libdecnumber/decContext.c

   1 /* Decimal context module for the decNumber C Library.
   2    Copyright (C) 2005, 2007, 2009 Free Software Foundation, Inc.
   3    Contributed by IBM Corporation.  Author Mike Cowlishaw.
   4
   5    This file is part of GCC.
   6
   7    GCC is free software; you can redistribute it and/or modify it under
   8    the terms of the GNU General Public License as published by the Free
   9    Software Foundation; either version 3, or (at your option) any later
  10    version.
  11
  12    GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13    WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15    for more details.
  16
  17 Under Section 7 of GPL version 3, you are granted additional
  18 permissions described in the GCC Runtime Library Exception, version
  19 3.1, as published by the Free Software Foundation.
  20
  21 You should have received a copy of the GNU General Public License and
  22 a copy of the GCC Runtime Library Exception along with this program;
  23 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  24 <http://www.gnu.org/licenses/>.  */
  25
  26 /* ------------------------------------------------------------------ */
  27 /* Decimal Context module                                             */
  28 /* ------------------------------------------------------------------ */
  29 /* This module comprises the routines for handling arithmetic         */
  30 /* context structures.                                                */
  31 /* ------------------------------------------------------------------ */
  32
  33 #include <string.h>           /* for strcmp */
  34 #include <stdio.h>            /* for printf if DECCHECK */
  35 #include "dconfig.h"          /* for GCC definitions */
  36 #include "decContext.h"       /* context and base types */
  37 #include "decNumberLocal.h"   /* decNumber local types, etc. */
  38
  39 /* compile-time endian tester [assumes sizeof(Int)>1] */
  40 static  const  Int mfcone=1;                 /* constant 1 */
  41 static  const  Flag *mfctop=(const Flag *)&mfcone; /* -> top byte */
  42 #define LITEND *mfctop             /* named flag; 1=little-endian */
  43
  44 /* ------------------------------------------------------------------ */
  45 /* round-for-reround digits                                           */
  46 /* ------------------------------------------------------------------ */
  47 const uByte DECSTICKYTAB[10]={1,1,2,3,4,6,6,7,8,9}; /* used if sticky */
  48
  49 /* ------------------------------------------------------------------ */
  50 /* Powers of ten (powers[n]==10**n, 0<=n<=9)                          */
  51 /* ------------------------------------------------------------------ */
  52 const uInt DECPOWERS[10]={1, 10, 100, 1000, 10000, 100000, 1000000,
  53                           10000000, 100000000, 1000000000};
  54
  55 /* ------------------------------------------------------------------ */
  56 /* decContextClearStatus -- clear bits in current status              */
  57 /*                                                                    */
  58 /*  context is the context structure to be queried                    */
  59 /*  mask indicates the bits to be cleared (the status bit that        */
  60 /*    corresponds to each 1 bit in the mask is cleared)               */
  61 /*  returns context                                                   */
  62 /*                                                                    */
  63 /* No error is possible.                                              */
  64 /* ------------------------------------------------------------------ */
  65 decContext *decContextClearStatus(decContext *context, uInt mask) {
  66   context->status&=~mask;
  67   return context;
  68   } /* decContextClearStatus */
  69
  70 /* ------------------------------------------------------------------ */
  71 /* decContextDefault -- initialize a context structure                */
  72 /*                                                                    */
  73 /*  context is the structure to be initialized                        */
  74 /*  kind selects the required set of default values, one of:          */
  75 /*      DEC_INIT_BASE       -- select ANSI X3-274 defaults            */
  76 /*      DEC_INIT_DECIMAL32  -- select IEEE 754 defaults, 32-bit       */
  77 /*      DEC_INIT_DECIMAL64  -- select IEEE 754 defaults, 64-bit       */
  78 /*      DEC_INIT_DECIMAL128 -- select IEEE 754 defaults, 128-bit      */
  79 /*      For any other value a valid context is returned, but with     */
  80 /*      Invalid_operation set in the status field.                    */
  81 /*  returns a context structure with the appropriate initial values.  */
  82 /* ------------------------------------------------------------------ */
  83 decContext * decContextDefault(decContext *context, Int kind) {
  84   /* set defaults... */
  85   context->digits=9;                         /* 9 digits */
  86   context->emax=DEC_MAX_EMAX;                /* 9-digit exponents */
  87   context->emin=DEC_MIN_EMIN;                /* .. balanced */
  88   context->round=DEC_ROUND_HALF_UP;          /* 0.5 rises */
  89   context->traps=DEC_Errors;                 /* all but informational */
  90   context->status=0;                         /* cleared */
  91   context->clamp=0;                          /* no clamping */
  92   #if DECSUBSET
  93   context->extended=0;                       /* cleared */
  94   #endif
  95   switch (kind) {
  96     case DEC_INIT_BASE:
  97       /* [use defaults] */
  98       break;
  99     case DEC_INIT_DECIMAL32:
 100       context->digits=7;                     /* digits */
 101       context->emax=96;                      /* Emax */
 102       context->emin=-95;                     /* Emin */
 103       context->round=DEC_ROUND_HALF_EVEN;    /* 0.5 to nearest even */
 104       context->traps=0;                      /* no traps set */
 105       context->clamp=1;                      /* clamp exponents */
 106       #if DECSUBSET
 107       context->extended=1;                   /* set */
 108       #endif
 109       break;
 110     case DEC_INIT_DECIMAL64:
 111       context->digits=16;                    /* digits */
 112       context->emax=384;                     /* Emax */
 113       context->emin=-383;                    /* Emin */
 114       context->round=DEC_ROUND_HALF_EVEN;    /* 0.5 to nearest even */
 115       context->traps=0;                      /* no traps set */
 116       context->clamp=1;                      /* clamp exponents */
 117       #if DECSUBSET
 118       context->extended=1;                   /* set */
 119       #endif
 120       break;
 121     case DEC_INIT_DECIMAL128:
 122       context->digits=34;                    /* digits */
 123       context->emax=6144;                    /* Emax */
 124       context->emin=-6143;                   /* Emin */
 125       context->round=DEC_ROUND_HALF_EVEN;    /* 0.5 to nearest even */
 126       context->traps=0;                      /* no traps set */
 127       context->clamp=1;                      /* clamp exponents */
 128       #if DECSUBSET
 129       context->extended=1;                   /* set */
 130       #endif
 131       break;
 132
 133     default:                                 /* invalid Kind */
 134       /* use defaults, and .. */
 135       decContextSetStatus(context, DEC_Invalid_operation); /* trap */
 136     }
 137
 138   return context;} /* decContextDefault */
 139
 140 /* ------------------------------------------------------------------ */
 141 /* decContextGetRounding -- return current rounding mode              */
 142 /*                                                                    */
 143 /*  context is the context structure to be queried                    */
 144 /*  returns the rounding mode                                         */
 145 /*                                                                    */
 146 /* No error is possible.                                              */
 147 /* ------------------------------------------------------------------ */
 148 enum rounding decContextGetRounding(decContext *context) {
 149   return context->round;
 150   } /* decContextGetRounding */
 151
 152 /* ------------------------------------------------------------------ */
 153 /* decContextGetStatus -- return current status                       */
 154 /*                                                                    */
 155 /*  context is the context structure to be queried                    */
 156 /*  returns status                                                    */
 157 /*                                                                    */
 158 /* No error is possible.                                              */
 159 /* ------------------------------------------------------------------ */
 160 uInt decContextGetStatus(decContext *context) {
 161   return context->status;
 162   } /* decContextGetStatus */
 163
 164 /* ------------------------------------------------------------------ */
 165 /* decContextRestoreStatus -- restore bits in current status          */
 166 /*                                                                    */
 167 /*  context is the context structure to be updated                    */
 168 /*  newstatus is the source for the bits to be restored               */
 169 /*  mask indicates the bits to be restored (the status bit that       */
 170 /*    corresponds to each 1 bit in the mask is set to the value of    */
 171 /*    the correspnding bit in newstatus)                              */
 172 /*  returns context                                                   */
 173 /*                                                                    */
 174 /* No error is possible.                                              */
 175 /* ------------------------------------------------------------------ */
 176 decContext *decContextRestoreStatus(decContext *context,
 177                                     uInt newstatus, uInt mask) {
 178   context->status&=~mask;               /* clear the selected bits */
 179   context->status|=(mask&newstatus);    /* or in the new bits */
 180   return context;
 181   } /* decContextRestoreStatus */
 182
 183 /* ------------------------------------------------------------------ */
 184 /* decContextSaveStatus -- save bits in current status                */
 185 /*                                                                    */
 186 /*  context is the context structure to be queried                    */
 187 /*  mask indicates the bits to be saved (the status bits that         */
 188 /*    correspond to each 1 bit in the mask are saved)                 */
 189 /*  returns the AND of the mask and the current status                */
 190 /*                                                                    */
 191 /* No error is possible.                                              */
 192 /* ------------------------------------------------------------------ */
 193 uInt decContextSaveStatus(decContext *context, uInt mask) {
 194   return context->status&mask;
 195   } /* decContextSaveStatus */
 196
 197 /* ------------------------------------------------------------------ */
 198 /* decContextSetRounding -- set current rounding mode                 */
 199 /*                                                                    */
 200 /*  context is the context structure to be updated                    */
 201 /*  newround is the value which will replace the current mode         */
 202 /*  returns context                                                   */
 203 /*                                                                    */
 204 /* No error is possible.                                              */
 205 /* ------------------------------------------------------------------ */
 206 decContext *decContextSetRounding(decContext *context,
 207                                   enum rounding newround) {
 208   context->round=newround;
 209   return context;
 210   } /* decContextSetRounding */
 211
 212 /* ------------------------------------------------------------------ */
 213 /* decContextSetStatus -- set status and raise trap if appropriate    */
 214 /*                                                                    */
 215 /*  context is the context structure to be updated                    */
 216 /*  status  is the DEC_ exception code                                */
 217 /*  returns the context structure                                     */
 218 /*                                                                    */
 219 /* Control may never return from this routine, if there is a signal   */
 220 /* handler and it takes a long jump.                                  */
 221 /* ------------------------------------------------------------------ */
 222 decContext * decContextSetStatus(decContext *context, uInt status) {
 223   context->status|=status;
 224   if (status & context->traps) raise(SIGFPE);
 225   return context;} /* decContextSetStatus */
 226
 227 /* ------------------------------------------------------------------ */
 228 /* decContextSetStatusFromString -- set status from a string + trap   */
 229 /*                                                                    */
 230 /*  context is the context structure to be updated                    */
 231 /*  string is a string exactly equal to one that might be returned    */
 232 /*            by decContextStatusToString                             */
 233 /*                                                                    */
 234 /*  The status bit corresponding to the string is set, and a trap     */
 235 /*  is raised if appropriate.                                         */
 236 /*                                                                    */
 237 /*  returns the context structure, unless the string is equal to      */
 238 /*    DEC_Condition_MU or is not recognized.  In these cases NULL is  */
 239 /*    returned.                                                       */
 240 /* ------------------------------------------------------------------ */
 241 decContext * decContextSetStatusFromString(decContext *context,
 242                                            const char *string) {
 243   if (strcmp(string, DEC_Condition_CS)==0)
 244     return decContextSetStatus(context, DEC_Conversion_syntax);
 245   if (strcmp(string, DEC_Condition_DZ)==0)
 246     return decContextSetStatus(context, DEC_Division_by_zero);
 247   if (strcmp(string, DEC_Condition_DI)==0)
 248     return decContextSetStatus(context, DEC_Division_impossible);
 249   if (strcmp(string, DEC_Condition_DU)==0)
 250     return decContextSetStatus(context, DEC_Division_undefined);
 251   if (strcmp(string, DEC_Condition_IE)==0)
 252     return decContextSetStatus(context, DEC_Inexact);
 253   if (strcmp(string, DEC_Condition_IS)==0)
 254     return decContextSetStatus(context, DEC_Insufficient_storage);
 255   if (strcmp(string, DEC_Condition_IC)==0)
 256     return decContextSetStatus(context, DEC_Invalid_context);
 257   if (strcmp(string, DEC_Condition_IO)==0)
 258     return decContextSetStatus(context, DEC_Invalid_operation);
 259   #if DECSUBSET
 260   if (strcmp(string, DEC_Condition_LD)==0)
 261     return decContextSetStatus(context, DEC_Lost_digits);
 262   #endif
 263   if (strcmp(string, DEC_Condition_OV)==0)
 264     return decContextSetStatus(context, DEC_Overflow);
 265   if (strcmp(string, DEC_Condition_PA)==0)
 266     return decContextSetStatus(context, DEC_Clamped);
 267   if (strcmp(string, DEC_Condition_RO)==0)
 268     return decContextSetStatus(context, DEC_Rounded);
 269   if (strcmp(string, DEC_Condition_SU)==0)
 270     return decContextSetStatus(context, DEC_Subnormal);
 271   if (strcmp(string, DEC_Condition_UN)==0)
 272     return decContextSetStatus(context, DEC_Underflow);
 273   if (strcmp(string, DEC_Condition_ZE)==0)
 274     return context;
 275   return NULL;  /* Multiple status, or unknown */
 276   } /* decContextSetStatusFromString */
 277
 278 /* ------------------------------------------------------------------ */
 279 /* decContextSetStatusFromStringQuiet -- set status from a string     */
 280 /*                                                                    */
 281 /*  context is the context structure to be updated                    */
 282 /*  string is a string exactly equal to one that might be returned    */
 283 /*            by decContextStatusToString                             */
 284 /*                                                                    */
 285 /*  The status bit corresponding to the string is set; no trap is     */
 286 /*  raised.                                                           */
 287 /*                                                                    */
 288 /*  returns the context structure, unless the string is equal to      */
 289 /*    DEC_Condition_MU or is not recognized.  In these cases NULL is  */
 290 /*    returned.                                                       */
 291 /* ------------------------------------------------------------------ */
 292 decContext * decContextSetStatusFromStringQuiet(decContext *context,
 293                                                 const char *string) {
 294   if (strcmp(string, DEC_Condition_CS)==0)
 295     return decContextSetStatusQuiet(context, DEC_Conversion_syntax);
 296   if (strcmp(string, DEC_Condition_DZ)==0)
 297     return decContextSetStatusQuiet(context, DEC_Division_by_zero);
 298   if (strcmp(string, DEC_Condition_DI)==0)
 299     return decContextSetStatusQuiet(context, DEC_Division_impossible);
 300   if (strcmp(string, DEC_Condition_DU)==0)
 301     return decContextSetStatusQuiet(context, DEC_Division_undefined);
 302   if (strcmp(string, DEC_Condition_IE)==0)
 303     return decContextSetStatusQuiet(context, DEC_Inexact);
 304   if (strcmp(string, DEC_Condition_IS)==0)
 305     return decContextSetStatusQuiet(context, DEC_Insufficient_storage);
 306   if (strcmp(string, DEC_Condition_IC)==0)
 307     return decContextSetStatusQuiet(context, DEC_Invalid_context);
 308   if (strcmp(string, DEC_Condition_IO)==0)
 309     return decContextSetStatusQuiet(context, DEC_Invalid_operation);
 310   #if DECSUBSET
 311   if (strcmp(string, DEC_Condition_LD)==0)
 312     return decContextSetStatusQuiet(context, DEC_Lost_digits);
 313   #endif
 314   if (strcmp(string, DEC_Condition_OV)==0)
 315     return decContextSetStatusQuiet(context, DEC_Overflow);
 316   if (strcmp(string, DEC_Condition_PA)==0)
 317     return decContextSetStatusQuiet(context, DEC_Clamped);
 318   if (strcmp(string, DEC_Condition_RO)==0)
 319     return decContextSetStatusQuiet(context, DEC_Rounded);
 320   if (strcmp(string, DEC_Condition_SU)==0)
 321     return decContextSetStatusQuiet(context, DEC_Subnormal);
 322   if (strcmp(string, DEC_Condition_UN)==0)
 323     return decContextSetStatusQuiet(context, DEC_Underflow);
 324   if (strcmp(string, DEC_Condition_ZE)==0)
 325     return context;
 326   return NULL;  /* Multiple status, or unknown */
 327   } /* decContextSetStatusFromStringQuiet */
 328
 329 /* ------------------------------------------------------------------ */
 330 /* decContextSetStatusQuiet -- set status without trap                */
 331 /*                                                                    */
 332 /*  context is the context structure to be updated                    */
 333 /*  status  is the DEC_ exception code                                */
 334 /*  returns the context structure                                     */
 335 /*                                                                    */
 336 /* No error is possible.                                              */
 337 /* ------------------------------------------------------------------ */
 338 decContext * decContextSetStatusQuiet(decContext *context, uInt status) {
 339   context->status|=status;
 340   return context;} /* decContextSetStatusQuiet */
 341
 342 /* ------------------------------------------------------------------ */
 343 /* decContextStatusToString -- convert status flags to a string       */
 344 /*                                                                    */
 345 /*  context is a context with valid status field                      */
 346 /*                                                                    */
 347 /*  returns a constant string describing the condition.  If multiple  */
 348 /*    (or no) flags are set, a generic constant message is returned.  */
 349 /* ------------------------------------------------------------------ */
 350 const char *decContextStatusToString(const decContext *context) {
 351   Int status=context->status;
 352
 353   /* test the five IEEE first, as some of the others are ambiguous when */
 354   /* DECEXTFLAG=0 */
 355   if (status==DEC_Invalid_operation    ) return DEC_Condition_IO;
 356   if (status==DEC_Division_by_zero     ) return DEC_Condition_DZ;
 357   if (status==DEC_Overflow             ) return DEC_Condition_OV;
 358   if (status==DEC_Underflow            ) return DEC_Condition_UN;
 359   if (status==DEC_Inexact              ) return DEC_Condition_IE;
 360
 361   if (status==DEC_Division_impossible  ) return DEC_Condition_DI;
 362   if (status==DEC_Division_undefined   ) return DEC_Condition_DU;
 363   if (status==DEC_Rounded              ) return DEC_Condition_RO;
 364   if (status==DEC_Clamped              ) return DEC_Condition_PA;
 365   if (status==DEC_Subnormal            ) return DEC_Condition_SU;
 366   if (status==DEC_Conversion_syntax    ) return DEC_Condition_CS;
 367   if (status==DEC_Insufficient_storage ) return DEC_Condition_IS;
 368   if (status==DEC_Invalid_context      ) return DEC_Condition_IC;
 369   #if DECSUBSET
 370   if (status==DEC_Lost_digits          ) return DEC_Condition_LD;
 371   #endif
 372   if (status==0                        ) return DEC_Condition_ZE;
 373   return DEC_Condition_MU;  /* Multiple errors */
 374   } /* decContextStatusToString */
 375
 376 /* ------------------------------------------------------------------ */
 377 /* decContextTestEndian -- test whether DECLITEND is set correctly    */
 378 /*                                                                    */
 379 /*  quiet is 1 to suppress message; 0 otherwise                       */
 380 /*  returns 0 if DECLITEND is correct                                 */
 381 /*          1 if DECLITEND is incorrect and should be 1               */
 382 /*         -1 if DECLITEND is incorrect and should be 0               */
 383 /*                                                                    */
 384 /* A message is displayed if the return value is not 0 and quiet==0.  */
 385 /*                                                                    */
 386 /* No error is possible.                                              */
 387 /* ------------------------------------------------------------------ */
 388 Int decContextTestEndian(Flag quiet) {
 389   Int res=0;                  /* optimist */
 390   uInt dle=(uInt)DECLITEND;   /* unsign */
 391   if (dle>1) dle=1;           /* ensure 0 or 1 */
 392
 393   if (LITEND!=DECLITEND) {
 394     const char *adj;
 395     if (!quiet) {
 396       if (LITEND) adj="little";
 397              else adj="big";
 398       printf("Warning: DECLITEND is set to %d, but this computer appears to be %s-endian\n",
 399              DECLITEND, adj);
 400       }
 401     res=(Int)LITEND-dle;
 402     }
 403   return res;
 404   } /* decContextTestEndian */
 405
 406 /* ------------------------------------------------------------------ */
 407 /* decContextTestSavedStatus -- test bits in saved status             */
 408 /*                                                                    */
 409 /*  oldstatus is the status word to be tested                         */
 410 /*  mask indicates the bits to be tested (the oldstatus bits that     */
 411 /*    correspond to each 1 bit in the mask are tested)                */
 412 /*  returns 1 if any of the tested bits are 1, or 0 otherwise         */
 413 /*                                                                    */
 414 /* No error is possible.                                              */
 415 /* ------------------------------------------------------------------ */
 416 uInt decContextTestSavedStatus(uInt oldstatus, uInt mask) {
 417   return (oldstatus&mask)!=0;
 418   } /* decContextTestSavedStatus */
 419
 420 /* ------------------------------------------------------------------ */
 421 /* decContextTestStatus -- test bits in current status                */
 422 /*                                                                    */
 423 /*  context is the context structure to be updated                    */
 424 /*  mask indicates the bits to be tested (the status bits that        */
 425 /*    correspond to each 1 bit in the mask are tested)                */
 426 /*  returns 1 if any of the tested bits are 1, or 0 otherwise         */
 427 /*                                                                    */
 428 /* No error is possible.                                              */
 429 /* ------------------------------------------------------------------ */
 430 uInt decContextTestStatus(decContext *context, uInt mask) {
 431   return (context->status&mask)!=0;
 432   } /* decContextTestStatus */
 433
 434 /* ------------------------------------------------------------------ */
 435 /* decContextZeroStatus -- clear all status bits                      */
 436 /*                                                                    */
 437 /*  context is the context structure to be updated                    */
 438 /*  returns context                                                   */
 439 /*                                                                    */
 440 /* No error is possible.                                              */
 441 /* ------------------------------------------------------------------ */
 442 decContext *decContextZeroStatus(decContext *context) {
 443   context->status=0;
 444   return context;
 445   } /* decContextZeroStatus */
 446