From 24055b8c49e2c491f0048d553d24707efe9f166c Mon Sep 17 00:00:00 2001
From: Linas Vepstas <linas@linas.org>
Date: Sun, 27 Jun 2004 20:06:36 +0000
Subject: [PATCH] add a shift-right (divide by two) function

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@10115 57a11ea4-9604-0410-9ed3-97b8803252fd
---
 src/engine/qofmath128.c | 22 ++++++++++++++++++++++
 src/engine/qofmath128.h |  3 +++
 2 files changed, 25 insertions(+)

diff --git a/src/engine/qofmath128.c b/src/engine/qofmath128.c
index 5b409cee41..99185ed38c 100644
--- a/src/engine/qofmath128.c
+++ b/src/engine/qofmath128.c
@@ -278,6 +278,28 @@ add128 (qofint128 a, qofint128 b)
   return sum;
 }
 
+/** Shift right by one bit (i.e. divide by two) */
+inline qofint128
+shift128 (qofint128 x)
+{
+  guint64 sbit = x.hi & 0x1;
+  x.hi >>= 1;
+  x.lo >>= 1;
+  if (sbit)
+  {
+    sbit = 1<<30;  /* in two step to avoid 1ULL<<63 */
+    sbit <<= 33;
+    x.lo |= sbit;
+    x.isbig = 1;
+    return x;
+  }
+  if (x.hi)
+  {
+    x.isbig = 1;
+  }
+  return x;
+}
+
 #ifdef TEST_128_BIT_MULT
 static void pr (gint64 a, gint64 b)
 {
diff --git a/src/engine/qofmath128.h b/src/engine/qofmath128.h
index a0b09c308c..e5fe11f60b 100644
--- a/src/engine/qofmath128.h
+++ b/src/engine/qofmath128.h
@@ -71,6 +71,9 @@ inline qofint128 lcm128 (guint64 a, guint64 b);
 /** Add a pair of 128-bit numbers, returning a 128-bit number */
 inline qofint128 add128 (qofint128 a, qofint128 b);
 
+/** Shift right by one bit (i.e. divide by two) */
+inline qofint128 shift128 (qofint128 x);
+
 #endif
 
 /** @} */