如何计算RSK上代币的总交易量？

你可以得到过去的日志

• 来自合约部署时的区块




• 直到当前块




• 由代币合约地址发出




• topics[0]事件签名的 keccak256在哪里

  在Transfer(address,address,uint256)事件的情况下，keccak256 哈希是0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef

由于事件的前两个参数被索引，它们出现在每个事件日志的topics[1]（发送者）和topics[2]（接收者）字段中。第三个参数（数量）未编入索引，因此其值位于data每个事件日志的字段中（以十六进制数表示）。

总交易量只是所有转移金额的总和（来自data现场）。

请注意，大多数 RPC 提供商只允许访问有限数量的历史块（例如最多 100 个块）。因此，您可能必须使用不同的提供商或您自己的完整节点才能访问更深的历史记录（例如 200 个区块）。

tl;dr= (1)web3.eth.Contract为 RDOC 部署地址初始化一个实例；然后 (2) call .getPastEvents('Transfer')，然后 (3) 聚合Transfer.value值的总和。

详细解答：

(1) 初始化合约实例

有一个 RPC 数据提供程序

GetBlock

，您可能认为它类似于支持 RSK的 Infura

。

为了查询大量数据，例如历史数据，Websockets 可以比 HTTP 更快/更高效，所以让我们使用他们的 Websockets RPC 端点来访问 RSK 主网：

wss://rsk.getblock.io/mainnet/websocket

// init web3 instance
const GETBLOCK_API_KEY = /* copy the API key from GetBlock dashboard */;
const rpcWebsocketsUrl =
`wss://rsk.getblock.io/mainnet/websocket`;
const rpcWebsocketsOptiOns= {
timeout: 5000, // ms
headers: {
'x-api-key': GETBLOCK_API_KEY,
},
};
const web3Provider = new Web3.providers.WebsocketProvider(
rpcWebsocketsUrl,
rpcWebsocketsOptions,
);
const web3 = new Web3(web3Provider);


一旦我们准备好 web3 实例，我们需要一个 ABI 和令牌智能合约的部署地址：

// init token contract instance
const tokenAbi = require('./abi.json'); // any standard ERC20 ABI will suffice for this purpose
const tokenAddress = '0x2d919f19d4892381d58edebeca66d5642cef1a1f'; // RDOC deployed address
const token = new web3.eth.Contract(tokenAbi, tokenAddress);


(2) 获取过去的Transfer事件

根据 ERC20 规范，每次在一个账户和另一个账户之间转移一定数量的代币时，ERC20 智能合约应该发出一个Transfer事件。此事件包含 3 个参数：

• 发件人地址，


• 收件人地址，


• 和金额。

（我们在这里只关心我们目标的数量）

In web3.js, to get past events, you should specify the range of block numbers,

and then query the past events using .getPastEvents().

Assuming we want to calculate the total transaction volume

of RDOC in the past week, we can use the total number of seconds in a week

divided by the number of seconds per block.

7 * (24 * 60 * 60) / 30 = 20160

Note that as with other blockchains, the time per block is approximate,

therefore this gives us the number of blocks in approximately 1 week.

The exact number of blocks can also be calculated by inspecting block timestamps

// get the range of blocks to query
const rangeNumberOfBlocks = 20160;
const latestBlockNumber = await web3.eth.getBlockNumber().toNumber();
const blockRange = {
fromBlock: latestBlockNumber - rangeNumberOfBlocks,
toBlock: latestBlockNumber,
};


Now we can query past events:

// get past `Transfer` events
const events = await token.getPastEvents(
'Transfer',
blockRange,
);


(3) calculate the aggregate

Each event in the events array contains the three event parameters,

as per the ERC20 specification, however, we are only interested in event.returnValues.value.

Note that this is returned as a BN (BigNumber),

and for good reason - it is a uint256, which is too large for Javascript's built in Number type.

Also note that this number has a certain number of decimal places that it should be divided by, also specified in the ERC20 specification.

// prepare for division for decimal places
const decimals = await token.methods.decimals().call();
const decimalsExp = new web3.utils.BN(10).pow(new web3.utils.BN(decimals));


For most tokens, including RDOC, we expect decimalsExp to be 1e18 (1000000000000000000).

Finally, we can loop over the events, and calculate the aggregate value.

Below I'm using .iadd() instead of .add() so that the addition can occur in-place,

so as to avoid reassignment/ memory allocation overhead (but this is optional).

const sum = new web3.utils.BN(0);
for (let eventIdx = 0; eventIdx const event = events[eventIdx];
sum.iadd(
new web3.utils.BN(event.returnValues.value),
);
}
const displaySum = sum.div(decimalsExp).toString();


displaySum should be the total amount of transacted RDOC for the selected time period.