Questions tagged [storage]
all questions regarding data and storage on the ethereum blockchain
350
questions
0
votes
1answer
13 views
Modify the state using returned variable (Array.push)
In my contact I want to have one place where I find an existing object(struct) and then use it in multiple places to read and modify it - but seems like it's not possible?
contract A
{
struct ...
0
votes
2answers
20 views
Set contract storage directly at deployment
Is there a way to pre-define a contracts storage when deploying it?
Say I want a mapping to be filled with 1000 entries but want to avoid having to pay gas for adding every entry on its own.
Since ...
1
vote
1answer
31 views
How to download the blockchain of a single ethereum contract’s address?
The blockchain required to run ethereum is several Terabytes large. This means more than 9 years would be required to download it with my connection speed.
In my case, I just want to know if the ...
0
votes
1answer
11 views
Does packing bools alongside addresses reduce storage costs?
Say I have a struct like this:
struct MyStruct {
bool foo;
uint256 bar;
uint256 baz;
address qux;
}
If I rewrite it like this:
struct MyStruct {
bool foo;
address qux;
...
0
votes
0answers
11 views
How to find which transaction cleared a specific address into a specific contract?
I have a contract with contains the following solidity code
mapping (address => mapping (bytes32)) public sealedBids;
But I failed to find in the solidity code which part can clear it.
As result,...
0
votes
1answer
34 views
How to save data using multiple structures and arrays in solidity?
How can i use multiple arrays please?
e.g: I have this contract:
pragma solidity >=0.4.21 <0.6.0;
contract SessionManagement {
struct ChargeProfileSegment{
uint startDateTimeSeg;...
0
votes
2answers
34 views
Decentralized database for ethereum?
I'm looking for a way to store data in a decentralized way such that I can access any record from within the smart contract, probably through oracles I guess?
I've been looking into gundb but not ...
0
votes
2answers
45 views
Why is storing via sstore more expensive than via events mechanism?
I just do not understand why emit Event(...) is cheaper than a = b. The only difference I noted between events and storage variables is that event logs is not accessible from Solidity. But both of ...
0
votes
1answer
98 views
Is it possible to insert some custom data in the DATA field of an Ethereum Transaction?
i am working on trying to get some data encoded/inserted into an ethereum transaction.
Let me describe my environment first, i am using Web3py, Ganache and Remix IDE. I am able to successfully ...
-1
votes
2answers
86 views
Truffle uint test script not updating storage variable, and strange behaviour
while testing I got a strange behavior of truffle, please see the subject smart contract code first
uint256 public burningRatePercent = 50;
function onlyOwnerSetBurningRate(uint256 ...
0
votes
1answer
22 views
Mappings inside functions to filter query
I have a struct and several boolean mappings that are used to keep track of struct's properties
struct Animal {
string species;
bytes32 ID;
}
mapping (bytes32 => Animal) public Animals;
...
0
votes
1answer
32 views
Return an array of structs using events?
I wan’t my function to spit out an array of structs. I know this is not straightforwardly possible. What is the best way for me to proceed? Should I loop through my array in my function and trigger ...
1
vote
0answers
10 views
What are the rules on persisting old transactions?
If a new node joins the network and attempts a full sync, it requires all transaction information from genesis to build up its chain state. To do this the transactions it receives must be the ...
1
vote
1answer
26 views
What is the benefit of leaving data in the stroage area instead of the log?
I did not write English well and used a translator. sorry :3
I would like to know the benefit of leaving data in the storage area rather than using the event log.
I know gas consumption has less log....
0
votes
1answer
29 views
CRUD storage pattern Infinite gas error when trying to implement in Remix
I'm trying to implement @robhitchens CRUD storage pattern in solidity, and I'm getting infinate gas costs when I import the library. Not sure where to go from here.
one of them:
Gas requirement of ...
0
votes
1answer
18 views
can't get struct in return
I am trying to execute unit tests for a solidity smart contract:
I have:
mapping (bytes16=>Device) public Device_Table
struct Device
{
bytes16 UUID;
bytes16 hardware_UUID;
string ...
0
votes
1answer
35 views
Multiple Inheritance at particular contract address
I'm attempting to have 4 different contracts sharing the same data fields. The reasoning behind having 4 instead of 1, is that the different functionality can be broken down so that it is cleaner, ...
2
votes
2answers
76 views
Where is the length of an array located in terms of memory layout?
For example, given the following cases:
uint[3] memory arr;
uint[] memory arr = new uint[](3);
Suppose I try to access arr from within an assembly block (using mload, for example).
Where (...
3
votes
2answers
48 views
returning the struct value in smart contract and experimental ABIEncoderV2
I am storing and returning the struct value by using mapping.
pragma solidity >=0.5.0 <0.7.0;
pragma experimental ABIEncoderV2;
contract Manage{
struct Policy{
string PolicyID ;
}
...
0
votes
2answers
42 views
Finding a better way to retrieve information about struct
I've run into a problem about getting information about the structs. The code is written below:
pragma solidity ^0.4.23;
contract Transport {
address public manager;
Batch[] public ...
2
votes
1answer
51 views
why a parameter must be “storage” or “memory”?
I am creating a token like this:
pragma solidity ^0.5.0;
import "../utils/math/SafeMath.sol";
contract ExampleDivisibleNFTs {
using SafeMath for uint256;
// Percentage of ownership over a ...
1
vote
1answer
24 views
How do programs on the 'Ethereum World Computer' compare to traditional programs or websites?
So this question has been bugging for me for a while and I can't seem to find the answer to it.
Context
I have been a web developer for many years.
When I access a website, any frontend code is run ...
1
vote
1answer
15 views
Doubt regarding gas cost
Consider im having to deal with 3 uint8 values each of which are to be stored for each user.
Is the gas cost the same if i use 3 different arrays or if i use a structure array which contains the 3 ...
0
votes
1answer
27 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
1answer
27 views
How to store and encrypt Keys?
I am developing chrome extension like metamask for the private Chain. I have generated the keys and using localStorage to store the Keys. But I am not sure whether I am going correct or not for ...
0
votes
1answer
35 views
Does ERC-20 balanceOf function cost no gas?
Given that this is a sample balanceOf function code:
function balanceOf(address tokenOwner) public view returns (uint balance) {
return balances[tokenOwner];
}
and this function is view function,...
1
vote
2answers
50 views
Mapping primary key of each struct in array to them-self
pragma solidity ^0.4.17;
contract Campaign{
struct Transaction {
address Creditor;
uint Amount;
}
Transaction[] public Transactionss;
mapping(address => Transaction) ...
3
votes
1answer
39 views
How is The Graph a decentralised solution?
I understand that querying for data on Ethereum is a pain in the neck and that The Graph indexes events so that developers can more easily get their most precious blockchain data.
However, I'm not ...
0
votes
0answers
10 views
What is the maximum storage size to store number of addresses in array? [duplicate]
I want to map multiple addresses using one address by doing this:
mapping (address => arrayOfAddresses[]) mappingName;
What is the maximum size of addresses I can store in that array?
0
votes
1answer
85 views
How to set multiple unit64 values in a uint256 variable
I have followed following answer for: Having trouble storing multiple values in a uint256.
For example, I want to pass four uint64 variables merged together as a single argument into smart contract ...
1
vote
1answer
49 views
Struct member access in web3 requires additional dummy field
If a struct contains a single field, then that field is inaccessible from web3. In the below example, field uint b must also be present in order to access field uint c from web3.
Of course, it's not ...
1
vote
1answer
20 views
Can anyone with part of the chain (e.g. a light node) read unencrypted transaction data?
I need clarification on the fact that "the blockchain is public and anyone can read it".
Given a node which is storing only, say, 1 block from the blockchain, can that node read the transaction data ...
1
vote
1answer
26 views
is there a list type in solidity?
I know there are dynamically sized arrays, but I need a data structure that can remove elements from the middle cheaply. Using pop() with a dynamically sized array should require a shift of every ...
0
votes
1answer
20 views
Unstructured storage proxies. Variables not being overwritten?
When using delegate call I was under the impression that storage slots declared in the proxy will be overwritten by the implementation.
Unstructured storage implementations declare bytes32 variables ...
0
votes
1answer
34 views
map multikey how-to?
I'm trying to create a map whose key is composed of two bytes32 keys.
I've tried with tuples-keys and struct-keys but both are rejected by the compiler.
I'm also thinking about "hashing" both keys ...
1
vote
2answers
22 views
Std set in solidity?
Is there any way or library to have a set in solidity that can be iterated like C++'s std::set?
library Set {
// We define a new struct datatype that will be used to
// hold its data in the ...
0
votes
1answer
25 views
Does increasing the size of array guarantees that new elements are initialized to default value?
I get an error when trying to initialize array inside a struct of an array and I find this post: https://github.com/ethereum/solidity/issues/4115 .
It seems that I have to work around by increasing ...
1
vote
1answer
37 views
Return each struct value from a key inside a mapping, where the key is also a value from array inside another mapping
I have a project that I'm working on and I'm trying to figure out a way to do as the title says. I'm looking for the easiest and/or cheapest way(gas wise) and since I'm stuck I'm open to better ways ...
2
votes
0answers
15 views
Most efficient way to get all non-zero storage locations for a smart contract?
I'm looking at a mainnet smart contract and want to figure out all storage positions/slots where the storage has a non-zero value.
Is there a way to do this other than replaying and tracing all ...
0
votes
2answers
60 views
how does Storing and Fetching data works in Smart contracts [closed]
Please help me out with these questions.
1)Where does the contract stores the data?
2)when we access the value of a variable form of a contract, how does it retrieve the latest value?
3)how is the ...
0
votes
1answer
44 views
Costs/efficiency of locating stored data on Ethereum
Based on the answer to this question, storing IPFS hashes on Ethereum could be done in 3 ways:
Store it as a string
Store it as a struct
Store it in event log
Ordered from most expensive to least ...
0
votes
1answer
93 views
error: data location must be storage or memory for parameter in funtion but none was given solidity [duplicate]
pragma solidity ^0.5.0;
contract Election{
//model a candidates
struct candidate
{
uint id;
string name;
uint votecount;
}
//store candidates
//fetch candidate
mapping(uint =...
1
vote
2answers
142 views
Reset all values in a mapping
I am trying to figure out how to have the balance of all players reset to (amount) when a certain condition happens. This is the function that will update a specific player balance. How do I make it ...
0
votes
1answer
26 views
How to push new struct to storage?
I get an error when trying to push the newRound struct to storage. How can it be fixed?
Error:
UnimplementedFeatureError: Copying of type struct Lottery.Ticket memory[] memory to storage not yet ...
0
votes
1answer
27 views
Cannot retrieve data from smartcontract during tests
I am writing truffle tests for my smart contract solidity version 0.4.24. The tests are emitting events to write data to memory through smart contract. But I am unable to retrieve data from functions.
...
0
votes
2answers
321 views
Default getter and setter for mapping in solidity
In my smart contract I've public mapping as mapping (uint=>User) public users where User is a Struct, so is there any way to get the values of this mapping using default getter.
For Example : If ...
0
votes
1answer
154 views
Invalid type for argument in function call. Invalid implicit conversion from mapping
I have defined struct for saving data to ethereum blockchain. I am using uint to map the data stored with a unique ID. I am using truffle framework to write smart contracts with solidity version: 0.4....
1
vote
3answers
329 views
how do I loop through a mapping of address [duplicate]
I have a mapping of list of struct (mapping (address => struct[]))
I'm having a trouble in how to display all them together in the front end (i'm using React js).
Thnx.
1
vote
3answers
39 views
What mechanism to use to pay for viewing another users data on blockchain
I am new to blockchain development and following some tutorials I have created a DApp that allows a user to save and view information. Now, i want to let another user view that saved information but ...
0
votes
1answer
93 views
How Ethereum blocks are stored?
Is each block on Ethereum blockchain stored as lots of files, a separate file per each block? Or a database? How does one can run Etherenum node shared over several servers?
