libdecnumber/dpd/decimal32.c

   1 /* Decimal 32-bit format module for the decNumber C Library.
   2    Copyright (C) 2005, 2007 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 /* Decimal 32-bit format module                                       */
  33 /* ------------------------------------------------------------------ */
  34 /* This module comprises the routines for decimal32 format numbers.   */
  35 /* Conversions are supplied to and from decNumber and String.         */
  36 /*                                                                    */
  37 /* This is used when decNumber provides operations, either for all    */
  38 /* operations or as a proxy between decNumber and decSingle.          */
  39 /*                                                                    */
  40 /* Error handling is the same as decNumber (qv.).                     */
  41 /* ------------------------------------------------------------------ */
  42 #include <string.h>           /* [for memset/memcpy] */
  43 #include <stdio.h>            /* [for printf] */
  44
  45 #include "dconfig.h"          /* GCC definitions */
  46 #define  DECNUMDIGITS  7      /* make decNumbers with space for 7 */
  47 #include "decNumber.h"        /* base number library */
  48 #include "decNumberLocal.h"   /* decNumber local types, etc. */
  49 #include "decimal32.h"        /* our primary include */
  50
  51 /* Utility tables and routines [in decimal64.c] */
  52 extern const uInt   COMBEXP[32], COMBMSD[32];
  53 extern const uShort DPD2BIN[1024];
  54 extern const uShort BIN2DPD[1000];
  55 extern const uByte  BIN2CHAR[4001];
  56
  57 extern void decDigitsToDPD(const decNumber *, uInt *, Int);
  58 extern void decDigitsFromDPD(decNumber *, const uInt *, Int);
  59
  60 #if DECTRACE || DECCHECK
  61 void decimal32Show(const decimal32 *);            /* for debug */
  62 extern void decNumberShow(const decNumber *);     /* .. */
  63 #endif
  64
  65 /* Useful macro */
  66 /* Clear a structure (e.g., a decNumber) */
  67 #define DEC_clear(d) memset(d, 0, sizeof(*d))
  68
  69 /* ------------------------------------------------------------------ */
  70 /* decimal32FromNumber -- convert decNumber to decimal32              */
  71 /*                                                                    */
  72 /*   ds is the target decimal32                                       */
  73 /*   dn is the source number (assumed valid)                          */
  74 /*   set is the context, used only for reporting errors               */
  75 /*                                                                    */
  76 /* The set argument is used only for status reporting and for the     */
  77 /* rounding mode (used if the coefficient is more than DECIMAL32_Pmax */
  78 /* digits or an overflow is detected).  If the exponent is out of the */
  79 /* valid range then Overflow or Underflow will be raised.             */
  80 /* After Underflow a subnormal result is possible.                    */
  81 /*                                                                    */
  82 /* DEC_Clamped is set if the number has to be 'folded down' to fit,   */
  83 /* by reducing its exponent and multiplying the coefficient by a      */
  84 /* power of ten, or if the exponent on a zero had to be clamped.      */
  85 /* ------------------------------------------------------------------ */
  86 decimal32 * decimal32FromNumber(decimal32 *d32, const decNumber *dn,
  87                               decContext *set) {
  88   uInt status=0;                   /* status accumulator */
  89   Int ae;                          /* adjusted exponent */
  90   decNumber  dw;                   /* work */
  91   decContext dc;                   /* .. */
  92   uInt comb, exp;                  /* .. */
  93   uInt uiwork;                     /* for macros */
  94   uInt targ=0;                     /* target 32-bit */
  95
  96   /* If the number has too many digits, or the exponent could be */
  97   /* out of range then reduce the number under the appropriate */
  98   /* constraints.  This could push the number to Infinity or zero, */
  99   /* so this check and rounding must be done before generating the */
 100   /* decimal32] */
 101   ae=dn->exponent+dn->digits-1;              /* [0 if special] */
 102   if (dn->digits>DECIMAL32_Pmax              /* too many digits */
 103    || ae>DECIMAL32_Emax                      /* likely overflow */
 104    || ae<DECIMAL32_Emin) {                   /* likely underflow */
 105     decContextDefault(&dc, DEC_INIT_DECIMAL32); /* [no traps] */
 106     dc.round=set->round;                     /* use supplied rounding */
 107     decNumberPlus(&dw, dn, &dc);             /* (round and check) */
 108     /* [this changes -0 to 0, so enforce the sign...] */
 109     dw.bits|=dn->bits&DECNEG;
 110     status=dc.status;                        /* save status */
 111     dn=&dw;                                  /* use the work number */
 112     } /* maybe out of range */
 113
 114   if (dn->bits&DECSPECIAL) {                      /* a special value */
 115     if (dn->bits&DECINF) targ=DECIMAL_Inf<<24;
 116      else {                                       /* sNaN or qNaN */
 117       if ((*dn->lsu!=0 || dn->digits>1)           /* non-zero coefficient */
 118        && (dn->digits<DECIMAL32_Pmax)) {          /* coefficient fits */
 119         decDigitsToDPD(dn, &targ, 0);
 120         }
 121       if (dn->bits&DECNAN) targ|=DECIMAL_NaN<<24;
 122        else targ|=DECIMAL_sNaN<<24;
 123       } /* a NaN */
 124     } /* special */
 125
 126    else { /* is finite */
 127     if (decNumberIsZero(dn)) {               /* is a zero */
 128       /* set and clamp exponent */
 129       if (dn->exponent<-DECIMAL32_Bias) {
 130         exp=0;                               /* low clamp */
 131         status|=DEC_Clamped;
 132         }
 133        else {
 134         exp=dn->exponent+DECIMAL32_Bias;     /* bias exponent */
 135         if (exp>DECIMAL32_Ehigh) {           /* top clamp */
 136           exp=DECIMAL32_Ehigh;
 137           status|=DEC_Clamped;
 138           }
 139         }
 140       comb=(exp>>3) & 0x18;             /* msd=0, exp top 2 bits .. */
 141       }
 142      else {                             /* non-zero finite number */
 143       uInt msd;                         /* work */
 144       Int pad=0;                        /* coefficient pad digits */
 145
 146       /* the dn is known to fit, but it may need to be padded */
 147       exp=(uInt)(dn->exponent+DECIMAL32_Bias);    /* bias exponent */
 148       if (exp>DECIMAL32_Ehigh) {                  /* fold-down case */
 149         pad=exp-DECIMAL32_Ehigh;
 150         exp=DECIMAL32_Ehigh;                      /* [to maximum] */
 151         status|=DEC_Clamped;
 152         }
 153
 154       /* fastpath common case */
 155       if (DECDPUN==3 && pad==0) {
 156         targ=BIN2DPD[dn->lsu[0]];
 157         if (dn->digits>3) targ|=(uInt)(BIN2DPD[dn->lsu[1]])<<10;
 158         msd=(dn->digits==7 ? dn->lsu[2] : 0);
 159         }
 160        else { /* general case */
 161         decDigitsToDPD(dn, &targ, pad);
 162         /* save and clear the top digit */
 163         msd=targ>>20;
 164         targ&=0x000fffff;
 165         }
 166
 167       /* create the combination field */
 168       if (msd>=8) comb=0x18 | ((exp>>5) & 0x06) | (msd & 0x01);
 169              else comb=((exp>>3) & 0x18) | msd;
 170       }
 171     targ|=comb<<26;                /* add combination field .. */
 172     targ|=(exp&0x3f)<<20;          /* .. and exponent continuation */
 173     } /* finite */
 174
 175   if (dn->bits&DECNEG) targ|=0x80000000;  /* add sign bit */
 176
 177   /* now write to storage; this is endian */
 178   UBFROMUI(d32->bytes, targ);      /* directly store the int */
 179
 180   if (status!=0) decContextSetStatus(set, status); /* pass on status */
 181   /* decimal32Show(d32); */
 182   return d32;
 183   } /* decimal32FromNumber */
 184
 185 /* ------------------------------------------------------------------ */
 186 /* decimal32ToNumber -- convert decimal32 to decNumber                */
 187 /*   d32 is the source decimal32                                      */
 188 /*   dn is the target number, with appropriate space                  */
 189 /* No error is possible.                                              */
 190 /* ------------------------------------------------------------------ */
 191 decNumber * decimal32ToNumber(const decimal32 *d32, decNumber *dn) {
 192   uInt msd;                        /* coefficient MSD */
 193   uInt exp;                        /* exponent top two bits */
 194   uInt comb;                       /* combination field */
 195   uInt sour;                       /* source 32-bit */
 196   uInt uiwork;                     /* for macros */
 197
 198   /* load source from storage; this is endian */
 199   sour=UBTOUI(d32->bytes);         /* directly load the int */
 200
 201   comb=(sour>>26)&0x1f;            /* combination field */
 202
 203   decNumberZero(dn);               /* clean number */
 204   if (sour&0x80000000) dn->bits=DECNEG; /* set sign if negative */
 205
 206   msd=COMBMSD[comb];               /* decode the combination field */
 207   exp=COMBEXP[comb];               /* .. */
 208
 209   if (exp==3) {                    /* is a special */
 210     if (msd==0) {
 211       dn->bits|=DECINF;
 212       return dn;                   /* no coefficient needed */
 213       }
 214     else if (sour&0x02000000) dn->bits|=DECSNAN;
 215     else dn->bits|=DECNAN;
 216     msd=0;                         /* no top digit */
 217     }
 218    else {                          /* is a finite number */
 219     dn->exponent=(exp<<6)+((sour>>20)&0x3f)-DECIMAL32_Bias; /* unbiased */
 220     }
 221
 222   /* get the coefficient */
 223   sour&=0x000fffff;                /* clean coefficient continuation */
 224   if (msd) {                       /* non-zero msd */
 225     sour|=msd<<20;                 /* prefix to coefficient */
 226     decDigitsFromDPD(dn, &sour, 3); /* process 3 declets */
 227     return dn;
 228     }
 229   /* msd=0 */
 230   if (!sour) return dn;            /* easy: coefficient is 0 */
 231   if (sour&0x000ffc00)             /* need 2 declets? */
 232     decDigitsFromDPD(dn, &sour, 2); /* process 2 declets */
 233    else
 234     decDigitsFromDPD(dn, &sour, 1); /* process 1 declet */
 235   return dn;
 236   } /* decimal32ToNumber */
 237
 238 /* ------------------------------------------------------------------ */
 239 /* to-scientific-string -- conversion to numeric string               */
 240 /* to-engineering-string -- conversion to numeric string              */
 241 /*                                                                    */
 242 /*   decimal32ToString(d32, string);                                  */
 243 /*   decimal32ToEngString(d32, string);                               */
 244 /*                                                                    */
 245 /*  d32 is the decimal32 format number to convert                     */
 246 /*  string is the string where the result will be laid out            */
 247 /*                                                                    */
 248 /*  string must be at least 24 characters                             */
 249 /*                                                                    */
 250 /*  No error is possible, and no status can be set.                   */
 251 /* ------------------------------------------------------------------ */
 252 char * decimal32ToEngString(const decimal32 *d32, char *string){
 253   decNumber dn;                         /* work */
 254   decimal32ToNumber(d32, &dn);
 255   decNumberToEngString(&dn, string);
 256   return string;
 257   } /* decimal32ToEngString */
 258
 259 char * decimal32ToString(const decimal32 *d32, char *string){
 260   uInt msd;                        /* coefficient MSD */
 261   Int  exp;                        /* exponent top two bits or full */
 262   uInt comb;                       /* combination field */
 263   char *cstart;                    /* coefficient start */
 264   char *c;                         /* output pointer in string */
 265   const uByte *u;                  /* work */
 266   char *s, *t;                     /* .. (source, target) */
 267   Int  dpd;                        /* .. */
 268   Int  pre, e;                     /* .. */
 269   uInt uiwork;                     /* for macros */
 270   uInt sour;                       /* source 32-bit */
 271
 272   /* load source from storage; this is endian */
 273   sour=UBTOUI(d32->bytes);         /* directly load the int */
 274
 275   c=string;                        /* where result will go */
 276   if (((Int)sour)<0) *c++='-';     /* handle sign */
 277
 278   comb=(sour>>26)&0x1f;            /* combination field */
 279   msd=COMBMSD[comb];               /* decode the combination field */
 280   exp=COMBEXP[comb];               /* .. */
 281
 282   if (exp==3) {
 283     if (msd==0) {                  /* infinity */
 284       strcpy(c,   "Inf");
 285       strcpy(c+3, "inity");
 286       return string;               /* easy */
 287       }
 288     if (sour&0x02000000) *c++='s'; /* sNaN */
 289     strcpy(c, "NaN");              /* complete word */
 290     c+=3;                          /* step past */
 291     if ((sour&0x000fffff)==0) return string; /* zero payload */
 292     /* otherwise drop through to add integer; set correct exp */
 293     exp=0; msd=0;                  /* setup for following code */
 294     }
 295    else exp=(exp<<6)+((sour>>20)&0x3f)-DECIMAL32_Bias; /* unbiased */
 296
 297   /* convert 7 digits of significand to characters */
 298   cstart=c;                        /* save start of coefficient */
 299   if (msd) *c++='0'+(char)msd;     /* non-zero most significant digit */
 300
 301   /* Now decode the declets.  After extracting each one, it is */
 302   /* decoded to binary and then to a 4-char sequence by table lookup; */
 303   /* the 4-chars are a 1-char length (significant digits, except 000 */
 304   /* has length 0).  This allows us to left-align the first declet */
 305   /* with non-zero content, then remaining ones are full 3-char */
 306   /* length.  We use fixed-length memcpys because variable-length */
 307   /* causes a subroutine call in GCC.  (These are length 4 for speed */
 308   /* and are safe because the array has an extra terminator byte.) */
 309   #define dpd2char u=&BIN2CHAR[DPD2BIN[dpd]*4];                   \
 310                    if (c!=cstart) {memcpy(c, u+1, 4); c+=3;}      \
 311                     else if (*u)  {memcpy(c, u+4-*u, 4); c+=*u;}
 312
 313   dpd=(sour>>10)&0x3ff;            /* declet 1 */
 314   dpd2char;
 315   dpd=(sour)&0x3ff;                /* declet 2 */
 316   dpd2char;
 317
 318   if (c==cstart) *c++='0';         /* all zeros -- make 0 */
 319
 320   if (exp==0) {                    /* integer or NaN case -- easy */
 321     *c='\0';                       /* terminate */
 322     return string;
 323     }
 324
 325   /* non-0 exponent */
 326   e=0;                             /* assume no E */
 327   pre=c-cstart+exp;
 328   /* [here, pre-exp is the digits count (==1 for zero)] */
 329   if (exp>0 || pre<-5) {           /* need exponential form */
 330     e=pre-1;                       /* calculate E value */
 331     pre=1;                         /* assume one digit before '.' */
 332     } /* exponential form */
 333
 334   /* modify the coefficient, adding 0s, '.', and E+nn as needed */
 335   s=c-1;                           /* source (LSD) */
 336   if (pre>0) {                     /* ddd.ddd (plain), perhaps with E */
 337     char *dotat=cstart+pre;
 338     if (dotat<c) {                 /* if embedded dot needed... */
 339       t=c;                              /* target */
 340       for (; s>=dotat; s--, t--) *t=*s; /* open the gap; leave t at gap */
 341       *t='.';                           /* insert the dot */
 342       c++;                              /* length increased by one */
 343       }
 344
 345     /* finally add the E-part, if needed; it will never be 0, and has */
 346     /* a maximum length of 3 digits (E-101 case) */
 347     if (e!=0) {
 348       *c++='E';                    /* starts with E */
 349       *c++='+';                    /* assume positive */
 350       if (e<0) {
 351         *(c-1)='-';                /* oops, need '-' */
 352         e=-e;                      /* uInt, please */
 353         }
 354       u=&BIN2CHAR[e*4];            /* -> length byte */
 355       memcpy(c, u+4-*u, 4);        /* copy fixed 4 characters [is safe] */
 356       c+=*u;                       /* bump pointer appropriately */
 357       }
 358     *c='\0';                       /* add terminator */
 359     /*printf("res %s\n", string); */
 360     return string;
 361     } /* pre>0 */
 362
 363   /* -5<=pre<=0: here for plain 0.ddd or 0.000ddd forms (can never have E) */
 364   t=c+1-pre;
 365   *(t+1)='\0';                          /* can add terminator now */
 366   for (; s>=cstart; s--, t--) *t=*s;    /* shift whole coefficient right */
 367   c=cstart;
 368   *c++='0';                             /* always starts with 0. */
 369   *c++='.';
 370   for (; pre<0; pre++) *c++='0';        /* add any 0's after '.' */
 371   /*printf("res %s\n", string); */
 372   return string;
 373   } /* decimal32ToString */
 374
 375 /* ------------------------------------------------------------------ */
 376 /* to-number -- conversion from numeric string                        */
 377 /*                                                                    */
 378 /*   decimal32FromString(result, string, set);                        */
 379 /*                                                                    */
 380 /*  result  is the decimal32 format number which gets the result of   */
 381 /*          the conversion                                            */
 382 /*  *string is the character string which should contain a valid      */
 383 /*          number (which may be a special value)                     */
 384 /*  set     is the context                                            */
 385 /*                                                                    */
 386 /* The context is supplied to this routine is used for error handling */
 387 /* (setting of status and traps) and for the rounding mode, only.     */
 388 /* If an error occurs, the result will be a valid decimal32 NaN.      */
 389 /* ------------------------------------------------------------------ */
 390 decimal32 * decimal32FromString(decimal32 *result, const char *string,
 391                                 decContext *set) {
 392   decContext dc;                             /* work */
 393   decNumber dn;                              /* .. */
 394
 395   decContextDefault(&dc, DEC_INIT_DECIMAL32); /* no traps, please */
 396   dc.round=set->round;                        /* use supplied rounding */
 397
 398   decNumberFromString(&dn, string, &dc);     /* will round if needed */
 399   decimal32FromNumber(result, &dn, &dc);
 400   if (dc.status!=0) {                        /* something happened */
 401     decContextSetStatus(set, dc.status);     /* .. pass it on */
 402     }
 403   return result;
 404   } /* decimal32FromString */
 405
 406 /* ------------------------------------------------------------------ */
 407 /* decimal32IsCanonical -- test whether encoding is canonical         */
 408 /*   d32 is the source decimal32                                      */
 409 /*   returns 1 if the encoding of d32 is canonical, 0 otherwise       */
 410 /* No error is possible.                                              */
 411 /* ------------------------------------------------------------------ */
 412 uInt decimal32IsCanonical(const decimal32 *d32) {
 413   decNumber dn;                         /* work */
 414   decimal32 canon;                      /* .. */
 415   decContext dc;                        /* .. */
 416   decContextDefault(&dc, DEC_INIT_DECIMAL32);
 417   decimal32ToNumber(d32, &dn);
 418   decimal32FromNumber(&canon, &dn, &dc);/* canon will now be canonical */
 419   return memcmp(d32, &canon, DECIMAL32_Bytes)==0;
 420   } /* decimal32IsCanonical */
 421
 422 /* ------------------------------------------------------------------ */
 423 /* decimal32Canonical -- copy an encoding, ensuring it is canonical   */
 424 /*   d32 is the source decimal32                                      */
 425 /*   result is the target (may be the same decimal32)                 */
 426 /*   returns result                                                   */
 427 /* No error is possible.                                              */
 428 /* ------------------------------------------------------------------ */
 429 decimal32 * decimal32Canonical(decimal32 *result, const decimal32 *d32) {
 430   decNumber dn;                         /* work */
 431   decContext dc;                        /* .. */
 432   decContextDefault(&dc, DEC_INIT_DECIMAL32);
 433   decimal32ToNumber(d32, &dn);
 434   decimal32FromNumber(result, &dn, &dc);/* result will now be canonical */
 435   return result;
 436   } /* decimal32Canonical */
 437
 438 #if DECTRACE || DECCHECK
 439 /* Macros for accessing decimal32 fields.  These assume the argument
 440    is a reference (pointer) to the decimal32 structure, and the
 441    decimal32 is in network byte order (big-endian) */
 442 /* Get sign */
 443 #define decimal32Sign(d)       ((unsigned)(d)->bytes[0]>>7)
 444
 445 /* Get combination field */
 446 #define decimal32Comb(d)       (((d)->bytes[0] & 0x7c)>>2)
 447
 448 /* Get exponent continuation [does not remove bias] */
 449 #define decimal32ExpCon(d)     ((((d)->bytes[0] & 0x03)<<4)           \
 450                              | ((unsigned)(d)->bytes[1]>>4))
 451
 452 /* Set sign [this assumes sign previously 0] */
 453 #define decimal32SetSign(d, b) {                                      \
 454   (d)->bytes[0]|=((unsigned)(b)<<7);}
 455
 456 /* Set exponent continuation [does not apply bias] */
 457 /* This assumes range has been checked and exponent previously 0; */
 458 /* type of exponent must be unsigned */
 459 #define decimal32SetExpCon(d, e) {                                    \
 460   (d)->bytes[0]|=(uByte)((e)>>4);                                     \
 461   (d)->bytes[1]|=(uByte)(((e)&0x0F)<<4);}
 462
 463 /* ------------------------------------------------------------------ */
 464 /* decimal32Show -- display a decimal32 in hexadecimal [debug aid]    */
 465 /*   d32 -- the number to show                                        */
 466 /* ------------------------------------------------------------------ */
 467 /* Also shows sign/cob/expconfields extracted - valid bigendian only */
 468 void decimal32Show(const decimal32 *d32) {
 469   char buf[DECIMAL32_Bytes*2+1];
 470   Int i, j=0;
 471
 472   if (DECLITEND) {
 473     for (i=0; i<DECIMAL32_Bytes; i++, j+=2) {
 474       sprintf(&buf[j], "%02x", d32->bytes[3-i]);
 475       }
 476     printf(" D32> %s [S:%d Cb:%02x Ec:%02x] LittleEndian\n", buf,
 477            d32->bytes[3]>>7, (d32->bytes[3]>>2)&0x1f,
 478            ((d32->bytes[3]&0x3)<<4)| (d32->bytes[2]>>4));
 479     }
 480    else {
 481     for (i=0; i<DECIMAL32_Bytes; i++, j+=2) {
 482       sprintf(&buf[j], "%02x", d32->bytes[i]);
 483       }
 484     printf(" D32> %s [S:%d Cb:%02x Ec:%02x] BigEndian\n", buf,
 485            decimal32Sign(d32), decimal32Comb(d32), decimal32ExpCon(d32));
 486     }
 487   } /* decimal32Show */
 488 #endif