Low-Level API¶

These are advanced, low-level API features that should, for most people not be necessary to worry about.

They are lightly documented here, and in the future will have more documentation, but the emphasis at this point is documenting the more common methods.

HDNode¶

A Hierarchical Deterministic Wallet represents a large tree of private keys which can reliably be reproduced from an initial seed. Each node in the tree is represended by an HDNode which can be descended into.

A mnemonic phrase represents a simple way to generate the initial seed.

See the BIP 32 Specification to learn more about HD Wallets and hardened vs non-hardened nodes.

See the BIP 39 Specification to learn more about Mnemonic Phrases.

Creating Instances¶

^HDNode . fromMnemonic ( mnemonic ): Create an HDNode from a mnemonic phrase.
^HDNode . fromSeed ( seed ): Create an HDNode from a seed.

Prototype¶

^prototype . privateKey: The hex string private key for this node.
^prototype . publicKey: The (compressed) public key for this node.
^prototype . chainCode: The chain code for this node.
^prototype . index: The index (from the parent) of this node (0 for the master node).
^prototype . depth: The depth within th hierarchy of this node.
^prototype . derivePath ( path ): Derive the path from this node. Path is slash (/) delimited path components. The first component may be “m” for master (which enforces the starting node is infact a master node) and each subsequent path component should be a positive integer (up to 31 bits), which can optionally include an apostrophe (‘) to indicate hardened derivation for that path components. See below for some examples.

Static Methods¶

^HDNode . mnemonicToEntropy ( mnemonic ): Convert a mnemonic to its binary entropy. (throws an error if the checksum is invalid)
^HDNode . entropyToMnemonic ( entropy ): Convert the binary entropy to the mnemonic phrase.
^HDNode . mnemonicToSeed ( mnemonic ): Compute the BIP39 seed from mnemonic.
^HDNode . isValidMnemonic ( string ): Returns true if and only if the string is a valid mnemonic (including the checksum)

Examples¶

var HDNode = ethers.HDNode;

var mnemonic = "radar blur cabbage chef fix engine embark joy scheme fiction master release";

var masterNode = HDNode.fromMnemonic(mnemonic);

var standardEthereum = masterNode.derivePath("m/44'/60'/0'/0/0");

Interface¶

The Interface Object is a meta-class that accepts a Solidity (or compitible) Application Binary Interface (ABI) and populates functions to deal with encoding and decoding the parameters to pass in and results returned.

Creating an Instance¶

new ^ethers . Interface ( abi ): Returns a new instance and populates the properties with the ABI constructor, methods and events. The abi may be either a JSON string or the parsed JSON Object.

Prototype¶

^prototype . abi: A copy of the ABI is returned, modifying this object will not alter the ABI.
^prototype . functions: An object of the functions available in the ABI, by name. (collissions are dropped)
^prototype . events: An object of the events available in the ABI, by name. (collisions are dropped)
^prototype . deployFunction ( bytecode [ , params... ]): The function to deploy the contract (compiled to bytecode) to the network, passing params into the ABI constructor. If the ABI does not have a constructor, a default one is generated.

Static Methods¶

^Interface . encodeParams( types , values ): Returns a hex string of the values encoded as the types. (throws if a value is invalid for the type)
^Interface . decodeParams( [ names , ] types , data ): Returns an Object by parsing data assuming types, with each parameter accessible as apositional parameters. If names is provided, each parameter is also accessible by its name. (throws if data is invalid for the types)

Examples¶

Creating an Interface Instance

var Interface = ethers.Interface;

var abi = [
    {
        constant: true,
        inputs:[],
        name: "getValue",
        outputs:[ { name: "value", type: "string"} ],
        type: "function"
    },
    {
        constant: false,
        inputs: [ { name: "value", type: "string" } ],
        name: "setValue",
        outputs: [],
        type: "function"
    },
    {
        anonymous: false,
        inputs:[
            { indexed:false, name: "oldValue", type: "string" },
            { indexed:false, name: "newValue", type: "string" }
        ],
        name: "valueChanged",
        type: "event"
    }
];

// NOTE: "interface" is a reserved keyword in JavaScript

var iface = new Interface(abi)

Call (Constant) Functions

var getValueInfo = iface.function.getValue();

console.log(getValueInfo);
// {
//     name: "getValue",
//     signature: "getValue()",
//     data: "0x20965255",
//     parse: function(result),
//     type: "call"
// }

// Here is the result of:
// provider.call({
//    to: "0x954De93D9f1Cd1e2e3AE5964F614CDcc821Fac64",
//    data: getValue.data,
// }).then(function(result) {
//    console.log(result);
// });
var getDataResult = "0x0000000000000000000000000000000000000000000000000000000000000020" +
                      "000000000000000000000000000000000000000000000000000000000000000b" +
                      "48656c6c6f20576f726c64000000000000000000000000000000000000000000"

 console.log(getValueInfo.parse(getDataResult));
 // {
 //    0: "Hello World",
 //    value: "Hello World",
 //    length: 1
 // }

Transaction (Non-Constant) Functions

var setValueInfo = iface.functions.setValue("Foobar!");

console.log(setValueInfo);
// {
//     name: "setValue",
//     signature: "setValue(string)",
//     data: "0x93a09352" +
//             "0000000000000000000000000000000000000000000000000000000000000020" +
//             "0000000000000000000000000000000000000000000000000000000000000007" +
//             "466f6f6261722100000000000000000000000000000000000000000000000000"
//     type: "transaction"
// }

// To send this to the network, you would sign and send the transaction:
// {
//     to: "0x954De93D9f1Cd1e2e3AE5964F614CDcc821Fac64",
//     data: setValueInfo.data,
//     gasLimit: someGasLimit,
//     gasPrice: someGasPrice,
//     nonce: yourTransactionCountForYourAddress
// }

Events

var valueChangedInfo = iface.events.valueChanged();

console.log(valueChangedInfo);
// {
//     name: "valueChanged",
//     inputs: (same as iface.abi[2].inputs,
//     parse: function(data),
//     signature: "valueChanged(string,string)",
//     topics: [
//         "0x68ad6719a0070b3bb2f866fa0d46c8123b18cefe9b387ddb4feb6647ca418435"
//     ]
// }

// To listen for this event:
provider.on(valueChangedInfo.topics, function(data) {
    var result = valueChangedInfo.parse(data);

    console.log(result);
    // {
    //     0: "Hello World",
    //     oldValue: "Hello World",
    //     1: "Foobar!",
    //     newValue: "Foobar!",
    // }
});

Provider (Sub-Classing)¶

See the Provider API for more common usage. This documentation is designed for developers that are sub-classing Provider.

Prototype¶

^prototype . perform ( method , params ): The only method needed to override in a subclass. All values are sanitized and defaults populated in params and the result is sanitized before returning. Returns a Promise, see the example below for overview of method and params.

Static Methods¶

^Provider . inherits ( childProvider ): Set up childProvider as an provider, inheriting the parent prototype and set up a prototype.inherits on the childProvider.
^Provider . fetchJSON ( url , body , processFunc ): Convenience method for returning a Promise with the result of fetching JSON from a url with an optional body. The optional processFunc is called on the parsed JSON before being passed to the Promise’s resolve. (throwing an error in the processFunc will cause the Promise to reject)

Examples¶

// The new provider Object
function DemoProvider(testnet, somethingElse) {
    Provide.call(this, testnet);

    utils.defineProperty(this, 'somethingElse', somethingElse);
}

// Inherit the Provider
Provider.inherits(DemoProvider);

// Override perform
utils.defineProperty(DemoProvider.prototype, 'perform', function(method, params) {
    switch (method) {
        case 'getBlockNumber':
            // Params:
            // { }

        case 'getGasPrice':
            // Params:
            // { }

        case 'getBalance':
            // Params:
            // {
            //     address: address,
            //     blockTag: blockTag
            // }

        case 'getTransactionCount':
            // Params:
            // {
            //     address: address,
            //     blockTag: blockTag
            // }

        case 'getCode':
            // Params:
            // {
            //     address: address,
            //     blockTag: blockTag
            // }

        case 'getStorageAt':
            // Params:
            // {
            //     address: address,
            //     position: hexString,
            //     blockTag: blockTag
            // }

        case 'sendTransaction':
            // Params:
            // {
            //     signedTransaction: hexString
            // }

        case 'getBlock':
            // Params:
            // Exactly one of the following will be specified, the other will be absent
            // {
            //     blockHash: blockHash,
            //     blockTag: blockTag
            // }

        case 'getTransaction':
            // Params:
            // {
            //     transactionHash: hexString
            // }

        case 'getTransactionReceipt':
            // Params:
            // {
            //     transactionHash: hexString
            // }

        case 'call':
            // Params:
            // {
            //     transaction: See Transaction Requests (on Providers API)
            // }

        case 'estimateGas':
            // Params:
            // {
            //     transaction: See Transaction Requests (on Providers API)
            // }

        case 'getLogs':
            // Params:
            // {
            //    address: address,
            //    fromBlock: blockTag,
            //    toBlock: blockTag,
            //    topics: array (possibly nested) of topics
            // }

        default:
            break;
    }

    return Promise.reject(new Error('not implemented - ' + method));
});

Signing Key¶

The SigningKey interface provides an abstraction around the secp256k1 elliptic curve cryptography library, which signs digests.

var SigningKey = ethers._SigningKey;

Creating Instances¶

A private key may be a any hex string or an Arrayish representing 32 bytes.

new ^ethers . _SigningKey ( privateKey ): Create a new SigningKey and compute the corresponding public key and address.

Prototype¶

^prototype . privateKey: The private key.
^prototype . publicKey: The compressed public key.
^prototype . address: The Ethereum address for this key pair.
^prototype . signDigest ( messageDigest ): The compressed public key

Static Methods¶

^_SigningKey . recover( digest, r, s, recoveryParam )

Given a message digest and the signature parameters r, s and recoveryParam compute the the address that signed the message.

^_SigningKey . getPublicKey( publicOrPrivateKey [, compressed] )

Given a publicOrPrivateKey, return the public key, optionally compressed.

default: compressed=false

^_SigningKey . publicKeyToAddress( publicOrPrivateKey )

Convert a publicOrPrivateKey to an Ethereum address.

Examples¶

var SigningKey = ethers._SigningKey;

var privateKey = '0x0123456789012345678901234567890123456789012345678901234567890123';
var signingKey = new SigningKey(privateKey);

console.log('Address: ' + signingKey.address;
// "Address: 0x14791697260E4c9A71f18484C9f997B308e59325"

var message = "Hello World";
var messageBytes = ethers.utils.toUtf8Bytes(message);
var messageDigest = ethers.utils.keccak256(messageBytes);

console.log("Digest: " + messageDigest);
// "Digest: 0x592fa743889fc7f92ac2a37bb1f5ba1daf2a5c84741ca0e0061d243a2e6707ba"

var signature = signingKey.signDigest(messageDigest);

console.log(signature);
// {
//    recoveryParam: 0,
//    r: "0x79f56f3422dc67f57b2aeeb0b20295a99ec90420b203177f83d419c98beda7fe",
//    s: "0x1a9d05433883bdc7e6d882740f4ea7921ef458a61b2cfe6197c2bb1bc47236fd"
// }

var recovered = SigningKey.recover(messageDigest, signature.r,
                    signature.s, signature.recoveryParam);

console.log("Recovered: " + recovered);
// "Recovered: 0x14791697260E4c9A71f18484C9f997B308e59325"

var publicKey = signingKey.publicKey;

console.log('Public Key: ' + publicKey);
// "Public Key: 0x026655feed4d214c261e0a6b554395596f1f1476a77d999560e5a8df9b8a1a3515"

var compressedPublicKey = SigningKey.getPublicKey(publicKey, true);
var uncompressedPublicKey = SigningKey.getPublicKey(publicKey, false);

console.log('Compressed: ' + compressedPublicKey);
// "Compressed: 0x026655feed4d214c261e0a6b554395596f1f1476a77d999560e5a8df9b8a1a3515"

console.log('Uncompressed: ' + uncompressedPublicKey);
// "Uncompressed: 0x046655feed4d214c261e0a6b554395596f1f1476a77d999560e5a8df9b8a1a35" +
// "15217e88dd05e938efdd71b2cce322bf01da96cd42087b236e8f5043157a9c068e"

var address = SigningKey.publicKeyToAddress(publicKey);

console.log('Address: ' + address);
// "Address: 0x14791697260E4c9A71f18484C9f997B308e59325"

Recursive-Length Prefixed Encoding (RLP)¶

This encoding method is used internally for several aspects of Ethereum, such as encoding transactions and determining contract addresses. For most developers this should not be necessary to use.

RLP can encode nested arrays, with data as hex strings and Uint8Array (or other non-Array arrayish objects). A decoded object will always have data represented as hex strings and Arrays.

See: https://github.com/ethereum/wiki/wiki/RLP

Static Methods¶

^RLP . encode( object ): Encodes an object as an RLP hex string. (throws an Error if the object contains invalid items)
^RLP . decode( hexStringOrArrayish ): Decode hexStringOrArrayish into the encoded object. (throws an Error if invalid RLP-coded data)

Examples¶

var RLP = requrie('ethers-utils/rlp');

var object = [ ["0x42"], "0x1234", [ [], [] ] ];

var encoded = rlp.encode(object);
console.log(encoded);
// 0xc8c142821234c2c0c0

var decoded = rlp.decode(encoded);
console.log(decoded);
// [ [ '0x42' ], '0x1234', [ [], [] ] ]