libdecnumber/decContext.c

   1 /* Decimal context module for the decNumber C Library.
   2    Copyright (C) 2005-2018 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 #ifdef DECCHECK
  35 #include <stdio.h>            /* for printf if DECCHECK */
  36 #endif
  37 #include "dconfig.h"          /* for GCC definitions */
  38 #include "decContext.h"       /* context and base types */
  39 #include "decNumberLocal.h"   /* decNumber local types, etc. */
  40
  41 /* compile-time endian tester [assumes sizeof(Int)>1] */
  42 static  const  Int mfcone=1;                 /* constant 1 */
  43 static  const  Flag *mfctop=(const Flag *)&mfcone; /* -> top byte */
  44 #define LITEND *mfctop             /* named flag; 1=little-endian */
  45
  46 /* ------------------------------------------------------------------ */
  47 /* round-for-reround digits                                           */
  48 /* ------------------------------------------------------------------ */
  49 const uByte DECSTICKYTAB[10]={1,1,2,3,4,6,6,7,8,9}; /* used if sticky */
  50
  51 /* ------------------------------------------------------------------ */
  52 /* Powers of ten (powers[n]==10**n, 0<=n<=9)                          */
  53 /* ------------------------------------------------------------------ */
  54 const uInt DECPOWERS[10]={1, 10, 100, 1000, 10000, 100000, 1000000,
  55                           10000000, 100000000, 1000000000};
  56
  57 /* ------------------------------------------------------------------ */
  58 /* decContextClearStatus -- clear bits in current status              */
  59 /*                                                                    */
  60 /*  context is the context structure to be queried                    */
  61 /*  mask indicates the bits to be cleared (the status bit that        */
  62 /*    corresponds to each 1 bit in the mask is cleared)               */
  63 /*  returns context                                                   */
  64 /*                                                                    */
  65 /* No error is possible.                                              */
  66 /* ------------------------------------------------------------------ */
  67 decContext *decContextClearStatus(decContext *context, uInt mask) {
  68   context->status&=~mask;
  69   return context;
  70   } /* decContextClearStatus */
  71
  72 /* ------------------------------------------------------------------ */
  73 /* decContextDefault -- initialize a context structure                */
  74 /*                                                                    */
  75 /*  context is the structure to be initialized                        */
  76 /*  kind selects the required set of default values, one of:          */
  77 /*      DEC_INIT_BASE       -- select ANSI X3-274 defaults            */
  78 /*      DEC_INIT_DECIMAL32  -- select IEEE 754 defaults, 32-bit       */
  79 /*      DEC_INIT_DECIMAL64  -- select IEEE 754 defaults, 64-bit       */
  80 /*      DEC_INIT_DECIMAL128 -- select IEEE 754 defaults, 128-bit      */
  81 /*      For any other value a valid context is returned, but with     */
  82 /*      Invalid_operation set in the status field.                    */
  83 /*  returns a context structure with the appropriate initial values.  */
  84 /* ------------------------------------------------------------------ */
  85 decContext * decContextDefault(decContext *context, Int kind) {
  86   /* set defaults... */
  87   context->digits=9;                         /* 9 digits */
  88   context->emax=DEC_MAX_EMAX;                /* 9-digit exponents */
  89   context->emin=DEC_MIN_EMIN;                /* .. balanced */
  90   context->round=DEC_ROUND_HALF_UP;          /* 0.5 rises */
  91   context->traps=DEC_Errors;                 /* all but informational */
  92   context->status=0;                         /* cleared */
  93   context->clamp=0;                          /* no clamping */
  94   #if DECSUBSET
  95   context->extended=0;                       /* cleared */
  96   #endif
  97   switch (kind) {
  98     case DEC_INIT_BASE:
  99       /* [use defaults] */
 100       break;
 101     case DEC_INIT_DECIMAL32:
 102       context->digits=7;                     /* digits */
 103       context->emax=96;                      /* Emax */
 104       context->emin=-95;                     /* Emin */
 105       context->round=DEC_ROUND_HALF_EVEN;    /* 0.5 to nearest even */
 106       context->traps=0;                      /* no traps set */
 107       context->clamp=1;                      /* clamp exponents */
 108       #if DECSUBSET
 109       context->extended=1;                   /* set */
 110       #endif
 111       break;
 112     case DEC_INIT_DECIMAL64:
 113       context->digits=16;                    /* digits */
 114       context->emax=384;                     /* Emax */
 115       context->emin=-383;                    /* Emin */
 116       context->round=DEC_ROUND_HALF_EVEN;    /* 0.5 to nearest even */
 117       context->traps=0;                      /* no traps set */
 118       context->clamp=1;                      /* clamp exponents */
 119       #if DECSUBSET
 120       context->extended=1;                   /* set */
 121       #endif
 122       break;
 123     case DEC_INIT_DECIMAL128:
 124       context->digits=34;                    /* digits */
 125       context->emax=6144;                    /* Emax */
 126       context->emin=-6143;                   /* Emin */
 127       context->round=DEC_ROUND_HALF_EVEN;    /* 0.5 to nearest even */
 128       context->traps=0;                      /* no traps set */
 129       context->clamp=1;                      /* clamp exponents */
 130       #if DECSUBSET
 131       context->extended=1;                   /* set */
 132       #endif
 133       break;
 134
 135     default:                                 /* invalid Kind */
 136       /* use defaults, and .. */
 137       decContextSetStatus(context, DEC_Invalid_operation); /* trap */
 138     }
 139
 140   return context;} /* decContextDefault */
 141
 142 /* ------------------------------------------------------------------ */
 143 /* decContextGetRounding -- return current rounding mode              */
 144 /*                                                                    */
 145 /*  context is the context structure to be queried                    */
 146 /*  returns the rounding mode                                         */
 147 /*                                                                    */
 148 /* No error is possible.                                              */
 149 /* ------------------------------------------------------------------ */
 150 enum rounding decContextGetRounding(decContext *context) {
 151   return context->round;
 152   } /* decContextGetRounding */
 153
 154 /* ------------------------------------------------------------------ */
 155 /* decContextGetStatus -- return current status                       */
 156 /*                                                                    */
 157 /*  context is the context structure to be queried                    */
 158 /*  returns status                                                    */
 159 /*                                                                    */
 160 /* No error is possible.                                              */
 161 /* ------------------------------------------------------------------ */
 162 uInt decContextGetStatus(decContext *context) {
 163   return context->status;
 164   } /* decContextGetStatus */
 165
 166 /* ------------------------------------------------------------------ */
 167 /* decContextRestoreStatus -- restore bits in current status          */
 168 /*                                                                    */
 169 /*  context is the context structure to be updated                    */
 170 /*  newstatus is the source for the bits to be restored               */
 171 /*  mask indicates the bits to be restored (the status bit that       */
 172 /*    corresponds to each 1 bit in the mask is set to the value of    */
 173 /*    the correspnding bit in newstatus)                              */
 174 /*  returns context                                                   */
 175 /*                                                                    */
 176 /* No error is possible.                                              */
 177 /* ------------------------------------------------------------------ */
 178 decContext *decContextRestoreStatus(decContext *context,
 179                                     uInt newstatus, uInt mask) {
 180   context->status&=~mask;               /* clear the selected bits */
 181   context->status|=(mask&newstatus);    /* or in the new bits */
 182   return context;
 183   } /* decContextRestoreStatus */
 184
 185 /* ------------------------------------------------------------------ */
 186 /* decContextSaveStatus -- save bits in current status                */
 187 /*                                                                    */
 188 /*  context is the context structure to be queried                    */
 189 /*  mask indicates the bits to be saved (the status bits that         */
 190 /*    correspond to each 1 bit in the mask are saved)                 */
 191 /*  returns the AND of the mask and the current status                */
 192 /*                                                                    */
 193 /* No error is possible.                                              */
 194 /* ------------------------------------------------------------------ */
 195 uInt decContextSaveStatus(decContext *context, uInt mask) {
 196   return context->status&mask;
 197   } /* decContextSaveStatus */
 198
 199 /* ------------------------------------------------------------------ */
 200 /* decContextSetRounding -- set current rounding mode                 */
 201 /*                                                                    */
 202 /*  context is the context structure to be updated                    */
 203 /*  newround is the value which will replace the current mode         */
 204 /*  returns context                                                   */
 205 /*                                                                    */
 206 /* No error is possible.                                              */
 207 /* ------------------------------------------------------------------ */
 208 decContext *decContextSetRounding(decContext *context,
 209                                   enum rounding newround) {
 210   context->round=newround;
 211   return context;
 212   } /* decContextSetRounding */
 213
 214 /* ------------------------------------------------------------------ */
 215 /* decContextSetStatus -- set status and raise trap if appropriate    */
 216 /*                                                                    */
 217 /*  context is the context structure to be updated                    */
 218 /*  status  is the DEC_ exception code                                */
 219 /*  returns the context structure                                     */
 220 /*                                                                    */
 221 /* Control may never return from this routine, if there is a signal   */
 222 /* handler and it takes a long jump.                                  */
 223 /* ------------------------------------------------------------------ */
 224 decContext * decContextSetStatus(decContext *context, uInt status) {
 225   context->status|=status;
 226   if (status & context->traps) raise(SIGFPE);
 227   return context;} /* decContextSetStatus */
 228
 229 /* ------------------------------------------------------------------ */
 230 /* decContextSetStatusFromString -- set status from a string + trap   */
 231 /*                                                                    */
 232 /*  context is the context structure to be updated                    */
 233 /*  string is a string exactly equal to one that might be returned    */
 234 /*            by decContextStatusToString                             */
 235 /*                                                                    */
 236 /*  The status bit corresponding to the string is set, and a trap     */
 237 /*  is raised if appropriate.                                         */
 238 /*                                                                    */
 239 /*  returns the context structure, unless the string is equal to      */
 240 /*    DEC_Condition_MU or is not recognized.  In these cases NULL is  */
 241 /*    returned.                                                       */
 242 /* ------------------------------------------------------------------ */
 243 decContext * decContextSetStatusFromString(decContext *context,
 244                                            const char *string) {
 245   if (strcmp(string, DEC_Condition_CS)==0)
 246     return decContextSetStatus(context, DEC_Conversion_syntax);
 247   if (strcmp(string, DEC_Condition_DZ)==0)
 248     return decContextSetStatus(context, DEC_Division_by_zero);
 249   if (strcmp(string, DEC_Condition_DI)==0)
 250     return decContextSetStatus(context, DEC_Division_impossible);
 251   if (strcmp(string, DEC_Condition_DU)==0)
 252     return decContextSetStatus(context, DEC_Division_undefined);
 253   if (strcmp(string, DEC_Condition_IE)==0)
 254     return decContextSetStatus(context, DEC_Inexact);
 255   if (strcmp(string, DEC_Condition_IS)==0)
 256     return decContextSetStatus(context, DEC_Insufficient_storage);
 257   if (strcmp(string, DEC_Condition_IC)==0)
 258     return decContextSetStatus(context, DEC_Invalid_context);
 259   if (strcmp(string, DEC_Condition_IO)==0)
 260     return decContextSetStatus(context, DEC_Invalid_operation);
 261   #if DECSUBSET
 262   if (strcmp(string, DEC_Condition_LD)==0)
 263     return decContextSetStatus(context, DEC_Lost_digits);
 264   #endif
 265   if (strcmp(string, DEC_Condition_OV)==0)
 266     return decContextSetStatus(context, DEC_Overflow);
 267   if (strcmp(string, DEC_Condition_PA)==0)
 268     return decContextSetStatus(context, DEC_Clamped);
 269   if (strcmp(string, DEC_Condition_RO)==0)
 270     return decContextSetStatus(context, DEC_Rounded);
 271   if (strcmp(string, DEC_Condition_SU)==0)
 272     return decContextSetStatus(context, DEC_Subnormal);
 273   if (strcmp(string, DEC_Condition_UN)==0)
 274     return decContextSetStatus(context, DEC_Underflow);
 275   if (strcmp(string, DEC_Condition_ZE)==0)
 276     return context;
 277   return NULL;  /* Multiple status, or unknown */
 278   } /* decContextSetStatusFromString */
 279
 280 /* ------------------------------------------------------------------ */
 281 /* decContextSetStatusFromStringQuiet -- set status from a string     */
 282 /*                                                                    */
 283 /*  context is the context structure to be updated                    */
 284 /*  string is a string exactly equal to one that might be returned    */
 285 /*            by decContextStatusToString                             */
 286 /*                                                                    */
 287 /*  The status bit corresponding to the string is set; no trap is     */
 288 /*  raised.                                                           */
 289 /*                                                                    */
 290 /*  returns the context structure, unless the string is equal to      */
 291 /*    DEC_Condition_MU or is not recognized.  In these cases NULL is  */
 292 /*    returned.                                                       */
 293 /* ------------------------------------------------------------------ */
 294 decContext * decContextSetStatusFromStringQuiet(decContext *context,
 295                                                 const char *string) {
 296   if (strcmp(string, DEC_Condition_CS)==0)
 297     return decContextSetStatusQuiet(context, DEC_Conversion_syntax);
 298   if (strcmp(string, DEC_Condition_DZ)==0)
 299     return decContextSetStatusQuiet(context, DEC_Division_by_zero);
 300   if (strcmp(string, DEC_Condition_DI)==0)
 301     return decContextSetStatusQuiet(context, DEC_Division_impossible);
 302   if (strcmp(string, DEC_Condition_DU)==0)
 303     return decContextSetStatusQuiet(context, DEC_Division_undefined);
 304   if (strcmp(string, DEC_Condition_IE)==0)
 305     return decContextSetStatusQuiet(context, DEC_Inexact);
 306   if (strcmp(string, DEC_Condition_IS)==0)
 307     return decContextSetStatusQuiet(context, DEC_Insufficient_storage);
 308   if (strcmp(string, DEC_Condition_IC)==0)
 309     return decContextSetStatusQuiet(context, DEC_Invalid_context);
 310   if (strcmp(string, DEC_Condition_IO)==0)
 311     return decContextSetStatusQuiet(context, DEC_Invalid_operation);
 312   #if DECSUBSET
 313   if (strcmp(string, DEC_Condition_LD)==0)
 314     return decContextSetStatusQuiet(context, DEC_Lost_digits);
 315   #endif
 316   if (strcmp(string, DEC_Condition_OV)==0)
 317     return decContextSetStatusQuiet(context, DEC_Overflow);
 318   if (strcmp(string, DEC_Condition_PA)==0)
 319     return decContextSetStatusQuiet(context, DEC_Clamped);
 320   if (strcmp(string, DEC_Condition_RO)==0)
 321     return decContextSetStatusQuiet(context, DEC_Rounded);
 322   if (strcmp(string, DEC_Condition_SU)==0)
 323     return decContextSetStatusQuiet(context, DEC_Subnormal);
 324   if (strcmp(string, DEC_Condition_UN)==0)
 325     return decContextSetStatusQuiet(context, DEC_Underflow);
 326   if (strcmp(string, DEC_Condition_ZE)==0)
 327     return context;
 328   return NULL;  /* Multiple status, or unknown */
 329   } /* decContextSetStatusFromStringQuiet */
 330
 331 /* ------------------------------------------------------------------ */
 332 /* decContextSetStatusQuiet -- set status without trap                */
 333 /*                                                                    */
 334 /*  context is the context structure to be updated                    */
 335 /*  status  is the DEC_ exception code                                */
 336 /*  returns the context structure                                     */
 337 /*                                                                    */
 338 /* No error is possible.                                              */
 339 /* ------------------------------------------------------------------ */
 340 decContext * decContextSetStatusQuiet(decContext *context, uInt status) {
 341   context->status|=status;
 342   return context;} /* decContextSetStatusQuiet */
 343
 344 /* ------------------------------------------------------------------ */
 345 /* decContextStatusToString -- convert status flags to a string       */
 346 /*                                                                    */
 347 /*  context is a context with valid status field                      */
 348 /*                                                                    */
 349 /*  returns a constant string describing the condition.  If multiple  */
 350 /*    (or no) flags are set, a generic constant message is returned.  */
 351 /* ------------------------------------------------------------------ */
 352 const char *decContextStatusToString(const decContext *context) {
 353   Int status=context->status;
 354
 355   /* test the five IEEE first, as some of the others are ambiguous when */
 356   /* DECEXTFLAG=0 */
 357   if (status==DEC_Invalid_operation    ) return DEC_Condition_IO;
 358   if (status==DEC_Division_by_zero     ) return DEC_Condition_DZ;
 359   if (status==DEC_Overflow             ) return DEC_Condition_OV;
 360   if (status==DEC_Underflow            ) return DEC_Condition_UN;
 361   if (status==DEC_Inexact              ) return DEC_Condition_IE;
 362
 363   if (status==DEC_Division_impossible  ) return DEC_Condition_DI;
 364   if (status==DEC_Division_undefined   ) return DEC_Condition_DU;
 365   if (status==DEC_Rounded              ) return DEC_Condition_RO;
 366   if (status==DEC_Clamped              ) return DEC_Condition_PA;
 367   if (status==DEC_Subnormal            ) return DEC_Condition_SU;
 368   if (status==DEC_Conversion_syntax    ) return DEC_Condition_CS;
 369   if (status==DEC_Insufficient_storage ) return DEC_Condition_IS;
 370   if (status==DEC_Invalid_context      ) return DEC_Condition_IC;
 371   #if DECSUBSET
 372   if (status==DEC_Lost_digits          ) return DEC_Condition_LD;
 373   #endif
 374   if (status==0                        ) return DEC_Condition_ZE;
 375   return DEC_Condition_MU;  /* Multiple errors */
 376   } /* decContextStatusToString */
 377
 378 /* ------------------------------------------------------------------ */
 379 /* decContextTestEndian -- test whether DECLITEND is set correctly    */
 380 /*                                                                    */
 381 /*  quiet is 1 to suppress message; 0 otherwise                       */
 382 /*  returns 0 if DECLITEND is correct                                 */
 383 /*          1 if DECLITEND is incorrect and should be 1               */
 384 /*         -1 if DECLITEND is incorrect and should be 0               */
 385 /*                                                                    */
 386 /* A message is displayed if the return value is not 0 and quiet==0.  */
 387 /*                                                                    */
 388 /* No error is possible.                                              */
 389 /* ------------------------------------------------------------------ */
 390 Int decContextTestEndian(Flag quiet) {
 391   Int res=0;                  /* optimist */
 392   uInt dle=(uInt)DECLITEND;   /* unsign */
 393   if (dle>1) dle=1;           /* ensure 0 or 1 */
 394
 395   if (LITEND!=DECLITEND) {
 396     if (!quiet) {
 397 #if DECCHECK
 398       const char *adj;
 399       if (LITEND) adj="little";
 400              else adj="big";
 401       printf("Warning: DECLITEND is set to %d, but this computer appears to be %s-endian\n",
 402              DECLITEND, adj);
 403 #endif
 404       }
 405     res=(Int)LITEND-dle;
 406     }
 407   return res;
 408   } /* decContextTestEndian */
 409
 410 /* ------------------------------------------------------------------ */
 411 /* decContextTestSavedStatus -- test bits in saved status             */
 412 /*                                                                    */
 413 /*  oldstatus is the status word to be tested                         */
 414 /*  mask indicates the bits to be tested (the oldstatus bits that     */
 415 /*    correspond to each 1 bit in the mask are tested)                */
 416 /*  returns 1 if any of the tested bits are 1, or 0 otherwise         */
 417 /*                                                                    */
 418 /* No error is possible.                                              */
 419 /* ------------------------------------------------------------------ */
 420 uInt decContextTestSavedStatus(uInt oldstatus, uInt mask) {
 421   return (oldstatus&mask)!=0;
 422   } /* decContextTestSavedStatus */
 423
 424 /* ------------------------------------------------------------------ */
 425 /* decContextTestStatus -- test bits in current status                */
 426 /*                                                                    */
 427 /*  context is the context structure to be updated                    */
 428 /*  mask indicates the bits to be tested (the status bits that        */
 429 /*    correspond to each 1 bit in the mask are tested)                */
 430 /*  returns 1 if any of the tested bits are 1, or 0 otherwise         */
 431 /*                                                                    */
 432 /* No error is possible.                                              */
 433 /* ------------------------------------------------------------------ */
 434 uInt decContextTestStatus(decContext *context, uInt mask) {
 435   return (context->status&mask)!=0;
 436   } /* decContextTestStatus */
 437
 438 /* ------------------------------------------------------------------ */
 439 /* decContextZeroStatus -- clear all status bits                      */
 440 /*                                                                    */
 441 /*  context is the context structure to be updated                    */
 442 /*  returns context                                                   */
 443 /*                                                                    */
 444 /* No error is possible.                                              */
 445 /* ------------------------------------------------------------------ */
 446 decContext *decContextZeroStatus(decContext *context) {
 447   context->status=0;
 448   return context;
 449   } /* decContextZeroStatus */
 450