add curveAdapter

contracts/SmartRoute/sampler/CurveSample.sol

@@ -0,0 +1,37 @@
+/*
+
+    Copyright 2021 DODO ZOO.
+    SPDX-License-Identifier: Apache-2.0
+
+*/
+
+pragma solidity 0.6.9;
+pragma experimental ABIEncoderV2;
+
+import "../intf/ICurve.sol";
+
+contract CurveSampler {
+   
+    function sampleFromCurve(
+        address curveAddress,
+        int128 fromTokenIdx,
+        int128 toTokenIdx,
+        uint256[] memory takerTokenAmounts
+    )
+        public
+        view
+        returns (uint256[] memory makerTokenAmounts)
+    {
+        uint256 numSamples = takerTokenAmounts.length;
+        makerTokenAmounts = new uint256[](numSamples);
+        for (uint256 i = 0; i < numSamples; i++) {
+            uint256 buyAmount = ICurve(curveAddress).get_dy_underlying(fromTokenIdx, toTokenIdx, takerTokenAmounts[i]);
+            makerTokenAmounts[i] = buyAmount;
+            // Break early if there are 0 amounts
+            if (makerTokenAmounts[i] == 0) {
+                break;
+            }
+        }
+        return makerTokenAmounts;
+    }
+}