--- /dev/null
+/* -*-c-*-
+ *
+ * $Id: grand.c,v 1.1 1999/12/10 23:16:01 mdw Exp $
+ *
+ * Generic interface to random number generators
+ *
+ * (c) 1999 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------*
+ *
+ * This file is part of Catacomb.
+ *
+ * Catacomb is free software; you can redistribute it and/or modify
+ * 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: grand.c,v $
+ * Revision 1.1 1999/12/10 23:16:01 mdw
+ * Generic interface.
+ *
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include <stddef.h>
+
+#include <mLib/bits.h>
+
+#include "grand.h"
+
+/*----- Main code ---------------------------------------------------------*/
+
+/* --- @grand_byte@ --- *
+ *
+ * Arguments: @grand *r@ = pointet to generic generator
+ *
+ * Returns: A uniformly-distributed pseudorandom integer in the interval
+ * %$[0, 256)$%.
+ */
+
+octet grand_byte(grand *r)
+{
+ if (r->ops->byte != grand_byte)
+ return (r->ops->byte(r));
+ else if (r->ops->word != grand_word)
+ return (r->ops->word(r) & 0xff);
+ else if (r->ops->fill != grand_fill) {
+ octet o;
+ r->ops->fill(r, &o, 1);
+ return (o);
+ } else
+ return (grand_range(r, 256));
+}
+
+/* --- @grand_word@ --- *
+ *
+ * Arguments: @grand *r@ = pointet to generic generator
+ *
+ * Returns: A uniformly-distributed pseudorandom integer in the interval
+ * %$[0, 2^{32})$%.
+ */
+
+uint32 grand_word(grand *r)
+{
+ if (r->ops->word != grand_word)
+ return (r->ops->word(r));
+ else {
+ octet b[4];
+ grand_fill(r, b, sizeof(b));
+ return (LOAD32(b));
+ }
+}
+
+/* --- @grand_range@ --- *
+ *
+ * Arguments: @grand *r@ = pointet to generic generator
+ * @uint32 l@ = limit for acceptable results
+ *
+ * Returns: A uniformly-distributed pseudorandom integer in the interval
+ * %$[0, l)$%.
+ */
+
+uint32 grand_range(grand *r, uint32 l)
+{
+ if (r->ops->range != grand_range)
+ return (r->ops->range(r, l));
+ else {
+ uint32 m, z;
+ uint32 (*w)(grand */*r*/);
+ uint32 x;
+
+ /* --- Decide where to get data from --- *
+ *
+ * The choice of %$2^{32} - 1$% as a limit when using @grand_word@ isn't
+ * wonderful, but working with %$2^{32}$% is awkward and the loss of a
+ * few return values isn't significant. The algorithm below still
+ * successfully returns uniformly distributed results.
+ */
+
+ if (r->ops->max) {
+ w = r->ops->raw;
+ m = r->ops->max;
+ } else {
+ w = grand_word;
+ m = 0xffffffff;
+ }
+
+ /* --- Work out maximum acceptable return value --- *
+ *
+ * This will be the highest multiple of @l@ less than @m@.
+ */
+
+ z = m - (m % l);
+ m = z / l;
+
+ /* --- Generate numbers until something acceptable is found --- *
+ *
+ * This will require an expected number of attempts less than 2.
+ */
+
+ do x = w(r); while (x >= z);
+ return (x / m);
+ }
+}
+
+/* --- @grand_fill@ --- *
+ *
+ * Arguments: @grand *r@ = pointet to generic generator
+ * @void *p@ = pointer to a buffer
+ * @size_t sz@ = size of the buffer
+ *
+ * Returns: ---
+ *
+ * Use: Fills a buffer with uniformly distributed pseudorandom bytes
+ * (see @grand_byte@).
+ */
+
+void grand_fill(grand *r, void *p, size_t sz)
+{
+ if (r->ops->fill != grand_fill)
+ r->ops->fill(r, p, sz);
+ else {
+ octet *q = p;
+ while (sz) {
+ *q++ = r->ops->byte(r);
+ sz--;
+ }
+ }
+}
+
+/*----- That's all, folks -------------------------------------------------*/