Questions tagged [bytes]

both the fixed-size array byte, bytes1...bytes32, and the dynamic array bytes types in Solidity

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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....
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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 ...
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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 ...
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36 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 ...
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228 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(...
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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!
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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'; ...
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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(...
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66 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 ...
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45 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 ...
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1answer
91 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. ...
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1answer
188 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/ ...
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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 ....
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30 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 ...
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How can I slice bytes, strings, and arrays in Solidity?

Is it possible to slice variables in Solidity?
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224 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 "...
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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 = ...
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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 = ...
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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 ...
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186 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 ...
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1answer
658 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, ...
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1answer
39 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[]...
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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 ...
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1answer
75 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", "...
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1answer
490 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 ...
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1answer
768 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 ...
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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); } //...
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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]; ...
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1answer
106 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). ...
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95 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(...
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2answers
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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 ...
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2answers
48 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 ...
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1answer
106 views

encoding several variables into a byte

I want to define a byte256 and I want to assign different sections of the byte to different variables, any literature or guidance is appreciated. for further clarity I want to do something like ...
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1answer
1k views

How to convert bytes32 to uint8 in solidity ^0.5.0?

I can see that conversions from bytes to uint used to be much easier in previous versions of solidity. Now, using the same syntax, I get this error: TypeError: Explicit type conversion not allowed ...
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How to check if bytes variable is empty?

I have a mapping in my smart contract with bytes32 keys and bytes values. How can I check if bytes value exists for specific key? Mapping is something like this: mapping(bytes32 => bytes) public ...
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3answers
2k views

Converting from bytes in 0.5.x?

I'd like to convert bytes into any other type. I.e. "0x57D80C61128d608857d5310BB514223Bb6011CAB" into the address 0x57D80C61128d608857d5310BB514223Bb6011CAB, "5" into the uint256 5 and so on. I have ...
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949 views

Call method with bytes argument from Truffle

When calling a Smart Contract method that requires a bytes parameter, truffle is not accepting the bytes parameter, no matter how I express it. All these tests fail on truffle: // ...
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1answer
194 views

Byte32 error, even after converting string to hex

I looked everywhere for people with similar problems, but I couldn't find anything. I am confused why I keep getting this error (yes, I know others have had this error too, but not for the same ...
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1answer
106 views

Bit manipulation (python vs solidity)

I am working on translating code from Python to Solidity and everything has worked up until this last loop. Cannot figure out where the difference is in the code (besides the bytes being in decimal ...
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1answer
394 views

Is there any way to return multiple structs (or the fields from them) in Solidity when one of the struct fields is of type `bytes`?

I would like to return structs keys from my contract to display on the frontend, ideally 10 at a time. I understand that if I make keyByOwner public I can return a single key at a time with the getter ...
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1answer
231 views

Bytes variables are connected

Why are these variables confounding? The returned result shows that both loops are effecting both bytes variables (second returns the same result). function mix() public returns (bytes) { ...
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57 views

How strings are stored in Solidity on a low level?

So, the question is in the title, let me describe scenario: I make raw rpc call via method eth_call to contract Token to a function name to get token name of type string. Below is my original ...
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1answer
2k views

Is it safe to use abi.encodePacked in production solidity code?

In my solidity game project, I am using this: if (king == keccak256(abi.encodePacked(player)){ //continue as king } else{ // not king } Where player data type is bytes and king is a player ...
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1answer
203 views

Why is the returndata of a function returning bytes formatted in a weird way?

Solidity 0.4.25. Consider this code contract A{ function test() public view returns (bytes){ bytes memory output = abi.encodePacked(bytes32(1)); return output; } } The ...
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168 views

Cant pass a byte into a function without an error

The code below compiles perfectly and seems to work, however when I try to call addTask like: "item1", 1, "i1", 1 I have tried every possible variation of quotes parenthesis, brackets... ...
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466 views

Assembly opcodes

I need some help understanding assembly functions pragma solidity ^0.4.23; contract Test { function addTest() public pure returns (uint c) { bytes memory b = new bytes(1024); assembly { c:...
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1answer
66 views

Representing biometric data with solidity variables — bytes 32 perhaps? [closed]

would like to know which variable type comes closest to representing biometric binary data? Assuming computing storage and power grows exponentially and network latency can be further reduced, would ...
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1answer
72 views

How to extract int128 from msg.data as first argument?

Let's say we have Ethereum smart contract with fallback function: event onDeposit(int128 indexed key, address from, uint amount); ... function () payable public { require(msg.value > 0); ...
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592 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
591 views

Make character count, count emoji's as 2

I have the following function: function getCharacterCount(string str) constant returns (uint length) { uint i=0; bytes memory string_rep = bytes(str); while (i<string_rep.length) {...