Questions tagged [calldata]

Questions about the "data" part in a transaction, which can be accessed by "msg.data". web3.eth.getTransaction calls this field "input".

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How to get the call graph of a mainchain transaction?

Simple question, but I couldn't find the answer. There are transactions like this one which involve many chained contracts. But as storage modify the functions being called and calldata doesn t ...
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1answer
77 views

What is a function selector?

I am reading an article, it says: To enable deployment on the Ethereum platform, the contract functions are compiled into EVM bytecode and a piece of code called function selector is added, ...
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30 views

member not found or not visible after argument-dependent lookup in mapping

pragma solidity >=0.4.0 <0.7.0; contract New{ mapping(address => string) public users; string name; address[] public userAddress ; //string[] public userNames; ...
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Call Arguments? and Explicit call?

I am trying to understand the arguments of the built-in Solidity's (or EVM's: I am not sure) call function. I know it has 4 arguments. I am trying to understand the call function at: Syntax Error in ...
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Calling private function from external - where are referenced type parameters stored in the end?

Let's assume we have something like: contract C { function externalFunction(uint256[] calldata data) external { privateFunction(data); } function privateFunction(uint256[] memory data)...
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1answer
20 views

pass storage through interface to library

Here is what am i doing: There is a library, accept storage argument as parameter, then do some math and return the result. And there is a contract to call the function in the library, and an extra ...
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2answers
90 views

Unable to make a transaction with Data using Java api ethSendRawTransaction

I am trying to make a transaction between two different accounts using Java. It works perfectly fine as long as I am not using "Data" parameter. My intent is not to call a smart contract but to make ...
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1answer
29 views

Understanding first evm word of reference types in assembly

Given the following function: function getArrayItems(bytes calldata) external returns ( bytes4 _signature, bytes32 _wutIsThis, bytes32 _length, bytes32 _firstItem ) { assembly { ...
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1answer
79 views

can anyone help to explain calldataload

In the Solidity documentation, the definition of calldataload is: calldataload(p) call data starting from position p (32 bytes) But I am really confused by what is call data. Is the call data of ...
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48 views

Proxy contract DELEGATECALL to pass a DYNAMIC array to a function in the target contract

I'm trying to get a Proxy contract to correctly do a delegatecall to a function in another 'target' contract. The problem is, that I need to pass a dynamic array as the parameter to this function. Q: ...
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3answers
108 views

Calldata with too many parameters

While reading https://solidity.readthedocs.io/en/v0.4.21/abi-spec.html#abi I was just thinking what happens when calldata contains more parameters/data than the function expects (I know first ...
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129 views

How to decode Tx data? Online tool?

Is there a fast way to decode the data returning from a Smart Contract call? I know there are github projects with JS libraries to decode this kind of data (such as https://github.com/ConsenSys/abi-...
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255 views

What is Calldata tag needed when a function has a string parameter?

I'm using: pragma solidity ^0.5.0; I have a function as below in my contract: function test(string a) external{ a="apple"; } An error shows up saying I need to add "calldata" to the parameter. ...
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294 views

Get the input data of a transaction with web3j

How can I retrieve transaction details (including the input data) from a txHash using Web3j? I tried the following method: public void buscarHhash(Web3j web3, String txHash) throws IOException { ...
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1answer
583 views

How to access string arguments from calldata in external functions? (0.5.X)

With the introduction of Solc 0.5.X , parameter memory locations for arrays (and strings/bytes) must be made explicit. For external functions, this memory location is required to be specified as ...
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1answer
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calldata keyword as parameter in solidity v0.5.0 function?

What purpose does the "calldata" serve in this parameter _owners? Is it a new keyword? function setup(address[] calldata _owners, uint256 _threshold, address to, bytes calldata data) Taken from ...
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2answers
57 views

Thinking through from traditional DB to ETH

I am looking for a data structure kind of like this: [ "data": { "id": 0, "hash" : "5feceb66ffc86f38d952786c6d696c79c2dbc239dd4e91b46729d73a27fb57e9", "owner" : 0, "status" : "...
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1answer
132 views

How does a contract's constructor work and load input values?

I set up the following contract: pragma solidity ^0.4.25; contract Simplest { uint x; constructor(bool _lucky) public { if (_lucky == true) { x = 7; } else { ...
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197 views

Solidity: msg.data vs bytes

This is a simple contract that has a function input_data(bytes data) and a simple fallback function that passes msg.data to function input_data. contract test_input_data{ address owner; event ...
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1answer
243 views

Call function by using bytesData. (call.value()())

Assume I have two contracts: contract A { function test1() public view returns(bool) { return false; } } contract B { function testCall(address addr, data) public view returns(...
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1answer
347 views

Web3j directly gets string from contract by eth_call

I just have a simple solidity contract: pragma solidity ^0.4.19; contract SampleContract { string value; function SampleContract() public { value = "hello world"; } ...
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93 views

delegatecall for Smart Contract versioning

I've a state variable address public current; which stores the address of the latest updated contract. This value can be modified with a function. Then, I've a function of this kind function ...
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3answers
341 views

How does MetaMask's TRANSACTION DATA work? How to interact with smart contracts by only using MetaMask?

I have this source code pragma solidity ^0.4.21; // Relevant part of the CaptureTheEther contract. contract CaptureTheEther { mapping (address => bytes32) public nicknameOf; function ...
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2answers
321 views

Solidity CALL and DELEGATECALL: messages and data format

I have some questions about Solidity CALL and DELEGATECALL. I have already read some related threads (link), but found no answers to my doubts. 1) Is there any difference in performing a CALL to a ...
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1answer
232 views

Assign metadata to a transaction

How can I append some (extra) data to a transaction that calls a contract method (with given parameters)? The transaction has only one 'data' field which is used to serialize the method call. If I ...
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1answer
406 views

How to send data to smart contract?

I have the variable w1_temp, which i need to send to contract I have the following code: var W1Temp = require('w1temp') var Web3 = require('web3') var web3 = new Web3() web3.setProvider(new web3....
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3answers
103 views

Can I send data to non-contract address?

Metamask allows to attach data to any transaction. What happens if I send some data with some ETH to existing non-contract address? Is that data recorded on the blockchain? Can I read it later?
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1answer
597 views

Contract call from a contract from a contract?

As I understand it, it is possible for a contract to call another contract by using othercontractaddress.call(gas_amount).value(eth amount)(tx data). Or in this case sender -> contract A -> ...
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1answer
337 views

Making call with contract instance vs making call with hashed method ID

As I understand there are two main ways to call a function in another contract. 1.) Using the 4 byte methodID ----> address.call(bytes4(sha3('foo()')) 2.) Using the contract ABI ---> ...
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1answer
245 views

Update dapp after contract transaction is mined

I made a web app that interacts with a smart contract, using truffle unbox webpack. My contract has a variable called sum and 2 functions: one called answer that increments the sum variable after it ...
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1answer
2k views

Decode Etherscan.io Contract Input Data

Reading my input data on etherscan, I see each value as hex values. Which is fine to read the addresses. But I would like to read the amounts [1] && [3] as numbers. Contract Method Function: ...
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2answers
512 views

Is sending some datas in the data field safe?

An airdrop ask to send it 0ETH with 150000 GAS and some datas in DATA field. Is it safe? What could be the aim of this transaction? Thanks.
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3answers
3k views

Decoding contract output of web3 eth call

I have written data to a contract using sendRawTransaction, and am trying to fetch it using web3.eth.call for the function : function checkRecord(uint id, bytes email) constant returns (uint id2, ...
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3k views

What is “data” param of rawTx? How to send ETH by using web3

I want to send eth by using web3 on testnet. Source address is 0xbddf0bf3ac858d7fb8a2bdda55884d61779ba5a9. The destination is 0x8005ceb675d2ff8c989cc95354438b9fab568681. I found the example on web3 ...
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4answers
2k views

How to decode input data from tx using python3?

I am trying to decode input data from token sale transactions. This is one of the transactions I am trying to parse 0xf7b7196ca9eab6e4fb6e7bce81aeb25a4edf04330e57b3c15bece9d260577e2b Which has the ...
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1answer
1k views

Using Ethereum to buy Tezos

I would like to use my Ethereum to buy Tezos. Does anyone know if Coinbase pass transaction data along with the transaction? Thanks.
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1answer
382 views

how to retrieve function call address from deployed contract for usage with MetaMask send + transaction data?

I've deployed a contract into my testrpc network. $ truffle deploy Using network 'development'. Running migration: 1_initial_migration.js Deploying Migrations... Migrations: ...
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1answer
85 views

Use accounts as datastore

I am rather new to Ethereum and I wonder if the following scenario is possible. I want/need to store some data encoded as a JWT in the blockchain and have it (publicly) accessible via an ID. Only the "...
5
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1answer
1k views

How to send a smart token transaction from one account to another account using JSON RPC interface

I would like to send amounts of a created token from one address to another. I would like to use eth_sendTransaction: eth_sendTransaction Creates new message call transaction or a contract creation,...
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2answers
5k views

How do I “Add Data” to a send transaction in Solidity

In myetherwallet, there is an +Advanced: Add Data Section where I can add data to the transaction. How can I add this same data in a transaction I make in Solidity?
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477 views

Call vs Delegate Call call data format

I'm using both call and delegatecall within an assembly block and i've noticed that when issuing a call I need to provide 4 bytes (sig) + any arguments, whereas for delegatecall I need to provide 4 ...
3
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1answer
308 views

How can I call arbitrary function with arbitrary parameters from Solidity?

I am working on a voting library that allows members of a voting-DAO-like organization to vote on arbitrary actions. Security considerations (I know, arbitrary code execution is evil...) and ...
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454 views

abstract way of calling internal function instead of `this.call(callData)`

In Solidity I can call an internal function (inside the same contract that is calling it) the "usual" way: myFunc(); or I can call it via .call, as discussed here or here: callData = bytes4(sha3("...
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5k views

What is msg.data?

Is msg.data equal to {from: addr1, data:something}? How to handle the data 'something'? when execution this code: web3.eth.sendTransaction({from: ..., to: addressOfE, data: something}); how to ...
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1answer
119 views

What is preventing malicious miners stealing data to steal smart contract rewards?

The motivation for this question is roughly along the lines of a puzzle contract -- whoever submits the correct solution to the puzzle gets a reward from the contract. I'm guessing that the 'thing' ...
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184 views

“No data is deployed on the contract address” [duplicate]

Following token tutorial on ethereum.org, get error message No data is deployed on the contract address Forgive me, but I am new to mist. How do I find the "MyAdvancedToken" in Mist?
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345 views

eth_sendTransaction for function with address type parameters

I'm interacting with my local private blockchain created using geth. I'm able to use eth_call, but now I have some problems with eth_sendTransaction. The signature of the function is this: function ...
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2answers
1k views

Generate contract data hex for 'confirm' function on eth multisig wallet

I have an account on a hardware wallet that is an owner of a standard multsig wallet contract. I want to be able to approve a transaction that is originated from a different wallet. If I have access ...
4
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1answer
791 views

How can I decode getData from a contract method call

I'm using myContractInstance.myMethod.getData() to be able to serialize a transaction: // Get the call data, so you can call the contract through some other means var myCallData = myContractInstance....
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2answers
739 views

Can msg.data be used as an identifier?

I'm looking at the multisig wallet implementation here and I see the usage of sha3(msg.data,block.number) being used as an identifier. What exactly is inside the msg.data and why is it unique enough ...