From 9faebd8078d8efb7a779681635ed0a0f214ef1c3 Mon Sep 17 00:00:00 2001
From: Tuomo Kriikkula <tuokri@tuta.io>
Date: Sun, 11 Aug 2024 00:09:29 +0300
Subject: [PATCH] Add BIsZero_Static37

---
 Classes/FCryptoBigInt.uc   | 16 +++++++++++++---
 Classes/FCryptoEC_Prime.uc |  3 +--
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/Classes/FCryptoBigInt.uc b/Classes/FCryptoBigInt.uc
index 7fb53c5..757216c 100644
--- a/Classes/FCryptoBigInt.uc
+++ b/Classes/FCryptoBigInt.uc
@@ -1256,9 +1256,7 @@ static final function ToMonty(
  * This function is called "BIsZero" because
  * "IsZero" would clash with Object::IsZero.
  */
-static final function int BIsZero(
-    const out array<int> X
-)
+static final function int BIsZero(const out array<int> X)
 {
     local int Z;
     local int U;
@@ -1271,6 +1269,18 @@ static final function int BIsZero(
     return ~(Z | -Z) >>> 31;
 }
 
+static final function int BIsZero_Static37(const out int X[37])
+{
+    local int Z;
+    local int U;
+
+    Z = 0;
+    for (U = (X[0] + 15) >>> 4; U > 0; --U)
+    {
+        Z = Z | X[U];
+    }
+    return ~(Z | -Z) >>> 31;
+}
 
 /*
  * Negate big integer conditionally. The value consists of 'len' words,
diff --git a/Classes/FCryptoEC_Prime.uc b/Classes/FCryptoEC_Prime.uc
index 445f8b6..7cf0949 100644
--- a/Classes/FCryptoEC_Prime.uc
+++ b/Classes/FCryptoEC_Prime.uc
@@ -283,8 +283,7 @@ static final function int RunCode(
             case 4:
                 break;
             default:
-                // TODO: need static variant for this too.
-                // R = R & (class'FCryptoBigInt'.static.BIsZero(T[D]));
+                R = R & class'FCryptoBigInt'.static.BIsZero_Static37(T[D].X);
                 break;
         }
     }