Sample code
pragma solidity 0.6.0;
contract GetPrice {
using SafeMath for uint256;
using SafeERC20 for ERC20;
// Vote Contract
VoteFactory _voteFactory;
event price(uint256 ethAmount, uint256 tokenAmount, uint256 blockNum, uint256 ethMultiple, uint256 tokenForEth);
event averagePrice(uint256 price);
/**
* @dev Initial
* @param voteFactory bsc mainnet: 0x494a300589ff35C2678fA2D3F3599D4f0651E1F4
*/
constructor (address voteFactory) public {
_voteFactory = VoteFactory(address(voteFactory));
}
/**
* @dev Get a single price
* @param token Token address of the price
*/
function getSinglePrice(address token) public payable {
// In consideration of future upgrades, the possibility of upgrading the price contract is not ruled out,
// and the voting contract must be used to query the price contract address.
OfferPrice _offerPrice = OfferPrice(address(_voteFactory.checkAddress("OfferPrice")));
// Request the latest price, return the eth quantity, token quantity, and effective price block number. For free now.
(uint256 ethAmount, uint256 tokenAmount, uint256 blockNum) = _offerPrice.updateAndCheckPriceNow.value(msg.value)(token);
uint256 ethMultiple = ethAmount.div(1 ether);
uint256 tokenForEth = 0;
if(ethMultiple > 0) {
ethMultiple = tokenAmount.div(ethMultiple);
}
// If the eth paid for the price is left, it needs to be processed.
// ........
emit price(ethAmount, tokenAmount, blockNum, ethMultiple, tokenForEth);
}
/**
* @dev Get multiple prices
* @param token The token address of the price
* @param priceNum Get the number of prices, sorted from the latest price
*/
function getBatchPrice(address token, uint256 priceNum) public payable {
// In consideration of future upgrades, the possibility of upgrading the price contract is not ruled out
// , and the voting contract must be used to query the price contract address.
OfferPrice _offerPrice = OfferPrice(address(_voteFactory.checkAddress("OfferPrice")));
/**
* The returned array is an integer multiple of 3, 3 data is a price data.
* Corresponding respectively, eth quantity, token quantity, effective price block number.
*/
uint256[] memory priceData = _offerPrice.updateAndCheckPriceList.value(msg.value)(token, priceNum);
// Data processing
uint256 allTokenForEth = 0;
uint256 priceDataNum = priceData.length.div(3);
for (uint256 i = 0; i < priceData.length; i += 3) {
uint256 ethMultiple = priceData[i].div(1 ether);
if(ethMultiple > 0) {
uint256 tokenForEth = priceData[i.add(1)].div(ethMultiple);
tokenForEth = priceData[i.add(1)].div(ethMultiple);
allTokenForEth = allTokenForEth.add(tokenForEth);
}
}
// Average price
uint256 calculationPrice = allTokenForEth.div(priceDataNum);
// If the eth paid for the price is left, it needs to be processed.
// ........
emit averagePrice(calculationPrice);
}
/**
* @dev Activate
* @param spxAddress SPXToken address
* @param spxAmount
*/
function activation(address spxAddress, uint256 spxAmount) public {
// In consideration of future upgrades, the possibility of upgrading the price contract is not ruled out,
// and the voting contract must be used to query the price contract address.
OfferPrice _offerPrice = OfferPrice(address(_voteFactory.checkAddress("OfferPrice")));
// Authorize SPX to price contract, tentative quantity is free
ERC20(spxAddress).safeApprove(address(_offerPrice), spxAmount);
// Activate
_offerPrice.activation();
}
// reveive eth method
receive() external payable {
}
}
// Vote Contract
interface VoteFactory {
// querry address
function checkAddress(string calldata name) external view returns (address contractAddress);
}
// Price Conctract
interface OfferPrice {
// Activate the use of price contracts
function activation() external;
// Update and check the latest price
function updateAndCheckPriceNow(address tokenAddress) external payable returns(uint256 ethAmount, uint256 erc20Amount, uint256 blockNum);
// Update and view the effective price list
function updateAndCheckPriceList(address tokenAddress, uint256 num) external payable returns (uint256[] memory);
}
library SafeERC20 {
using SafeMath for uint256;
using Address for address;
function safeTransfer(ERC20 token, address to, uint256 value) internal {
callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
}
function safeTransferFrom(ERC20 token, address from, address to, uint256 value) internal {
callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
}
function safeApprove(ERC20 token, address spender, uint256 value) internal {
require((value == 0) || (token.allowance(address(this), spender) == 0),
"SafeERC20: approve from non-zero to non-zero allowance"
);
callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
}
function safeIncreaseAllowance(ERC20 token, address spender, uint256 value) internal {
uint256 newAllowance = token.allowance(address(this), spender).add(value);
callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
}
function safeDecreaseAllowance(ERC20 token, address spender, uint256 value) internal {
uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
}
function callOptionalReturn(ERC20 token, bytes memory data) private {
require(address(token).isContract(), "SafeERC20: call to non-contract");
(bool success, bytes memory returndata) = address(token).call(data);
require(success, "SafeERC20: low-level call failed");
if (returndata.length > 0) {
require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
}
}
}
interface ERC20 {
function totalSupply() external view returns (uint256);
function balanceOf(address account) external view returns (uint256);
function transfer(address recipient, uint256 amount) external returns (bool);
function allowance(address owner, address spender) external view returns (uint256);
function approve(address spender, uint256 amount) external returns (bool);
function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
event Transfer(address indexed from, address indexed to, uint256 value);
event Approval(address indexed owner, address indexed spender, uint256 value);
}
library SafeMath {
function add(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 c = a + b;
require(c >= a, "SafeMath: addition overflow");
return c;
}
function sub(uint256 a, uint256 b) internal pure returns (uint256) {
return sub(a, b, "SafeMath: subtraction overflow");
}
function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
require(b <= a, errorMessage);
uint256 c = a - b;
return c;
}
function mul(uint256 a, uint256 b) internal pure returns (uint256) {
if (a == 0) {
return 0;
}
uint256 c = a * b;
require(c / a == b, "SafeMath: multiplication overflow");
return c;
}
function div(uint256 a, uint256 b) internal pure returns (uint256) {
return div(a, b, "SafeMath: division by zero");
}
function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
require(b > 0, errorMessage);
uint256 c = a / b;
return c;
}
function mod(uint256 a, uint256 b) internal pure returns (uint256) {
return mod(a, b, "SafeMath: modulo by zero");
}
function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
require(b != 0, errorMessage);
return a % b;
}
}
library Address {
function isContract(address account) internal view returns (bool) {
bytes32 codehash;
bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
assembly { codehash := extcodehash(account) }
return (codehash != accountHash && codehash != 0x0);
}
function sendValue(address payable recipient, uint256 amount) internal {
require(address(this).balance >= amount, "Address: insufficient balance");
(bool success, ) = recipient.call.value(amount)("");
require(success, "Address: unable to send value, recipient may have reverted");
}
}