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    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 decimal64 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 16        /* we need decNumbers with space for 16 */
  43 #include "config.h"
  44 #include "decNumber.h"          /* base number library */
  45 #include "decNumberLocal.h"     /* decNumber local types, etc. */
  46 #include "decimal64.h"          /* our primary include */
  47 #include "decUtility.h"         /* utility routines */
  48
  49 #if DECTRACE || DECCHECK
  50 void decimal64Show (const decimal64 *); /* 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 /* decimal64FromNumber -- convert decNumber to decimal64              */
  60 /*                                                                    */
  61 /*   ds is the target decimal64                                       */
  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 DECIMAL64_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 decimal64 *
  76 decimal64FromNumber (decimal64 * d64, 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 > DECIMAL64_Pmax   /* too many digits */
  92           || ae > DECIMAL64_Emax        /* likely overflow */
  93           || ae < DECIMAL64_Emin)
  94         {                       /* likely underflow */
  95           decContextDefault (&dc, DEC_INIT_DECIMAL64);  /* [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 decimal64] */
 104     }
 105
 106   DEC_clear (d64);              /* 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 < DECIMAL64_Pmax))
 116             {                   /* coefficient fits */
 117               decDensePackCoeff (dn, d64->bytes, sizeof (d64->bytes), 0);
 118             }
 119           if (dn->bits & DECNAN)
 120             top = DECIMAL_NaN;
 121           else
 122             top = DECIMAL_sNaN;
 123         }
 124       d64->bytes[0] = top;
 125     }
 126   else if (decNumberIsZero (dn))
 127     {                           /* a zero */
 128       /* set and clamp exponent */
 129       if (dn->exponent < -DECIMAL64_Bias)
 130         {
 131           exp = 0;
 132           status |= DEC_Clamped;
 133         }
 134       else
 135         {
 136           exp = dn->exponent + DECIMAL64_Bias;  /* bias exponent */
 137           if (exp > DECIMAL64_Ehigh)
 138             {                   /* top clamp */
 139               exp = DECIMAL64_Ehigh;
 140               status |= DEC_Clamped;
 141             }
 142         }
 143       comb = (exp >> 5) & 0x18; /* combination field */
 144       d64->bytes[0] = (uByte) (comb << 2);
 145       exp &= 0xff;              /* remaining exponent bits */
 146       decimal64SetExpCon (d64, 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 + DECIMAL64_Bias);     /* bias exponent */
 154       if (exp > DECIMAL64_Ehigh)
 155         {                       /* fold-down case */
 156           pad = exp - DECIMAL64_Ehigh;
 157           exp = DECIMAL64_Ehigh;        /* [to maximum] */
 158           status |= DEC_Clamped;
 159         }
 160
 161       decDensePackCoeff (dn, d64->bytes, sizeof (d64->bytes), pad);
 162
 163       /* save and clear the top digit */
 164       msd = ((unsigned) d64->bytes[1] >> 2) & 0x0f;
 165       d64->bytes[1] &= 0x03;
 166       /* create the combination field */
 167       if (msd >= 8)
 168         comb = 0x18 | (msd & 0x01) | ((exp >> 7) & 0x06);
 169       else
 170         comb = (msd & 0x07) | ((exp >> 5) & 0x18);
 171       d64->bytes[0] = (uByte) (comb << 2);
 172       exp &= 0xff;              /* remaining exponent bits */
 173       decimal64SetExpCon (d64, exp);
 174     }
 175
 176   if (isneg)
 177     decimal64SetSign (d64, 1);
 178   if (status != 0)
 179     decContextSetStatus (set, status);  /* pass on status */
 180
 181   /*decimal64Show(d64); */
 182   return d64;
 183 }
 184
 185 /* ------------------------------------------------------------------ */
 186 /* decimal64ToNumber -- convert decimal64 to decNumber                */
 187 /*   d64 is the source decimal64                                      */
 188 /*   dn is the target number, with appropriate space                  */
 189 /* No error is possible.                                              */
 190 /* ------------------------------------------------------------------ */
 191 decNumber *
 192 decimal64ToNumber (const decimal64 * d64, decNumber * dn)
 193 {
 194   uInt msd;                     /* coefficient MSD */
 195   decimal64 wk;                 /* working copy, if needed */
 196   uInt top = d64->bytes[0] & 0x7f;      /* top byte, less sign bit */
 197   decNumberZero (dn);           /* clean target */
 198   /* set the sign if negative */
 199   if (decimal64Sign (d64))
 200     dn->bits = DECNEG;
 201
 202   if (top >= 0x78)
 203     {                           /* is a special */
 204       if ((top & 0x7c) == (DECIMAL_Inf & 0x7c))
 205         dn->bits |= DECINF;
 206       else if ((top & 0x7e) == (DECIMAL_NaN & 0x7e))
 207         dn->bits |= DECNAN;
 208       else
 209         dn->bits |= DECSNAN;
 210       msd = 0;                  /* no top digit */
 211     }
 212   else
 213     {                           /* have a finite number */
 214       uInt comb = top >> 2;     /* combination field */
 215       uInt exp;                 /* exponent */
 216
 217       if (comb >= 0x18)
 218         {
 219           msd = 8 + (comb & 0x01);
 220           exp = (comb & 0x06) << 7;     /* MSBs */
 221         }
 222       else
 223         {
 224           msd = comb & 0x07;
 225           exp = (comb & 0x18) << 5;
 226         }
 227       dn->exponent = exp + decimal64ExpCon (d64) - DECIMAL64_Bias;      /* remove bias */
 228     }
 229
 230   /* get the coefficient, unless infinite */
 231   if (!(dn->bits & DECINF))
 232     {
 233       Int bunches = DECIMAL64_Pmax / 3; /* coefficient full bunches to convert */
 234       Int odd = 0;              /* assume MSD is 0 (no odd bunch) */
 235       if (msd != 0)
 236         {                       /* coefficient has leading non-0 digit */
 237           /* make a copy of the decimal64, with an extra bunch which has */
 238           /* the top digit ready for conversion */
 239           wk = *d64;            /* take a copy */
 240           wk.bytes[0] = 0;      /* clear all but coecon */
 241           wk.bytes[1] &= 0x03;  /* .. */
 242           wk.bytes[1] |= (msd << 2);    /* and prefix MSD */
 243           odd++;                /* indicate the extra */
 244           d64 = &wk;            /* use the work copy */
 245         }
 246       decDenseUnpackCoeff (d64->bytes, sizeof (d64->bytes), dn, bunches, odd);
 247     }
 248   return dn;
 249 }
 250
 251 /* ------------------------------------------------------------------ */
 252 /* to-scientific-string -- conversion to numeric string               */
 253 /* to-engineering-string -- conversion to numeric string              */
 254 /*                                                                    */
 255 /*   decimal64ToString(d64, string);                                  */
 256 /*   decimal64ToEngString(d64, string);                               */
 257 /*                                                                    */
 258 /*  d64 is the decimal64 format number to convert                     */
 259 /*  string is the string where the result will be laid out            */
 260 /*                                                                    */
 261 /*  string must be at least 24 characters                             */
 262 /*                                                                    */
 263 /*  No error is possible, and no status can be set.                   */
 264 /* ------------------------------------------------------------------ */
 265 char *
 266 decimal64ToString (const decimal64 * d64, char *string)
 267 {
 268   decNumber dn;                 /* work */
 269   decimal64ToNumber (d64, &dn);
 270   decNumberToString (&dn, string);
 271   return string;
 272 }
 273
 274 char *
 275 decimal64ToEngString (const decimal64 * d64, char *string)
 276 {
 277   decNumber dn;                 /* work */
 278   decimal64ToNumber (d64, &dn);
 279   decNumberToEngString (&dn, string);
 280   return string;
 281 }
 282
 283 /* ------------------------------------------------------------------ */
 284 /* to-number -- conversion from numeric string                        */
 285 /*                                                                    */
 286 /*   decimal64FromString(result, string, set);                        */
 287 /*                                                                    */
 288 /*  result  is the decimal64 format number which gets the result of   */
 289 /*          the conversion                                            */
 290 /*  *string is the character string which should contain a valid      */
 291 /*          number (which may be a special value)                     */
 292 /*  set     is the context                                            */
 293 /*                                                                    */
 294 /* The context is supplied to this routine is used for error handling */
 295 /* (setting of status and traps) and for the rounding mode, only.     */
 296 /* If an error occurs, the result will be a valid decimal64 NaN.      */
 297 /* ------------------------------------------------------------------ */
 298 decimal64 *
 299 decimal64FromString (decimal64 * result, const char *string, decContext * set)
 300 {
 301   decContext dc;                /* work */
 302   decNumber dn;                 /* .. */
 303
 304   decContextDefault (&dc, DEC_INIT_DECIMAL64);  /* no traps, please */
 305   dc.round = set->round;        /* use supplied rounding */
 306
 307   decNumberFromString (&dn, string, &dc);       /* will round if needed */
 308
 309   decimal64FromNumber (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 /* decimal64Show -- display a single in hexadecimal [debug aid]       */
 320 /*   d64 -- the number to show                                        */
 321 /* ------------------------------------------------------------------ */
 322 /* Also shows sign/cob/expconfields extracted */
 323 void
 324 decimal64Show (const decimal64 * d64)
 325 {
 326   char buf[DECIMAL64_Bytes * 2 + 1];
 327   Int i, j;
 328   j = 0;
 329   for (i = 0; i < DECIMAL64_Bytes; i++)
 330     {
 331       sprintf (&buf[j], "%02x", d64->bytes[i]);
 332       j = j + 2;
 333     }
 334   printf (" D64> %s [S:%d Cb:%02x E:%d]\n", buf,
 335           decimal64Sign (d64), decimal64Comb (d64), decimal64ExpCon (d64));
 336 }
 337 #endif