Purpose of the cyber.token smart contract development

The system smart contract cyber.token provides token management functions, generates new tokens and stores information about created tokens and provides an ability to conduct mutual settlements between accounts as well.

The cyber.token smart contract includes the following actions: create, issue, retire, transfer, bulktransfer, payment, bulkpayment, claim, open and close.

The create action

The create action is applied to create a token to supply it into the system. This action has the following form:

[[eosio::action]] void create(
    name   issuer,
    asset  maximum_supply
);

Parameters:

• issuer — account name which creates the token to supply it into the system.

• maximum_supply — a structure value containing the fields:

  • maximum number of tokens supplied;

  • token symbol (data type that uniquely identifies the token). This is a structure value containing fields:

    • token name, consisting of a set of capital letters;

    • field that specifies a token cost accuracy in the form of decimal places number.

The issuer account is authorized to supply and withdraw tokens from circulation in the system. The create action can be executed by the token smart contract only. In order to perform this action, the signature of the validators is required. Use of the bandwidth resources (RAM) is charged to the issuer account.

The issue action

The issue action is applied to put a token into circulation in the system. This action has the following form:

[[eosio::action]] void issue(
    name to,  
    asset quantity,  
    string memo
);

Parameters:

• to — recipient account to balance of which the tokens are transferred.

• quantity — number of the supplied tokens. This is a structure value containing fields:

  • number of the supplied tokens in the system;

  • a token symbol. This is a structure value containing fields:

    • the token name, consisting of a set of capital letters;

    • the field that specifies a token cost accuracy in the form of decimal places number.

• memo — memo text that clarifies a meaning (necessity) of the token emission in the system. The text volume should not exceed 384 symbols including blanks.

When the create action is performed, the token symbol and the account name issuer are put into the table. When executing the issue action, the token character is taken from the resulting quantity value. The account issuer can be determined via using this symbol and table data. The number of supplied tokens should not exceed maximum_supply value specified in the create action. Use of the bandwidth resources (RAM) is charged to the issuer account.

To perform the create action, the issuer account authorization is required.

The retire action

The retire action is used to withdraw a certain number of tokens from the system. This action has the following form:

[[eosio::action]] void retire(
    asset quantity,
    string memo
);

Parameters:

• quantity — number of withdrawn tokens.

• memo — a memo text clarifying a purpose of withdrawing tokens from circulation.

Use of the bandwidth resources (RAM) is charged to the issuer account. The number of tokens withdrawn from circulation is also removed from issuer account balance, so this account can not withdraw tokens more than he/she has them on own balance.

To perform this action, the issuer account authorization is required.

The transfer action

The transfer action is used to transfer tokens from one account to another. This action has the following form:

[[eosio::action]] void transfer(
    name from,
    name to,
    asset quantity,
    string  memo
);

Parameters:

• from — sender account from balance of which the tokens are withdrawn.

• to — recipient account to balance of which the tokens are transferred.

• quantity — number of tokens to be transferred. This value should be greater than zero.

• memo — a memo text that clarifies a meaning of the token transfer.

The action is performed with sending a notification to smart contracts of the sender and recipient of tokens. Sending the notification is an internal action and looks similar to the transfer action . The difference is the «sending a notification» action is not performed on cyber.token, but on smart contracts of sender and recipient of the notification (for example, if the vesting smart contract receives a notification, it automatically charges tokens on the vesting balance).

To perform the transfer action, the from account authorization is required.

Use of the bandwidth (RAM) resources is charged either to sending account or to receiving account, depending on who signed the transaction. If the open action was previously performed, none of them should pay bandwidth, since the record already created in database is used.

Note: If sender account pays for used resources (RAM) for a recipient account, then there is the possibility of spending the entire share of memory allocated to the recipient account. To avoid such cases when performing the action transfer, additional actions have been implemented in cyber.token. These are open and close. Functional purposes of these actions are the creation and deletion of an entry in the database before and after (not during) performing transfer respectively.

The bulktransfer action

The action bulktransfer is used to transfer tokens from one account's balance to the balances of several accounts (for example, for paying rewards for a post). This action has the following form:

[[eosio::action]] void bulktransfer(
    name from,
    vector<recipient> recipients
)

Parameters:

• from — sender account from balance of which the tokens are withdrawn.

• recipients — array (list) of token recipients. Each array element is a structure containing fields:

  • to — recipient account to balance of which the tokens are transferred;

  • quantity — number of tokens to be transferred to account to. This value should be greater than zero;

  • memo — a memo text that clarifies a meaning of the token transfer. The text volume should not exceed 384 symbols including blanks.

The restrictions imposed on the bulktransfer action:

• transfer of various types tokens is not allowed;

• transfer of tokens to itself is not allowed, that is, the list of recipients should not contain the account name from.

It is allowed in the recipients list to specify the same account name to more than once. The action is performed with sending a notification to smart contracts of the sender and recipient of tokens in the same way as transfer.

To perform bulktransfer, it is required a signature of the account from.

The payment action

The payment action like the transfer action is used to transfer funds from one account to another. This action has the following form:

[[eosio::action]] void payment(
    name  from,
    name  to,
    const asset& quantity,
    const string& memo
)

Parameters:

• from — sender account from balance of which the tokens are withdrawn.

• to — account name which is a recipient token.

• quantity — number of tokens to be transferred to account name to. This value should be greater than zero.

• memo — a memo text that clarifies a meaning of the token transfer. The text volume should not exceed 384 symbols including blanks.

Unlike transfer, when performing payment action, notifications are not sent and funds are transferred not to the recipient account balance , but to the payment-intermediary balance. To withdraw funds from the payment balance, the recipient account to should additionally perform the action claim.

The action payment is a more secure option to transfer tokens. To perform payment, it is required a signature of the account from.

The bulkpayment action

The action bulktransfer is used to transfer tokens from one account's balance to several accounts (for example, for paying rewards to curators and beneficiaries for a post). The bulkpayment action has the following form:

[[eosio::action]] void bulkpayment(
    name from,
    vector<recipient> recipients
)

Parameters:

• from — sender account from balance of which the tokens are withdrawn.

• recipients — array (list) of token recipients. Each array element is a structure containing fields:

  • to — account name which is a recipient token;

  • quantity — number of tokens to be transferred to account name to. This value should be greater than zero;

  • memo — a memo text that clarifies a meaning of the token transfer. The text volume should not exceed 384 symbols including blanks.

The restrictions imposed on the bulkpayment action:

• transfer of various types tokens is not allowed;

• transfer of tokens to itself is not allowed, that is, the list of recipients should not contain the account name from.

  Unlike bulktransfer, when performing bulkpayment action, notifications are not sent and funds are transferred not to the recipient accounts balances , but to the payment (intermediary) balance. To withdraw funds from the payment balance, each of the recipient accounts should additionally perform the action claim.

The action bulkpayment is a more secure option to transfer tokens. To perform bulkpayment, it is required a signature of the account from.

The claim action

The claim action is used to transfer funds from the payment balance to an account balance. This action has the following form:

[[eosio::action]] void claim(
    name owner,
    asset quantity
)

Parameters:

• owner — account name to whose balance the funds are transferred.

• quantity — requested number of tokens to be transfered. This number must not exceed the number of tokens that are on the payment balance and which are owned by the owner account.

Performing the claim action requires a signature of the owner account.

The open action

The open action is used to create a record in database. This entry must contain an account name which should pay for the memory used, as well as a symbol for which this entry is created. The open action has the following form:

[[eosio::action]] void open(
    name owner,
    symbol symbol,
    name ram_payer
);

Parameters:

• owner — account name to which the memory is allocated.

• symbol — symbol for which the entry is being created.

• ram_payer — account name that pays for the used memory.

Performing the open action requires a signature of the ram_payer account.

The close action

The close action is an opposite of open and is used to free allocated memory in database. The close action has the following form:

[[eosio::action]] void close(
    name owner,
    symbol symbol
);

Parameters:

• owner — account name to which the memory was allocated.

• symbol — a symbol for which the entry is deleted.

To perform this action, it is necessary to have two zero balances of the account owner:

• zero token balance (determined by the symbol);

• zero payment balance.

Obtaining statistical information about system tokens

To obtain statistical information on tokens, two tables, currency_stats and account, are used in the cyber.token smart contract.

The currency_stats table has the following form:

struct [[eosio::table]] currency_stats {
    asset supply;
    asset max_supply;
    name issuer;
};

Parameters:

• supply — number of a certain type tokens that have been supplied in the system.

• max_supply — maximum possible number of this type tokens in circulation.

• issuer — account name which has supplied this type tokens in the system.

Primary key for table currency_stats is a character value in the asset. This value is used to determine the token. having information about a token it is easily to obtain its supply value — the number of tokens released into circulation, as well as the account name issuer.

The account table has the following form:

struct [[eosio::table]] account {
    asset balance;
    asset payments;
};

A scope of the table is determined by the account name.