From 0d0279cc7ff02ffedd5bead7a5241fade204b01b Mon Sep 17 00:00:00 2001
From: vit9696 <vit9696@users.noreply.github.com>
Date: Sun, 31 Jan 2021 04:57:40 +0300
Subject: [PATCH] OcGuardLib: Add U16 arithmetics

---
 Include/Acidanthera/Library/OcGuardLib.h | 21 ++++++++
 Library/OcGuardLib/BitOverflow.c         | 67 ++++++++++++++++++++++++
 2 files changed, 88 insertions(+)

diff --git a/Include/Acidanthera/Library/OcGuardLib.h b/Include/Acidanthera/Library/OcGuardLib.h
index 3050d583..4866fab5 100644
--- a/Include/Acidanthera/Library/OcGuardLib.h
+++ b/Include/Acidanthera/Library/OcGuardLib.h
@@ -56,6 +56,27 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
 // and multiplication with addition (A*B+C) support.
 //
 
+BOOLEAN
+OcOverflowAddU16 (
+  UINT16  A,
+  UINT16  B,
+  UINT16  *Result
+  );
+
+BOOLEAN
+OcOverflowSubU16 (
+  UINT16  A,
+  UINT16  B,
+  UINT16  *Result
+  );
+
+BOOLEAN
+OcOverflowMulU16 (
+  UINT16  A,
+  UINT16  B,
+  UINT16  *Result
+  );
+
 BOOLEAN
 OcOverflowAddU32 (
   UINT32  A,
diff --git a/Library/OcGuardLib/BitOverflow.c b/Library/OcGuardLib/BitOverflow.c
index 1bb76b4c..643216d2 100644
--- a/Library/OcGuardLib/BitOverflow.c
+++ b/Library/OcGuardLib/BitOverflow.c
@@ -26,6 +26,73 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
 // target C99 compliance rather than performance.
 //
 
+BOOLEAN
+OcOverflowAddU16 (
+  UINT16  A,
+  UINT16  B,
+  UINT16  *Result
+  )
+{
+#if defined(OC_HAS_TYPE_GENERIC_BUILTINS)
+  return __builtin_add_overflow(A, B, Result);
+#else
+  UINT32  Temp;
+
+  //
+  // I believe casting will be faster on X86 at least.
+  //
+  Temp    = A + B;
+  *Result = (UINT16) Temp;
+  if (Temp <= MAX_UINT16) {
+    return FALSE;
+  }
+
+  return TRUE;
+#endif
+}
+
+BOOLEAN
+OcOverflowSubU16 (
+  UINT16  A,
+  UINT16  B,
+  UINT16  *Result
+  )
+{
+#if defined(OC_HAS_TYPE_GENERIC_BUILTINS)
+  return __builtin_sub_overflow(A, B, Result);
+#else
+  *Result = (UINT16) (A - B);
+
+  if (A >= B) {
+    return FALSE;
+  }
+
+  return TRUE;
+#endif
+}
+
+BOOLEAN
+OcOverflowMulU16 (
+  UINT16  A,
+  UINT16  B,
+  UINT16  *Result
+  )
+{
+#if defined(OC_HAS_TYPE_GENERIC_BUILTINS)
+  return __builtin_mul_overflow(A, B, Result);
+#else
+  UINT32  Temp;
+
+  Temp    = (UINT32) A * B;
+  *Result = (UINT16) Temp;
+  if (Temp <= MAX_UINT32) {
+    return FALSE;
+  }
+
+  return TRUE;
+#endif
+}
+
 BOOLEAN
 OcOverflowAddU32 (
   UINT32  A,
-- 
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