src/rrd_rpncalc.c

   1 /****************************************************************************
   2  * RRDtool 1.0.28  Copyright Tobias Oetiker, 1997 - 2002
   3  ****************************************************************************
   4  * rrd_rpncalc.c  RPN calculator functions
   5  ****************************************************************************/
   6
   7 #include "rrd_tool.h"
   8 #include "rrd_rpncalc.h"
   9 #include <limits.h>
  10
  11 short addop2str(enum op_en op, enum op_en op_type, char *op_str,
  12             char **result_str, unsigned short *offset);
  13 int tzoffset(time_t); /* used to implement LTIME */
  14
  15 short rpn_compact(rpnp_t *rpnp, rpn_cdefds_t **rpnc, short *count)
  16 {
  17     short i;
  18     *count = 0;
  19     /* count the number of rpn nodes */
  20     while(rpnp[*count].op != OP_END) (*count)++;
  21     if (++(*count) > DS_CDEF_MAX_RPN_NODES) {
  22         rrd_set_error("Maximum %d RPN nodes permitted",
  23                       DS_CDEF_MAX_RPN_NODES);
  24         return -1;
  25     }
  26
  27     /* allocate memory */
  28     *rpnc = (rpn_cdefds_t *) calloc(*count,sizeof(rpn_cdefds_t));
  29     for (i = 0; rpnp[i].op != OP_END; i++)
  30     {
  31         (*rpnc)[i].op = (char) rpnp[i].op;
  32         if (rpnp[i].op == OP_NUMBER) {
  33             /* rpnp.val is a double, rpnc.val is a short */
  34             double temp = floor(rpnp[i].val);
  35             if (temp < SHRT_MIN || temp > SHRT_MAX) {
  36                 rrd_set_error(
  37                     "constants must be integers in the interval (%d, %d)",
  38                     SHRT_MIN, SHRT_MAX);
  39                 free(*rpnc);
  40                 return -1;
  41             }
  42             (*rpnc)[i].val = (short) temp;
  43           } else if (rpnp[i].op == OP_VARIABLE ||
  44                                  rpnp[i].op == OP_PREV_OTHER) {
  45             (*rpnc)[i].val = (short) rpnp[i].ptr;
  46         }
  47     }
  48     /* terminate the sequence */
  49     (*rpnc)[(*count) - 1].op = OP_END;
  50     return 0;
  51 }
  52
  53 rpnp_t * rpn_expand(rpn_cdefds_t *rpnc)
  54 {
  55     short i;
  56     rpnp_t *rpnp;
  57
  58     /* DS_CDEF_MAX_RPN_NODES is small, so at the expense of some wasted
  59      * memory we avoid any reallocs */
  60     rpnp = (rpnp_t *) calloc(DS_CDEF_MAX_RPN_NODES,sizeof(rpnp_t));
  61     if (rpnp == NULL) return NULL;
  62     for (i = 0; rpnc[i].op != OP_END; ++i)
  63     {
  64         rpnp[i].op = (long) rpnc[i].op;
  65         if (rpnp[i].op == OP_NUMBER) {
  66             rpnp[i].val = (double) rpnc[i].val;
  67           } else if (rpnp[i].op == OP_VARIABLE ||
  68                                  rpnp[i].op == OP_PREV_OTHER) {
  69             rpnp[i].ptr = (long) rpnc[i].val;
  70         }
  71     }
  72     /* terminate the sequence */
  73     rpnp[i].op = OP_END;
  74     return rpnp;
  75 }
  76
  77 /* rpn_compact2str: convert a compact sequence of RPN operator nodes back
  78  * into a CDEF string. This function is used by rrd_dump.
  79  * arguments:
  80  *  rpnc: an array of compact RPN operator nodes
  81  *  ds_def: a pointer to the data source definition section of an RRD header
  82  *   for lookup of data source names by index
  83  *  str: out string, memory is allocated by the function, must be freed by the
  84  *   the caller */
  85 void rpn_compact2str(rpn_cdefds_t *rpnc,ds_def_t *ds_def,char **str)
  86 {
  87     unsigned short i,offset = 0;
  88     char buffer[7]; /* short as a string */
  89
  90     for (i = 0; rpnc[i].op != OP_END; i++)
  91     {
  92         if (i > 0) (*str)[offset++] = ',';
  93
  94 #define add_op(VV,VVV) \
  95           if (addop2str(rpnc[i].op, VV, VVV, str, &offset) == 1) continue;
  96
  97         if (rpnc[i].op == OP_NUMBER) {
  98             /* convert a short into a string */
  99 #ifdef WIN32
 100             _itoa(rpnc[i].val,buffer,10);
 101 #else
 102             sprintf(buffer,"%d",rpnc[i].val);
 103 #endif
 104             add_op(OP_NUMBER,buffer)
 105                 }
 106
 107         if (rpnc[i].op == OP_VARIABLE) {
 108             char *ds_name = ds_def[rpnc[i].val].ds_nam;
 109             add_op(OP_VARIABLE, ds_name)
 110                 }
 111
 112           if (rpnc[i].op == OP_PREV_OTHER) {
 113                 char *ds_name = ds_def[rpnc[i].val].ds_nam;
 114                 add_op(OP_VARIABLE, ds_name)
 115           }
 116
 117 #undef add_op
 118
 119 #define add_op(VV,VVV) \
 120           if (addop2str(rpnc[i].op, VV, #VVV, str, &offset) == 1) continue;
 121
 122           add_op(OP_ADD,+)
 123           add_op(OP_SUB,-)
 124           add_op(OP_MUL,*)
 125           add_op(OP_DIV,/)
 126           add_op(OP_MOD,%)
 127           add_op(OP_SIN,SIN)
 128           add_op(OP_COS,COS)
 129           add_op(OP_LOG,LOG)
 130           add_op(OP_FLOOR,FLOOR)
 131           add_op(OP_CEIL,CEIL)
 132           add_op(OP_EXP,EXP)
 133           add_op(OP_DUP,DUP)
 134           add_op(OP_EXC,EXC)
 135           add_op(OP_POP,POP)
 136           add_op(OP_LT,LT)
 137           add_op(OP_LE,LE)
 138           add_op(OP_GT,GT)
 139           add_op(OP_GE,GE)
 140           add_op(OP_EQ,EQ)
 141           add_op(OP_IF,IF)
 142           add_op(OP_MIN,MIN)
 143           add_op(OP_MAX,MAX)
 144           add_op(OP_LIMIT,LIMIT)
 145           add_op(OP_UNKN,UNKN)
 146           add_op(OP_UN,UN)
 147           add_op(OP_NEGINF,NEGINF)
 148           add_op(OP_NE,NE)
 149           add_op(OP_PREV,PREV)
 150           add_op(OP_INF,INF)
 151           add_op(OP_ISINF,ISINF)
 152           add_op(OP_NOW,NOW)
 153           add_op(OP_LTIME,LTIME)
 154           add_op(OP_TIME,TIME)
 155
 156 #undef add_op
 157               }
 158     (*str)[offset] = '\0';
 159
 160 }
 161
 162 short addop2str(enum op_en op, enum op_en op_type, char *op_str,
 163                 char **result_str, unsigned short *offset)
 164 {
 165     if (op == op_type) {
 166         short op_len;
 167         op_len = strlen(op_str);
 168         *result_str =  (char *) rrd_realloc(*result_str,
 169                                             (op_len + 1 + *offset)*sizeof(char));
 170         if (*result_str == NULL) {
 171             rrd_set_error("failed to alloc memory in addop2str");
 172             return -1;
 173         }
 174         strncpy(&((*result_str)[*offset]),op_str,op_len);
 175         *offset += op_len;
 176         return 1;
 177     }
 178     return 0;
 179 }
 180
 181 void parseCDEF_DS(char *def,rrd_t *rrd, int ds_idx)
 182 {
 183     rpnp_t *rpnp = NULL;
 184     rpn_cdefds_t *rpnc = NULL;
 185     short count, i;
 186
 187     rpnp = rpn_parse((void*) rrd, def, &lookup_DS);
 188     if (rpnp == NULL) {
 189         rrd_set_error("failed to parse computed data source %s", def);
 190         return;
 191     }
 192     /* Check for OP nodes not permitted in COMPUTE DS.
 193      * Moved this check from within rpn_compact() because it really is
 194      * COMPUTE DS specific. This is less efficient, but creation doesn't
 195      * occur too often. */
 196     for (i = 0; rpnp[i].op != OP_END; i++) {
 197         if (rpnp[i].op == OP_TIME || rpnp[i].op == OP_LTIME ||
 198             rpnp[i].op == OP_PREV)
 199         {
 200             rrd_set_error(
 201                 "operators time, ltime and prev not supported with DS COMPUTE");
 202             free(rpnp);
 203             return;
 204         }
 205     }
 206     if (rpn_compact(rpnp,&rpnc,&count) == -1) {
 207         free(rpnp);
 208         return;
 209     }
 210     /* copy the compact rpn representation over the ds_def par array */
 211     memcpy((void*) &(rrd -> ds_def[ds_idx].par[DS_cdef]),
 212            (void*) rpnc, count*sizeof(rpn_cdefds_t));
 213     free(rpnp);
 214     free(rpnc);
 215 }
 216
 217 /* lookup a data source name in the rrd struct and return the index,
 218  * should use ds_match() here except:
 219  * (1) need a void * pointer to the rrd
 220  * (2) error handling is left to the caller
 221  */
 222 long lookup_DS(void *rrd_vptr,char *ds_name)
 223 {
 224     int i;
 225     rrd_t *rrd;
 226
 227     rrd = (rrd_t *) rrd_vptr;
 228
 229     for (i = 0; i < rrd -> stat_head -> ds_cnt; ++i)
 230     {
 231         if(strcmp(ds_name,rrd -> ds_def[i].ds_nam) == 0)
 232             return i;
 233     }
 234     /* the caller handles a bad data source name in the rpn string */
 235     return -1;
 236 }
 237
 238 /* rpn_parse : parse a string and generate a rpnp array; modified
 239  * str2rpn() originally included in rrd_graph.c
 240  * arguments:
 241  * key_hash: a transparent argument passed to lookup(); conceptually this
 242  *    is a hash object for lookup of a numeric key given a variable name
 243  * expr: the string RPN expression, including variable names
 244  * lookup(): a function that retrieves a numeric key given a variable name
 245  */
 246 rpnp_t *
 247 rpn_parse(void *key_hash,char *expr,long (*lookup)(void *,char*)){
 248     int pos=0;
 249     long steps=-1;
 250     rpnp_t  *rpnp;
 251     char vname[30];
 252
 253     rpnp=NULL;
 254
 255     while(*expr){
 256         if ((rpnp = (rpnp_t *) rrd_realloc(rpnp, (++steps + 2)*
 257                                        sizeof(rpnp_t)))==NULL){
 258             return NULL;
 259         }
 260
 261         else if((sscanf(expr,"%lf%n",&rpnp[steps].val,&pos) == 1) && (expr[pos] == ',')){
 262             rpnp[steps].op = OP_NUMBER;
 263             expr+=pos;
 264         }
 265
 266 #define match_op(VV,VVV) \
 267         else if (strncmp(expr, #VVV, strlen(#VVV))==0){ \
 268             rpnp[steps].op = VV; \
 269             expr+=strlen(#VVV); \
 270         }
 271
 272
 273 #define match_op_param(VV,VVV) \
 274         else if (sscanf(expr, #VVV "(%[a-z0-9]s)",vname) == 1) { \
 275           int length = 0; \
 276           if ((length = strlen(#VVV)+strlen(vname)+2, \
 277               expr[length] == ',' || expr[length] == '\0') ) { \
 278              rpnp[steps].op = VV; \
 279              rpnp[steps].ptr = (*lookup)(key_hash,vname); \
 280              if (rpnp[steps].ptr < 0) { \
 281                            free(rpnp); \
 282                            return NULL; \
 283                          } else expr+=length; \
 284           } \
 285         }
 286
 287         match_op(OP_ADD,+)
 288         match_op(OP_SUB,-)
 289         match_op(OP_MUL,*)
 290         match_op(OP_DIV,/)
 291         match_op(OP_MOD,%)
 292         match_op(OP_SIN,SIN)
 293         match_op(OP_COS,COS)
 294         match_op(OP_LOG,LOG)
 295         match_op(OP_FLOOR,FLOOR)
 296         match_op(OP_CEIL,CEIL)
 297         match_op(OP_EXP,EXP)
 298         match_op(OP_DUP,DUP)
 299         match_op(OP_EXC,EXC)
 300         match_op(OP_POP,POP)
 301         match_op(OP_LT,LT)
 302         match_op(OP_LE,LE)
 303         match_op(OP_GT,GT)
 304         match_op(OP_GE,GE)
 305         match_op(OP_EQ,EQ)
 306         match_op(OP_IF,IF)
 307         match_op(OP_MIN,MIN)
 308         match_op(OP_MAX,MAX)
 309         match_op(OP_LIMIT,LIMIT)
 310           /* order is important here ! .. match longest first */
 311         match_op(OP_UNKN,UNKN)
 312         match_op(OP_UN,UN)
 313         match_op(OP_NEGINF,NEGINF)
 314         match_op(OP_NE,NE)
 315           match_op_param(OP_PREV_OTHER,PREV)
 316         match_op(OP_PREV,PREV)
 317         match_op(OP_INF,INF)
 318         match_op(OP_ISINF,ISINF)
 319         match_op(OP_NOW,NOW)
 320         match_op(OP_LTIME,LTIME)
 321         match_op(OP_TIME,TIME)
 322
 323 #undef match_op
 324
 325
 326             else if ((sscanf(expr,"%29[_A-Za-z0-9]%n",
 327                              vname,&pos) == 1)
 328                      && ((rpnp[steps].ptr = (*lookup)(key_hash,vname)) != -1)){
 329                 rpnp[steps].op = OP_VARIABLE;
 330                 expr+=pos;
 331             }
 332
 333         else {
 334             free(rpnp);
 335             return NULL;
 336         }
 337         if (*expr == 0)
 338             break;
 339         if (*expr == ',')
 340             expr++;
 341         else {
 342             free(rpnp);
 343             return NULL;
 344         }
 345     }
 346     rpnp[steps+1].op = OP_END;
 347     return rpnp;
 348 }
 349
 350 void
 351 rpnstack_init(rpnstack_t *rpnstack)
 352 {
 353     rpnstack -> s = NULL;
 354     rpnstack -> dc_stacksize = 0;
 355     rpnstack -> dc_stackblock = 100;
 356 }
 357
 358 void
 359 rpnstack_free(rpnstack_t *rpnstack)
 360 {
 361    if (rpnstack -> s != NULL)
 362           free(rpnstack -> s);
 363    rpnstack -> dc_stacksize = 0;
 364 }
 365
 366 /* rpn_calc: run the RPN calculator; also performs variable substitution;
 367  * moved and modified from data_calc() originally included in rrd_graph.c
 368  * arguments:
 369  * rpnp : an array of RPN operators (including variable references)
 370  * rpnstack : the initialized stack
 371  * data_idx : when data_idx is a multiple of rpnp.step, the rpnp.data pointer
 372  *   is advanced by rpnp.ds_cnt; used only for variable substitution
 373  * output : an array of output values; OP_PREV assumes this array contains
 374  *   the "previous" value at index position output_idx-1; the definition of
 375  *   "previous" depends on the calling environment
 376  * output_idx : an index into the output array in which to store the output
 377  *   of the RPN calculator
 378  * returns: -1 if the computation failed (also calls rrd_set_error)
 379  *           0 on success
 380  */
 381 short
 382 rpn_calc(rpnp_t *rpnp, rpnstack_t *rpnstack, long data_idx,
 383                 rrd_value_t *output, int output_idx)
 384 {
 385     int rpi;
 386     long stptr = -1;
 387
 388     /* process each op from the rpn in turn */
 389     for (rpi=0; rpnp[rpi].op != OP_END; rpi++){
 390         /* allocate or grow the stack */
 391         if (stptr + 5 > rpnstack -> dc_stacksize){
 392             /* could move this to a separate function */
 393             rpnstack -> dc_stacksize += rpnstack -> dc_stackblock;
 394             rpnstack -> s = rrd_realloc(rpnstack -> s,
 395                         (rpnstack -> dc_stacksize)*sizeof(*(rpnstack -> s)));
 396             if (rpnstack -> s == NULL){
 397                 rrd_set_error("RPN stack overflow");
 398                 return -1;
 399             }
 400         }
 401
 402 #define stackunderflow(MINSIZE)                         \
 403         if(stptr<MINSIZE){                              \
 404             rrd_set_error("RPN stack underflow");       \
 405             return -1;                                  \
 406         }
 407
 408         switch (rpnp[rpi].op){
 409             case OP_NUMBER:
 410                 rpnstack -> s[++stptr] = rpnp[rpi].val;
 411                 break;
 412             case OP_VARIABLE:
 413                 /* Sanity check: VDEFs shouldn't make it here */
 414                 if (rpnp[rpi].ds_cnt == 0) {
 415                     rrd_set_error("VDEF made it into rpn_calc... aborting");
 416                     return -1;
 417                 } else {
 418                     /* make sure we pull the correct value from
 419                      * the *.data array. Adjust the pointer into
 420                      * the array acordingly. Advance the ptr one
 421                      * row in the rra (skip over non-relevant
 422                      * data sources)
 423                      */
 424                     rpnstack -> s[++stptr] =  *(rpnp[rpi].data);
 425                     if (data_idx % rpnp[rpi].step == 0){
 426                         rpnp[rpi].data += rpnp[rpi].ds_cnt;
 427                     }
 428                 }
 429                 break;
 430             case OP_PREV:
 431                 if ((output_idx-1) <= 0) {
 432                     rpnstack -> s[++stptr] = DNAN;
 433                 } else {
 434                     rpnstack -> s[++stptr] = output[output_idx-1];
 435                 }
 436                 break;
 437         case OP_PREV_OTHER:
 438           if ((output_idx-1) <= 0) {
 439                 rpnstack -> s[++stptr] = DNAN;
 440           } else {
 441                 rpnstack -> s[++stptr] = rpnp[rpnp[rpi].ptr].data[output_idx-1];
 442           }
 443           break;
 444             case OP_UNKN:
 445                 rpnstack -> s[++stptr] = DNAN;
 446                 break;
 447             case OP_INF:
 448                 rpnstack -> s[++stptr] = DINF;
 449                 break;
 450             case OP_NEGINF:
 451                 rpnstack -> s[++stptr] = -DINF;
 452                 break;
 453             case OP_NOW:
 454                 rpnstack -> s[++stptr] = (double)time(NULL);
 455                 break;
 456             case OP_TIME:
 457                 /* HACK: this relies on the data_idx being the time,
 458                 ** which the within-function scope is unaware of */
 459                 rpnstack -> s[++stptr] = (double) data_idx;
 460                 break;
 461             case OP_LTIME:
 462                 rpnstack -> s[++stptr] =
 463                         (double) tzoffset(data_idx) + (double)data_idx;
 464                 break;
 465             case OP_ADD:
 466                 stackunderflow(1);
 467                 rpnstack -> s[stptr-1]  = rpnstack -> s[stptr-1]
 468                                         + rpnstack -> s[stptr];
 469                 stptr--;
 470                 break;
 471             case OP_SUB:
 472                 stackunderflow(1);
 473                 rpnstack -> s[stptr-1]  = rpnstack -> s[stptr-1]
 474                                         - rpnstack -> s[stptr];
 475                 stptr--;
 476                 break;
 477             case OP_MUL:
 478                 stackunderflow(1);
 479                 rpnstack -> s[stptr-1]  = (rpnstack -> s[stptr-1])
 480                                         * (rpnstack -> s[stptr]);
 481                 stptr--;
 482                 break;
 483             case OP_DIV:
 484                 stackunderflow(1);
 485                 rpnstack -> s[stptr-1]  = rpnstack -> s[stptr-1]
 486                                         / rpnstack -> s[stptr];
 487                 stptr--;
 488                 break;
 489             case OP_MOD:
 490                 stackunderflow(1);
 491                 rpnstack -> s[stptr-1]= fmod(   rpnstack -> s[stptr-1]
 492                                                 ,rpnstack -> s[stptr]);
 493                 stptr--;
 494                 break;
 495             case OP_SIN:
 496                 stackunderflow(0);
 497                 rpnstack -> s[stptr] = sin(rpnstack -> s[stptr]);
 498                 break;
 499             case OP_COS:
 500                 stackunderflow(0);
 501                 rpnstack -> s[stptr] = cos(rpnstack -> s[stptr]);
 502                 break;
 503             case OP_CEIL:
 504                 stackunderflow(0);
 505                 rpnstack -> s[stptr] = ceil(rpnstack -> s[stptr]);
 506                 break;
 507             case OP_FLOOR:
 508                 stackunderflow(0);
 509                 rpnstack -> s[stptr] = floor(rpnstack -> s[stptr]);
 510                 break;
 511             case OP_LOG:
 512                 stackunderflow(0);
 513                 rpnstack -> s[stptr] = log(rpnstack -> s[stptr]);
 514                 break;
 515             case OP_DUP:
 516                 stackunderflow(0);
 517                 rpnstack -> s[stptr+1] = rpnstack -> s[stptr];
 518                 stptr++;
 519                 break;
 520             case OP_POP:
 521                 stackunderflow(0);
 522                 stptr--;
 523                 break;
 524             case OP_EXC:
 525                 stackunderflow(1);
 526                 {
 527                     double dummy;
 528                     dummy = rpnstack -> s[stptr] ;
 529                     rpnstack -> s[stptr] = rpnstack -> s[stptr-1];
 530                     rpnstack -> s[stptr-1] = dummy;
 531                 }
 532                 break;
 533             case OP_EXP:
 534                 stackunderflow(0);
 535                 rpnstack -> s[stptr] = exp(rpnstack -> s[stptr]);
 536                 break;
 537             case OP_LT:
 538                 stackunderflow(1);
 539                 if (isnan(rpnstack -> s[stptr-1]))
 540                     ;
 541                 else if (isnan(rpnstack -> s[stptr]))
 542                     rpnstack -> s[stptr-1] = rpnstack -> s[stptr];
 543                 else
 544                     rpnstack -> s[stptr-1] = rpnstack -> s[stptr-1] <
 545                                         rpnstack -> s[stptr] ? 1.0 : 0.0;
 546                 stptr--;
 547                 break;
 548             case OP_LE:
 549                 stackunderflow(1);
 550                 if (isnan(rpnstack -> s[stptr-1]))
 551                     ;
 552                 else if (isnan(rpnstack -> s[stptr]))
 553                     rpnstack -> s[stptr-1] = rpnstack -> s[stptr];
 554                 else
 555                     rpnstack -> s[stptr-1] = rpnstack -> s[stptr-1] <=
 556                                         rpnstack -> s[stptr] ? 1.0 : 0.0;
 557                 stptr--;
 558                 break;
 559             case OP_GT:
 560                 stackunderflow(1);
 561                 if (isnan(rpnstack -> s[stptr-1]))
 562                     ;
 563                 else if (isnan(rpnstack -> s[stptr]))
 564                     rpnstack -> s[stptr-1] = rpnstack -> s[stptr];
 565                 else
 566                     rpnstack -> s[stptr-1] = rpnstack -> s[stptr-1] >
 567                                         rpnstack -> s[stptr] ? 1.0 : 0.0;
 568                 stptr--;
 569                 break;
 570             case OP_GE:
 571                 stackunderflow(1);
 572                 if (isnan(rpnstack -> s[stptr-1]))
 573                     ;
 574                 else if (isnan(rpnstack -> s[stptr]))
 575                     rpnstack -> s[stptr-1] = rpnstack -> s[stptr];
 576                 else
 577                     rpnstack -> s[stptr-1] = rpnstack -> s[stptr-1] >=
 578                                         rpnstack -> s[stptr] ? 1.0 : 0.0;
 579                 stptr--;
 580                 break;
 581             case OP_NE:
 582                 stackunderflow(1);
 583                 if (isnan(rpnstack -> s[stptr-1]))
 584                     ;
 585                 else if (isnan(rpnstack -> s[stptr]))
 586                     rpnstack -> s[stptr-1] = rpnstack -> s[stptr];
 587                 else
 588                     rpnstack -> s[stptr-1] = rpnstack -> s[stptr-1] ==
 589                                         rpnstack -> s[stptr] ? 0.0 : 1.0;
 590                 stptr--;
 591                 break;
 592             case OP_EQ:
 593                 stackunderflow(1);
 594                 if (isnan(rpnstack -> s[stptr-1]))
 595                     ;
 596                 else if (isnan(rpnstack -> s[stptr]))
 597                     rpnstack -> s[stptr-1] = rpnstack -> s[stptr];
 598                 else
 599                     rpnstack -> s[stptr-1] = rpnstack -> s[stptr-1] ==
 600                                         rpnstack -> s[stptr] ? 1.0 : 0.0;
 601                 stptr--;
 602                 break;
 603             case OP_IF:
 604                 stackunderflow(2);
 605                 rpnstack->s[stptr-2] = rpnstack->s[stptr-2] != 0.0 ?
 606                                 rpnstack->s[stptr-1] : rpnstack->s[stptr];
 607                 stptr--;
 608                 stptr--;
 609                 break;
 610             case OP_MIN:
 611                 stackunderflow(1);
 612                 if (isnan(rpnstack->s[stptr-1]))
 613                     ;
 614                 else if (isnan(rpnstack->s[stptr]))
 615                     rpnstack->s[stptr-1] = rpnstack->s[stptr];
 616                 else if (rpnstack->s[stptr-1] > rpnstack->s[stptr])
 617                     rpnstack->s[stptr-1] = rpnstack->s[stptr];
 618                 stptr--;
 619                 break;
 620             case OP_MAX:
 621                 stackunderflow(1);
 622                 if (isnan(rpnstack->s[stptr-1]))
 623                ;
 624                 else if (isnan(rpnstack->s[stptr]))
 625                     rpnstack->s[stptr-1] = rpnstack->s[stptr];
 626                 else if (rpnstack->s[stptr-1] < rpnstack->s[stptr])
 627                     rpnstack->s[stptr-1] = rpnstack->s[stptr];
 628                 stptr--;
 629                 break;
 630             case OP_LIMIT:
 631                 stackunderflow(2);
 632                 if (isnan(rpnstack->s[stptr-2]))
 633                     ;
 634                 else if (isnan(rpnstack->s[stptr-1]))
 635                     rpnstack->s[stptr-2] = rpnstack->s[stptr-1];
 636                 else if (isnan(rpnstack->s[stptr]))
 637                     rpnstack->s[stptr-2] = rpnstack->s[stptr];
 638                 else if (rpnstack->s[stptr-2] < rpnstack->s[stptr-1])
 639                     rpnstack->s[stptr-2] = DNAN;
 640                 else if (rpnstack->s[stptr-2] > rpnstack->s[stptr])
 641                     rpnstack->s[stptr-2] = DNAN;
 642                 stptr-=2;
 643                 break;
 644             case OP_UN:
 645                 stackunderflow(0);
 646                 rpnstack->s[stptr] = isnan(rpnstack->s[stptr]) ? 1.0 : 0.0;
 647                 break;
 648             case OP_ISINF:
 649                 stackunderflow(0);
 650                 rpnstack->s[stptr] = isinf(rpnstack->s[stptr]) ? 1.0 : 0.0;
 651                 break;
 652             case OP_END:
 653                 break;
 654        }
 655 #undef stackunderflow
 656    }
 657    if(stptr!=0){
 658        rrd_set_error("RPN final stack size != 1");
 659        return -1;
 660    }
 661
 662    output[output_idx] = rpnstack->s[0];
 663    return 0;
 664 }
 665
 666 /* figure out what the local timezone offset for any point in
 667    time was. Return it in seconds */
 668 int
 669 tzoffset( time_t now ){
 670     int gm_sec, gm_min, gm_hour, gm_yday, gm_year,
 671         l_sec, l_min, l_hour, l_yday, l_year;
 672     struct tm *t;
 673     int off;
 674     t = gmtime(&now);
 675     gm_sec = t->tm_sec;
 676     gm_min = t->tm_min;
 677     gm_hour = t->tm_hour;
 678     gm_yday = t->tm_yday;
 679     gm_year = t->tm_year;
 680     t = localtime(&now);
 681     l_sec = t->tm_sec;
 682     l_min = t->tm_min;
 683     l_hour = t->tm_hour;
 684     l_yday = t->tm_yday;
 685     l_year = t->tm_year;
 686     off = (l_sec-gm_sec)+(l_min-gm_min)*60+(l_hour-gm_hour)*3600;
 687     if ( l_yday > gm_yday || l_year > gm_year){
 688         off += 24*3600;
 689     } else if ( l_yday < gm_yday || l_year < gm_year){
 690         off -= 24*3600;
 691     }
 692    return off;
 693 }
 694