dlls/msvcrt/bnum.h

   1 /*
   2  * Copyright 2020 Piotr Caban for CodeWeavers
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2.1 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with this library; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  17  */
  18
  19 #ifndef __WINE_BNUM_H
  20 #define __WINE_BNUM_H
  21
  22 #define EXP_BITS 11
  23 #define MANT_BITS 53
  24
  25 static const int p10s[] = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000 };
  26
  27 #define LIMB_DIGITS 9           /* each DWORD stores up to 9 digits */
  28 #define LIMB_MAX 1000000000     /* 10^9 */
  29
  30 #define BNUM_PREC64 128         /* data size needed to store 64-bit double */
  31 #define BNUM_PREC80 2048        /* data size needed to store 80-bit double */
  32
  33 /* bnum represents real number with fixed decimal point */
  34 struct bnum {
  35     int b; /* least significant digit position */
  36     int e; /* most significant digit position + 1 */
  37     int size; /* data buffer size in DWORDS (power of 2) */
  38     DWORD data[1]; /* circular buffer, base 10 number */
  39 };
  40
  41 static inline int bnum_idx(struct bnum *b, int idx)
  42 {
  43     return idx & (b->size - 1);
  44 }
  45
  46 /* Returns TRUE if new most significant limb was added */
  47 static inline BOOL bnum_lshift(struct bnum *b, int shift)
  48 {
  49     DWORD rest = 0;
  50     ULONGLONG tmp;
  51     int i;
  52
  53     /* The limbs number can change by up to 1 so shift <= 29 */
  54     assert(shift <= 29);
  55
  56     for(i=b->b; i<b->e; i++) {
  57         tmp = ((ULONGLONG)b->data[bnum_idx(b, i)] << shift) + rest;
  58         rest = tmp / LIMB_MAX;
  59         b->data[bnum_idx(b, i)] = tmp % LIMB_MAX;
  60
  61         if(i == b->b && !b->data[bnum_idx(b, i)])
  62             b->b++;
  63     }
  64
  65     if(rest) {
  66         b->data[bnum_idx(b, b->e)] = rest;
  67         b->e++;
  68
  69         if(bnum_idx(b, b->b) == bnum_idx(b, b->e)) {
  70             if(b->data[bnum_idx(b, b->b)]) b->data[bnum_idx(b, b->b+1)] |= 1;
  71             b->b++;
  72         }
  73         return TRUE;
  74     }
  75     return FALSE;
  76 }
  77
  78 /* Returns TRUE if most significant limb was removed */
  79 static inline BOOL bnum_rshift(struct bnum *b, int shift)
  80 {
  81     DWORD tmp, rest = 0;
  82     BOOL ret = FALSE;
  83     int i;
  84
  85     /* Compute LIMB_MAX << shift without accuracy loss */
  86     assert(shift <= 9);
  87
  88     for(i=b->e-1; i>=b->b; i--) {
  89         tmp = b->data[bnum_idx(b, i)] & ((1<<shift)-1);
  90         b->data[bnum_idx(b, i)] = (b->data[bnum_idx(b, i)] >> shift) + rest;
  91         rest = (LIMB_MAX >> shift) * tmp;
  92         if(i==b->e-1 && !b->data[bnum_idx(b, i)]) {
  93             b->e--;
  94             ret = TRUE;
  95         }
  96     }
  97
  98     if(rest) {
  99         if(bnum_idx(b, b->b-1) == bnum_idx(b, b->e)) {
 100             if(rest) b->data[bnum_idx(b, b->b)] |= 1;
 101         } else {
 102             b->b--;
 103             b->data[bnum_idx(b, b->b)] = rest;
 104         }
 105     }
 106     return ret;
 107 }
 108
 109 static inline void bnum_mult(struct bnum *b, int mult)
 110 {
 111     DWORD rest = 0;
 112     ULONGLONG tmp;
 113     int i;
 114
 115     assert(mult <= LIMB_MAX);
 116
 117     for(i=b->b; i<b->e; i++) {
 118         tmp = ((ULONGLONG)b->data[bnum_idx(b, i)] * mult) + rest;
 119         rest = tmp / LIMB_MAX;
 120         b->data[bnum_idx(b, i)] = tmp % LIMB_MAX;
 121
 122         if(i == b->b && !b->data[bnum_idx(b, i)])
 123             b->b++;
 124     }
 125
 126     if(rest) {
 127         b->data[bnum_idx(b, b->e)] = rest;
 128         b->e++;
 129
 130         if(bnum_idx(b, b->b) == bnum_idx(b, b->e)) {
 131             if(b->data[bnum_idx(b, b->b)]) b->data[bnum_idx(b, b->b+1)] |= 1;
 132             b->b++;
 133         }
 134     }
 135 }
 136
 137 #endif /* __WINE_BNUM_H */