To apply predefined system operations, built-in functions are defined. For example, account value transfer is implemented using transfer built-in function. Each built-in function consists of triggering conditions and a function. The triggering condition is given by a database path pattern and whenever a new value is written on the path patten, the function is called. If the function fails, the transaction triggered the function call also fails.
Transfer
{
'/transfer/{from_addr}/{to_addr}/{transfer_id}/value': _transfer(value, context) {
// Check (the balance of from_addr) >= value
// Decrement the balance of from_addr by value
// Increment the balance of to_addr by value
}
}
Deposit
{
'/deposit/{service_id}/{addr}/{deposit_id}/value': _deposit(value, context) {
// Check (the balance of addr) >= value
// Decrement the balance of addr by value
// Increment the value of /deposit_accounts/$service_id/$addr by value
// Set /deposit_accounts/$service_id/$addr/expire_at as
// transaction's timestamp + service's deposit lockup time, which is
// configured at /deposit_accounts/$service_id/config/lockup_duration
}
}
Withdraw
{
'/withdraw/{service_id}/{addr}/{withdraw_id}/value': _withdraw(value, context) {
// Check the value at (/deposit_accounts/$service_id/$addr/value) >= value
// Check (deposit_accounts/$service_id/$addr/expire_at) >= current time
// Decrement the value of /deposit_accounts/$service_id/$addr by value
// Increment the balance of addr by value
}
}
