Syntax

exchange.IO("hash", ...)

Computes hash digests and HMACs, signs with the private key configured on the exchange object, and so on. Its parameters are the same as those of the Encode function. On a Web3 exchange object it is commonly used for keccak256 hashes, such as method selectors and EIP-712 digests.


    
    
    
exchange.IO(k, algo, inputFormat, outputFormat, data)


    
    
    
exchange.IO(k, algo, inputFormat, outputFormat, data, keyFormat, key)

Examples

Compute a method selector, an HMAC and an ABI encoding, and sign a hash with the configured private key.


    javascript
    
    
function main() {
    // Method selector: the first 4 bytes of keccak256("transfer(address,uint256)")
    var h = exchange.IO("hash", "keccak256", "raw", "hex", "transfer(address,uint256)")
    Log("selector:", "0x" + h.slice(0, 8))
    // Output: 0xa9059cbb

    // Hash hex data; the output has no 0x
    Log(exchange.IO("hash", "keccak256", "hex", "hex", "0x1234"))

    // HMAC-SHA256: the last two arguments are the key format and the key
    Log(exchange.IO("hash", "sha256", "string", "base64", "message", "string", "secret"))

    // ABI-encode a uint256
    Log(exchange.IO("hash", "abi.uint256", "string", "hex", "1000"))

    // Sign a 32-byte hash with the configured key: 65 bytes r‖s‖v, v is 0 or 1
    Log(exchange.IO("hash", "sign", "hex", "hex", h))
}


    python
    
    
def main():
    # Method selector: the first 4 bytes of keccak256("transfer(address,uint256)")
    h = exchange.IO("hash", "keccak256", "raw", "hex", "transfer(address,uint256)")
    Log("selector:", "0x" + h[:8])
    # Output: 0xa9059cbb

    # Hash hex data; the output has no 0x
    Log(exchange.IO("hash", "keccak256", "hex", "hex", "0x1234"))

    # HMAC-SHA256: the last two arguments are the key format and the key
    Log(exchange.IO("hash", "sha256", "string", "base64", "message", "string", "secret"))

    # ABI-encode a uint256
    Log(exchange.IO("hash", "abi.uint256", "string", "hex", "1000"))

    # Sign a 32-byte hash with the configured key: 65 bytes r‖s‖v, v is 0 or 1
    Log(exchange.IO("hash", "sign", "hex", "hex", h))


    rust
    
    
fn main() {
    // Method selector: the first 4 bytes of keccak256("transfer(address,uint256)")
    let hv = exchange.IO(("hash", "keccak256", "raw", "hex", "transfer(address,uint256)"));
    let Ok(hv) = hv else { return };
    let h = hv.as_str().unwrap_or("").to_string();
    Log!("selector:", format!("0x{}", &h[..8]));
    // Output: 0xa9059cbb

    // Hash hex data; the output has no 0x
    Log!(exchange.IO(("hash", "keccak256", "hex", "hex", "0x1234")));

    // HMAC-SHA256: the last two arguments are the key format and the key;
    // pass a Vec<Arg> when there are more than 6 arguments
    let args: Vec<Arg> = ["hash", "sha256", "string", "base64", "message", "string", "secret"]
        .iter().map(|s| Arg::Str(s.to_string())).collect();
    Log!(exchange.IO(args));

    // ABI-encode a uint256
    Log!(exchange.IO(("hash", "abi.uint256", "string", "hex", "1000")));

    // Sign a 32-byte hash with the configured key: 65 bytes r‖s‖v, v is 0 or 1
    Log!(exchange.IO(("hash", "sign", "hex", "hex", h.as_str())));
}

Returns

Type	Description
string / object	Returns the result encoded according to `outputFormat`; `unzip` returns an object keyed by file name. Returns a null value on failure, with the error in `GetLastError()`.

Arguments

Name	Type	Required	Description
k	string	Yes	Function of `exchange.IO()`; `hash` means hashing, signing and similar computations.
algo	string	Yes	Algorithm: digests (such as `sha256` or `keccak256`, with HMAC support), format conversion (`raw`, `string`), signing (`sign`, `signTx`), ABI encoding (`abi.<type>`), and Ed25519, character sets, AES and compression; see the remarks for all values.
inputFormat	string	Yes	The format of `data`: `raw`, `string` (the bytes of the string), `hex` (`0x` prefix optional), `base64`, `base64.url`, `base64.rawurl`.
outputFormat	string	Yes	The output format: `hex` (without `0x`), `base64`, `base64.url`, `base64.rawurl`, `raw`, `string` (the output must be valid UTF-8 text).
data	string	Yes	The data to process, parsed according to `inputFormat`.
keyFormat	string	No	The format of `key`, with the same values as `inputFormat`.
key	string	No	The key: the HMAC key, the private key used by `sign` (for example its hex when `keyFormat` is `hex`), or the ed25519 or AES key. Required for `ed25519` and `aes.*`. An AES key is 16, 24 or 32 bytes; the IV is the first 16 bytes of the key and no padding is applied (cbc and ecb need data whose length is a multiple of 16).