X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/d3409d5ecf2492cff862616de72a580d1a8e8dc0..813390c45f438f411662b1a55678e63f11681eb4:/mp-mem.c

diff --git a/mp-mem.c b/mp-mem.c
index 2f75365..fcb6c4d 100644
--- a/mp-mem.c
+++ b/mp-mem.c
@@ -1,13 +1,13 @@
 /* -*-c-*-
  *
- * $Id: mp-mem.c,v 1.1 1999/11/17 18:02:16 mdw Exp $
+ * $Id: mp-mem.c,v 1.8 2004/04/08 16:17:32 mdw Exp $
  *
  * Memory management for multiprecision numbers
  *
  * (c) 1999 Straylight/Edgeware
  */
 
-/*----- Licensing notice --------------------------------------------------* 
+/*----- Licensing notice --------------------------------------------------*
  *
  * This file is part of Catacomb.
  *
@@ -15,32 +15,51 @@
  * it under the terms of the GNU Library General Public License as
  * published by the Free Software Foundation; either version 2 of the
  * License, or (at your option) any later version.
- * 
+ *
  * Catacomb is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU Library General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU Library General Public
  * License along with Catacomb; if not, write to the Free
  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  * MA 02111-1307, USA.
  */
 
-/*----- Revision history --------------------------------------------------* 
- *
- * $Log: mp-mem.c,v $
- * Revision 1.1  1999/11/17 18:02:16  mdw
- * New multiprecision integer arithmetic suite.
- *
- */
-
 /*----- Header files ------------------------------------------------------*/
 
+#include <mLib/sub.h>
+
+
 #include "mp.h"
 
 /*----- Main code ---------------------------------------------------------*/
 
+/* --- @mp_new@ --- *
+ *
+ * Arguments:	@size_t sz@ = size of vector required
+ *		@unsigned f@ = flags to set
+ *
+ * Returns:	Pointer to a new MP structure.
+ *
+ * Use:		Allocates a new multiprecision integer.  The data space is
+ *		allocated from either the standard global or secret arena,
+ *		depending on the initial flags requested.
+ */
+
+mp *mp_new(size_t sz, unsigned f)
+{
+  mp *m = CREATE(mp);
+  m->a = (f & MP_BURN) ? MPARENA_SECURE : MPARENA_GLOBAL;
+  m->v = mpalloc(m->a, sz);
+  m->vl = m->v + sz;
+  m->sz = sz;
+  m->f = f & ~(MP_CONST | MP_DESTROYED);
+  m->ref = 1;
+  return (m);
+}
+
 /* --- @mp_create@ --- *
  *
  * Arguments:	@size_t sz@ = size of vector required
@@ -55,14 +74,40 @@
 mp *mp_create(size_t sz)
 {
   mp *m = CREATE(mp);
-  m->v = MP_ALLOC(sz);
+  m->v = mpalloc(MPARENA_GLOBAL, sz);
   m->vl = m->v + sz;
   m->sz = sz;
+  m->a = MPARENA_GLOBAL;
   m->f = MP_UNDEF;
   m->ref = 1;
   return (m);
 }
 
+/* --- @mp_createsecure@ --- *
+ *
+ * Arguments:	@size_t sz@ = size of vector required
+ *
+ * Returns:	Pointer to pristine new MP structure with enough memory
+ *		bolted onto it.
+ *
+ * Use:		Creates a new multiprecision integer with indeterminate
+ *		contents.  The integer has a single reference.  The integer's
+ *		data space is allocated from the secure arena.  Its burn flag
+ *		is set.
+ */
+
+mp *mp_createsecure(size_t sz)
+{
+  mp *m = CREATE(mp);
+  m->v = mpalloc(MPARENA_SECURE, sz);
+  m->vl = m->v + sz;
+  m->sz = sz;
+  m->a = MPARENA_SECURE;
+  m->f = MP_UNDEF | MP_BURN;
+  m->ref = 1;
+  return (m);
+}
+
 /* --- @mp_build@ --- *
  *
  * Arguments:	@mp *m@ = pointer to an MP block to fill in
@@ -82,6 +127,7 @@ void mp_build(mp *m, mpw *v, mpw *vl)
   m->v = v;
   m->vl = vl;
   m->sz = vl - v;
+  m->a = MPARENA_GLOBAL;
   m->f = MP_CONST;
   m->ref = 1;
 }
@@ -99,11 +145,12 @@ void mp_build(mp *m, mpw *v, mpw *vl)
 
 void mp_destroy(mp *m)
 {
-  if (m->f & MP_CONST)
-    return;
+  assert(((void)"Destroying a free integer", !(m->f & MP_DESTROYED)));
+  assert(((void)"Attempted to destroy a constant", !(m->f & MP_CONST)));
   if (m->f & MP_BURN)
     memset(m->v, 0, MPWS(m->sz));
-  MP_FREE(m->v);
+  mpfree(m->a, m->v);
+  m->f |= MP_DESTROYED;
   DESTROY(m);
 }
 
@@ -129,7 +176,7 @@ mp *mp_copy(mp *m) { return MP_COPY(m); }
  *		If there are no more references, the integer is destroyed.
  */
 
-void mp_drop(mp *m) { MP_DROP(m); }
+void mp_drop(mp *m) { if (m) MP_DROP(m); }
 
 /* --- @mp_split@ --- *
  *
@@ -150,9 +197,8 @@ mp *mp_split(mp *m) { MP_SPLIT(m); return (m); }
  *
  * Returns:	---
  *
- * Use:		Resizes the vector containing the integer's digits.  The new
- *		size must be at least as large as the current integer's
- *		length.  This isn't really intended for client use.
+ * Use:		Changes an integer's size.  The length and value are not
+ *		changed.  It is an error to
  */
 
 void mp_resize(mp *m, size_t sz) { MP_RESIZE(m, sz); }
@@ -160,28 +206,131 @@ void mp_resize(mp *m, size_t sz) { MP_RESIZE(m, sz); }
 /* --- @mp_ensure@ --- *
  *
  * Arguments:	@mp *m@ = pointer to a multiprecision integer
- *		@size_t sz@ = required size
+ *		@size_t sz@ = required length
  *
  * Returns:	---
  *
- * Use:		Ensures that the integer has enough space for @sz@ digits.
- *		The value is not changed.
+ * Use:		Changes an integer's length.  If there is not enough space
+ *		allocated for the new length then the size is increased.  It
  */
 
 void mp_ensure(mp *m, size_t sz) { MP_ENSURE(m, sz); }
 
-/* --- @mp_modify@ --- *
+/* --- @mp_dest@ --- *
  *
- * Arguments:	@mp *m@ = pointer to a multiprecision integer
- *		@size_t sz@ = size required
+ * Arguments:	@mp *m@ = a suggested destination integer
+ *		@size_t sz@ = size required for result, in digits
+ *		@unsigned f@ = various flags
+ *
+ * Returns:	A pointer to an appropriate destination.
+ *
+ * Use:		Converts a suggested destination into a real destination with
+ *		the required properties.  If the real destination is @d@,
+ *		then the following properties will hold:
+ *
+ *		  * @d@ will have exactly one reference.
  *
- * Returns:	Pointer to the integer (possibly different).
+ *		  * If @m@ is not @MP_NEW@, then the contents of @m@ will not
+ *		    change, unless @f@ has the @MP_UNDEF@ flag set.
  *
- * Use:		Prepares an integer to be overwritten.  It's split off from
- *		other references to the same integer, and sufficient space is
- *		allocated.
+ *		  * If @m@ is not @MP_NEW@, then he reference count of @m@ on
+ *		    entry is equal to the sum of the counts of @d@ and @m@ on
+ *		    exit.
+ *
+ *		  * The size of @d@ will be at least @sz@.
+ *
+ *		  * If @f@ has the @MP_BURN@ flag set, then @d@ will be
+ *		    allocated from @MPARENA_SECURE@.
+ *
+ *		Understanding this function is crucial to using Catacomb's
+ *		multiprecision integer library effectively.
  */
 
-mp *mp_modify(mp *m, size_t sz) { MP_MODIFY(m, sz); return (m); }
+mp *mp_dest(mp *m, size_t sz, unsigned f)
+{
+  /* --- If no destination, make one --- */
+
+  if (m == MP_NEWSEC)
+    m = mp_new(sz, f | MP_UNDEF | MP_BURN);
+  else if (m == MP_NEW)
+    m = mp_new(sz, f | MP_UNDEF);
+  else {
+    size_t len = MP_LEN(m);
+    unsigned undef = (m->f | f) & MP_UNDEF;
+
+    /* --- If the value must be preserved, the block can't shrink --- */
+
+    if (!undef && sz < len)
+      sz = len;
+
+    /* --- Otherwise check whether the destination is suitable --- */
+
+    if (m->ref > 1 || (m->f & MP_CONST) ||
+	sz > m->sz || ((f & ~m->f) & MP_BURN)) {
+
+      /* --- No -- allocate a new buffer --- *
+       *
+       * The buffer must be secure if (a) the caller requested a secure
+       * buffer, or (b) the old buffer is secure and I'm not allowed to
+       * discard the old contents.
+       */
+
+      mparena *a;
+      mpw *v;
+
+      if ((f & MP_BURN) || (!undef && (m->f & MP_BURN)))
+	a = MPARENA_SECURE;
+      else
+	a = MPARENA_GLOBAL;
+      v = mpalloc(a, sz);
+
+      /* --- Copy the data over --- */
+
+      if (!undef) {
+	memcpy(v, m->v, MPWS(len));
+	if (sz - len > 0)
+	  memset(v + len, 0, MPWS(sz - len));
+      }
+
+      /* --- If @m@ has other references, make a new node --- *
+       *
+       * Otherwise dispose of the old buffer.
+       */
+
+      if (!(m->f & MP_CONST) && m->ref == 1) {
+	if (m->f & MP_BURN)
+	  memset(m->v, 0, MPWS(m->sz));
+	mpfree(m->a, m->v);
+      } else {
+	mp *mm = CREATE(mp);
+	mm->ref = 1;
+	mm->f = m->f;
+	m->ref--;
+	m = mm;
+      }
+
+      /* --- Fix up the node --- */
+
+      m->v = v;
+      m->vl = v + sz;
+      m->sz = sz;
+      m->f = ((m->f & ~(MP_CONST | MP_BURN)) |
+	      (f & (MP_BURN | MP_UNDEF)));
+      m->a = a;
+    }
+
+    /* --- If the number is growing in its buffer, fix it up --- */
+
+    else if (sz > len) {
+      if (!undef)
+	memset(m->vl, 0, MPWS(sz - len));
+      m->vl = m->v + sz;
+    }
+  }
+
+  /* --- Done --- */
+
+  return (m);
+}
 
 /*----- That's all, folks -------------------------------------------------*/