1 files changed, 87 insertions, 0 deletions
diff --git a/contracts/core/contracts/utils/SafeMath/SafeMath.sol b/contracts/core/contracts/utils/SafeMath/SafeMath.sol
new file mode 100644
index 000000000..2855edb9d
--- /dev/null
+++ b/contracts/core/contracts/utils/SafeMath/SafeMath.sol
@@ -0,0 +1,87 @@
+pragma solidity 0.4.24;
+
+
+contract SafeMath {
+
+    function safeMul(uint256 a, uint256 b)
+        internal
+        pure
+        returns (uint256)
+    {
+        if (a == 0) {
+            return 0;
+        }
+        uint256 c = a * b;
+        require(
+            c / a == b,
+            "UINT256_OVERFLOW"
+        );
+        return c;
+    }
+
+    function safeDiv(uint256 a, uint256 b)
+        internal
+        pure
+        returns (uint256)
+    {
+        uint256 c = a / b;
+        return c;
+    }
+
+    function safeSub(uint256 a, uint256 b)
+        internal
+        pure
+        returns (uint256)
+    {
+        require(
+            b <= a,
+            "UINT256_UNDERFLOW"
+        );
+        return a - b;
+    }
+
+    function safeAdd(uint256 a, uint256 b)
+        internal
+        pure
+        returns (uint256)
+    {
+        uint256 c = a + b;
+        require(
+            c >= a,
+            "UINT256_OVERFLOW"
+        );
+        return c;
+    }
+
+    function max64(uint64 a, uint64 b)
+        internal
+        pure
+        returns (uint256)
+    {
+        return a >= b ? a : b;
+    }
+
+    function min64(uint64 a, uint64 b)
+        internal
+        pure
+        returns (uint256)
+    {
+        return a < b ? a : b;
+    }
+
+    function max256(uint256 a, uint256 b)
+        internal
+        pure
+        returns (uint256)
+    {
+        return a >= b ? a : b;
+    }
+
+    function min256(uint256 a, uint256 b)
+        internal
+        pure
+        returns (uint256)
+    {
+        return a < b ? a : b;
+    }
+}