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In Solidity, how can I convert the sender address to a string?

The comments in How to convert an address to bytes in Solidity? did not provide a working solution

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25
function toString(address x) returns (string) {
    bytes memory b = new bytes(20);
    for (uint i = 0; i < 20; i++)
        b[i] = byte(uint8(uint(x) / (2**(8*(19 - i)))));
    return string(b);
}

You can quickly test and see that the returned string is ABI encoded.

Here is an example of converting msg.sender to a string:

contract C {
    string public senderString;

    function toString(address x) returns (string) {
        bytes memory b = new bytes(20);
        for (uint i = 0; i < 20; i++)
            b[i] = byte(uint8(uint(x) / (2**(8*(19 - i)))));
        return string(b);
    }

    function test() {
        senderString = toString(msg.sender);
    }
}
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  • 3
    Does not work tested in Remix with Solidity 0.4.15 – Viktor Nov 22 '17 at 3:21
  • 1
    Hi. I'm trying to convert this to C# and I'm struggling. Am I right in assuming that the argument x is of type "address" and address is an array of bytes? Also, is it correct to assume that uint(x) is a cast to uint? This is the part I don't understand. How do you cast an array of bytes to a single uint? What am I missing here? – Melbourne Developer Dec 28 '17 at 22:38
  • 1
    @MelbourneDeveloper One way to consider is that x is 20 bytes (not array) big-endian left-padded to 32 bytes. There is no need to cast if you read the bytes in big-endian: it's just to make Solidity's type checker happy. It looks like BigInteger may be helpful msdn.microsoft.com/en-us/library/dd268207.aspx, you'll need to be careful since it uses little-endian, but shouldn't need to cast and can divide like given in the answer. – eth♦ Dec 30 '17 at 15:09
  • It works, but the result is not a human-readable string. For a human-readable string, see toAsciiString example in the other answer. – rustyx Apr 9 '18 at 13:22
  • None of these codes work. – Radeg90 Jul 8 '19 at 9:10
11

I was not able to read the ABI-encoded string with web3.js. Therefore I added some conversion to the ascii-characters:

function toAsciiString(address x) returns (string) {
    bytes memory s = new bytes(40);
    for (uint i = 0; i < 20; i++) {
        byte b = byte(uint8(uint(x) / (2**(8*(19 - i)))));
        byte hi = byte(uint8(b) / 16);
        byte lo = byte(uint8(b) - 16 * uint8(hi));
        s[2*i] = char(hi);
        s[2*i+1] = char(lo);            
    }
    return string(s);
}

function char(byte b) returns (byte c) {
    if (uint8(b) < 10) return byte(uint8(b) + 0x30);
    else return byte(uint8(b) + 0x57);
}
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  • 1
    There was a problem with the function char(byte b). "TypeError: Operator < not compatible with types bytes1 and int_const 10" I suppose this comparison does work anyway since you probably meant if b is a number then add 0x30 to it. But how do you know if a byte is less than 10 or not anyways? – Billie Jan 16 '19 at 12:25
  • if (b < 10) has to be changed to if (uint8(b) < 10), then the Operator < not compatible with types bytes1 ... error is fixed. I made an edit to the answer. Hope it gets approved. – Jack O'neill Sep 5 '19 at 13:35
  • Thanks for the answer - so far this works in v0.5.10 – pizzarob Sep 5 '19 at 15:04
4

This is method to convert address to hex string:

function toString(address account) public pure returns(string memory) {
    return toString(abi.encodePacked(account));
}

function toString(uint256 value) public pure returns(string memory) {
    return toString(abi.encodePacked(value));
}

function toString(bytes32 value) public pure returns(string memory) {
    return toString(abi.encodePacked(value));
}

function toString(bytes memory data) public pure returns(string memory) {
    bytes memory alphabet = "0123456789abcdef";

    bytes memory str = new bytes(2 + data.length * 2);
    str[0] = '0';
    str[1] = 'x';
    for (uint i = 0; i < data.length; i++) {
        str[2+i*2] = alphabet[uint(uint8(data[i] >> 4))];
        str[3+i*2] = alphabet[uint(uint8(data[i] & 0x0f))];
    }
    return string(str);
}
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0
function toString(address x) internal pure returns (string) {
    bytes memory b = new bytes(20);
    for (uint i = 0; i < 20; i++)
        b[i] = byte(uint8(uint(x) / (2**(8*(19 - i)))));
    return string(b);
}

Use internal pure keyword, otherwise you will get a warning. For more information about pure function.

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