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   1 /* -*-c-*-
   2  *
   3  * $Id: mp-mem.c,v 1.6 2004/04/03 03:30:22 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 1.6  2004/04/03 03:30:22  mdw
  34  * Fix long-standing stupidity in @mp_dest@.
  35  *
  36  * Revision 1.5  2001/06/16 12:57:00  mdw
  37  * Implement some missing functions.
  38  *
  39  * Revision 1.4  2001/02/03 12:00:29  mdw
  40  * Now @mp_drop@ checks its argument is non-NULL before attempting to free
  41  * it.  Note that the macro version @MP_DROP@ doesn't do this.
  42  *
  43  * Revision 1.3  2000/06/17 11:45:09  mdw
  44  * Major memory management overhaul.  Added arena support.  Use the secure
  45  * arena for secret integers.  Replace and improve the MP management macros
  46  * (e.g., replace MP_MODIFY by MP_DEST).
  47  *
  48  * Revision 1.2  1999/12/10 23:19:02  mdw
  49  * Improve error-checking.
  50  *
  51  * Revision 1.1  1999/11/17 18:02:16  mdw
  52  * New multiprecision integer arithmetic suite.
  53  *
  54  */
  55
  56 /*----- Header files ------------------------------------------------------*/
  57
  58 #include <mLib/sub.h>
  59
  60
  61 #include "mp.h"
  62
  63 /*----- Main code ---------------------------------------------------------*/
  64
  65 /* --- @mp_new@ --- *
  66  *
  67  * Arguments:   @size_t sz@ = size of vector required
  68  *              @unsigned f@ = flags to set
  69  *
  70  * Returns:     Pointer to a new MP structure.
  71  *
  72  * Use:         Allocates a new multiprecision integer.  The data space is
  73  *              allocated from either the standard global or secret arena,
  74  *              depending on the initial flags requested.
  75  */
  76
  77 mp *mp_new(size_t sz, unsigned f)
  78 {
  79   mp *m = CREATE(mp);
  80   m->a = (f & MP_BURN) ? MPARENA_SECURE : MPARENA_GLOBAL;
  81   m->v = mpalloc(m->a, sz);
  82   m->vl = m->v + sz;
  83   m->sz = sz;
  84   m->f = f & ~(MP_CONST | MP_DESTROYED);
  85   m->ref = 1;
  86   return (m);
  87 }
  88
  89 /* --- @mp_create@ --- *
  90  *
  91  * Arguments:   @size_t sz@ = size of vector required
  92  *
  93  * Returns:     Pointer to pristine new MP structure with enough memory
  94  *              bolted onto it.
  95  *
  96  * Use:         Creates a new multiprecision integer, initially zero.  The
  97  *              integer has a single reference.
  98  */
  99
 100 mp *mp_create(size_t sz)
 101 {
 102   mp *m = CREATE(mp);
 103   m->v = mpalloc(MPARENA_GLOBAL, sz);
 104   m->vl = m->v + sz;
 105   m->sz = sz;
 106   m->a = MPARENA_GLOBAL;
 107   m->f = MP_UNDEF;
 108   m->ref = 1;
 109   return (m);
 110 }
 111
 112 /* --- @mp_createsecure@ --- *
 113  *
 114  * Arguments:   @size_t sz@ = size of vector required
 115  *
 116  * Returns:     Pointer to pristine new MP structure with enough memory
 117  *              bolted onto it.
 118  *
 119  * Use:         Creates a new multiprecision integer with indeterminate
 120  *              contents.  The integer has a single reference.  The integer's
 121  *              data space is allocated from the secure arena.  Its burn flag
 122  *              is set.
 123  */
 124
 125 mp *mp_createsecure(size_t sz)
 126 {
 127   mp *m = CREATE(mp);
 128   m->v = mpalloc(MPARENA_SECURE, sz);
 129   m->vl = m->v + sz;
 130   m->sz = sz;
 131   m->a = MPARENA_SECURE;
 132   m->f = MP_UNDEF | MP_BURN;
 133   m->ref = 1;
 134   return (m);
 135 }
 136
 137 /* --- @mp_build@ --- *
 138  *
 139  * Arguments:   @mp *m@ = pointer to an MP block to fill in
 140  *              @mpw *v@ = pointer to a word array
 141  *              @mpw *vl@ = pointer just past end of array
 142  *
 143  * Returns:     ---
 144  *
 145  * Use:         Creates a multiprecision integer representing some smallish
 146  *              number.  You must provide storage for the number and dispose
 147  *              of it when you've finished with it.  The number is marked as
 148  *              constant while it exists.
 149  */
 150
 151 void mp_build(mp *m, mpw *v, mpw *vl)
 152 {
 153   m->v = v;
 154   m->vl = vl;
 155   m->sz = vl - v;
 156   m->f = MP_CONST;
 157   m->ref = 1;
 158 }
 159
 160 /* --- @mp_destroy@ --- *
 161  *
 162  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 163  *
 164  * Returns:     ---
 165  *
 166  * Use:         Destroys a multiprecision integer. The reference count isn't
 167  *              checked.  Don't use this function if you don't know what
 168  *              you're doing: use @mp_drop@ instead.
 169  */
 170
 171 void mp_destroy(mp *m)
 172 {
 173   assert(((void)"Destroying a free integer", !(m->f & MP_DESTROYED)));
 174   assert(((void)"Attempted to destroy a constant", !(m->f & MP_CONST)));
 175   if (m->f & MP_BURN)
 176     memset(m->v, 0, MPWS(m->sz));
 177   mpfree(m->a, m->v);
 178   m->f |= MP_DESTROYED;
 179   DESTROY(m);
 180 }
 181
 182 /* --- @mp_copy@ --- *
 183  *
 184  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 185  *
 186  * Returns:     A copy of the given multiprecision integer.
 187  *
 188  * Use:         Copies the given integer.  In fact you just get another
 189  *              reference to the same old one again.
 190  */
 191
 192 mp *mp_copy(mp *m) { return MP_COPY(m); }
 193
 194 /* --- @mp_drop@ --- *
 195  *
 196  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 197  *
 198  * Returns:     ---
 199  *
 200  * Use:         Drops a reference to an integer which isn't wanted any more.
 201  *              If there are no more references, the integer is destroyed.
 202  */
 203
 204 void mp_drop(mp *m) { if (m) MP_DROP(m); }
 205
 206 /* --- @mp_split@ --- *
 207  *
 208  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 209  *
 210  * Returns:     A reference to the same integer, possibly with a different
 211  *              address.
 212  *
 213  * Use:         Splits off a modifiable version of the integer referred to.
 214  */
 215
 216 mp *mp_split(mp *m) { MP_SPLIT(m); return (m); }
 217
 218 /* --- @mp_resize@ --- *
 219  *
 220  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 221  *              @size_t sz@ = new size
 222  *
 223  * Returns:     ---
 224  *
 225  * Use:         Changes an integer's size.  The length and value are not
 226  *              changed.  It is an error to
 227  */
 228
 229 void mp_resize(mp *m, size_t sz) { MP_RESIZE(m, sz); }
 230
 231 /* --- @mp_ensure@ --- *
 232  *
 233  * Arguments:   @mp *m@ = pointer to a multiprecision integer
 234  *              @size_t sz@ = required length
 235  *
 236  * Returns:     ---
 237  *
 238  * Use:         Changes an integer's length.  If there is not enough space
 239  *              allocated for the new length then the size is increased.  It
 240  */
 241
 242 void mp_ensure(mp *m, size_t sz) { MP_ENSURE(m, sz); }
 243
 244 /* --- @mp_dest@ --- *
 245  *
 246  * Arguments:   @mp *m@ = a suggested destination integer
 247  *              @size_t sz@ = size required for result, in digits
 248  *              @unsigned f@ = various flags
 249  *
 250  * Returns:     A pointer to an appropriate destination.
 251  *
 252  * Use:         Converts a suggested destination into a real destination with
 253  *              the required properties.  If the real destination is @d@,
 254  *              then the following properties will hold:
 255  *
 256  *                * @d@ will have exactly one reference.
 257  *
 258  *                * If @m@ is not @MP_NEW@, then the contents of @m@ will not
 259  *                  change, unless @f@ has the @MP_UNDEF@ flag set.
 260  *
 261  *                * If @m@ is not @MP_NEW@, then he reference count of @m@ on
 262  *                  entry is equal to the sum of the counts of @d@ and @m@ on
 263  *                  exit.
 264  *
 265  *                * The size of @d@ will be at least @sz@.
 266  *
 267  *                * If @f@ has the @MP_BURN@ flag set, then @d@ will be
 268  *                  allocated from @MPARENA_SECURE@.
 269  *
 270  *              Understanding this function is crucial to using Catacomb's
 271  *              multiprecision integer library effectively.
 272  */
 273
 274 mp *mp_dest(mp *m, size_t sz, unsigned f)
 275 {
 276   /* --- If no destination, make one --- */
 277
 278   if (m == MP_NEWSEC)
 279     m = mp_new(sz, f | MP_UNDEF | MP_BURN);
 280   else if (m == MP_NEW)
 281     m = mp_new(sz, f | MP_UNDEF);
 282   else {
 283     size_t len = MP_LEN(m);
 284     unsigned undef = (m->f | f) & MP_UNDEF;
 285
 286     /* --- If the value must be preserved, the block can't shrink --- */
 287
 288     if (!undef && sz < len)
 289       sz = len;
 290
 291     /* --- Otherwise check whether the destination is suitable --- */
 292
 293     if (m->ref > 1 || (m->f & MP_CONST) ||
 294         sz > m->sz || !((f & ~m->f) & MP_BURN)) {
 295
 296       /* --- No -- allocate a new buffer --- *
 297        *
 298        * The buffer must be secure if (a) the caller requested a secure
 299        * buffer, or (b) the old buffer is secure and I'm not allowed to
 300        * discard the old contents.
 301        */
 302
 303       mparena *a;
 304       mpw *v;
 305
 306       if ((f & MP_BURN) || (!undef && (m->f & MP_BURN)))
 307         a = MPARENA_SECURE;
 308       else
 309         a = MPARENA_GLOBAL;
 310       v = mpalloc(a, sz);
 311
 312       /* --- Copy the data over --- */
 313
 314       if (!undef) {
 315         memcpy(v, m->v, MPWS(len));
 316         if (sz - len > 0)
 317           memset(v + len, 0, MPWS(sz - len));
 318       }
 319
 320       /* --- If @m@ has other references, make a new node --- *
 321        *
 322        * Otherwise dispose of the old buffer.
 323        */
 324
 325       if (!(m->f & MP_CONST) && m->ref == 1) {
 326         if (m->f & MP_BURN)
 327           memset(m->v, 0, MPWS(m->sz));
 328         mpfree(m->a, m->v);
 329       } else {
 330         mp *mm = CREATE(mp);
 331         mm->ref = 1;
 332         mm->f = m->f;
 333         m->ref--;
 334         m = mm;
 335       }
 336
 337       /* --- Fix up the node --- */
 338
 339       m->v = v;
 340       m->vl = v + sz;
 341       m->sz = sz;
 342       m->f = ((m->f & ~(MP_CONST | MP_BURN)) |
 343               (f & (MP_BURN | MP_UNDEF)));
 344       m->a = a;
 345     }
 346
 347     /* --- If the number is growing in its buffer, fix it up --- */
 348
 349     else if (sz > len) {
 350       if (!undef)
 351         memset(m->vl, 0, MPWS(sz - len));
 352       m->vl = m->v + sz;
 353     }
 354   }
 355
 356   /* --- Done --- */
 357
 358   return (m);
 359 }
 360
 361 /*----- That's all, folks -------------------------------------------------*/