libdecnumber/decimal64.c

   1 /* Decimal 64-bit format module for the decNumber C Library
   2    Copyright (C) 2005 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 2, 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    You should have received a copy of the GNU General Public License
  18    along with GCC; see the file COPYING.  If not, write to the Free
  19    Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
  20    02110-1301, USA.  */
  21
  22 /* ------------------------------------------------------------------ */
  23 /* This module comprises the routines for decimal64 format numbers.   */
  24 /* Conversions are supplied to and from decNumber and String.         */
  25 /*                                                                    */
  26 /* No arithmetic routines are included; decNumber provides these.     */
  27 /*                                                                    */
  28 /* Error handling is the same as decNumber (qv.).                     */
  29 /* ------------------------------------------------------------------ */
  30 #include <string.h>             /* [for memset/memcpy] */
  31 #include <stdio.h>              /* [for printf] */
  32
  33 #define  DECNUMDIGITS 16        /* we need decNumbers with space for 16 */
  34 #include "config.h"
  35 #include "decNumber.h"          /* base number library */
  36 #include "decNumberLocal.h"     /* decNumber local types, etc. */
  37 #include "decimal64.h"          /* our primary include */
  38 #include "decUtility.h"         /* utility routines */
  39
  40 #if DECTRACE || DECCHECK
  41 void decimal64Show (const decimal64 *); /* for debug */
  42 void decNumberShow (const decNumber *); /* .. */
  43 #endif
  44
  45 /* Useful macro */
  46 /* Clear a structure (e.g., a decNumber) */
  47 #define DEC_clear(d) memset(d, 0, sizeof(*d))
  48
  49 /* ------------------------------------------------------------------ */
  50 /* decimal64FromNumber -- convert decNumber to decimal64              */
  51 /*                                                                    */
  52 /*   ds is the target decimal64                                       */
  53 /*   dn is the source number (assumed valid)                          */
  54 /*   set is the context, used only for reporting errors               */
  55 /*                                                                    */
  56 /* The set argument is used only for status reporting and for the     */
  57 /* rounding mode (used if the coefficient is more than DECIMAL64_Pmax */
  58 /* digits or an overflow is detected).  If the exponent is out of the */
  59 /* valid range then Overflow or Underflow will be raised.             */
  60 /* After Underflow a subnormal result is possible.                    */
  61 /*                                                                    */
  62 /* DEC_Clamped is set if the number has to be 'folded down' to fit,   */
  63 /* by reducing its exponent and multiplying the coefficient by a      */
  64 /* power of ten, or if the exponent on a zero had to be clamped.      */
  65 /* ------------------------------------------------------------------ */
  66 decimal64 *
  67 decimal64FromNumber (decimal64 * d64, const decNumber * dn, decContext * set)
  68 {
  69   uInt status = 0;              /* status accumulator */
  70   Int pad = 0;                  /* coefficient pad digits */
  71   decNumber dw;                 /* work */
  72   decContext dc;                /* .. */
  73   uByte isneg = dn->bits & DECNEG;      /* non-0 if original sign set */
  74   uInt comb, exp;               /* work */
  75
  76   /* If the number is finite, and has too many digits, or the exponent */
  77   /* could be out of range then we reduce the number under the */
  78   /* appropriate constraints */
  79   if (!(dn->bits & DECSPECIAL))
  80     {                           /* not a special value */
  81       Int ae = dn->exponent + dn->digits - 1;   /* adjusted exponent */
  82       if (dn->digits > DECIMAL64_Pmax   /* too many digits */
  83           || ae > DECIMAL64_Emax        /* likely overflow */
  84           || ae < DECIMAL64_Emin)
  85         {                       /* likely underflow */
  86           decContextDefault (&dc, DEC_INIT_DECIMAL64);  /* [no traps] */
  87           dc.round = set->round;        /* use supplied rounding */
  88           decNumberPlus (&dw, dn, &dc); /* (round and check) */
  89           /* [this changes -0 to 0, but it will be restored below] */
  90           status |= dc.status;  /* save status */
  91           dn = &dw;             /* use the work number */
  92         }
  93       /* [this could have pushed number to Infinity or zero, so this */
  94       /* rounding must be done before we generate the decimal64] */
  95     }
  96
  97   DEC_clear (d64);              /* clean the target */
  98   if (dn->bits & DECSPECIAL)
  99     {                           /* a special value */
 100       uByte top;                /* work */
 101       if (dn->bits & DECINF)
 102         top = DECIMAL_Inf;
 103       else
 104         {                       /* sNaN or qNaN */
 105           if ((*dn->lsu != 0 || dn->digits > 1) /* non-zero coefficient */
 106               && (dn->digits < DECIMAL64_Pmax))
 107             {                   /* coefficient fits */
 108               decDensePackCoeff (dn, d64->bytes, sizeof (d64->bytes), 0);
 109             }
 110           if (dn->bits & DECNAN)
 111             top = DECIMAL_NaN;
 112           else
 113             top = DECIMAL_sNaN;
 114         }
 115       d64->bytes[0] = top;
 116     }
 117   else if (decNumberIsZero (dn))
 118     {                           /* a zero */
 119       /* set and clamp exponent */
 120       if (dn->exponent < -DECIMAL64_Bias)
 121         {
 122           exp = 0;
 123           status |= DEC_Clamped;
 124         }
 125       else
 126         {
 127           exp = dn->exponent + DECIMAL64_Bias;  /* bias exponent */
 128           if (exp > DECIMAL64_Ehigh)
 129             {                   /* top clamp */
 130               exp = DECIMAL64_Ehigh;
 131               status |= DEC_Clamped;
 132             }
 133         }
 134       comb = (exp >> 5) & 0x18; /* combination field */
 135       d64->bytes[0] = (uByte) (comb << 2);
 136       exp &= 0xff;              /* remaining exponent bits */
 137       decimal64SetExpCon (d64, exp);
 138     }
 139   else
 140     {                           /* non-zero finite number */
 141       uInt msd;                 /* work */
 142
 143       /* we have a dn that fits, but it may need to be padded */
 144       exp = (uInt) (dn->exponent + DECIMAL64_Bias);     /* bias exponent */
 145       if (exp > DECIMAL64_Ehigh)
 146         {                       /* fold-down case */
 147           pad = exp - DECIMAL64_Ehigh;
 148           exp = DECIMAL64_Ehigh;        /* [to maximum] */
 149           status |= DEC_Clamped;
 150         }
 151
 152       decDensePackCoeff (dn, d64->bytes, sizeof (d64->bytes), pad);
 153
 154       /* save and clear the top digit */
 155       msd = ((unsigned) d64->bytes[1] >> 2) & 0x0f;
 156       d64->bytes[1] &= 0x03;
 157       /* create the combination field */
 158       if (msd >= 8)
 159         comb = 0x18 | (msd & 0x01) | ((exp >> 7) & 0x06);
 160       else
 161         comb = (msd & 0x07) | ((exp >> 5) & 0x18);
 162       d64->bytes[0] = (uByte) (comb << 2);
 163       exp &= 0xff;              /* remaining exponent bits */
 164       decimal64SetExpCon (d64, exp);
 165     }
 166
 167   if (isneg)
 168     decimal64SetSign (d64, 1);
 169   if (status != 0)
 170     decContextSetStatus (set, status);  /* pass on status */
 171
 172   /*decimal64Show(d64); */
 173   return d64;
 174 }
 175
 176 /* ------------------------------------------------------------------ */
 177 /* decimal64ToNumber -- convert decimal64 to decNumber                */
 178 /*   d64 is the source decimal64                                      */
 179 /*   dn is the target number, with appropriate space                  */
 180 /* No error is possible.                                              */
 181 /* ------------------------------------------------------------------ */
 182 decNumber *
 183 decimal64ToNumber (const decimal64 * d64, decNumber * dn)
 184 {
 185   uInt msd;                     /* coefficient MSD */
 186   decimal64 wk;                 /* working copy, if needed */
 187   uInt top = d64->bytes[0] & 0x7f;      /* top byte, less sign bit */
 188   decNumberZero (dn);           /* clean target */
 189   /* set the sign if negative */
 190   if (decimal64Sign (d64))
 191     dn->bits = DECNEG;
 192
 193   if (top >= 0x78)
 194     {                           /* is a special */
 195       if ((top & 0x7c) == (DECIMAL_Inf & 0x7c))
 196         dn->bits |= DECINF;
 197       else if ((top & 0x7e) == (DECIMAL_NaN & 0x7e))
 198         dn->bits |= DECNAN;
 199       else
 200         dn->bits |= DECSNAN;
 201       msd = 0;                  /* no top digit */
 202     }
 203   else
 204     {                           /* have a finite number */
 205       uInt comb = top >> 2;     /* combination field */
 206       uInt exp;                 /* exponent */
 207
 208       if (comb >= 0x18)
 209         {
 210           msd = 8 + (comb & 0x01);
 211           exp = (comb & 0x06) << 7;     /* MSBs */
 212         }
 213       else
 214         {
 215           msd = comb & 0x07;
 216           exp = (comb & 0x18) << 5;
 217         }
 218       dn->exponent = exp + decimal64ExpCon (d64) - DECIMAL64_Bias;      /* remove bias */
 219     }
 220
 221   /* get the coefficient, unless infinite */
 222   if (!(dn->bits & DECINF))
 223     {
 224       Int bunches = DECIMAL64_Pmax / 3; /* coefficient full bunches to convert */
 225       Int odd = 0;              /* assume MSD is 0 (no odd bunch) */
 226       if (msd != 0)
 227         {                       /* coefficient has leading non-0 digit */
 228           /* make a copy of the decimal64, with an extra bunch which has */
 229           /* the top digit ready for conversion */
 230           wk = *d64;            /* take a copy */
 231           wk.bytes[0] = 0;      /* clear all but coecon */
 232           wk.bytes[1] &= 0x03;  /* .. */
 233           wk.bytes[1] |= (msd << 2);    /* and prefix MSD */
 234           odd++;                /* indicate the extra */
 235           d64 = &wk;            /* use the work copy */
 236         }
 237       decDenseUnpackCoeff (d64->bytes, sizeof (d64->bytes), dn, bunches, odd);
 238     }
 239   return dn;
 240 }
 241
 242 /* ------------------------------------------------------------------ */
 243 /* to-scientific-string -- conversion to numeric string               */
 244 /* to-engineering-string -- conversion to numeric string              */
 245 /*                                                                    */
 246 /*   decimal64ToString(d64, string);                                  */
 247 /*   decimal64ToEngString(d64, string);                               */
 248 /*                                                                    */
 249 /*  d64 is the decimal64 format number to convert                     */
 250 /*  string is the string where the result will be laid out            */
 251 /*                                                                    */
 252 /*  string must be at least 24 characters                             */
 253 /*                                                                    */
 254 /*  No error is possible, and no status can be set.                   */
 255 /* ------------------------------------------------------------------ */
 256 char *
 257 decimal64ToString (const decimal64 * d64, char *string)
 258 {
 259   decNumber dn;                 /* work */
 260   decimal64ToNumber (d64, &dn);
 261   decNumberToString (&dn, string);
 262   return string;
 263 }
 264
 265 char *
 266 decimal64ToEngString (const decimal64 * d64, char *string)
 267 {
 268   decNumber dn;                 /* work */
 269   decimal64ToNumber (d64, &dn);
 270   decNumberToEngString (&dn, string);
 271   return string;
 272 }
 273
 274 /* ------------------------------------------------------------------ */
 275 /* to-number -- conversion from numeric string                        */
 276 /*                                                                    */
 277 /*   decimal64FromString(result, string, set);                        */
 278 /*                                                                    */
 279 /*  result  is the decimal64 format number which gets the result of   */
 280 /*          the conversion                                            */
 281 /*  *string is the character string which should contain a valid      */
 282 /*          number (which may be a special value)                     */
 283 /*  set     is the context                                            */
 284 /*                                                                    */
 285 /* The context is supplied to this routine is used for error handling */
 286 /* (setting of status and traps) and for the rounding mode, only.     */
 287 /* If an error occurs, the result will be a valid decimal64 NaN.      */
 288 /* ------------------------------------------------------------------ */
 289 decimal64 *
 290 decimal64FromString (decimal64 * result, const char *string, decContext * set)
 291 {
 292   decContext dc;                /* work */
 293   decNumber dn;                 /* .. */
 294
 295   decContextDefault (&dc, DEC_INIT_DECIMAL64);  /* no traps, please */
 296   dc.round = set->round;        /* use supplied rounding */
 297
 298   decNumberFromString (&dn, string, &dc);       /* will round if needed */
 299
 300   decimal64FromNumber (result, &dn, &dc);
 301   if (dc.status != 0)
 302     {                           /* something happened */
 303       decContextSetStatus (set, dc.status);     /* .. pass it on */
 304     }
 305   return result;
 306 }
 307
 308 #if DECTRACE || DECCHECK
 309 /* ------------------------------------------------------------------ */
 310 /* decimal64Show -- display a single in hexadecimal [debug aid]       */
 311 /*   d64 -- the number to show                                        */
 312 /* ------------------------------------------------------------------ */
 313 /* Also shows sign/cob/expconfields extracted */
 314 void
 315 decimal64Show (const decimal64 * d64)
 316 {
 317   char buf[DECIMAL64_Bytes * 2 + 1];
 318   Int i, j;
 319   j = 0;
 320   for (i = 0; i < DECIMAL64_Bytes; i++)
 321     {
 322       sprintf (&buf[j], "%02x", d64->bytes[i]);
 323       j = j + 2;
 324     }
 325   printf (" D64> %s [S:%d Cb:%02x E:%d]\n", buf,
 326           decimal64Sign (d64), decimal64Comb (d64), decimal64ExpCon (d64));
 327 }
 328 #endif