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‎.circleci/config.yml

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version: 2
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jobs:
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build:
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docker:
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- image: circleci/node:10
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steps:
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- checkout
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- restore_cache:
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keys:
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- v1-dependencies-{{ checksum "package.json" }}
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- v1-dependencies-
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- run: yarn
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- save_cache:
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key: v1-dependencies-{{ checksum "package.json" }}
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paths:
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- node_modules
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- run: yarn prettier:check
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- run: yarn compile
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- run: yarn test

‎.gitattributes

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*.sol linguist-language=Solidity

‎.gitignore

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build/
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node_modules/

‎.mocharc.json

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{
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"extension": ["ts"],
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"spec": "./test/**/*.spec.ts",
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"require": "ts-node/register"
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}

‎.prettierrc

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{
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"semi": false,
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"singleQuote": true,
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"printWidth": 120
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}

‎LICENSE

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‎README.md

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# Uniswap v2 Smart Contracts
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[![CircleCI](https://circleci.com/gh/Uniswap/uniswap-v2-oracle-example.svg?style=svg)](https://circleci.com/gh/Uniswap/uniswap-v2-oracle-example)
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## Local Development
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The following assumes the use of `node@^10`.
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### Clone Repository
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```
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git clone https://github.com/Uniswap/uniswap-v2-oracle-example.git
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cd uniswap-v2-oracle-example
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```
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### Install Dependencies
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```
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yarn
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```
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### Compile Contracts and Run Tests
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```
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yarn compile
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yarn test
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```

‎contracts/UniswapV2OracleExample.sol

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pragma solidity 0.5.13;
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import "./interfaces/IUniswapV2OracleExample.sol";
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import "./interfaces/IUniswapV2Factory.sol";
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import "./interfaces/IUniswapV2.sol";
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import "./libraries/SafeMath.sol";
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import "./libraries/Math.sol";
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import "./libraries/UQ128x128.sol";
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contract UniswapV2OracleExample is IUniswapV2OracleExample {
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using SafeMath for uint;
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using UQ128x128 for uint;
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address public exchangeAddress;
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uint private priceCumulative0;
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uint private priceCumulative1;
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uint64 private priceCumulative0Overflow;
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uint64 private priceCumulative1Overflow;
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uint64 private blockNumber;
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uint64 private blockTimestamp;
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uint public price0;
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uint public price1;
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uint constant public period = 24 hours;
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constructor(address factory, address tokenA, address tokenB) public {
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exchangeAddress = IUniswapV2Factory(factory).getExchange(tokenA, tokenB);
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}
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function quote0(uint128 amount0) public view returns (uint amount1) {
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amount1 = UQ128x128.decode(price1.qmul(amount0));
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}
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function quote1(uint128 amount1) public view returns (uint amount0) {
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amount0 = UQ128x128.decode(price0.qmul(amount1));
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}
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function initialize() public {
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require(blockNumber == 0, "UniswapV2Oracle: ALREADY_INITIALIZED");
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IUniswapV2 uniswap = IUniswapV2(exchangeAddress);
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if (block.number > uniswap.blockNumber()) uniswap.sync();
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priceCumulative0 = uniswap.priceCumulative0();
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priceCumulative1 = uniswap.priceCumulative1();
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priceCumulative0Overflow = uniswap.priceCumulative0Overflow();
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priceCumulative1Overflow = uniswap.priceCumulative1Overflow();
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blockNumber = uint64(block.number);
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// don't set blockTimestamp so that the first call to update sets the price without time discounting
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}
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function update() public {
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require(blockNumber != 0, "UniswapV2Oracle: NOT_INITIALIZED");
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IUniswapV2 uniswap = IUniswapV2(exchangeAddress);
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if (block.number > uniswap.blockNumber()) uniswap.sync();
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uint priceCumulative0New = uniswap.priceCumulative0();
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uint priceCumulative0NewOverflow = uniswap.priceCumulative0Overflow();
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uint priceCumulative1New = uniswap.priceCumulative1();
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uint priceCumulative1NewOverflow = uniswap.priceCumulative1Overflow();
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(uint priceCumulative0Delta, uint priceCumulative0DeltaOverflow) = Math.sub512(
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priceCumulative0New,
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priceCumulative0NewOverflow,
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priceCumulative0,
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priceCumulative0Overflow
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);
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(uint priceCumulative1Delta, uint priceCumulative1DeltaOverflow) = Math.sub512(
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priceCumulative1New,
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priceCumulative1NewOverflow,
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priceCumulative1,
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priceCumulative1Overflow
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);
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// fail on overflow
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require(priceCumulative0DeltaOverflow == 0 && priceCumulative1DeltaOverflow == 0, "UniswapV2Oracle: OVERFLOW");
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uint blocksElapsed = block.number - blockNumber;
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uint price0New = priceCumulative0Delta / blocksElapsed;
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uint price1New = priceCumulative1Delta / blocksElapsed;
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uint secondsElapsed = block.timestamp - blockTimestamp; // solium-disable-line security/no-block-members
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if (secondsElapsed < period) {
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price0 = (price0.mul(period.sub(secondsElapsed)).add(price0New.mul(secondsElapsed))) / period;
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price1 = (price1.mul(period.sub(secondsElapsed)).add(price1New.mul(secondsElapsed))) / period;
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} else {
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price0 = price0New;
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price1 = price1New;
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}
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priceCumulative0 = priceCumulative0New;
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priceCumulative1 = priceCumulative1New;
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priceCumulative0Overflow = uint64(priceCumulative0NewOverflow);
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priceCumulative1Overflow = uint64(priceCumulative1NewOverflow);
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blockNumber = uint64(block.number);
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blockTimestamp = uint64(block.timestamp); // solium-disable-line security/no-block-members
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}
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}

‎contracts/interfaces/IUniswapV2.sol

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pragma solidity 0.5.13;
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interface IUniswapV2 {
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event LiquidityMinted(
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address indexed sender,
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address indexed recipient,
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uint amount0,
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uint amount1,
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uint128 reserve0,
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uint128 reserve1,
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uint liquidity
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);
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event LiquidityBurned(
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address indexed sender,
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address indexed recipient,
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uint amount0,
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uint amount1,
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uint128 reserve0,
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uint128 reserve1,
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uint liquidity
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);
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event Swap(
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address indexed sender,
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address indexed recipient,
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uint amount0,
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uint amount1,
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uint128 reserve0,
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uint128 reserve1,
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address input
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);
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function factory() external view returns (address);
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function token0() external view returns (address);
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function token1() external view returns (address);
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function reserve0() external view returns (uint128);
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function reserve1() external view returns (uint128);
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function priceCumulative0() external view returns (uint);
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function priceCumulative1() external view returns (uint);
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function priceCumulative0Overflow() external view returns (uint64);
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function priceCumulative1Overflow() external view returns (uint64);
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function blockNumber() external view returns (uint64);
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function getInputPrice(uint inputAmount, uint inputReserve, uint outputReserve) external pure returns (uint);
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function mintLiquidity(address recipient) external returns (uint liquidity);
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function burnLiquidity(address recipient) external returns (uint amount0, uint amount1);
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function swap0(address recipient) external returns (uint amount1);
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function swap1(address recipient) external returns (uint amount0);
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function sync() external;
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}

‎contracts/interfaces/IUniswapV2Factory.sol

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pragma solidity 0.5.13;
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interface IUniswapV2Factory {
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event ExchangeCreated(address indexed token0, address indexed token1, address exchange, uint256 exchangeNumber);
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function exchangeBytecode() external view returns (bytes memory);
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function sortTokens(address tokenA, address tokenB) external pure returns (address, address);
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function getExchange(address tokenA, address tokenB) external view returns (address);
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function getTokens(address exchange) external view returns (address, address);
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function exchanges(uint) external view returns (address);
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function exchangesCount() external view returns (uint);
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function createExchange(address tokenA, address tokenB) external returns (address exchange);
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}

‎contracts/interfaces/IUniswapV2OracleExample.sol

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pragma solidity 0.5.13;
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interface IUniswapV2OracleExample {
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function exchangeAddress() external returns (address);
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function price0() external returns (uint);
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function price1() external returns (uint);
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function period() external returns (uint);
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function quote0(uint128 amount0) external view returns (uint amount1);
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function quote1(uint128 amount1) external view returns (uint amount0);
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function initialize() external;
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function update() external;
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}

‎contracts/libraries/Math.sol

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pragma solidity 0.5.13;
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library Math {
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function sub512(uint x0, uint x1, uint y0, uint y1) internal pure returns (uint z0, uint z1) {
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assembly { // solium-disable-line security/no-inline-assembly
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z0 := sub(x0, y0)
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z1 := sub(sub(x1, y1), lt(x0, y0))
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}
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}
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}

‎contracts/libraries/SafeMath.sol

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pragma solidity 0.5.13;
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library SafeMath {
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function add(uint x, uint y) internal pure returns (uint z) {
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require((z = x + y) >= x, "ds-math-add-overflow");
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}
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function sub(uint x, uint y) internal pure returns (uint z) {
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require((z = x - y) <= x, "ds-math-sub-underflow");
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}
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function mul(uint x, uint y) internal pure returns (uint z) {
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require(y == 0 || (z = x * y) / y == x, "ds-math-mul-overflow");
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}
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}

‎contracts/libraries/UQ128x128.sol

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pragma solidity 0.5.13;
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library UQ128x128 {
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uint constant Q128 = 2**128;
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function qmul(uint x, uint128 y) internal pure returns (uint z) {
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z = x * y;
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}
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function decode(uint y) internal pure returns (uint128 z) {
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return uint128(y / Q128);
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}
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}

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