libdecnumber/decPacked.c

   1 /* Packed decimal conversion module for the decNumber C Library.
   2    Copyright (C) 2007, 2009 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 /* Packed Decimal conversion module                                   */
  28 /* ------------------------------------------------------------------ */
  29 /* This module comprises the routines for Packed Decimal format       */
  30 /* numbers.  Conversions are supplied to and from decNumber, which in */
  31 /* turn supports:                                                     */
  32 /*   conversions to and from string                                   */
  33 /*   arithmetic routines                                              */
  34 /*   utilities.                                                       */
  35 /* Conversions from decNumber to and from densely packed decimal      */
  36 /* formats are provided by the decimal32 through decimal128 modules.  */
  37 /* ------------------------------------------------------------------ */
  38
  39 #include <string.h>           /* for NULL */
  40 #include "decNumber.h"        /* base number library */
  41 #include "decPacked.h"        /* packed decimal */
  42 #include "decNumberLocal.h"   /* decNumber local types, etc. */
  43
  44 /* ------------------------------------------------------------------ */
  45 /* decPackedFromNumber -- convert decNumber to BCD Packed Decimal     */
  46 /*                                                                    */
  47 /*   bcd    is the BCD bytes                                          */
  48 /*   length is the length of the BCD array                            */
  49 /*   scale  is the scale result                                       */
  50 /*   dn     is the decNumber                                          */
  51 /*   returns bcd, or NULL if error                                    */
  52 /*                                                                    */
  53 /* The number is converted to a BCD packed decimal byte array,        */
  54 /* right aligned in the bcd array, whose length is indicated by the   */
  55 /* second parameter.  The final 4-bit nibble in the array will be a   */
  56 /* sign nibble, C (1100) for + and D (1101) for -.  Unused bytes and  */
  57 /* nibbles to the left of the number are set to 0.                    */
  58 /*                                                                    */
  59 /* scale is set to the scale of the number (this is the exponent,     */
  60 /* negated).  To force the number to a specified scale, first use the */
  61 /* decNumberRescale routine, which will round and change the exponent */
  62 /* as necessary.                                                      */
  63 /*                                                                    */
  64 /* If there is an error (that is, the decNumber has too many digits   */
  65 /* to fit in length bytes, or it is a NaN or Infinity), NULL is       */
  66 /* returned and the bcd and scale results are unchanged.  Otherwise   */
  67 /* bcd is returned.                                                   */
  68 /* ------------------------------------------------------------------ */
  69 uByte * decPackedFromNumber(uByte *bcd, Int length, Int *scale,
  70                             const decNumber *dn) {
  71   const Unit *up=dn->lsu;     /* Unit array pointer */
  72   uByte obyte, *out;          /* current output byte, and where it goes */
  73   Int indigs=dn->digits;      /* digits processed */
  74   uInt cut=DECDPUN;           /* downcounter per Unit */
  75   uInt u=*up;                 /* work */
  76   uInt nib;                   /* .. */
  77   #if DECDPUN<=4
  78   uInt temp;                  /* .. */
  79   #endif
  80
  81   if (dn->digits>length*2-1                  /* too long .. */
  82    ||(dn->bits & DECSPECIAL)) return NULL;   /* .. or special -- hopeless */
  83
  84   if (dn->bits&DECNEG) obyte=DECPMINUS;      /* set the sign .. */
  85    else                obyte=DECPPLUS;
  86   *scale=-dn->exponent;                      /* .. and scale */
  87
  88   /* loop from lowest (rightmost) byte */
  89   out=bcd+length-1;                          /* -> final byte */
  90   for (; out>=bcd; out--) {
  91     if (indigs>0) {
  92       if (cut==0) {
  93         up++;
  94         u=*up;
  95         cut=DECDPUN;
  96         }
  97       #if DECDPUN<=4
  98         temp=(u*6554)>>16;         /* fast /10 */
  99         nib=u-X10(temp);
 100         u=temp;
 101       #else
 102         nib=u%10;                  /* cannot use *6554 trick :-( */
 103         u=u/10;
 104       #endif
 105       obyte|=(nib<<4);
 106       indigs--;
 107       cut--;
 108       }
 109     *out=obyte;
 110     obyte=0;                       /* assume 0 */
 111     if (indigs>0) {
 112       if (cut==0) {
 113         up++;
 114         u=*up;
 115         cut=DECDPUN;
 116         }
 117       #if DECDPUN<=4
 118         temp=(u*6554)>>16;         /* as above */
 119         obyte=(uByte)(u-X10(temp));
 120         u=temp;
 121       #else
 122         obyte=(uByte)(u%10);
 123         u=u/10;
 124       #endif
 125       indigs--;
 126       cut--;
 127       }
 128     } /* loop */
 129
 130   return bcd;
 131   } /* decPackedFromNumber */
 132
 133 /* ------------------------------------------------------------------ */
 134 /* decPackedToNumber -- convert BCD Packed Decimal to a decNumber     */
 135 /*                                                                    */
 136 /*   bcd    is the BCD bytes                                          */
 137 /*   length is the length of the BCD array                            */
 138 /*   scale  is the scale associated with the BCD integer              */
 139 /*   dn     is the decNumber [with space for length*2 digits]         */
 140 /*   returns dn, or NULL if error                                     */
 141 /*                                                                    */
 142 /* The BCD packed decimal byte array, together with an associated     */
 143 /* scale, is converted to a decNumber.  The BCD array is assumed full */
 144 /* of digits, and must be ended by a 4-bit sign nibble in the least   */
 145 /* significant four bits of the final byte.                           */
 146 /*                                                                    */
 147 /* The scale is used (negated) as the exponent of the decNumber.      */
 148 /* Note that zeros may have a sign and/or a scale.                    */
 149 /*                                                                    */
 150 /* The decNumber structure is assumed to have sufficient space to     */
 151 /* hold the converted number (that is, up to length*2-1 digits), so   */
 152 /* no error is possible unless the adjusted exponent is out of range, */
 153 /* no sign nibble was found, or a sign nibble was found before the    */
 154 /* final nibble.  In these error cases, NULL is returned and the      */
 155 /* decNumber will be 0.                                               */
 156 /* ------------------------------------------------------------------ */
 157 decNumber * decPackedToNumber(const uByte *bcd, Int length,
 158                               const Int *scale, decNumber *dn) {
 159   const uByte *last=bcd+length-1;  /* -> last byte */
 160   const uByte *first;              /* -> first non-zero byte */
 161   uInt  nib;                       /* work nibble */
 162   Unit  *up=dn->lsu;               /* output pointer */
 163   Int   digits;                    /* digits count */
 164   Int   cut=0;                     /* phase of output */
 165
 166   decNumberZero(dn);               /* default result */
 167   last=&bcd[length-1];
 168   nib=*last & 0x0f;                /* get the sign */
 169   if (nib==DECPMINUS || nib==DECPMINUSALT) dn->bits=DECNEG;
 170    else if (nib<=9) return NULL;   /* not a sign nibble */
 171
 172   /* skip leading zero bytes [final byte is always non-zero, due to sign] */
 173   for (first=bcd; *first==0;) first++;
 174   digits=(last-first)*2+1;              /* calculate digits .. */
 175   if ((*first & 0xf0)==0) digits--;     /* adjust for leading zero nibble */
 176   if (digits!=0) dn->digits=digits;     /* count of actual digits [if 0, */
 177                                         /* leave as 1] */
 178
 179   /* check the adjusted exponent; note that scale could be unbounded */
 180   dn->exponent=-*scale;                 /* set the exponent */
 181   if (*scale>=0) {                      /* usual case */
 182     if ((dn->digits-*scale-1)<-DECNUMMAXE) {      /* underflow */
 183       decNumberZero(dn);
 184       return NULL;}
 185     }
 186    else { /* -ve scale; +ve exponent */
 187     /* need to be careful to avoid wrap, here, also BADINT case */
 188     if ((*scale<-DECNUMMAXE)            /* overflow even without digits */
 189          || ((dn->digits-*scale-1)>DECNUMMAXE)) { /* overflow */
 190       decNumberZero(dn);
 191       return NULL;}
 192     }
 193   if (digits==0) return dn;             /* result was zero */
 194
 195   /* copy the digits to the number's units, starting at the lsu */
 196   /* [unrolled] */
 197   for (;;) {                            /* forever */
 198     /* left nibble first */
 199     nib=(unsigned)(*last & 0xf0)>>4;
 200     /* got a digit, in nib */
 201     if (nib>9) {decNumberZero(dn); return NULL;}
 202
 203     if (cut==0) *up=(Unit)nib;
 204      else *up=(Unit)(*up+nib*DECPOWERS[cut]);
 205     digits--;
 206     if (digits==0) break;               /* got them all */
 207     cut++;
 208     if (cut==DECDPUN) {
 209       up++;
 210       cut=0;
 211       }
 212     last--;                             /* ready for next */
 213     nib=*last & 0x0f;                   /* get right nibble */
 214     if (nib>9) {decNumberZero(dn); return NULL;}
 215
 216     /* got a digit, in nib */
 217     if (cut==0) *up=(Unit)nib;
 218      else *up=(Unit)(*up+nib*DECPOWERS[cut]);
 219     digits--;
 220     if (digits==0) break;               /* got them all */
 221     cut++;
 222     if (cut==DECDPUN) {
 223       up++;
 224       cut=0;
 225       }
 226     } /* forever */
 227
 228   return dn;
 229   } /* decPackedToNumber */
 230