git.distorted.org.uk Git - u/mdw/catacomb/blob - math/mp-mem.c

   1 /* -*-c-*-
   2  *
   3  * Memory management for multiprecision numbers
   4  *
   5  * (c) 1999 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of Catacomb.
  11  *
  12  * Catacomb is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU Library General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * Catacomb is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License along with Catacomb; if not, write to the Free
  24  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  25  * MA 02111-1307, USA.
  26  */
  27
  28 /*----- Header files ------------------------------------------------------*/
  29
  30 #include <mLib/sub.h>
  31
  32
  33 #include "mp.h"
  34
  35 /*----- Main code ---------------------------------------------------------*/
  36
  37 /* --- @mp_new@ --- *
  38  *
  39  * Arguments:   @size_t sz@ = size of vector required
  40  *              @unsigned f@ = flags to set
  41  *
  42  * Returns:     Pointer to a new MP structure.
  43  *
  44  * Use:         Allocates a new multiprecision integer.  The data space is
  45  *              allocated from either the standard global or secret arena,
  46  *              depending on the initial flags requested.
  47  */
  48
  49 mp *mp_new(size_t sz, unsigned f)
  50 {
  51   mp *m = CREATE(mp);
  52   m->a = (f & MP_BURN) ? MPARENA_SECURE : MPARENA_GLOBAL;
  53   m->v = mpalloc(m->a, sz);
  54   m->vl = m->v + sz;
  55   m->sz = sz;
  56   m->f = f & ~(MP_CONST | MP_DESTROYED);
  57   m->ref = 1;
  58   return (m);
  59 }
  60
  61 /* --- @mp_create@ --- *
  62  *
  63  * Arguments:   @size_t sz@ = size of vector required
  64  *
  65  * Returns:     Pointer to pristine new MP structure with enough memory
  66  *              bolted onto it.
  67  *
  68  * Use:         Creates a new multiprecision integer, initially zero.  The
  69  *              integer has a single reference.
  70  */
  71
  72 mp *mp_create(size_t sz)
  73 {
  74   mp *m = CREATE(mp);
  75   m->v = mpalloc(MPARENA_GLOBAL, sz);
  76   m->vl = m->v + sz;
  77   m->sz = sz;
  78   m->a = MPARENA_GLOBAL;
  79   m->f = MP_UNDEF;
  80   m->ref = 1;
  81   return (m);
  82 }
  83
  84 /* --- @mp_createsecure@ --- *
  85  *
  86  * Arguments:   @size_t sz@ = size of vector required
  87  *
  88  * Returns:     Pointer to pristine new MP structure with enough memory
  89  *              bolted onto it.
  90  *
  91  * Use:         Creates a new multiprecision integer with indeterminate
  92  *              contents.  The integer has a single reference.  The integer's
  93  *              data space is allocated from the secure arena.  Its burn flag
  94  *              is set.
  95  */
  96
  97 mp *mp_createsecure(size_t sz)
  98 {
  99   mp *m = CREATE(mp);
 100   m->v = mpalloc(MPARENA_SECURE, sz);
 101   m->vl = m->v + sz;
 102   m->sz = sz;
 103   m->a = MPARENA_SECURE;
 104   m->f = MP_UNDEF | MP_BURN;
 105   m->ref = 1;
 106   return (m);
 107 }
 108
 109 /* --- @mp_build@ --- *
 110  *
 111  * Arguments:   @mp *m@ = pointer to an MP block to fill in
 112  *              @mpw *v@ = pointer to a word array
 113  *              @mpw *vl@ = pointer just past end of array
 114  *
 115  * Returns:     ---
 116  *
 117  * Use:         Creates a multiprecision integer representing some smallish
 118  *              number.  You must provide storage for the number and dispose
 119  *              of it when you've finished with it.  The number is marked as
 120  *              constant while it exists.
 121  */
 122
 123 void mp_build(mp *m, mpw *v, mpw *vl)
 124 {
 125   m->v = v;
 126   m->vl = vl;
 127   m->sz = vl - v;
 128   m->a = MPARENA_GLOBAL;
 129   m->f = MP_CONST;
 130   m->ref = 1;
 131 }
 132
 133 /* --- @mp_destroy@ --- *
 134  *
 135  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 136  *
 137  * Returns:     ---
 138  *
 139  * Use:         Destroys a multiprecision integer. The reference count isn't
 140  *              checked.  Don't use this function if you don't know what
 141  *              you're doing: use @mp_drop@ instead.
 142  */
 143
 144 void mp_destroy(mp *m)
 145 {
 146   assert(((void)"Destroying a free integer", !(m->f & MP_DESTROYED)));
 147   assert(((void)"Attempted to destroy a constant", !(m->f & MP_CONST)));
 148   if (m->f & MP_BURN)
 149     memset(m->v, 0, MPWS(m->sz));
 150   mpfree(m->a, m->v);
 151   m->f |= MP_DESTROYED;
 152   DESTROY(m);
 153 }
 154
 155 /* --- @mp_copy@ --- *
 156  *
 157  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 158  *
 159  * Returns:     A copy of the given multiprecision integer.
 160  *
 161  * Use:         Copies the given integer.  In fact you just get another
 162  *              reference to the same old one again.
 163  */
 164
 165 mp *mp_copy(mp *m) { return MP_COPY(m); }
 166
 167 /* --- @mp_drop@ --- *
 168  *
 169  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 170  *
 171  * Returns:     ---
 172  *
 173  * Use:         Drops a reference to an integer which isn't wanted any more.
 174  *              If there are no more references, the integer is destroyed.
 175  */
 176
 177 void mp_drop(mp *m) { if (m) MP_DROP(m); }
 178
 179 /* --- @mp_split@ --- *
 180  *
 181  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 182  *
 183  * Returns:     A reference to the same integer, possibly with a different
 184  *              address.
 185  *
 186  * Use:         Splits off a modifiable version of the integer referred to.
 187  */
 188
 189 mp *mp_split(mp *m) { MP_SPLIT(m); return (m); }
 190
 191 /* --- @mp_resize@ --- *
 192  *
 193  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 194  *              @size_t sz@ = new size
 195  *
 196  * Returns:     ---
 197  *
 198  * Use:         Changes an integer's size.  The length and value are not
 199  *              changed.  It is an error to
 200  */
 201
 202 void mp_resize(mp *m, size_t sz) { MP_RESIZE(m, sz); }
 203
 204 /* --- @mp_ensure@ --- *
 205  *
 206  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 207  *              @size_t sz@ = required length
 208  *
 209  * Returns:     ---
 210  *
 211  * Use:         Changes an integer's length.  If there is not enough space
 212  *              allocated for the new length then the size is increased.  It
 213  */
 214
 215 void mp_ensure(mp *m, size_t sz) { MP_ENSURE(m, sz); }
 216
 217 /* --- @mp_dest@ --- *
 218  *
 219  * Arguments:   @mp *m@ = a suggested destination integer
 220  *              @size_t sz@ = size required for result, in digits
 221  *              @unsigned f@ = various flags
 222  *
 223  * Returns:     A pointer to an appropriate destination.
 224  *
 225  * Use:         Converts a suggested destination into a real destination with
 226  *              the required properties.  If the real destination is @d@,
 227  *              then the following properties will hold:
 228  *
 229  *                * @d@ will have exactly one reference.
 230  *
 231  *                * If @m@ is not @MP_NEW@, then the contents of @m@ will not
 232  *                  change, unless @f@ has the @MP_UNDEF@ flag set.
 233  *
 234  *                * If @m@ is not @MP_NEW@, then he reference count of @m@ on
 235  *                  entry is equal to the sum of the counts of @d@ and @m@ on
 236  *                  exit.
 237  *
 238  *                * The size of @d@ will be at least @sz@.
 239  *
 240  *                * If @f@ has the @MP_BURN@ flag set, then @d@ will be
 241  *                  allocated from @MPARENA_SECURE@.
 242  *
 243  *              Understanding this function is crucial to using Catacomb's
 244  *              multiprecision integer library effectively.
 245  */
 246
 247 mp *mp_dest(mp *m, size_t sz, unsigned f)
 248 {
 249   /* --- If no destination, make one --- */
 250
 251   if (m == MP_NEWSEC)
 252     m = mp_new(sz, f | MP_UNDEF | MP_BURN);
 253   else if (m == MP_NEW)
 254     m = mp_new(sz, f | MP_UNDEF);
 255   else {
 256     size_t len = MP_LEN(m);
 257     unsigned undef = (m->f | f) & MP_UNDEF;
 258
 259     /* --- If the value must be preserved, the block can't shrink --- */
 260
 261     if (!undef && sz < len)
 262       sz = len;
 263
 264     /* --- Otherwise check whether the destination is suitable --- */
 265
 266     if (m->ref > 1 || (m->f & MP_CONST) ||
 267         sz > m->sz || ((f & ~m->f) & MP_BURN)) {
 268
 269       /* --- No -- allocate a new buffer --- *
 270        *
 271        * The buffer must be secure if (a) the caller requested a secure
 272        * buffer, or (b) the old buffer is secure and I'm not allowed to
 273        * discard the old contents.
 274        */
 275
 276       mparena *a;
 277       mpw *v;
 278
 279       if ((f & MP_BURN) || (!undef && (m->f & MP_BURN)))
 280         a = MPARENA_SECURE;
 281       else
 282         a = MPARENA_GLOBAL;
 283       v = mpalloc(a, sz);
 284
 285       /* --- Copy the data over --- */
 286
 287       if (!undef) {
 288         memcpy(v, m->v, MPWS(len));
 289         if (sz - len > 0)
 290           memset(v + len, 0, MPWS(sz - len));
 291       }
 292
 293       /* --- If @m@ has other references, make a new node --- *
 294        *
 295        * Otherwise dispose of the old buffer.
 296        */
 297
 298       if (!(m->f & MP_CONST) && m->ref == 1) {
 299         if (m->f & MP_BURN)
 300           memset(m->v, 0, MPWS(m->sz));
 301         mpfree(m->a, m->v);
 302       } else {
 303         mp *mm = CREATE(mp);
 304         mm->ref = 1;
 305         mm->f = m->f;
 306         m->ref--;
 307         m = mm;
 308       }
 309
 310       /* --- Fix up the node --- */
 311
 312       m->v = v;
 313       m->vl = v + sz;
 314       m->sz = sz;
 315       m->f = ((m->f & ~(MP_CONST | MP_BURN)) |
 316               (f & (MP_BURN | MP_UNDEF)));
 317       m->a = a;
 318     }
 319
 320     /* --- If the number is growing in its buffer, fix it up --- */
 321
 322     else if (sz > len) {
 323       if (!undef)
 324         memset(m->vl, 0, MPWS(sz - len));
 325       m->vl = m->v + sz;
 326     }
 327   }
 328
 329   /* --- Done --- */
 330
 331   return (m);
 332 }
 333
 334 /*----- That's all, folks -------------------------------------------------*/