The Etheria hex bounds check paired with the byte extractor
Historical Significance
Deploying one function on its own to see whether it works is what testing looked like before test frameworks and before a public test network was in common use: the check went to mainnet, was called, and was redeployed when it was wrong. The run of attempts records the bug and the fix in the order they happened, which source control alone would not show, because only the deployed bytes prove which version was believed to be correct at the time.
Context
Frontier era deployment by Cyrus Adkisson, the author of Etheria.
Key Facts
Description
The last of four standalone blockHexCoordsValid deployments on 14 October 2015, carrying the corrected validator alongside getUint8FromByte32, the helper Etheria uses to pull a single byte out of a bytes32 by index. Both functions are in the form that reached Etheria v0.85 and v0.9.
Source Verified
Heuristic Analysis
The following characteristics were detected through bytecode analysis and may not be accurate.
Frontier Era
The initial release of Ethereum. A bare-bones implementation for technical users.
Bytecode Overview
Verified Source Available
Source verified through compiler archaeology and exact bytecode matching.
View Verification ProofShow source code (Solidity)
// Submitted by EthereumHistory (ethereumhistory.com)
contract HexValidator
{
function blockHexCoordsValid(int8 x, int8 y) constant returns (bool)
{
if(-33 <= y && y <= 33)
{
if(y % 2 != 0 ) // odd
{
if(-50 <= x && x <= 49)
return true;
}
else // even
{
if(-49 <= x && x <= 49)
return true;
}
}
else
{
uint8 absx;
uint8 absy;
if(x < 0)
absx = uint8(x*-1);
else
absx = uint8(x);
if(y < 0)
absy = uint8(y*-1);
else
absy = uint8(y);
if((y >= 0 && x >= 0) || (y < 0 && x > 0)) // first or 4th quadrants
{
if(y % 2 != 0 ) // odd
{
if (((absx*2) + (absy*3)) <= 198)
return true;
}
else // even
{
if ((((absx+1)*2) + ((absy-1)*3)) <= 198)
return true;
}
}
else
{
if(y % 2 == 0 ) // even
{
if (((absx*2) + (absy*3)) <= 198)
return true;
}
else // odd
{
if ((((absx+1)*2) + ((absy-1)*3)) <= 198)
return true;
}
}
}
return false;
}
function getUint8FromByte32(bytes32 _b32, uint8 byteindex) public constant returns(uint8) {
uint numdigits = 64;
uint buint = uint(_b32);
uint upperpowervar = 16 ** (numdigits - (byteindex*2)); // @i=0 upperpowervar=16**64 (SEE EXCEPTION BELOW), @i=1 upperpowervar=16**62, @i upperpowervar=16**60
uint lowerpowervar = 16 ** (numdigits - 2 - (byteindex*2)); // @i=0 upperpowervar=16**62, @i=1 upperpowervar=16**60, @i upperpowervar=16**58
uint postheadchop;
if(byteindex == 0)
postheadchop = buint; //for byteindex 0, buint is just the input number. 16^64 is out of uint range, so this exception has to be made.
else
postheadchop = buint % upperpowervar; // @i=0 _b32=a1b2c3d4... postheadchop=a1b2c3d4, @i=1 postheadchop=b2c3d4, @i=2 postheadchop=c3d4
uint remainder = postheadchop % lowerpowervar; // @i=0 remainder=b2c3d4, @i=1 remainder=c3d4, @i=2 remainder=d4
uint evenedout = postheadchop - remainder; // @i=0 evenedout=a1000000, @i=1 remainder=b20000, @i=2 remainder=c300
uint b = evenedout / lowerpowervar; // @i=0 b=a1 (to uint), @i=1 b=b2, @i=2 b=c3
return uint8(b);
}
}External Links
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