libdecnumber/decimal32.c

   1 /* Decimal 32-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    In addition to the permissions in the GNU General Public License,
  13    the Free Software Foundation gives you unlimited permission to link
  14    the compiled version of this file into combinations with other
  15    programs, and to distribute those combinations without any
  16    restriction coming from the use of this file.  (The General Public
  17    License restrictions do apply in other respects; for example, they
  18    cover modification of the file, and distribution when not linked
  19    into a combine executable.)
  20
  21    GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  22    WARRANTY; without even the implied warranty of MERCHANTABILITY or
  23    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  24    for more details.
  25
  26    You should have received a copy of the GNU General Public License
  27    along with GCC; see the file COPYING.  If not, write to the Free
  28    Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
  29    02110-1301, USA.  */
  30
  31 /* ------------------------------------------------------------------ */
  32 /* This module comprises the routines for decimal32 format numbers.   */
  33 /* Conversions are supplied to and from decNumber and String.         */
  34 /*                                                                    */
  35 /* No arithmetic routines are included; decNumber provides these.     */
  36 /*                                                                    */
  37 /* Error handling is the same as decNumber (qv.).                     */
  38 /* ------------------------------------------------------------------ */
  39 #include <string.h>             /* [for memset/memcpy] */
  40 #include <stdio.h>              /* [for printf] */
  41
  42 #define  DECNUMDIGITS  7        /* we need decNumbers with space for 7 */
  43 #include "config.h"
  44 #include "decNumber.h"          /* base number library */
  45 #include "decNumberLocal.h"     /* decNumber local types, etc. */
  46 #include "decimal32.h"          /* our primary include */
  47 #include "decUtility.h"         /* utility routines */
  48
  49 #if DECTRACE || DECCHECK
  50 void decimal32Show (const decimal32 *); /* for debug */
  51 void decNumberShow (const decNumber *); /* .. */
  52 #endif
  53
  54 /* Useful macro */
  55 /* Clear a structure (e.g., a decNumber) */
  56 #define DEC_clear(d) memset(d, 0, sizeof(*d))
  57
  58 /* ------------------------------------------------------------------ */
  59 /* decimal32FromNumber -- convert decNumber to decimal32              */
  60 /*                                                                    */
  61 /*   ds is the target decimal32                                       */
  62 /*   dn is the source number (assumed valid)                          */
  63 /*   set is the context, used only for reporting errors               */
  64 /*                                                                    */
  65 /* The set argument is used only for status reporting and for the     */
  66 /* rounding mode (used if the coefficient is more than DECIMAL32_Pmax */
  67 /* digits or an overflow is detected).  If the exponent is out of the */
  68 /* valid range then Overflow or Underflow will be raised.             */
  69 /* After Underflow a subnormal result is possible.                    */
  70 /*                                                                    */
  71 /* DEC_Clamped is set if the number has to be 'folded down' to fit,   */
  72 /* by reducing its exponent and multiplying the coefficient by a      */
  73 /* power of ten, or if the exponent on a zero had to be clamped.      */
  74 /* ------------------------------------------------------------------ */
  75 decimal32 *
  76 decimal32FromNumber (decimal32 * d32, const decNumber * dn, decContext * set)
  77 {
  78   uInt status = 0;              /* status accumulator */
  79   Int pad = 0;                  /* coefficient pad digits */
  80   decNumber dw;                 /* work */
  81   decContext dc;                /* .. */
  82   uByte isneg = dn->bits & DECNEG;      /* non-0 if original sign set */
  83   uInt comb, exp;               /* work */
  84
  85   /* If the number is finite, and has too many digits, or the exponent */
  86   /* could be out of range then we reduce the number under the */
  87   /* appropriate constraints */
  88   if (!(dn->bits & DECSPECIAL))
  89     {                           /* not a special value */
  90       Int ae = dn->exponent + dn->digits - 1;   /* adjusted exponent */
  91       if (dn->digits > DECIMAL32_Pmax   /* too many digits */
  92           || ae > DECIMAL32_Emax        /* likely overflow */
  93           || ae < DECIMAL32_Emin)
  94         {                       /* likely underflow */
  95           decContextDefault (&dc, DEC_INIT_DECIMAL32);  /* [no traps] */
  96           dc.round = set->round;        /* use supplied rounding */
  97           decNumberPlus (&dw, dn, &dc); /* (round and check) */
  98           /* [this changes -0 to 0, but it will be restored below] */
  99           status |= dc.status;  /* save status */
 100           dn = &dw;             /* use the work number */
 101         }
 102       /* [this could have pushed number to Infinity or zero, so this */
 103       /* rounding must be done before we generate the decimal32] */
 104     }
 105
 106   DEC_clear (d32);              /* clean the target */
 107   if (dn->bits & DECSPECIAL)
 108     {                           /* a special value */
 109       uByte top;                /* work */
 110       if (dn->bits & DECINF)
 111         top = DECIMAL_Inf;
 112       else
 113         {                       /* sNaN or qNaN */
 114           if ((*dn->lsu != 0 || dn->digits > 1) /* non-zero coefficient */
 115               && (dn->digits < DECIMAL32_Pmax))
 116             {                   /* coefficient fits */
 117               decDensePackCoeff (dn, d32->bytes, sizeof (d32->bytes), 0);
 118             }
 119           if (dn->bits & DECNAN)
 120             top = DECIMAL_NaN;
 121           else
 122             top = DECIMAL_sNaN;
 123         }
 124       d32->bytes[0] = top;
 125     }
 126   else if (decNumberIsZero (dn))
 127     {                           /* a zero */
 128       /* set and clamp exponent */
 129       if (dn->exponent < -DECIMAL32_Bias)
 130         {
 131           exp = 0;
 132           status |= DEC_Clamped;
 133         }
 134       else
 135         {
 136           exp = dn->exponent + DECIMAL32_Bias;  /* bias exponent */
 137           if (exp > DECIMAL32_Ehigh)
 138             {                   /* top clamp */
 139               exp = DECIMAL32_Ehigh;
 140               status |= DEC_Clamped;
 141             }
 142         }
 143       comb = (exp >> 3) & 0x18; /* combination field */
 144       d32->bytes[0] = (uByte) (comb << 2);
 145       exp &= 0x3f;              /* remaining exponent bits */
 146       decimal32SetExpCon (d32, exp);
 147     }
 148   else
 149     {                           /* non-zero finite number */
 150       uInt msd;                 /* work */
 151
 152       /* we have a dn that fits, but it may need to be padded */
 153       exp = (uInt) (dn->exponent + DECIMAL32_Bias);     /* bias exponent */
 154
 155       if (exp > DECIMAL32_Ehigh)
 156         {                       /* fold-down case */
 157           pad = exp - DECIMAL32_Ehigh;
 158           exp = DECIMAL32_Ehigh;        /* [to maximum] */
 159           status |= DEC_Clamped;
 160         }
 161
 162       decDensePackCoeff (dn, d32->bytes, sizeof (d32->bytes), pad);
 163
 164       /* save and clear the top digit */
 165       msd = ((unsigned) d32->bytes[1] >> 4);
 166       d32->bytes[1] &= 0x0f;
 167       /* create the combination field */
 168       if (msd >= 8)
 169         comb = 0x18 | (msd & 0x01) | ((exp >> 5) & 0x06);
 170       else
 171         comb = (msd & 0x07) | ((exp >> 3) & 0x18);
 172       d32->bytes[0] = (uByte) (comb << 2);
 173       exp &= 0x3f;              /* remaining exponent bits */
 174       decimal32SetExpCon (d32, exp);
 175     }
 176
 177   if (isneg)
 178     decimal32SetSign (d32, 1);
 179   if (status != 0)
 180     decContextSetStatus (set, status);  /* pass on status */
 181
 182   /*decimal32Show(d32); */
 183   return d32;
 184 }
 185
 186 /* ------------------------------------------------------------------ */
 187 /* decimal32ToNumber -- convert decimal32 to decNumber                */
 188 /*   d32 is the source decimal32                                      */
 189 /*   dn is the target number, with appropriate space                  */
 190 /* No error is possible.                                              */
 191 /* ------------------------------------------------------------------ */
 192 decNumber *
 193 decimal32ToNumber (const decimal32 * d32, decNumber * dn)
 194 {
 195   uInt msd;                     /* coefficient MSD */
 196   decimal32 wk;                 /* working copy, if needed */
 197   uInt top = d32->bytes[0] & 0x7f;      /* top byte, less sign bit */
 198   decNumberZero (dn);           /* clean target */
 199   /* set the sign if negative */
 200   if (decimal32Sign (d32))
 201     dn->bits = DECNEG;
 202
 203   if (top >= 0x78)
 204     {                           /* is a special */
 205       if ((top & 0x7c) == (DECIMAL_Inf & 0x7c))
 206         dn->bits |= DECINF;
 207       else if ((top & 0x7e) == (DECIMAL_NaN & 0x7e))
 208         dn->bits |= DECNAN;
 209       else
 210         dn->bits |= DECSNAN;
 211       msd = 0;                  /* no top digit */
 212     }
 213   else
 214     {                           /* have a finite number */
 215       uInt comb = top >> 2;     /* combination field */
 216       uInt exp;                 /* working exponent */
 217
 218       if (comb >= 0x18)
 219         {
 220           msd = 8 + (comb & 0x01);
 221           exp = (comb & 0x06) << 5;     /* MSBs */
 222         }
 223       else
 224         {
 225           msd = comb & 0x07;
 226           exp = (comb & 0x18) << 3;
 227         }
 228       dn->exponent = exp + decimal32ExpCon (d32) - DECIMAL32_Bias;      /* remove bias */
 229     }
 230
 231   /* get the coefficient, unless infinite */
 232   if (!(dn->bits & DECINF))
 233     {
 234       Int bunches = DECIMAL32_Pmax / 3; /* coefficient full bunches to convert */
 235       Int odd = 0;              /* assume MSD is 0 (no odd bunch) */
 236       if (msd != 0)
 237         {                       /* coefficient has leading non-0 digit */
 238           /* make a copy of the decimal32, with an extra bunch which has */
 239           /* the top digit ready for conversion */
 240           wk = *d32;            /* take a copy */
 241           wk.bytes[0] = 0;      /* clear all but coecon */
 242           wk.bytes[1] &= 0x0f;  /* .. */
 243           wk.bytes[1] |= (msd << 4);    /* and prefix MSD */
 244           odd++;                /* indicate the extra */
 245           d32 = &wk;            /* use the work copy */
 246         }
 247       decDenseUnpackCoeff (d32->bytes, sizeof (d32->bytes), dn, bunches, odd);
 248     }
 249   return dn;
 250 }
 251
 252 /* ------------------------------------------------------------------ */
 253 /* to-scientific-string -- conversion to numeric string               */
 254 /* to-engineering-string -- conversion to numeric string              */
 255 /*                                                                    */
 256 /*   decimal32ToString(d32, string);                                  */
 257 /*   decimal32ToEngString(d32, string);                               */
 258 /*                                                                    */
 259 /*  d32 is the decimal32 format number to convert                     */
 260 /*  string is the string where the result will be laid out            */
 261 /*                                                                    */
 262 /*  string must be at least 24 characters                             */
 263 /*                                                                    */
 264 /*  No error is possible, and no status can be set.                   */
 265 /* ------------------------------------------------------------------ */
 266 char *
 267 decimal32ToString (const decimal32 * d32, char *string)
 268 {
 269   decNumber dn;                 /* work */
 270   decimal32ToNumber (d32, &dn);
 271   decNumberToString (&dn, string);
 272   return string;
 273 }
 274
 275 char *
 276 decimal32ToEngString (const decimal32 * d32, char *string)
 277 {
 278   decNumber dn;                 /* work */
 279   decimal32ToNumber (d32, &dn);
 280   decNumberToEngString (&dn, string);
 281   return string;
 282 }
 283
 284 /* ------------------------------------------------------------------ */
 285 /* to-number -- conversion from numeric string                        */
 286 /*                                                                    */
 287 /*   decimal32FromString(result, string, set);                        */
 288 /*                                                                    */
 289 /*  result  is the decimal32 format number which gets the result of   */
 290 /*          the conversion                                            */
 291 /*  *string is the character string which should contain a valid      */
 292 /*          number (which may be a special value)                     */
 293 /*  set     is the context                                            */
 294 /*                                                                    */
 295 /* The context is supplied to this routine is used for error handling */
 296 /* (setting of status and traps) and for the rounding mode, only.     */
 297 /* If an error occurs, the result will be a valid decimal32 NaN.      */
 298 /* ------------------------------------------------------------------ */
 299 decimal32 *
 300 decimal32FromString (decimal32 * result, const char *string, decContext * set)
 301 {
 302   decContext dc;                /* work */
 303   decNumber dn;                 /* .. */
 304
 305   decContextDefault (&dc, DEC_INIT_DECIMAL32);  /* no traps, please */
 306   dc.round = set->round;        /* use supplied rounding */
 307
 308   decNumberFromString (&dn, string, &dc);       /* will round if needed */
 309   decimal32FromNumber (result, &dn, &dc);
 310   if (dc.status != 0)
 311     {                           /* something happened */
 312       decContextSetStatus (set, dc.status);     /* .. pass it on */
 313     }
 314   return result;
 315 }
 316
 317 #if DECTRACE || DECCHECK
 318 /* ------------------------------------------------------------------ */
 319 /* decimal32Show -- display a single in hexadecimal [debug aid]       */
 320 /*   d32 -- the number to show                                        */
 321 /* ------------------------------------------------------------------ */
 322 /* Also shows sign/cob/expconfields extracted */
 323 void
 324 decimal32Show (const decimal32 * d32)
 325 {
 326   char buf[DECIMAL32_Bytes * 2 + 1];
 327   Int i, j;
 328   j = 0;
 329   for (i = 0; i < DECIMAL32_Bytes; i++)
 330     {
 331       sprintf (&buf[j], "%02x", d32->bytes[i]);
 332       j = j + 2;
 333     }
 334   printf (" D32> %s [S:%d Cb:%02x E:%d]\n", buf,
 335           decimal32Sign (d32), decimal32Comb (d32), decimal32ExpCon (d32));
 336 }
 337 #endif