token_transfer.cpp

void token::transfer( const name&    from,
                      const name&    to,
                      const asset&   quantity,
                      const string&  memo )
{
    check( from != to, "cannot transfer to self" );
    require_auth( from );
    check( is_account( to ), "to account does not exist");
    auto sym = quantity.symbol.code();
    stats statstable( get_self(), sym.raw() );
    const auto& st = statstable.get( sym.raw() );

    require_recipient( from );
    require_recipient( to );

    check( quantity.is_valid(), "invalid quantity" );
    check( quantity.amount > 0, "must transfer positive quantity" );
    check( quantity.symbol == st.supply.symbol, "symbol precision mismatch" );
    check( memo.size() <= 256, "memo has more than 256 bytes" );

    auto payer = has_auth( to ) ? to : from;

    sub_balance( from, quantity );
    add_balance( to, quantity, payer );
}