From 75e09b3c4b9d50b23e02b4531748e1121c6db420 Mon Sep 17 00:00:00 2001
From: "H. Peter Anvin" <hpa@linux.intel.com>
Date: Tue, 20 Mar 2012 16:20:43 -0700
Subject: Add pbn_mulus_add()

Add pbn_mulus_add(); equivalent to pbn_muls() except:

a) it takes an unsigned multiplier, and
b) it takes a second single-limb unsigned addend.

It thus computes <long> * <short1> + <short2>; this is highly useful
in base conversion.
---
 Makefile        |  3 ++-
 pbn.h           |  3 +++
 pbn_mulus_add.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 56 insertions(+), 1 deletion(-)
 create mode 100644 pbn_mulus_add.c

diff --git a/Makefile b/Makefile
index 7b3cbfb..8c51013 100644
--- a/Makefile
+++ b/Makefile
@@ -4,7 +4,8 @@ LDFLAGS	=
 AR	= ar
 RANLIB	= ranlib
 
-LIBOBJ	= pbn_add.o pbn_cmp.o pbn_dump.o pbn_init.o pbn_mul.o pbn_muls.o \
+LIBOBJ	= pbn_add.o pbn_cmp.o pbn_dump.o pbn_init.o \
+	  pbn_mul.o pbn_muls.o pbn_mulus_add.o \
 	  pbn_shift.o pbn_and.o pbn_or.o pbn_xor.o pbn_bit.o pbn_ctz.o \
 	  pbn_abs.o pbn_div.o pbn_divs.o
 
diff --git a/pbn.h b/pbn.h
index afc5249..27cf9b4 100644
--- a/pbn.h
+++ b/pbn.h
@@ -67,6 +67,7 @@ int pbn_cmp(const struct pbn *, const struct pbn *);
 int pbn_abscmp(const struct pbn *, const struct pbn *);
 struct pbn *pbn_mul(struct pbn *, struct pbn *);
 struct pbn *pbn_muls(struct pbn *, pbn_slimb_t);
+struct pbn *pbn_mulus_add(struct pbn *, pbn_limb_t, pbn_limb_t);
 int pbn_div(struct pbn **, struct pbn **, struct pbn *, struct pbn *);
 int pbn_divs(struct pbn **, pbn_slimb_t *, struct pbn *, pbn_slimb_t);
 struct pbn *pbn_abs(struct pbn *);
@@ -76,6 +77,8 @@ struct pbn *pbn_shl(struct pbn *, int);
 struct pbn *pbn_and(struct pbn *, struct pbn *);
 struct pbn *pbn_or(struct pbn *, struct pbn *);
 struct pbn *pbn_xor(struct pbn *, struct pbn *);
+/* pbn_ctz() does NOT consume a reference! */
+int pbn_ctz(const struct pbn *);
 
 struct pbn *pbn_set_bit(struct pbn *, int);
 struct pbn *pbn_clr_bit(struct pbn *, int);
diff --git a/pbn_mulus_add.c b/pbn_mulus_add.c
new file mode 100644
index 0000000..23ec240
--- /dev/null
+++ b/pbn_mulus_add.c
@@ -0,0 +1,51 @@
+/* ----------------------------------------------------------------------- *
+ *
+ *   Copyright 2007 H. Peter Anvin - All Rights Reserved
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU Lesser General Public License as
+ *   published by the Free Software Foundation, Inc.,
+ *   59 Temple Place Ste 330, Boston MA 02111-1307, USA; version 2.1,
+ *   incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * pbn_mulus_add.c
+ *
+ * Multiply a PBN with a single limb unsigned number, and add a single
+ * limb unsigned number.
+ */
+
+#include "pbnint.h"
+
+struct pbn *pbn_mulus_add(struct pbn *s1, pbn_limb_t s2, pbn_limb_t c)
+{
+    size_t i, len;
+    struct pbn *d;
+    pbn_limb_t *s1p, *dp;
+    pbn_2limb_t t;
+
+    if (unlikely(s1->bits == 0)) {
+        pbn_free(s1);
+	return pbn_uint(c);
+    }
+
+    len = (s1->bits+PBN_LIMB_BITS-1) >> PBN_LIMB_SHIFT;
+
+    d = pbn_new(len+1);
+    d->minus = s1->minus;
+
+    s1p = s1->num;
+    dp  = d->num;
+    for (i = 0; i < len; i++) {
+	t = (pbn_2limb_t)*s1p++ * s2 + c;
+        *dp++ = (pbn_limb_t)t;
+        c = t >> PBN_LIMB_BITS;
+    }
+    *dp = c;
+
+    pbn_free(s1);
+
+    return pbn_adjust_bits(d);
+}
-- 
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