Submission 05f64b64...
pragma solidity ^0.4.23;
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) external view returns(bytes output) {
assembly {
0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
0xEFEFEFEFEFEFEFEFEFEFEFEFEFEFEFEFEFEFEFEFEFEFEFEFEFEFEFEFEFEFEFEF
0x9000000000000000000000000000000000000000000000000000000000000000
0x0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F
2 0x24 calldataload div
dup1 iszero no_bytes jumpi
0x44
0x40
dup7 4 eq four_byte jumpi
dup7 1 eq one_byte jumpi
loop_start:
dup2 calldataload
dup8
dup2 dup9 or not
dup8 mulmod add
dup5 and
16 dup2 div or
0x20 mstore
4 mload 6 mload 8 mload 10 mload 12 mload 14 mload 16 mload 18 mload
20 mload 22 mload 24 mload 26 mload 28 mload 30 mload 32 mload
48 mstore8 47 mstore8 46 mstore8 45 mstore8 44 mstore8 43 mstore8 42 mstore8 41 mstore8
40 mstore8 39 mstore8 38 mstore8 37 mstore8 36 mstore8 35 mstore8 34 mstore8
33 mload dup2 mstore
dup2 0x20 add calldataload
dup8
dup2 dup9 or not
dup8 mulmod add
dup5 and
16 dup2 div or
0x20 mstore
4 mload 6 mload 8 mload 10 mload 12 mload 14 mload 16 mload 18 mload
20 mload 22 mload 24 mload 26 mload 28 mload 30 mload 32 mload
48 mstore8 47 mstore8 46 mstore8 45 mstore8 44 mstore8 43 mstore8 42 mstore8 41 mstore8
40 mstore8 39 mstore8 38 mstore8 37 mstore8 36 mstore8 35 mstore8 34 mstore8
33 mload dup2 0x10 add mstore
0x20 add
swap1 0x40 add
swap1
dup2 calldatasize gt
loop_start jumpi
loop_end:
pop pop
0x20 0x00 mstore
dup1 0x20 mstore
0x40 add 0x0
dup2 mstore
dup1 0x1f and iszero
skip jumpi
0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFE0 and 0x20 add
skip:
0
return
pop pop pop pop
no_bytes:
0x40 0x00 return
one_byte:
calldataload(0x44)
dup6
dup2 dup6 or not
// multiply by 2**255 + 2**252, trigger integer overflow so that
// every 5th bit becomes every (4th + 1st) bit
dup6
mulmod
// combine back into w
add
// mask out the top 4 bits of every byte
dup2 and
dup1 1 byte // 0b
swap1 0 byte // 0a
16 mul or // ab
0x40 mstore8
0x00 0x41 mstore
0x01 0x20 mstore
0x20 0x00 mstore
0x60 0x00 return
four_byte:
dup2 calldataload
dup8
dup2 dup9 or not
dup8 mulmod add
dup5 and
16 dup2 div or
0x20 mstore
4 mload 6 mload 8 mload
36 mstore8 35 mstore8 34 mstore8
33 mload dup2 mstore
0x20 0x00 mstore
4 0x20 mstore
0x0 0x44 mstore
0x60
0
return
}
}
}