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".
76
questions
0
votes
0answers
21 views
Call Type Explained [duplicate]
I have yet to come across a well explained definition of all the call types in one place.
* One of call
* Callcode
* Delegatecall
* Staticcall
Would be very grateful if someone could explain the ...
1
vote
1answer
58 views
What data is in 'calldataload'?
I want to parse event logs that are generated by the contract shown below, which assigns different sections of calldataload to the 4 Topics, and the Data section, of the event logs.
Topic 0 receives ...
5
votes
1answer
145 views
When should I use calldata and when should I use memory?
I have seen people use both memory and calldata keywords when writing Solidity. Specifically, they are used when declaring function parameters.
When should I use memory and when should I use calldata?...
0
votes
1answer
26 views
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 ...
4
votes
1answer
233 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, ...
0
votes
1answer
160 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;
...
0
votes
0answers
25 views
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 ...
1
vote
0answers
20 views
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)...
0
votes
1answer
35 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 ...
0
votes
2answers
160 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 ...
2
votes
1answer
42 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 {
...
4
votes
1answer
167 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 ...
1
vote
0answers
78 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: ...
1
vote
3answers
164 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 ...
1
vote
0answers
168 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-...
asked Jan 23 '19 at 9:28
Juan Ignacio Pérez Sacristán
2,7333 gold badges24 silver badges57 bronze badges
0
votes
1answer
504 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. ...
1
vote
1answer
461 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 {
...
1
vote
1answer
830 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 ...
5
votes
1answer
3k views
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 ...
1
vote
2answers
63 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" : "...
1
vote
2answers
423 views
How calldata is stored in memory?
When I execute this:
bytes8 h = 0x000008dfe2f440000733c;
t.call.gas(0x7e0b0)(bytes4(keccak256("enter(bytes8)")),0x8dfe2f440000733c0000000,h);
the calldata is :
0: ...
2
votes
1answer
198 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 {
...
0
votes
1answer
286 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 ...
2
votes
1answer
286 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(...
0
votes
1answer
556 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";
}
...
4
votes
2answers
1k views
What is calldata?
What is calldata? I learned that there are three types of memories:
Storage
Memory
Stack
In the Ethereum docs, it says that the function parameters are of type memory by default.
However, I've also ...
1
vote
0answers
100 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 ...
2
votes
3answers
478 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 ...
3
votes
2answers
355 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 ...
2
votes
1answer
287 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 ...
1
vote
1answer
577 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....
2
votes
3answers
119 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?
1
vote
1answer
640 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 -> ...
6
votes
1answer
390 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 ---> ...
0
votes
1answer
258 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 ...
4
votes
1answer
3k 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: ...
6
votes
2answers
556 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.
1
vote
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, ...
4
votes
2answers
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 ...
5
votes
4answers
3k 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 ...
0
votes
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.
1
vote
1answer
397 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: ...
0
votes
1answer
87 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
votes
1answer
2k 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,...
3
votes
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?
2
votes
0answers
497 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
votes
1answer
338 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 ...
asked May 4 '17 at 11:35
Validity Labs - Sebastian
6,9782 gold badges27 silver badges58 bronze badges
1
vote
0answers
493 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("...
asked May 1 '17 at 16:11
Validity Labs - Sebastian
6,9782 gold badges27 silver badges58 bronze badges
13
votes
2answers
6k 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 ...
1
vote
1answer
122 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' ...
