> ## Documentation Index
> Fetch the complete documentation index at: https://mohai.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Bank

## Abstract

The x/bank module in Stable SDK only provides basic token management features. Every token can be transferred to any account without any restriction and users cannot delegate other account for transferring their tokens to other accounts. For these reasons, the bank precompiled contract offers additional authorization and delegation features on top of the existing x/bank module in Stable SDK.

## Contents

1. [Concepts](/coreMechanics/SystemModulesPrecompiles/bank#concepts)
2. [Configuration](/coreMechanics/SystemModulesPrecompiles/bank#configuration)
3. [Methods](/coreMechanics/SystemModulesPrecompiles/bank#methods)
4. [Events](/coreMechanics/SystemModulesPrecompiles/bank#events)

## Concepts

This precompiled contract provides ERC20 standard methods - such as <code>transfer</code> and <code>balanceOf</code> for transfer and <code>transferFrom</code>, <code>approve</code> and <code>allowance</code> for delegation. These methods can be called directly without requiring the contract address to be registered.

However, <code>mint</code> and <code>burn</code> methods require the contract address to be whitelisted, registered by the <code>x/precompile</code> module.

```
func (p *Precompile) mint(
  ctx sdk.Context,
  contract *vm.Contract,
  denom string,
  method *abi.Method,
  stateDB vm.StateDB,
  args []interface{},
) ([]byte, error) {
  // ...

  // mint method is only allowed for the registered caller contract
  if _, err := precompilecommon.CheckPermissions(ctx, p.precompileKeeper, contract.CallerAddress, CallerPermissions); err != nil {
    return nil, err
  }
```

Additional verification process can guarantee that token contract, calling this precompiled contract, is authorized.

Governance proposal is required to register token contract address and its denom to whitelist in <code>x/precompile</code> module.

## Configuration

Contract address and gas cost is predefined.

### Contract Address

* <code>0x0000000000000000000000000000000000001000</code> for gUSDT (gas token)
* <code>0x0000000000000000000000000000000000001003</code> for STABLE (governance token)

## Methods

### mint

Mints requested amount of new tokens and transfer to the account. The amount of tokens to be minted must be greater than zero.

<code>PrecompiledBankMint</code> is emitted when the tokens are successfully minted and transferred to the account.

NOTE:

* Minting governance token minting is prohibited.
* Caller contracts calling mint method are must be registered in x/precompile module.

#### Inputs

| Name   | Type    | Description                              |
| ------ | ------- | ---------------------------------------- |
| to     | address | the address to receive the minted tokens |
| amount | uint256 | the amount of tokens to be minted        |

#### Outputs

| Name    | Type | Description                                                               |
| ------- | ---- | ------------------------------------------------------------------------- |
| success | bool | true if the tokens are successfully minted and transferred to the account |

### burn

Burns requested amount of tokens from the account. The amount of tokens to be burned must be greater than zero.

<code>PrecompiledBankBurn</code> is emitted when the tokens are successfully burned.

NOTE:

* Burning governance token is prohibited.
* Caller contracts calling mint method are must be registered in x/precompile module.

#### Inputs

| Name   | Type    | Description                       |
| ------ | ------- | --------------------------------- |
| from   | address | the address to burn the tokens    |
| amount | uint256 | the amount of tokens to be burned |

#### Outputs

| Name    | Type | Description                                |
| ------- | ---- | ------------------------------------------ |
| success | bool | true if the tokens are successfully burned |

### transfer

Transfers requested amount of tokens from sender to the recipient. Token must be set sendable. The amount of tokens to be transferred must be greater than zero.

<code>PrecompiledBankTransfer</code> is emitted when the tokens are successfully transferred.

#### Inputs

| Name   | Type    | Description                            |
| ------ | ------- | -------------------------------------- |
| to     | address | the address to receive the tokens      |
| amount | uint256 | the amount of tokens to be transferred |

#### Outputs

| Name    | Type | Description                                     |
| ------- | ---- | ----------------------------------------------- |
| success | bool | true if the tokens are successfully transferred |

### transferFrom

Transfers requested amount of tokens from owner to recipient by authorized spender within the limits of the allowance. Token must be set sendable. The amount of tokens to be transferred must be greater than zero and less than or equal to the current allowance.

<code>PrecompiledBankTransfer</code> is emitted when the tokens are successfully transferred.

#### Inputs

| Name   | Type    | Description                            |
| ------ | ------- | -------------------------------------- |
| from   | address | the address to transfer the tokens     |
| to     | address | the address to receive the tokens      |
| amount | uint256 | the amount of tokens to be transferred |

#### Outputs

| Name    | Type | Description                                     |
| ------- | ---- | ----------------------------------------------- |
| success | bool | true if the tokens are successfully transferred |

### multiTransfer

Transfers tokens from single account to multiple accounts. Token must be set sendable.

The amount of tokens to be transferred to each recipient must be greater than zero.

<code>PrecompiledBankTransfer</code> is emitted per each recipient when the tokens are successfully transferred.

#### Inputs

| Name   | Type       | Description                                              |
| ------ | ---------- | -------------------------------------------------------- |
| to     | address\[] | the addresses to receive the transferred tokens          |
| amount | uint256\[] | the amount of tokens to be transferred to each recipient |

#### Outputs

| Name    | Type | Description                                                       |
| ------- | ---- | ----------------------------------------------------------------- |
| success | bool | true if the tokens are successfully transferred to each recipient |

### approve

Authorizes a spender to transfer tokens from the owner’s account. The amount of tokens to be authorized must be greater than zero.

<code>PrecompiledBankApproval</code> is emitted when the authorization is successfully set.

#### Inputs

| Name    | Type    | Description                           |
| ------- | ------- | ------------------------------------- |
| spender | address | the address to authorize              |
| value   | uint256 | the amount of tokens to be authorized |

#### Outputs

| Name    | Type | Description                                   |
| ------- | ---- | --------------------------------------------- |
| success | bool | true if the authorization is successfully set |

### revoke

Revokes the authorization of spender for transferring tokens from owner.

<code>PrecompiledBankRevoke</code> is emitted when the authorization is successfully revoked.

#### Inputs

| Name    | Type                          | Description |
| ------- | ----------------------------- | ----------- |
| spender | address	the address to revoke |             |

#### Outputs

| Name    | Type | Description                                       |
| ------- | ---- | ------------------------------------------------- |
| success | bool | true if the authorization is successfully revoked |

### balanceOf

Returns balance of tokens from the account.

#### Inputs

| Name    | Type    | Description                              |
| ------- | ------- | ---------------------------------------- |
| account | address | the address to get the balance of tokens |

#### Outputs

| Name    | Type    | Description                         |
| ------- | ------- | ----------------------------------- |
| balance | uint256 | the amount of tokens in the account |

### totalSupply

Returns total supply of tokens.

#### Inputs

none

#### Outputs

| Name        | Type    | Description                |
| ----------- | ------- | -------------------------- |
| totalSupply | uint256 | the total amount of tokens |

### allowance

Returns the amount which spender is still allowed to withdraw from owner.

#### Inputs

| Name    | Type    | Description                |
| ------- | ------- | -------------------------- |
| owner   | address | the address of the owner   |
| spender | address | the address of the spender |

#### Outputs

| Name   | Type    | Description                     |
| ------ | ------- | ------------------------------- |
| amount | uint256 | the amount of tokens authorized |

## Events

All events emitted from this precompiled contract are prefixed with PrecompiledBank. To avoid ambiguity, token contract calling this precompiled contract should avoid using event names with the same prefix.

### PrecompiledBankMint

| Name   | Type    | Indexed | Description                              |
| ------ | ------- | ------- | ---------------------------------------- |
| from   | address | Y       | the address that minted the tokens       |
| to     | address | Y       | the address to receive the minted tokens |
| amount | uint256 | N       | the amount of tokens minted              |

### PrecompiledBankBurn

| Name   | Type    | Indexed | Description                        |
| ------ | ------- | ------- | ---------------------------------- |
| from   | address | Y       | the address that burned the tokens |
| to     | address | Y       | not used in this method            |
| amount | uint256 | N       | the amount of tokens burned        |

### PrecompiledBankTransfer

| Name   | Type    | Indexed | Description                                   |
| ------ | ------- | ------- | --------------------------------------------- |
| from   | address | Y       | the address that transferred the tokens       |
| to     | address | Y       | the address to receive the transferred tokens |
| amount | uint256 | N       | the amount of tokens transferred              |

### PrecompiledBankApproval

| Name    | Type    | Indexed | Description                            |
| ------- | ------- | ------- | -------------------------------------- |
| owner   | address | Y       | the address that authorized the tokens |
| spender | address | Y       | the address to authorize               |
| value   | uint256 | N       | the amount of tokens authorized        |

### PrecompiledBankRevoke

| Name    | Type    | Indexed | Description                         |
| ------- | ------- | ------- | ----------------------------------- |
| owner   | address | Y       | the address that revoked the tokens |
| spender | address | Y       | the address to revoke               |
| value   | uint256 | N       | the amount of tokens authorized     |