or a status reply.
 429          * Error are returned as a single element table with 'err' field.
 430          * Status replies are returned as single elment table with 'ok' field */
 431         lua_pushstring(lua,"err");
 432         lua_gettable(lua,-2);
 433         t = lua_type(lua,-1);
 434         if (t == LUA_TSTRING) {
 435             sds err = sdsnew(lua_tostring(lua,-1));
 436             sdsmapchars(err,"\r\n","  ",2);
 437             addReplySds(c,sdscatprintf(sdsempty(),"-%s\r\n",err));
 438             sdsfree(err);
 439             lua_pop(lua,2);
 440             return;
 441         }
 442
 443         lua_pop(lua,1);
 444         lua_pushstring(lua,"ok");
 445         lua_gettable(lua,-2);
 446         t = lua_type(lua,-1);
 447         if (t == LUA_TSTRING) {
 448             sds ok = sdsnew(lua_tostring(lua,-1));
 449             sdsmapchars(ok,"\r\n","  ",2);
 450             addReplySds(c,sdscatprintf(sdsempty(),"+%s\r\n",ok));
 451             sdsfree(ok);
 452             lua_pop(lua,1);
 453         } else {
 454             void *replylen = addDeferredMultiBulkLength(c);
 455             int j = 1, mbulklen = 0;
 456
 457             lua_pop(lua,1); /* Discard the 'ok' field value we popped */
 458             while(1) {
 459                 lua_pushnumber(lua,j++);
 460                 lua_gettable(lua,-2);
 461                 t = lua_type(lua,-1);
 462                 if (t == LUA_TNIL) {
 463                     lua_pop(lua,1);
 464                     break;
 465                 }
 466                 luaReplyToRedisReply(c, lua);
 467                 mbulklen++;
 468             }
 469             setDeferredMultiBulkLength(c,replylen,mbulklen);
 470         }
 471         break;
 472     default:
 473         addReply(c,shared.nullbulk);
 474     }
 475     lua_pop(lua,1);
 476 }
 477
 478 /* Set an array of Redis String Objects as a Lua array (table) stored into a
 479  * global variable. */
 480 void luaSetGlobalArray(lua_State *lua, char *var, robj **elev, int elec) {
 481     int j;
 482
 483     lua_newtable(lua);
 484     for (j = 0; j < elec; j++) {
 485         lua_pushlstring(lua,(char*)elev[j]->ptr,sdslen(elev[j]->ptr));
 486         lua_rawseti(lua,-2,j+1);
 487     }
 488     lua_setglobal(lua,var);
 489 }
 490
 491 /* Define a lua function with the specified function name and body.
 492  * The function name musts be a 2 characters long string, since all the
 493  * functions we defined in the Lua context are in the form:
 494  *
 495  *   f_<hex sha1 sum>
 496  *
 497  * On success REDIS_OK is returned, and nothing is left on the Lua stack.
 498  * On error REDIS_ERR is returned and an appropriate error is set in the
 499  * client context. */
 500 int luaCreateFunction(redisClient *c, lua_State *lua, char *funcname, robj *body) {
 501     sds funcdef = sdsempty();
 502
 503     lua_pop(lua,1); /* remove the nil from the stack */
 504     funcdef = sdscat(funcdef,"function ");
 505     funcdef = sdscatlen(funcdef,funcname,42);
 506     funcdef = sdscatlen(funcdef," ()\n",4);
 507     funcdef = sdscatlen(funcdef,body->ptr,sdslen(body->ptr));
 508     funcdef = sdscatlen(funcdef,"\nend\n",5);
 509
 510     if (luaL_loadbuffer(lua,funcdef,sdslen(funcdef),"func definition")) {
 511         addReplyErrorFormat(c,"Error compiling script (new function): %s\n",
 512             lua_tostring(lua,-1));
 513         lua_pop(lua,1);
 514         sdsfree(funcdef);
 515         return REDIS_ERR;
 516     }
 517     sdsfree(funcdef);
 518     if (lua_pcall(lua,0,0,0)) {
 519         addReplyErrorFormat(c,"Error running script (new function): %s\n",
 520             lua_tostring(lua,-1));
 521         lua_pop(lua,1);
 522         return REDIS_ERR;
 523     }
 524
 525     /* We also save a SHA1 -> Original script map in a dictionary
 526      * so that we can replicate / write in the AOF all the
 527      * EVALSHA commands as EVAL using the original script. */
 528     {
 529         int retval = dictAdd(server.lua_scripts,
 530                              sdsnewlen(funcname+2,40),body);
 531         redisAssertWithInfo(c,NULL,retval == DICT_OK);
 532         incrRefCount(body);
 533     }
 534     return REDIS_OK;
 535 }
 536
 537 void evalGenericCommand(redisClient *c, int evalsha) {
 538     lua_State *lua = server.lua;
 539     char funcname[43];
 540     long long numkeys;
 541
 542     /* We want the same PRNG sequence at every call so that our PRNG is
 543      * not affected by external state. */
 544     redisSrand48(0);
 545
 546     /* We set this flag to zero to remember that so far no random command
 547      * was called. This way we can allow the user to call commands like
 548      * SRANDMEMBER or RANDOMKEY from Lua scripts as far as no write command
 549      * is called (otherwise the replication and AOF would end with non
 550      * deterministic sequences).
 551      *
 552      * Thanks to this flag we'll raise an error every time a write command
 553      * is called after a random command was used. */
 554     server.lua_random_dirty = 0;
 555
 556     /* Get the number of arguments that are keys */
 557     if (getLongLongFromObjectOrReply(c,c->argv[2],&numkeys,NULL) != REDIS_OK)
 558         return;
 559     if (numkeys > (c->argc - 3)) {
 560         addReplyError(c,"Number of keys can't be greater than number of args");
 561         return;
 562     }
 563
 564     /* We obtain the script SHA1, then check if this function is already
 565      * defined into the Lua state */
 566     funcname[0] = 'f';
 567     funcname[1] = '_';
 568     if (!evalsha) {
 569         /* Hash the code if this is an EVAL call */
 570         hashScript(funcname+2,c->argv[1]->ptr,sdslen(c->argv[1]->ptr));
 571     } else {
 572         /* We already have the SHA if it is a EVALSHA */
 573         int j;
 574         char *sha = c->argv[1]->ptr;
 575
 576         for (j = 0; j < 40; j++)
 577             funcname[j+2] = tolower(sha[j]);
 578         funcname[42] = '\0';
 579     }
 580
 581     /* Try to lookup the Lua function */
 582     lua_getglobal(lua, funcname);
 583     if (lua_isnil(lua,1)) {
 584         /* Function not defined... let's define it if we have the
 585          * body of the funciton. If this is an EVALSHA call we can just
 586          * return an error. */
 587         if (evalsha) {
 588             addReply(c, shared.noscripterr);
 589             lua_pop(lua,1); /* remove the nil from the stack */
 590             return;
 591         }
 592         if (luaCreateFunction(c,lua,funcname,c->argv[1]) == REDIS_ERR) return;
 593         /* Now the following is guaranteed to return non nil */
 594         lua_getglobal(lua, funcname);
 595         redisAssert(!lua_isnil(lua,1));
 596     }
 597
 598     /* Populate the argv and keys table accordingly to the arguments that
 599      * EVAL received. */
 600     luaSetGlobalArray(lua,"KEYS",c->argv+3,numkeys);
 601     luaSetGlobalArray(lua,"ARGV",c->argv+3+numkeys,c->argc-3-numkeys);
 602
 603     /* Select the right DB in the context of the Lua client */
 604     selectDb(server.lua_client,c->db->id);
 605
 606     /* Set an hook in order to be able to stop the script execution if it
 607      * is running for too much time.
 608      * We set the hook only if the time limit is enabled as the hook will
 609      * make the Lua script execution slower. */
 610     if (server.lua_time_limit > 0) {
 611         lua_sethook(lua,luaMaskCountHook,LUA_MASKCOUNT,100000);
 612         server.lua_time_start = ustime()/1000;
 613     } else {
 614         lua_sethook(lua,luaMaskCountHook,0,0);
 615     }
 616
 617     /* At this point whatever this script was never seen before or if it was
 618      * already defined, we can call it. We have zero arguments and expect
 619      * a single return value. */
 620     if (lua_pcall(lua,0,1,0)) {
 621         selectDb(c,server.lua_client->db->id); /* set DB ID from Lua client */
 622         addReplyErrorFormat(c,"Error running script (call to %s): %s\n",
 623             funcname, lua_tostring(lua,-1));
 624         lua_pop(lua,1);
 625         lua_gc(lua,LUA_GCCOLLECT,0);
 626         return;
 627     }
 628     selectDb(c,server.lua_client->db->id); /* set DB ID from Lua client */
 629     luaReplyToRedisReply(c,lua);
 630     lua_gc(lua,LUA_GCSTEP,1);
 631
 632     /* If we have slaves attached we want to replicate this command as
 633      * EVAL instead of EVALSHA. We do this also in the AOF as currently there
 634      * is no easy way to propagate a command in a different way in the AOF
 635      * and in the replication link.
 636      *
 637      * IMPROVEMENT POSSIBLE:
 638      * 1) Replicate this command as EVALSHA in the AOF.
 639      * 2) Remember what slave already received a given script, and replicate
 640      *    the EVALSHA against this slaves when possible.
 641      */
 642     if (evalsha) {
 643         robj *script = dictFetchValue(server.lua_scripts,c->argv[1]->ptr);
 644
 645         redisAssertWithInfo(c,NULL,script != NULL);
 646         rewriteClientCommandArgument(c,0,
 647             resetRefCount(createStringObject("EVAL",4)));
 648         rewriteClientCommandArgument(c,1,script);
 649     }
 650 }
 651
 652 void evalCommand(redisClient *c) {
 653     evalGenericCommand(c,0);
 654 }
 655
 656 void evalShaCommand(redisClient *c) {
 657     if (sdslen(c->argv[1]->ptr) != 40) {
 658         /* We know that a match is not possible if the provided SHA is
 659          * not the right length. So we return an error ASAP, this way
 660          * evalGenericCommand() can be implemented without string length
 661          * sanity check */
 662         addReply(c, shared.noscripterr);
 663         return;
 664     }
 665     evalGenericCommand(c,1);
 666 }
 667
 668 /* We replace math.random() with our implementation that is not affected
 669  * by specific libc random() implementations and will output the same sequence
 670  * (for the same seed) in every arch. */
 671
 672 /* The following implementation is the one shipped with Lua itself but with
 673  * rand() replaced by redisLrand48(). */
 674 int redis_math_random (lua_State *L) {
 675   /* the `%' avoids the (rare) case of r==1, and is needed also because on
 676      some systems (SunOS!) `rand()' may return a value larger than RAND_MAX */
 677   lua_Number r = (lua_Number)(redisLrand48()%REDIS_LRAND48_MAX) /
 678                                 (lua_Number)REDIS_LRAND48_MAX;
 679   switch (lua_gettop(L)) {  /* check number of arguments */
 680     case 0: {  /* no arguments */
 681       lua_pushnumber(L, r);  /* Number between 0 and 1 */
 682       break;
 683     }
 684     case 1: {  /* only upper limit */
 685       int u = luaL_checkint(L, 1);
 686       luaL_argcheck(L, 1<=u, 1, "interval is empty");
 687       lua_pushnumber(L, floor(r*u)+1);  /* int between 1 and `u' */
 688       break;
 689     }
 690     case 2: {  /* lower and upper limits */
 691       int l = luaL_checkint(L, 1);
 692       int u = luaL_checkint(L, 2);
 693       luaL_argcheck(L, l<=u, 2, "interval is empty");
 694       lua_pushnumber(L, floor(r*(u-l+1))+l);  /* int between `l' and `u' */
 695       break;
 696     }
 697     default: return luaL_error(L, "wrong number of arguments");
 698   }
 699   return 1;
 700 }
 701
 702 int redis_math_randomseed (lua_State *L) {
 703   redisSrand48(luaL_checkint(L, 1));
 704   return 0;
 705 }
 706
 707 /* ---------------------------------------------------------------------------
 708  * SCRIPT command for script environment introspection and control
 709  * ------------------------------------------------------------------------- */
 710
 711 void scriptCommand(redisClient *c) {
 712     if (c->argc == 2 && !strcasecmp(c->argv[1]->ptr,"flush")) {
 713         scriptingReset();
 714         addReply(c,shared.ok);
 715         server.dirty++; /* Replicating this command is a good idea. */
 716     } else if (c->argc >= 2 && !strcasecmp(c->argv[1]->ptr,"exists")) {
 717         int j;
 718
 719         addReplyMultiBulkLen(c, c->argc-2);
 720         for (j = 2; j < c->argc; j++) {
 721             if (dictFind(server.lua_scripts,c->argv[j]->ptr))
 722                 addReply(c,shared.cone);
 723             else
 724                 addReply(c,shared.czero);
 725         }
 726     } else if (c->argc == 3 && !strcasecmp(c->argv[1]->ptr,"load")) {
 727         /* We obtain the script SHA1, then check if this function is already
 728          * defined into the Lua state */
 729         char funcname[43];
 730
 731         funcname[0] = 'f';
 732         funcname[1] = '_';
 733         hashScript(funcname+2,c->argv[2]->ptr,sdslen(c->argv[2]->ptr));
 734         if (luaCreateFunction(c,server.lua,funcname,c->argv[2]) == REDIS_ERR)
 735             return;
 736         addReply(c,shared.ok);
 737     } else {
 738         addReplyError(c, "Unknown SCRIPT subcommand or wrong # of args.");
 739     }
 740 }