Etherium

[Jsydog222]

URI schemes

This QR code generator supports URI across three different use-cases:

1. Sending ETH

2. Invoking function of a contract

3. Sending ERC20 tokens

We cover these 3 different cases using a parameter called 'mode'. The details are outlined below.

1. Sending ETH

URI scheme used to send ETH between accounts conforms early EIP67 proposals and Bitcoin scheme.

This is built to be backward compatible.

ethereum:<address>[?from=<sender_address>][?value=<ethamount>][?gas=<suggestedGas>]

Parameters:

1. to | String | required - The address of the recipient account

2. from | String | optional - Address of the tx sender. Defaults to current active account of the sender app

3. value | Number | optional - Amount of ETH to send. Measured in wei. Defaults to 0.

4. gas | Number | optional - Recommended amount of gas. Defaults to 21000.

These are the only parameters needed for this use-case.

For the other use-cases, the mode field allows for defining the structure of the resulting JSON. The URI scheme to invoke the contract's function uses JSON to encode the parameters specified.

Possible inputs for the mode field:

• contract_function

• erc20__transfer

• erc20__approve

• erc20__transferFrom

These are explored in more detail below.

2. Invoke function of a contract

That mode is utilized by specifying "mode: "contract_function".

Example of the transfer method using an ERC20 token:

{

  "to": "0xcontractaddress",

  "from": "0xsenderaddress",

  "value": 0,

  "gas": 100000,

  "mode": "contract_function",

  "functionSignature": {

    "name": "transfer",

    "payable": false,

    "args": [

      {

        "name": "to",

        "type": "address"

      },

      {

        "name": "value",

        "type": "uint"

      }

    ]

  },

  "argsDefaults": [

    {

      "name": "to",

      "value": "0xtokensrecipient"

    },

    {

      "name": "value",

      "value": 1000000000000000000

    }

  ]

}

Parameters:

1. to | String | required - Recipient address

2. from | String | optional - Sender address. Defaults to current active user account

3. value | Number | optional - Amount of ETH to send. Measured in wei. Defaults to 0.

4. gas | Number | optional - Recommended amount of gas. Defaults to 21000.

5. mode | String | required - Mode of invocation. Expected value: contract_function

6. functionSignature | Object | required - Object that defines signature of invoked function. It is used only if "mode" == "function"

   1. name | String | required - Name of the invoked function

   2. payable | Boolean | required - Defines whether function is able to receive ETH or not. (value should be zero if false)

   3. args | Array | optional - Contains list of function`s arguments. If this parameter is present - it must contain at least one element. If this parameter is not present - we assume that function do not have arguments.

      1. type | String | required - Type of the argument: uint, uint8, int32, address, bool and so on.

      2. name | String | required - Name of the argument. Used to generate GUI for the transaction.

      In fact, argument of Solidity function can be unnamed - this is OK if you develop a smart contract.

      But QR codes are used to pass tx details between different wallets and GUI must be nice.

      Therefore unnamed input fields in GUI are not possible. Therefore this parameter is required.

7. argsDefaults | Array | optional - Array with default values for function arguments. If this parameter is present - it must contain at least one element. We do not require to provide defaults of all args.

   1. name | String | required - Name of the argument. Should be equal to the name of one of arguments from functionSignature

   2. value | Any | required - Default value for the function argument

3. Template for ERC20 tokens

The 3 extra subtypes were added since ERC20 tokens are very popular.

To make it easier to send tokens between accounts we predefine function signatures for the methods from ERC20 specification:

1. "mode": "erc20__transfer" will result in function transfer(address to, uint value) returns (bool success)

2. "mode": "erc20__approve" => function approve(address spender, uint value) returns (bool success)

3. "mode": "erc20__transferFrom" => function transferFrom(address from, address to, uint value) returns (bool success)

Example for transfer method:

{

  "to": "0xcontractaddress",

  "from": "0xsenderaddress",

  "gas": 100000,

  "mode": "erc20__transfer",

  "argsDefaults": [

    {

      "name": "to",

      "value": "0xtokensrecipient"

    }

  ]

}

Functionally, this is similar to the previous example.

Parameters:

1. to | String | required - Recipient address

2. from | String | optional - Sender address. Defaults to current active account of the sender user

3. gas | Number | optional - Recommended amount of gas. Defaults to 21000.

4. mode | String | required - Mode of invocation. Expected value: erc20__transfer, erc20__approve, erc20__transferFrom

5. argsDefaults | Array | optional - Array with default values for function arguments.

   1. name | String | required - Name of the argument. Should be equal to the name of one of arguments from functionSignature

   2. value | Any | required - Default value for the function argument

Originally posted by @mezrin in #67