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   1 /* -*-c-*-
   2  *
   3  * $Id: mp-mem.c,v 1.4 2001/02/03 12:00:29 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 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: mp-mem.c,v $
  33  * Revision 1.4  2001/02/03 12:00:29  mdw
  34  * Now @mp_drop@ checks its argument is non-NULL before attempting to free
  35  * it.  Note that the macro version @MP_DROP@ doesn't do this.
  36  *
  37  * Revision 1.3  2000/06/17 11:45:09  mdw
  38  * Major memory management overhaul.  Added arena support.  Use the secure
  39  * arena for secret integers.  Replace and improve the MP management macros
  40  * (e.g., replace MP_MODIFY by MP_DEST).
  41  *
  42  * Revision 1.2  1999/12/10 23:19:02  mdw
  43  * Improve error-checking.
  44  *
  45  * Revision 1.1  1999/11/17 18:02:16  mdw
  46  * New multiprecision integer arithmetic suite.
  47  *
  48  */
  49
  50 /*----- Header files ------------------------------------------------------*/
  51
  52 #include <mLib/sub.h>
  53
  54
  55 #include "mp.h"
  56
  57 /*----- Main code ---------------------------------------------------------*/
  58
  59 /* --- @mp_new@ --- *
  60  *
  61  * Arguments:   @size_t sz@ = size of vector required
  62  *              @unsigned f@ = flags to set
  63  *
  64  * Returns:     Pointer to a new MP structure.
  65  *
  66  * Use:         Allocates a new multiprecision integer.  The data space is
  67  *              allocated from either the standard global or secret arena,
  68  *              depending on the initial flags requested.
  69  */
  70
  71 mp *mp_new(size_t sz, unsigned f)
  72 {
  73   mp *m = CREATE(mp);
  74   m->a = (f & MP_BURN) ? MPARENA_SECURE : MPARENA_GLOBAL;
  75   m->v = mpalloc(m->a, sz);
  76   m->vl = m->v + sz;
  77   m->sz = sz;
  78   m->f = f & ~(MP_CONST | MP_DESTROYED);
  79   m->ref = 1;
  80   return (m);
  81 }
  82
  83 /* --- @mp_create@ --- *
  84  *
  85  * Arguments:   @size_t sz@ = size of vector required
  86  *
  87  * Returns:     Pointer to pristine new MP structure with enough memory
  88  *              bolted onto it.
  89  *
  90  * Use:         Creates a new multiprecision integer, initially zero.  The
  91  *              integer has a single reference.
  92  */
  93
  94 mp *mp_create(size_t sz)
  95 {
  96   mp *m = CREATE(mp);
  97   m->v = mpalloc(MPARENA_GLOBAL, sz);
  98   m->vl = m->v + sz;
  99   m->sz = sz;
 100   m->a = MPARENA_GLOBAL;
 101   m->f = MP_UNDEF;
 102   m->ref = 1;
 103   return (m);
 104 }
 105
 106 /* --- @mp_createsecure@ --- *
 107  *
 108  * Arguments:   @size_t sz@ = size of vector required
 109  *
 110  * Returns:     Pointer to pristine new MP structure with enough memory
 111  *              bolted onto it.
 112  *
 113  * Use:         Creates a new multiprecision integer with indeterminate
 114  *              contents.  The integer has a single reference.  The integer's
 115  *              data space is allocated from the secure arena.  Its burn flag
 116  *              is set.
 117  */
 118
 119 mp *mp_createsecure(size_t sz)
 120 {
 121   mp *m = CREATE(mp);
 122   m->v = mpalloc(MPARENA_SECURE, sz);
 123   m->vl = m->v + sz;
 124   m->sz = sz;
 125   m->a = MPARENA_SECURE;
 126   m->f = MP_UNDEF | MP_BURN;
 127   m->ref = 1;
 128   return (m);
 129 }
 130
 131 /* --- @mp_build@ --- *
 132  *
 133  * Arguments:   @mp *m@ = pointer to an MP block to fill in
 134  *              @mpw *v@ = pointer to a word array
 135  *              @mpw *vl@ = pointer just past end of array
 136  *
 137  * Returns:     ---
 138  *
 139  * Use:         Creates a multiprecision integer representing some smallish
 140  *              number.  You must provide storage for the number and dispose
 141  *              of it when you've finished with it.  The number is marked as
 142  *              constant while it exists.
 143  */
 144
 145 void mp_build(mp *m, mpw *v, mpw *vl)
 146 {
 147   m->v = v;
 148   m->vl = vl;
 149   m->sz = vl - v;
 150   m->f = MP_CONST;
 151   m->ref = 1;
 152 }
 153
 154 /* --- @mp_destroy@ --- *
 155  *
 156  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 157  *
 158  * Returns:     ---
 159  *
 160  * Use:         Destroys a multiprecision integer. The reference count isn't
 161  *              checked.  Don't use this function if you don't know what
 162  *              you're doing: use @mp_drop@ instead.
 163  */
 164
 165 void mp_destroy(mp *m)
 166 {
 167   assert(((void)"Destroying a free integer", !(m->f & MP_DESTROYED)));
 168   assert(((void)"Attempted to destroy a constant", !(m->f & MP_CONST)));
 169   if (m->f & MP_BURN)
 170     memset(m->v, 0, MPWS(m->sz));
 171   mpfree(m->a, m->v);
 172   m->f |= MP_DESTROYED;
 173   DESTROY(m);
 174 }
 175
 176 /* --- @mp_copy@ --- *
 177  *
 178  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 179  *
 180  * Returns:     A copy of the given multiprecision integer.
 181  *
 182  * Use:         Copies the given integer.  In fact you just get another
 183  *              reference to the same old one again.
 184  */
 185
 186 mp *mp_copy(mp *m) { return MP_COPY(m); }
 187
 188 /* --- @mp_drop@ --- *
 189  *
 190  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 191  *
 192  * Returns:     ---
 193  *
 194  * Use:         Drops a reference to an integer which isn't wanted any more.
 195  *              If there are no more references, the integer is destroyed.
 196  */
 197
 198 void mp_drop(mp *m) { if (m) MP_DROP(m); }
 199
 200 /* --- @mp_split@ --- *
 201  *
 202  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 203  *
 204  * Returns:     A reference to the same integer, possibly with a different
 205  *              address.
 206  *
 207  * Use:         Splits off a modifiable version of the integer referred to.
 208  */
 209
 210 mp *mp_split(mp *m)
 211 {
 212 /*   if ((m->f & MP_CONST) || m->ref > 1) { */
 213 /*     size_t len = MP_LEN(m); */
 214 /*     mp *mm = mp_new(len, m->f); */
 215 /*     if (!(m->f & MP_UNDEF)) */
 216 /*       memcpy(mm->v, m->v, MPWS(len)); */
 217 /*     m->ref--; */
 218 /*     m = mm; */
 219 /*   } */
 220   MP_SPLIT(m);
 221   return (m);
 222 }
 223
 224 /* --- @mp_resize@ --- *
 225  *
 226  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 227  *              @size_t sz@ = new size
 228  *
 229  * Returns:     ---
 230  *
 231  * Use:         Changes an integer's size.  The length and value are not
 232  *              changed.  It is an error to
 233  */
 234
 235 void mp_resize(mp *m, size_t sz)
 236 {
 237 /*   mparena *a = (m->f & MP_BURN) ? MPARENA_SECURE : MPARENA_GLOBAL; */
 238 /*   mpw *v; */
 239 /*   size_t len = MP_LEN(m); */
 240 /*   assert(((void)"can't make size less than length", sz >= len)); */
 241 /*   v = mpalloc(a, sz); */
 242 /*   if (!(m->f & MP_UNDEF)) */
 243 /*     memcpy(v, m->v, MPWS(len)); */
 244 /*   if (m->f & MP_BURN) */
 245 /*     memset(m->v, 0, MPWS(m->sz)); */
 246 /*   mpfree(m->a, m->v); */
 247 /*   m->a = a; */
 248 /*   m->v = v; */
 249 /*   m->vl = v + len; */
 250 }
 251
 252 /* --- @mp_ensure@ --- *
 253  *
 254  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 255  *              @size_t sz@ = required length
 256  *
 257  * Returns:     ---
 258  *
 259  * Use:         Changes an integer's length.  If there is not enough space
 260  *              allocated for the new length then the size is increased.  It
 261  */
 262
 263 void mp_ensure(mp *m, size_t sz)
 264 {
 265 /*   size_t len = MP_LEN(m); */
 266 /*   if (sz >= len) { */
 267 /*     if (sz > m->sz) */
 268 /*       mp_resize(m, sz); */
 269 /*     if (!(m->f & MP_UNDEF) && sz > len) */
 270 /*       memset(m->vl, 0, MPWS(sz - len)); */
 271 /*     m->vl = m->v + sz; */
 272 /*   } */
 273 }
 274
 275 /* --- @mp_dest@ --- *
 276  *
 277  * Arguments:   @mp *m@ = a suggested destination integer
 278  *              @size_t sz@ = size required for result, in digits
 279  *              @unsigned f@ = various flags
 280  *
 281  * Returns:     A pointer to an appropriate destination.
 282  *
 283  * Use:         Converts a suggested destination into a real destination with
 284  *              the required properties.  If the real destination is @d@,
 285  *              then the following properties will hold:
 286  *
 287  *                * @d@ will have exactly one reference.
 288  *
 289  *                * If @m@ is not @MP_NEW@, then the contents of @m@ will not
 290  *                  change, unless @f@ has the @MP_UNDEF@ flag set.
 291  *
 292  *                * If @m@ is not @MP_NEW@, then he reference count of @m@ on
 293  *                  entry is equal to the sum of the counts of @d@ and @m@ on
 294  *                  exit.
 295  *
 296  *                * The size of @d@ will be at least @sz@.
 297  *
 298  *                * If @f@ has the @MP_BURN@ flag set, then @d@ will be
 299  *                  allocated from @MPARENA_SECURE@.
 300  *
 301  *              Understanding this function is crucial to using Catacomb's
 302  *              multiprecision integer library effectively.
 303  */
 304
 305 mp *mp_dest(mp *m, size_t sz, unsigned f)
 306 {
 307   /* --- If no destination, make one --- */
 308
 309   if (m == MP_NEWSEC)
 310     m = mp_new(sz, f | MP_UNDEF | MP_BURN);
 311   else if (m == MP_NEW)
 312     m = mp_new(sz, f | MP_UNDEF);
 313   else {
 314     size_t len = MP_LEN(m);
 315     unsigned undef = (m->f | f) & MP_UNDEF;
 316
 317     /* --- If the value must be preserved, the block can't shrink --- */
 318
 319     if (!undef && sz < len)
 320       sz = len;
 321
 322     /* --- Otherwise check whether the destination is suitable --- */
 323
 324     if (m->ref > 1 || (m->f & MP_CONST) ||
 325         m->sz > len || !((f & ~m->f) & MP_BURN)) {
 326
 327       /* --- No -- allocate a new buffer --- *
 328        *
 329        * The buffer must be secure if (a) the caller requested a secure
 330        * buffer, or (b) the old buffer is secure and I'm not allowed to
 331        * discard the old contents.
 332        */
 333
 334       mparena *a;
 335       mpw *v;
 336
 337       if ((f & MP_BURN) || (!undef && (m->f & MP_BURN)))
 338         a = MPARENA_SECURE;
 339       else
 340         a = MPARENA_GLOBAL;
 341       v = mpalloc(a, sz);
 342
 343       /* --- Copy the data over --- */
 344
 345       if (!undef) {
 346         memcpy(v, m->v, MPWS(len));
 347         if (sz - len > 0)
 348           memset(v + len, 0, MPWS(sz - len));
 349       }
 350
 351       /* --- If @m@ has other references, make a new node --- *
 352        *
 353        * Otherwise dispose of the old buffer.
 354        */
 355
 356       if (!(m->f & MP_CONST) && m->ref == 1) {
 357         if (m->f & MP_BURN)
 358           memset(m->v, 0, MPWS(m->sz));
 359         mpfree(m->a, m->v);
 360       } else {
 361         mp *mm = CREATE(mp);
 362         mm->ref = 1;
 363         mm->f = m->f;
 364         m->ref--;
 365         m = mm;
 366       }
 367
 368       /* --- Fix up the node --- */
 369
 370       m->v = v;
 371       m->vl = v + sz;
 372       m->sz = sz;
 373       m->f = ((m->f & ~(MP_CONST | MP_BURN)) |
 374               (f & (MP_BURN | MP_UNDEF)));
 375       m->a = a;
 376     }
 377
 378     /* --- If the number is growing in its buffer, fix it up --- */
 379
 380     else if (sz > len) {
 381       if (!undef)
 382         memset(m->vl, 0, MPWS(sz - len));
 383       m->vl = m->v + sz;
 384     }
 385   }
 386
 387   /* --- Done --- */
 388
 389   return (m);
 390 }
 391
 392 /*----- That's all, folks -------------------------------------------------*/