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