Submission 5c68567e...
/**
* This file is part of the 1st Solidity Gas Golfing Contest.
*
* This work is licensed under Creative Commons Attribution ShareAlike 3.0.
* https://creativecommons.org/licenses/by-sa/3.0/
*/
pragma solidity 0.4.24;
contract HexDecoder {
/**
* @dev Decodes a hex-encoded input string, returning it in binary.
*
* Input strings may be of any length, but will always be a multiple of two
* bytes long, and will not contain any non-hexadecimal characters.
*
* @param input The hex-encoded input.
* @return The decoded output.
*/
function decode(string input) public pure returns(bytes output) {
bytes memory chars = bytes(input);
uint length = chars.length / 2;
output = new bytes(length);
for (uint i = 0; i < length; i += 16) {
assembly {
let w := mload(add(chars, add(mul(i, 2), 32)))
let r := add(
and(w, 0x0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F),
mul(div(and(w, 0x4040404040404040404040404040404040404040404040404040404040404040), 0x40), 9)
)
r := and(or(r, div(r, 0x10)), 0x00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff)
r := and(or(r, div(r, 0x100)), 0x0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff)
r := and(or(r, div(r, 0x10000)), 0x00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff)
r := and(or(r, div(r, 0x100000000)), 0x0000000000000000ffffffffffffffff0000000000000000ffffffffffffffff)
r := and(or(r, div(r, 0x10000000000000000)), 0x00000000000000000000000000000000ffffffffffffffffffffffffffffffff)
mstore(add(output, add(i, 32)), mul(r, 0x100000000000000000000000000000000))
}
}
}
}