How to convert byte array to bytes32 in solidity

Question

I want to know the syntax to convert a byte array to bytes32 in solidity.

This is a follow up to the question- How to store Public Key in Ethereum contract?

I want to retrieve the PublicKey stored as byte array.

Kindly advise me know how this could be accomplished.

Thanks.

Answer 1

Here is a way to extract bytes32 out of a bytes array:

function bytesToBytes32(bytes b, uint offset) private pure returns (bytes32) {
  bytes32 out;

  for (uint i = 0; i < 32; i++) {
    out |= bytes32(b[offset + i] & 0xFF) >> (i * 8);
  }
  return out;
}

Answer 2

You can use bytes32 directly in the contract's constructor and then retrieve the attribute through a getter:

contract PubKey {
         bytes32 pubKey;

         function PubKey(bytes32 initKey) {
             pubKey = initKey;
         }

         function getPubKey() constant returns (bytes32) {

            return pubKey;

         }
    }

Also, have a look at this question for type conversion details in solidity.

.

Answer 3

bytes memory toBeConvert = "xxxxx";
bytes32 converted;

assembly {
    encoded := mload(add(result, 32))
}

If you only want to do the conversion, try this. But make sure to add requires in production env.

Answer 4

You can slice the data if it's in the calldata:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

contract Slice {
    function bytesToBytes32(bytes calldata b) external pure returns (bytes32) {
        return bytes32(b[:32]);
    }
}