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

   1 /* -*-c-*-
   2  *
   3  * $Id: mp-mem.c,v 1.8 2004/04/08 16:17:32 mdw Exp $
   4  *
   5  * Memory management for multiprecision numbers
   6  *
   7  * (c) 1999 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 /*----- Header files ------------------------------------------------------*/
  31
  32 #include <mLib/sub.h>
  33
  34
  35 #include "mp.h"
  36
  37 /*----- Main code ---------------------------------------------------------*/
  38
  39 /* --- @mp_new@ --- *
  40  *
  41  * Arguments:   @size_t sz@ = size of vector required
  42  *              @unsigned f@ = flags to set
  43  *
  44  * Returns:     Pointer to a new MP structure.
  45  *
  46  * Use:         Allocates a new multiprecision integer.  The data space is
  47  *              allocated from either the standard global or secret arena,
  48  *              depending on the initial flags requested.
  49  */
  50
  51 mp *mp_new(size_t sz, unsigned f)
  52 {
  53   mp *m = CREATE(mp);
  54   m->a = (f & MP_BURN) ? MPARENA_SECURE : MPARENA_GLOBAL;
  55   m->v = mpalloc(m->a, sz);
  56   m->vl = m->v + sz;
  57   m->sz = sz;
  58   m->f = f & ~(MP_CONST | MP_DESTROYED);
  59   m->ref = 1;
  60   return (m);
  61 }
  62
  63 /* --- @mp_create@ --- *
  64  *
  65  * Arguments:   @size_t sz@ = size of vector required
  66  *
  67  * Returns:     Pointer to pristine new MP structure with enough memory
  68  *              bolted onto it.
  69  *
  70  * Use:         Creates a new multiprecision integer, initially zero.  The
  71  *              integer has a single reference.
  72  */
  73
  74 mp *mp_create(size_t sz)
  75 {
  76   mp *m = CREATE(mp);
  77   m->v = mpalloc(MPARENA_GLOBAL, sz);
  78   m->vl = m->v + sz;
  79   m->sz = sz;
  80   m->a = MPARENA_GLOBAL;
  81   m->f = MP_UNDEF;
  82   m->ref = 1;
  83   return (m);
  84 }
  85
  86 /* --- @mp_createsecure@ --- *
  87  *
  88  * Arguments:   @size_t sz@ = size of vector required
  89  *
  90  * Returns:     Pointer to pristine new MP structure with enough memory
  91  *              bolted onto it.
  92  *
  93  * Use:         Creates a new multiprecision integer with indeterminate
  94  *              contents.  The integer has a single reference.  The integer's
  95  *              data space is allocated from the secure arena.  Its burn flag
  96  *              is set.
  97  */
  98
  99 mp *mp_createsecure(size_t sz)
 100 {
 101   mp *m = CREATE(mp);
 102   m->v = mpalloc(MPARENA_SECURE, sz);
 103   m->vl = m->v + sz;
 104   m->sz = sz;
 105   m->a = MPARENA_SECURE;
 106   m->f = MP_UNDEF | MP_BURN;
 107   m->ref = 1;
 108   return (m);
 109 }
 110
 111 /* --- @mp_build@ --- *
 112  *
 113  * Arguments:   @mp *m@ = pointer to an MP block to fill in
 114  *              @mpw *v@ = pointer to a word array
 115  *              @mpw *vl@ = pointer just past end of array
 116  *
 117  * Returns:     ---
 118  *
 119  * Use:         Creates a multiprecision integer representing some smallish
 120  *              number.  You must provide storage for the number and dispose
 121  *              of it when you've finished with it.  The number is marked as
 122  *              constant while it exists.
 123  */
 124
 125 void mp_build(mp *m, mpw *v, mpw *vl)
 126 {
 127   m->v = v;
 128   m->vl = vl;
 129   m->sz = vl - v;
 130   m->a = MPARENA_GLOBAL;
 131   m->f = MP_CONST;
 132   m->ref = 1;
 133 }
 134
 135 /* --- @mp_destroy@ --- *
 136  *
 137  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 138  *
 139  * Returns:     ---
 140  *
 141  * Use:         Destroys a multiprecision integer. The reference count isn't
 142  *              checked.  Don't use this function if you don't know what
 143  *              you're doing: use @mp_drop@ instead.
 144  */
 145
 146 void mp_destroy(mp *m)
 147 {
 148   assert(((void)"Destroying a free integer", !(m->f & MP_DESTROYED)));
 149   assert(((void)"Attempted to destroy a constant", !(m->f & MP_CONST)));
 150   if (m->f & MP_BURN)
 151     memset(m->v, 0, MPWS(m->sz));
 152   mpfree(m->a, m->v);
 153   m->f |= MP_DESTROYED;
 154   DESTROY(m);
 155 }
 156
 157 /* --- @mp_copy@ --- *
 158  *
 159  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 160  *
 161  * Returns:     A copy of the given multiprecision integer.
 162  *
 163  * Use:         Copies the given integer.  In fact you just get another
 164  *              reference to the same old one again.
 165  */
 166
 167 mp *mp_copy(mp *m) { return MP_COPY(m); }
 168
 169 /* --- @mp_drop@ --- *
 170  *
 171  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 172  *
 173  * Returns:     ---
 174  *
 175  * Use:         Drops a reference to an integer which isn't wanted any more.
 176  *              If there are no more references, the integer is destroyed.
 177  */
 178
 179 void mp_drop(mp *m) { if (m) MP_DROP(m); }
 180
 181 /* --- @mp_split@ --- *
 182  *
 183  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 184  *
 185  * Returns:     A reference to the same integer, possibly with a different
 186  *              address.
 187  *
 188  * Use:         Splits off a modifiable version of the integer referred to.
 189  */
 190
 191 mp *mp_split(mp *m) { MP_SPLIT(m); return (m); }
 192
 193 /* --- @mp_resize@ --- *
 194  *
 195  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 196  *              @size_t sz@ = new size
 197  *
 198  * Returns:     ---
 199  *
 200  * Use:         Changes an integer's size.  The length and value are not
 201  *              changed.  It is an error to
 202  */
 203
 204 void mp_resize(mp *m, size_t sz) { MP_RESIZE(m, sz); }
 205
 206 /* --- @mp_ensure@ --- *
 207  *
 208  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 209  *              @size_t sz@ = required length
 210  *
 211  * Returns:     ---
 212  *
 213  * Use:         Changes an integer's length.  If there is not enough space
 214  *              allocated for the new length then the size is increased.  It
 215  */
 216
 217 void mp_ensure(mp *m, size_t sz) { MP_ENSURE(m, sz); }
 218
 219 /* --- @mp_dest@ --- *
 220  *
 221  * Arguments:   @mp *m@ = a suggested destination integer
 222  *              @size_t sz@ = size required for result, in digits
 223  *              @unsigned f@ = various flags
 224  *
 225  * Returns:     A pointer to an appropriate destination.
 226  *
 227  * Use:         Converts a suggested destination into a real destination with
 228  *              the required properties.  If the real destination is @d@,
 229  *              then the following properties will hold:
 230  *
 231  *                * @d@ will have exactly one reference.
 232  *
 233  *                * If @m@ is not @MP_NEW@, then the contents of @m@ will not
 234  *                  change, unless @f@ has the @MP_UNDEF@ flag set.
 235  *
 236  *                * If @m@ is not @MP_NEW@, then he reference count of @m@ on
 237  *                  entry is equal to the sum of the counts of @d@ and @m@ on
 238  *                  exit.
 239  *
 240  *                * The size of @d@ will be at least @sz@.
 241  *
 242  *                * If @f@ has the @MP_BURN@ flag set, then @d@ will be
 243  *                  allocated from @MPARENA_SECURE@.
 244  *
 245  *              Understanding this function is crucial to using Catacomb's
 246  *              multiprecision integer library effectively.
 247  */
 248
 249 mp *mp_dest(mp *m, size_t sz, unsigned f)
 250 {
 251   /* --- If no destination, make one --- */
 252
 253   if (m == MP_NEWSEC)
 254     m = mp_new(sz, f | MP_UNDEF | MP_BURN);
 255   else if (m == MP_NEW)
 256     m = mp_new(sz, f | MP_UNDEF);
 257   else {
 258     size_t len = MP_LEN(m);
 259     unsigned undef = (m->f | f) & MP_UNDEF;
 260
 261     /* --- If the value must be preserved, the block can't shrink --- */
 262
 263     if (!undef && sz < len)
 264       sz = len;
 265
 266     /* --- Otherwise check whether the destination is suitable --- */
 267
 268     if (m->ref > 1 || (m->f & MP_CONST) ||
 269         sz > m->sz || ((f & ~m->f) & MP_BURN)) {
 270
 271       /* --- No -- allocate a new buffer --- *
 272        *
 273        * The buffer must be secure if (a) the caller requested a secure
 274        * buffer, or (b) the old buffer is secure and I'm not allowed to
 275        * discard the old contents.
 276        */
 277
 278       mparena *a;
 279       mpw *v;
 280
 281       if ((f & MP_BURN) || (!undef && (m->f & MP_BURN)))
 282         a = MPARENA_SECURE;
 283       else
 284         a = MPARENA_GLOBAL;
 285       v = mpalloc(a, sz);
 286
 287       /* --- Copy the data over --- */
 288
 289       if (!undef) {
 290         memcpy(v, m->v, MPWS(len));
 291         if (sz - len > 0)
 292           memset(v + len, 0, MPWS(sz - len));
 293       }
 294
 295       /* --- If @m@ has other references, make a new node --- *
 296        *
 297        * Otherwise dispose of the old buffer.
 298        */
 299
 300       if (!(m->f & MP_CONST) && m->ref == 1) {
 301         if (m->f & MP_BURN)
 302           memset(m->v, 0, MPWS(m->sz));
 303         mpfree(m->a, m->v);
 304       } else {
 305         mp *mm = CREATE(mp);
 306         mm->ref = 1;
 307         mm->f = m->f;
 308         m->ref--;
 309         m = mm;
 310       }
 311
 312       /* --- Fix up the node --- */
 313
 314       m->v = v;
 315       m->vl = v + sz;
 316       m->sz = sz;
 317       m->f = ((m->f & ~(MP_CONST | MP_BURN)) |
 318               (f & (MP_BURN | MP_UNDEF)));
 319       m->a = a;
 320     }
 321
 322     /* --- If the number is growing in its buffer, fix it up --- */
 323
 324     else if (sz > len) {
 325       if (!undef)
 326         memset(m->vl, 0, MPWS(sz - len));
 327       m->vl = m->v + sz;
 328     }
 329   }
 330
 331   /* --- Done --- */
 332
 333   return (m);
 334 }
 335
 336 /*----- That's all, folks -------------------------------------------------*/