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contracts/lib/SafeERC20.sol

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+/*
+
+    Copyright 2020 DODO ZOO.
+    SPDX-License-Identifier: Apache-2.0
+    This is a simplified version of OpenZepplin's SafeERC20 library
+
+*/
+
+pragma solidity 0.6.9;
+pragma experimental ABIEncoderV2;
+
+import {IERC20} from "../intf/IERC20.sol";
+import {SafeMath} from "./SafeMath.sol";
+
+
+/**
+ * @title SafeERC20
+ * @dev Wrappers around ERC20 operations that throw on failure (when the token
+ * contract returns false). Tokens that return no value (and instead revert or
+ * throw on failure) are also supported, non-reverting calls are assumed to be
+ * successful.
+ * To use this library you can add a `using SafeERC20 for ERC20;` statement to your contract,
+ * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
+ */
+library SafeERC20 {
+    using SafeMath for uint256;
+
+    function safeTransfer(
+        IERC20 token,
+        address to,
+        uint256 value
+    ) internal {
+        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
+    }
+
+    function safeTransferFrom(
+        IERC20 token,
+        address from,
+        address to,
+        uint256 value
+    ) internal {
+        _callOptionalReturn(
+            token,
+            abi.encodeWithSelector(token.transferFrom.selector, from, to, value)
+        );
+    }
+
+    /**
+     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
+     * on the return value: the return value is optional (but if data is returned, it must not be false).
+     * @param token The token targeted by the call.
+     * @param data The call data (encoded using abi.encode or one of its variants).
+     */
+    function _callOptionalReturn(IERC20 token, bytes memory data) private {
+        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
+        // we're implementing it ourselves.
+
+        // A Solidity high level call has three parts:
+        //  1. The target address is checked to verify it contains contract code
+        //  2. The call itself is made, and success asserted
+        //  3. The return value is decoded, which in turn checks the size of the returned data.
+        // solhint-disable-next-line max-line-length
+
+        // solhint-disable-next-line avoid-low-level-calls
+        (bool success, bytes memory returndata) = address(token).call(data);
+        require(success, "SafeERC20: low-level call failed");
+
+        if (returndata.length > 0) {
+            // Return data is optional
+            // solhint-disable-next-line max-line-length
+            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
+        }
+    }
+}