Questions tagged [bytes]
both the fixed-size array byte, bytes1...bytes32, and the dynamic array bytes types in Solidity
138
questions
0
votes
1answer
19 views
How to load the first 4 bytes from a bytes calldata var?
It is common for calldata to be encoded as bytes calldata when developing contracts in Solidity.
I need to extract the function selector from such a bytes var. What's the best way to load the first 4 ...
0
votes
1answer
13 views
What is the most gas-efficient way to hard-code a bytes array?
I need to hardcode some multi-Kb bytes into my smart contract. So far, the best way I have found to do this is to use abi.encodePacked...
return abi.encodePacked(
abi.encodePacked(
...
0
votes
1answer
20 views
String to Bytes Converts to Incorrect Value
I have a string array stored in memory as
https://cloudflare-ipfs.com/ipfs/QmSXDsFeNaPa3CJKmn8WKBnA421Zv5r3Ra8n71LZhvEi9s
This should convert to ...
1
vote
0answers
8 views
Encode String to byte[] to invoke method via web3j
I have a method in a contract that receives a bytes object. Web3J generated code in Java translates it to a byte[] object as parameters.
I have the correct String "0x....." thet represents ...
0
votes
1answer
137 views
Decode raw data within Solidity
If I only have the raw input data of a contract call, what would be the best way to decode it into readable form within Solidity?
"[INPUT]":"...
0
votes
1answer
160 views
How do I encode a uint256 as bytes to feed to a function "sliceuint", with web3.js and solidity?
I have a function from a library:
function sliceUint(bytes bs, uint start)
internal pure
returns (uint)
{
require(bs.length >= start + 32, "slicing out of range&...
2
votes
2answers
326 views
Converting bytes memory to bytes calldata
I am getting the following error:
Error: Type bytes memory is not implicitly convertible to expected type bytes calldata.
So I was wondering if it was possible to convert from bytes memory to bytes ...
0
votes
1answer
17 views
Is it possible to encode and decode two consequent byte arrays (with unknown sizes) using `abi.encode` and `abi.decode`?
Is it possible to encode and decode two consequent bytes using abi.encode and abi.decode (as following)?
bytes memory data = abi.encode(data1, data2);
// later on
(bytes memory data1_recovered, bytes ...
0
votes
1answer
76 views
Member "concat" not found or not visible after argument-dependent lookup
I'm trying to concatenate a series of strings but I'm getting the following error:
TypeError: Member "concat" not found or not visible after argument-dependent lookup in bytes storage ...
0
votes
0answers
29 views
Solidity: Convert hex-string variable into bytes [duplicate]
I am looking for an option to efficiently convert a string passed to a function as a parameter, interpreted as hex, into bytes. In Solidity.
I.e. doing the same that this piece of code would do
bytes ...
0
votes
1answer
262 views
Is it cheaper to store a string or convert it to bytes32 with abi.encodePacked()?
For example, in the code below, would it be cheaper to store the string in a mapping? Or to convert it to bytes32 and store it as bytes32 then convert it back to a string whenever I call it with ...
0
votes
1answer
34 views
Solidity: How to represent bytes32 as string
This may be simple in other languages but I can't figure out how to do it in Solidity.
I have a bytes32 like this 0x05416460deb76d57af601be17e777b93592d8d4d4a4096c57876a91c84f4a712.
I don't want to ...
0
votes
0answers
15 views
Can cheaper transactions be created by brute forcing RLP-encoded V,R,S values with leading zeros
When I make a raw txn using RLP-encoding I note that the VRS values are not deterministic. Sometimes the R and S values can have leading zeros, these get omitted, thus making the transaction data ...
1
vote
0answers
66 views
How to measure Solidity variables size?
After reading different smart contracts from Uniswap teams and others, I understand that they stricly optimize the data to be stored on-chain, but how can they know what is the minimum size needed for ...
0
votes
1answer
21 views
Why would the type byte[] waste 31 bytes of space for each element?
The Solidity Docs (v0.8.4) states:
The type byte[] is an array of bytes, but due to padding rules, it wastes 31 bytes of space for each element (except in storage). It is better to use the bytes type ...
4
votes
1answer
133 views
How do you handle the hex prefix without the value (only "0x")?
First, I'm caling function foo() (from another contract) that returns me a uint in the form of bytes.
Then, I'm using BytesLib.toUint(foo(), 0) to retrieve the uint.
When the value is supposed to be 1,...
0
votes
1answer
88 views
error comparing two bytes memory
I am testing a smart contract in Remix and I get the following error when trying to compare two bytes memory using "==":
TypeError: Operator == not compatible with types bytes memory and ...
1
vote
0answers
7 views
Check string similarity percentage
How can I efficiently check the similarity of two strings? Or better yet, if I have an array of strings, I want to check that the given string is less than e.g. 80 % similar to any of the other ...
0
votes
0answers
20 views
How much is the biggest BytesX type in solidity? (Bytes32?)
I'm trying to keep it simple while returning and array of strings. I want to return a fixed bytesX array with small text. How much is the possible X in the BytesX type?
In Remix it seems to be Bytes32....
0
votes
2answers
527 views
How to assign a value to a bytes variable?
The function keccak256 () takes a bytes variable. You can't pass it bytes3 or byte []; it has to be of type bytes.
How do you set that to a specific value?
Here are some things I've tried, and the ...
0
votes
0answers
35 views
Passing a hash value to function
I'm trying to authenticate users by comparing the hashes created by backend server and contract. Seems like "byte32" values cannot be coerced into strings. So, instead I'm converting it into ...
0
votes
1answer
115 views
String To bytes Error
I am trying to take user input strings and convert them to bytes32 and bytes5 for a contract built in Solidity 5.11, I tried 32 and 5 character long random strings respectively however they are not ...
1
vote
1answer
578 views
Why does retrieving stored data cost so much compared to using calldata in Solidity?
I have a function that I need to pass an arbitrary length array of addresses to. In remix, just calling a function that has an address[] costs around 30k gas for an array of 5 addresses:
function fun(...
1
vote
1answer
85 views
In Solidity, Is there any situation, when string is necessary?
In Solidity, Is there any situation, when string is necessary? Please can u explain when I should use string instead of bytes or bytesN? Thanks!
0
votes
1answer
131 views
How to use initialize a bytes array with abi data?
To initialize a bytes array with the bool value True encoded as ABI data, I'm attempting to do it like this:
bytes memory arr = '0x0000000000000000000000000000000000000000000000000000000000000001';
...
0
votes
0answers
255 views
Convert address to bytes8
I want to convert address to bytes8, but I only managed to convert address to bytes this way:
bytes memory shortAddress = new bytes(8);
for(uint i = 0; i < 8; i++) {
shortAddress[i] = byte(uint8(...
0
votes
2answers
196 views
How do you call a fallback function that uses msg.data for parameters
I am trying to complete a homework assignment, so I am not doing something malicious. The goal is to learn the vulnerabilities of contracts. I want to call the fallback function of wallet to trigger ...
0
votes
1answer
71 views
Write uints as bytes to create one larger bytes
I would like to take three uints and essentially concatenate them together as one bytes variable. What's the simplest way I can do that? I've seen many posts about people writing full-blown code to ...
1
vote
1answer
114 views
Error: Invalid bytes6 value
I'm trying to create a TicketPurchaser application. Here is the whole code for the smart contract, although I think the problem I'm asking about is a type error, most of the code is not important.
...
2
votes
1answer
361 views
Decoding call inputs
Using a smart contract's ABI and the input data from a transaction on Etherscan, I am able to decode the input data using this tool: https://lab.miguelmota.com/ethereum-input-data-decoder/example/
...
0
votes
0answers
42 views
How to check if key exists in array of bytes? [duplicate]
I have an array of bytes10 inside a mapping, like this:
mapping(uint => bytes10[]) public Players;
I want to check if a certain index exists in the bytes10 array.
I tried to check it with ....
0
votes
1answer
47 views
Why does declaring returns type bytes memory give a compiler error?
If we have the following code:
pragma solidity >= 0.5;
contract stringsContract {
function takesTwo(string memory str, uint idx) public pure returns (bytes memory) {
bytes memory ...
5
votes
1answer
3k views
How can I slice bytes, strings, and arrays in Solidity?
Is it possible to slice variables in Solidity?
1
vote
1answer
480 views
Bytes memory as a function parameter increase gas cost
I've a smartcontract compiled with pragma solidity ^0.4.0; version and one function receives a bytes parameters which contain a long string. In these version it doesnt need to set the parameters as "...
2
votes
0answers
84 views
Performing a C-like pointer increment in Solidity
I have a memory or calldata struct with an attribute of type byte[]. I want to have a memory variable with that data, except for the first n Bytes.
In C, you'd just write
typename variablename = ...
0
votes
1answer
32 views
Can I call a contract function in the "data" element via web3, especially when I am using conversion to bytes?
In other words, say In Python I have something like that:
signed_txn = w3.eth.account.signTransaction(dict(
nonce=w3.eth.getTransactionCount('0x0000000000000000000000000000000'),
gasPrice = ...
0
votes
1answer
26 views
Is it possible to store an array of bytes (so something like bytes[])?
Edit
The original question below seems to work as expected. The issue happens with the call return data is empty. When the response is nothing, the code below fails.
The following works, but is ...
0
votes
1answer
351 views
Proper way to save a public key as bytes in a contract
I need to save public keys in many contracts.
Despite that this choice costs, I store them as bytes (I know that the best way is to split the key and store it to different bytes32 constants, but that ...
1
vote
1answer
1k views
web3 - web3.utils.toHex zeros length
I'm trying to send 12 integer as bytes to a contract function. If I use
web3.utils.toHex(12)
the variable will become 0xc
The problem is that when contract function parses bytes, it reads uint256, ...
0
votes
1answer
44 views
Combine BytesX and BytesY to create BytesZ?
I am working on a Solidity Smart Contract (^0.5.10) where I want to return an array of Ratings elements.
struct Ratings {
address restaurant
uint8 score
};
Since returning Rating[], string[]...
1
vote
2answers
250 views
How to convert string to bytes256 or arbitrary bytes?
I already know how to convert bytes32ToString and stringToBytes32:
function bytes32ToString(bytes32 x)
public
pure
returns (string memory)
{
bytes memory ...
0
votes
1answer
85 views
Remix - Pass bytesX to function
Using Remix, I can't pass a set of bytes ["0xee", "0xff", "0xgg", "0xhh", "0xii"] to my function
function foo(bytes5 input) {
// Do something
}
I've already tried all these formats:
["0xee", "...
1
vote
1answer
888 views
Solidity: Convert from "bytes memory" to "address"
I'm using solidity 0.5.0 and when i try to compile my contract it's giving me this error
Explicit type conversion not allowed from "bytes memory" to "address"
my code is this:
/// @dev get broker ...
0
votes
1answer
2k views
Solidity, problem with bytes decoding
back with another question towards solidity Guru's. I am trying to call a method which takes bytes array as an input, but either I am encoding this parameter wrongly or decoding it wrongly. Solidity ...
5
votes
2answers
3k views
Solidity Invalid implicit conversion from string memory to bytes memory requested
pragma solidity ^0.5
contract ProofOfExistence {
// ... some code here
function proofFor(string memory document) public view returns(bytes32) {
return sha256(document);
}
//...
2
votes
1answer
476 views
How to set byte in fixed-size byte array?
function computePairId(bytes20 base, bytes20 quote) public view returns (bytes4) {
bytes32 pairHash = sha256(abi.encodePacked(base ^ quote));
bytes4 pairId;
pairId[0] = pairHash[28];
...
1
vote
1answer
186 views
Read more than 32 bytes from memory (Assembly)
Assume I am passing a variable bytes (memory) to a function. This variable corresponds to A concatenated with B where A is of size 32 and B is 96 bytes, how can I return A (bytes32) and B (bytes).
...
0
votes
1answer
108 views
How to get the last n bytes of a bytes32 in assembly?
I have the following code:
function getBytes5() public returns (bytes5) {
uint256 x = now;
bytes memory inBytes = new bytes(32);
bytes5 outBytes5;
assembly {
mstore(...
2
votes
2answers
3k views
How to compare two bytes32?
I was using strings before I read that using bytes is gas cheaper. Now I changed my strings to bytes32 but I don't know how to compare them. I need to check if two bytes32 are equal in the require ...
2
votes
2answers
67 views
Validate bytes16 argument size
I have a function which accepts one bytes16 argument.
function start(
bytes16 reference
)
I have some events which I use to track behaviour, using reference as the index. Everything works ...
