How can I modify bytes32 result to uint?

Question

I want to separate three last digits of the most recent block header hash and get the result as uint.

I can get the answer as bytes32 by this code, but how can I change this result to uint?

contract test
{
    bytes32 lastblockhashused;
    uint lastblocknumberused;

    function test()
    {
        lastblocknumberused = (block.number-1)  ;               
        lastblockhashused = block.blockhash(lastblocknumberused);
    }

    function getTest1() constant returns (bytes32) {
        bytes32 number1 =lastblockhashused;
        return number1 & 0xfff;
    }
}

score 8 · Answer 1 · answered Apr 29 '16 at 12:36

8

You can simply cast a bytes32 to uint with uint(number1).

answered Apr 29 '16 at 12:36

Nick Johnson

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I have additional question related to this http://ethereum.stackexchange.com/questions/3461/why-cant-i-pass-this-functions-value-to-variable – Matias Apr 29 '16 at 15:52
2

Not anymore as of solidity ^0.5.0 – Paul Razvan Berg Jan 17 '19 at 15:26
@PaulRazvanBerg how are we supose to do this conversion on 0.5.0 ++ ? – João Quintanilha Aug 03 '20 at 15:53
@JoãoQuintanilha I don't know .. but there must be a soluton here somewhere. – Paul Razvan Berg Aug 03 '20 at 17:08

score 7 · Accepted Answer · answered Apr 29 '16 at 14:47

7

Or just do away with your number1 variable completely, while also remembering to change the return type:

function getTest1() constant returns (uint) {
        return uint(lastblockhashused) & 0xfff;
    }

answered Apr 29 '16 at 14:47

Richard Horrocks

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I tried this in sol version 0.5.12 and it didn't work. Am I missing something? – João Quintanilha Aug 03 '20 at 15:52

euri10 · Answer 3 · 2016-05-12T12:06:17.967

2

you can use @pipermerriam excellent library : ethereum-string-utils with the function

function bytesToUInt(uint v) constant returns (uint ret)

It does exacxtly what you want.

It's usable as a library copying the .sol or using contract calls against via 0xcca8353a18e7ab7b3d094ee1f9ddc91bdf2ca6a4

edited May 12 '16 at 12:06

answered May 12 '16 at 08:18

euri10

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Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference. – q9f May 12 '16 at 11:52

How can I modify bytes32 result to uint?

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