Questions tagged [storage]
all questions regarding data and storage on the ethereum blockchain
404
questions
0
votes
0answers
12 views
Clarification on how Calldata persists on the blockchain and how Optimistic Rollups use it
So I see that a lot of optimistic rollup solutions say that they store the chain's transaction data on Ethereum via "calldata" which is way cheaper in gas costs than contract storage (I ...
0
votes
0answers
15 views
Storing Struct inside an array. Help Please
I am designing an EHR System that will store patient records (with a unique ID) and separated by the date and Hospital entered. I am able to enter data in Hospital struct mapping to the Record struct, ...
0
votes
0answers
21 views
Making sure a string (input/output) is less then 64 characters
I'm working though some basic solidity tutorials using remix. I'm having trouble with the concept that there is no way to edit a string built into the language. In other programing languages I would ...
0
votes
1answer
81 views
How to get data location for string > 31 length
The documentation says:
bytes and string are encoded identically. For byte arrays that store
data which is 32 or more bytes long, the main slot stores length * 2 +
1 and the data is stored as usual ...
0
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0answers
15 views
Performance of Dapps when millions of records to be fetched
I am thinking of Dapp with react js and ethereum. Using IPFS for data storage. Let's assume that blockchain holds millions of hash addresses from IPFS.
I need to show those millions of records and ...
0
votes
0answers
17 views
Type struct Mycontract.User memory is not implicitly convertible to expected type struct Mycontract.User storage pointer
pragma solidity >=0.5.0 <0.7.0;
contract Mycontract{
uint256 a;
struct User
{ string name; }
User[] users;
function foo() public{
**User storage user=User("hey&...
0
votes
1answer
28 views
The below code gets compiled but when foo is called invalid opcode error is thrown
pragma solidity >=0.5.0 <0.7.0;
contract Mycontract{
uint256 a;
struct User
{ string name; }
User[] users;
function foo() public{
User storage user=users[0];
...
0
votes
1answer
42 views
Ethereum Smartcontracts with YottaChain
I am very much curious about this new storage system YottaChain.
Can someone point me good articles/videos/sources as a reference to go through and understand its implementation with ethereum smart-...
0
votes
1answer
25 views
why x(function setArr) is not being returned?
pragma solidity >=0.5.0 <0.7.0;
contract Example{
uint256[3] x;
function setArr(uint256[3] memory y) public returns(uint256[3] memory){
x=y;
return getArr(x);
}
...
0
votes
1answer
18 views
Understanding data location
pragma solidity ^0.5.16;
contract mycontract{
uint256 public a;
function foo(string calldata _name) external {
string memory names;
names = _name;
getname(names);
...
0
votes
1answer
18 views
DeclarationError: Uninitialized storage pointer. Struct error when running truffle tests
I've seen other similar questions but they don't explain why this error happens and/or they are case specific questions. So, I have this code:
pragma solidity >=0.4.22 <0.7.0;
contract ...
1
vote
1answer
32 views
DApp Development- how to update dapp and keep existing data
Compare to web application that separate the application and database, we can update the application and keep the existing data.
Could you suggest me how to update dapp and keep the existing data?
0
votes
1answer
27 views
Issue with dynamic matrices in solidity
I have a matrix in solidity like that
string x[][]
I'm trying to write functions to return rows and colums
The following code works well:
// SPDX-License-Identifier: unlicensed
pragma solidity ^0.6.0;
...
0
votes
1answer
20 views
When using mapping, why use an address over bytes32?
From an end user standpoint, they will never want to use the address for searching for mapped data when they could just submit a username for function parameters, so is there any specific reason why ...
0
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0answers
12 views
Data storage : mapping vs sub contract deployment
I read over few website, tutorials and answered question here on SE. There is a huge warning about deploying new contract just to store datas.
i.e. :
bad
uint256 public amount;
bool public isAdmin;...
0
votes
1answer
27 views
Passing storage of one library to another library
I have two libraries: A and B as well as contract C using them.
Library B, in one of its functions, needs to call a couple of functions defined for A.Storage.
The code below compiles, tests are ...
0
votes
0answers
34 views
Storing data directly on chain
Im trying to store data directly on the blockchain, not on a smartcountract as they have a limit of what they can handle and it would slow down the chain to go above the limit.
My initial plan is to ...
0
votes
1answer
38 views
Mapping didn't storing unique values
I wrote this piece of code with the goal to store unique documents hash. Used mapping to accomplished that.
pragma solidity ^0.5.16;
contract DocumentHash{
string public documentHash;
...
0
votes
1answer
41 views
How does Smart-contract's storage works?
I keep hearing that for each contract there is a storage as contiguous array (to have constant O(1) lookup) with 2^256 slots, 32 byte each, available. But it cannot physically be true. How is it ...
0
votes
1answer
45 views
How can I make an off-chain call to get the data stored at a specific storage slot on-chain? [duplicate]
I want to get data from on-chain that is not explicitly available through a getter. For example, if I know that there is data at position ...
0
votes
1answer
64 views
Nested Structs with Mappings Inside
I have the following code:
// SPDX-License-Identifier: MIT
pragma solidity >=0.4.22 <0.7.0;
pragma experimental ABIEncoderV2;
contract VenueRegistry{
struct Queue{
uint head;
...
0
votes
0answers
31 views
ERC20 balance Storage Address key - how to tell which key belongs to which wallet address
I am trying to derive changes of account storage by mapping accounts (here, the accounts represent the key address in the ERC20 balances mapping mapping(address => uint256)) to their corresponding ...
0
votes
1answer
16 views
Is data copied or referenced from local storage to global storage?
For example, when a struct is initialised to storage in a function, then assigned to a global state variable such as an array or mapping type, does the local struct get copied to the global state ...
0
votes
1answer
44 views
When and where do I set ERC721 tokens' data?
I am currently working on a smart contract to sell ERC721 tokens. I understand that my code should have a function that allows me (the owner) to mint a token and add it to a list which stores all the ...
1
vote
1answer
22 views
Is transaction history available as a part of the blockchain implementation, or do I have to implement saving token history myself
I am implementing a CryptoKitties style of ERC721 tokens, to be deployed on Ethereum. But I am not clear how to implement the transaction history of the individual token?
For example all the ...
0
votes
0answers
19 views
Smart Contact to store data from XLS/CSV file
Is there any existing code/work on how to store data written in an XLS file into Ethereum (geth) using a smart contract? I am trying to publish data that is written in an XLS file onto the Ethereum ...
0
votes
0answers
14 views
How to save/read mappings within struct?
I am trying to create a mapping inside struct and then create a mapping of the struct. Take a look at below example:
// ------------------------------------------------------------------------
...
1
vote
1answer
31 views
Is it cheaper overall to store a keccak hash or to store a ripemd(keccak) hash?
As titled. I'm learning to build a DApp and I'm wondering if it's worth it to add the extra RIPEMD layer over keccak for a shorter hash to reduce storage costs.
3
votes
2answers
26 views
Set and delete storage variable in same tx
I did some poking around and didn't see an answer... and I figure someone knows this off the top of their head.
Question: what is the gas cost associated with setting and deleting a storage variable ...
0
votes
0answers
22 views
How do I determine the data storage structure that corresponds to a specific storage address?
My goal is to understand the details of the 1st bZx exploit. I am using the State Changes section of Etherscan to help me accomplish this. Some state changes affect the storage of certain data ...
1
vote
0answers
25 views
Why Does Ethereum Not Support A Native (Non Smart Contract) Form Of Multi-Sig? [duplicate]
After becoming a victim of exchange fraud and witnessing how it negatively impacted the lives of hundreds of others, I'm currently undergoing a study of all the past cryptocurrency exchange hack/fraud ...
1
vote
3answers
116 views
Can the mapping storage change after contract deployment?
I am beginner in mapping.I work on Truffle and Ganache. I deploy the following contract:
pragma solidity ^0.5.12;
contract customerFinder{
mapping(uint256 => address payable) public ...
0
votes
1answer
112 views
Searching for a value in a dynamic array
I understand that for loops on dynamic arrays are a big no no in Solidity, so I am trying to find an alternative to this problem.
Goal:
From a dynamic array of numbers, I am trying to extract the ...
3
votes
2answers
115 views
Map or Array…?
I'm having a huge dilemma! I'm developping a smart contract that has, let's say Struct A and Struct B. Because I want to have a function retrieving all objects type A and B, I created a Struct All ...
2
votes
1answer
32 views
Whats the best way of translating this struct?
Let's say I must have this data structure:
āāā Operations (struct)
ā āāā date_begining (uint)
ā āāā date_end (uint)
ā āāā responsible (address)
ā āāā type **(?)**
ā āāā Observation (...
0
votes
2answers
79 views
Costs of storing an empty dynamic array of length 2**256-1 vs length 4
If the array is completely empty, is it more expensive to store uint[] of length 2**256-1 vs of length 4?
0
votes
0answers
19 views
Where's a contract storage stored exactly and how does it interact with the blockchain? [duplicate]
From what I've understood a contract is a special account that gets initialized with a 256 bit array and this array is stored as the root hash of a merkle tree, is that correct?
But where is this ...
0
votes
1answer
43 views
Is it possible to set a struct property as undefined or null?
In JavaScript we're able to have:
Object {
a: number;
b?: string;
c: number;
d?: string;
}
b and d being optional, these can be left out during variable initialisation. Is this possible in ...
0
votes
1answer
89 views
Read and write products using solidity
I am new to Solidity, trying to store a product in the purchaser wallet and retrieve the information from the owner wallet. I have some ideas but didn't know which one will be best.
To store an ...
1
vote
1answer
34 views
Fire transaction from contract
I have a contract holding a mapping like this: mapping (address => User) users. How can I get the contract to automatically fire a transaction/event when a certain condition is met? For example, ...
0
votes
1answer
87 views
How to properly initialize nested storage array/struct?
contract Contract {
struct A {
int a;
}
struct B {
A[] as;
}
mapping(address => B[]) bs;
function addB(B memory b) {
bs[msg.sender].push(...???...);
}
}
I have nested hell of arrays and ...
0
votes
1answer
32 views
How data is stored in Ethereum blockchain?
If I become a full node in Ethereum and retrieve the current state, how all this data is going to be stored in my physical drive?
0
votes
0answers
155 views
Efficient way to save and retrieve hash in blockchain
I am learning Ethereum using Geth. I have a private blockchain and I am saving hashes through a REST API (python web service). I have readed I can save hash values using maps (mapping data type) and ...
0
votes
1answer
35 views
Storing name values off-chain in events and web3.js
Somewhere I read the advice to store name (title, geographical name, people name, etc.) value off-chain in events.
But if a value is stored in an event, is there an efficient way to retrieve its ...
1
vote
1answer
220 views
Storing multiple values in one key mapping (Solidity)
Can I store multiple values in one key mapping in solidity? like I can retrieve all of the values if I use that one mapping key? Is this possible?
0
votes
0answers
46 views
Safe usage of delegatecall
Hey guys I have a few questions about delegatecall.
The setup:
I have 2 contracts A and B.
A has 2 uint state variables
B has 4 uint state variables
To ensure storage layout compatibility, B ...
0
votes
1answer
16 views
A smart contract's storage problem , further ERC ļ¼
Er .. I have a question about smart contract , a single smart contract's storage capacity
Follow the answer is this questionļ¼
Is there a (theoretical) limit for amount of data that a contract can ...
0
votes
4answers
125 views
Mutating slot 0 of a storage array in Solidity assembly
Have been working on a function allow users to edit specific types of state using Solidity assembly, and ran into some unexpected behavior.
According to the documentation, for a storage array arr ...
1
vote
1answer
24 views
arrays and structs for function arguments
A lot of contracts and libraries with functions that use arrays and structs for arguments. Structs can themselves include arrays, structs and mappings. For example:
function doSomething(MyStruct ...
0
votes
1answer
28 views
Can you have an array of mappings? The mappings have an address key and a struct value
Can you have an array of mappings?
I want to have mappings with addresses as keys and structs as the value.
I want to store these addresses in an array and iterate through them.
so far it looks like ...
