Feat/rpow function (#74)

* Delete DSMath lib

Added private function _rpow to AbstractCompoundRateKeeper

* update rpow

Make func internal for test reasons

* Update AbstractCompoundRateKeeper.sol

* rpow changed to private

Check if base or exponent equal to 0 removed

* Update AbstractCompoundRateKeeper.sol

* Optimization

rpow is renamed to raiseToPower
precision taken not as func parameter but from the global scope
upd to version 2.6.6

* minor style

---------

Co-authored-by: Artem Chystiakov <artem.ch31@gmail.com>

Author: aritkulova

contracts/compound-rate-keeper/AbstractCompoundRateKeeper.sol

@@ -6,8 +6,6 @@ import {Math} from "@openzeppelin/contracts/utils/math/Math.sol";
 
 import {ICompoundRateKeeper} from "../interfaces/compound-rate-keeper/ICompoundRateKeeper.sol";
 
-import {DSMath} from "../libs/math/DSMath.sol";
-
 import {PRECISION} from "../utils/Globals.sol";
 
 /**
@@ -24,7 +22,6 @@ import {PRECISION} from "../utils/Globals.sol";
  */
 abstract contract AbstractCompoundRateKeeper is ICompoundRateKeeper, Initializable {
     using Math for uint256;
-    using DSMath for uint256;
 
     uint256 private _capitalizationRate;
     uint64 private _capitalizationPeriod;
@@ -96,9 +93,9 @@ abstract contract AbstractCompoundRateKeeper is ICompoundRateKeeper, Initializab
         uint256 rate_ = _currentRate;
 
         if (capitalizationPeriodsNum_ != 0) {
-            uint256 capitalizationPeriodRate_ = capitalizationRate_.rpow(
-                capitalizationPeriodsNum_,
-                PRECISION
+            uint256 capitalizationPeriodRate_ = _raiseToPower(
+                capitalizationRate_,
+                capitalizationPeriodsNum_
             );
             rate_ = (rate_ * capitalizationPeriodRate_) / PRECISION;
         }
@@ -203,6 +200,25 @@ abstract contract AbstractCompoundRateKeeper is ICompoundRateKeeper, Initializab
         emit CapitalizationPeriodChanged(capitalizationPeriod_);
     }
 
+    /**
+     * @notice Implementation of exponentiation by squaring with fixed precision
+     * @dev Checks if base or exponent equal to 0 done before
+     */
+    function _raiseToPower(
+        uint256 base_,
+        uint256 exponent_
+    ) private pure returns (uint256 result_) {
+        result_ = exponent_ & 1 == 0 ? PRECISION : base_;
+
+        while ((exponent_ >>= 1) > 0) {
+            base_ = (base_ * base_) / PRECISION;
+
+            if (exponent_ & 1 == 1) {
+                result_ = (result_ * base_) / PRECISION;
+            }
+        }
+    }
+
     /**
      * @notice The private function to get the maximal possible compound rate
      */

contracts/libs/math/DSMath.sol

@@ -1,6 +1,6 @@
 {
   "name": "@solarity/solidity-lib",
-  "version": "2.6.5",
+  "version": "2.6.6",
   "license": "MIT",
   "author": "Distributed Lab",
   "readme": "README.md",

contracts/mock/libs/math/DSMathMock.sol

@@ -1,6 +1,6 @@
 {
   "name": "@solarity/solidity-lib",
-  "version": "2.6.5",
+  "version": "2.6.6",
   "license": "MIT",
   "author": "Distributed Lab",
   "description": "Solidity Library by Distributed Lab",