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Module `0x1::TransactionFee`

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<a name="0x1_TransactionFee"></a>

Module 0x1::TransactionFee

Functions to initialize, accumulated, and burn transaction fees.

<pre><code><b>use</b> <a href="Diem.md#0x1_Diem">0x1::Diem</a>; <b>use</b> <a href="DiemTimestamp.md#0x1_DiemTimestamp">0x1::DiemTimestamp</a>; <b>use</b> <a href="../../../../../../move-stdlib/docs/Errors.md#0x1_Errors">0x1::Errors</a>; <b>use</b> <a href="Roles.md#0x1_Roles">0x1::Roles</a>; <b>use</b> <a href="XDX.md#0x1_XDX">0x1::XDX</a>; <b>use</b> <a href="XUS.md#0x1_XUS">0x1::XUS</a>; </code></pre>

<a name="0x1_TransactionFee_TransactionFee"></a>

Resource TransactionFee

The <code><a href="TransactionFee.md#0x1_TransactionFee">TransactionFee</a></code> resource holds a preburn resource for each fiat <code>CoinType</code> that can be collected as a transaction fee.

<pre><code><b>struct</b> <a href="TransactionFee.md#0x1_TransactionFee">TransactionFee</a>&lt;CoinType&gt; has key </code></pre> <details> <summary>Fields</summary> <dl> <dt> <code>balance: <a href="Diem.md#0x1_Diem_Diem">Diem::Diem</a>&lt;CoinType&gt;</code> </dt> <dd> </dd> <dt> <code>preburn: <a href="Diem.md#0x1_Diem_Preburn">Diem::Preburn</a>&lt;CoinType&gt;</code> </dt> <dd> </dd> </dl> </details>

<a name="@Constants_0"></a>

Constants

<a name="0x1_TransactionFee_ETRANSACTION_FEE"></a>

A <code><a href="TransactionFee.md#0x1_TransactionFee">TransactionFee</a></code> resource is not in the required state

<pre><code><b>const</b> <a href="TransactionFee.md#0x1_TransactionFee_ETRANSACTION_FEE">ETRANSACTION_FEE</a>: u64 = 0; </code></pre>

<a name="0x1_TransactionFee_initialize"></a>

Function initialize

Called in genesis. Sets up the needed resources to collect transaction fees from the <code><a href="TransactionFee.md#0x1_TransactionFee">TransactionFee</a></code> resource with the TreasuryCompliance account.

<pre><code><b>public</b> <b>fun</b> <a href="TransactionFee.md#0x1_TransactionFee_initialize">initialize</a>(tc_account: &signer) </code></pre> <details> <summary>Implementation</summary> <pre><code><b>public</b> <b>fun</b> <a href="TransactionFee.md#0x1_TransactionFee_initialize">initialize</a>( tc_account: &signer, ) { <a href="DiemTimestamp.md#0x1_DiemTimestamp_assert_genesis">DiemTimestamp::assert_genesis</a>(); <a href="Roles.md#0x1_Roles_assert_treasury_compliance">Roles::assert_treasury_compliance</a>(tc_account); // accept fees in all the currencies <a href="TransactionFee.md#0x1_TransactionFee_add_txn_fee_currency">add_txn_fee_currency</a>&lt;<a href="XUS.md#0x1_XUS">XUS</a>&gt;(tc_account); } </code></pre> </details> <details> <summary>Specification</summary> <pre><code><b>include</b> <a href="DiemTimestamp.md#0x1_DiemTimestamp_AbortsIfNotGenesis">DiemTimestamp::AbortsIfNotGenesis</a>; <b>include</b> <a href="Roles.md#0x1_Roles_AbortsIfNotTreasuryCompliance">Roles::AbortsIfNotTreasuryCompliance</a>{account: tc_account}; <b>include</b> <a href="TransactionFee.md#0x1_TransactionFee_AddTxnFeeCurrencyAbortsIf">AddTxnFeeCurrencyAbortsIf</a>&lt;<a href="XUS.md#0x1_XUS">XUS</a>&gt;; <b>ensures</b> <a href="TransactionFee.md#0x1_TransactionFee_is_initialized">is_initialized</a>(); <b>ensures</b> <a href="TransactionFee.md#0x1_TransactionFee_spec_transaction_fee">spec_transaction_fee</a>&lt;<a href="XUS.md#0x1_XUS">XUS</a>&gt;().balance.value == 0; </code></pre>

<a name="0x1_TransactionFee_AddTxnFeeCurrencyAbortsIf"></a>

<pre><code><b>schema</b> <a href="TransactionFee.md#0x1_TransactionFee_AddTxnFeeCurrencyAbortsIf">AddTxnFeeCurrencyAbortsIf</a>&lt;CoinType&gt; { <b>include</b> <a href="Diem.md#0x1_Diem_AbortsIfNoCurrency">Diem::AbortsIfNoCurrency</a>&lt;CoinType&gt;; <b>aborts_if</b> <b>exists</b>&lt;<a href="TransactionFee.md#0x1_TransactionFee">TransactionFee</a>&lt;CoinType&gt;&gt;(@TreasuryCompliance) <b>with</b> <a href="../../../../../../move-stdlib/docs/Errors.md#0x1_Errors_ALREADY_PUBLISHED">Errors::ALREADY_PUBLISHED</a>; } </code></pre> </details>

<a name="0x1_TransactionFee_is_coin_initialized"></a>

Function is_coin_initialized

<pre><code><b>public</b> <b>fun</b> <a href="TransactionFee.md#0x1_TransactionFee_is_coin_initialized">is_coin_initialized</a>&lt;CoinType&gt;(): bool </code></pre> <details> <summary>Implementation</summary> <pre><code><b>public</b> <b>fun</b> <a href="TransactionFee.md#0x1_TransactionFee_is_coin_initialized">is_coin_initialized</a>&lt;CoinType&gt;(): bool { <b>exists</b>&lt;<a href="TransactionFee.md#0x1_TransactionFee">TransactionFee</a>&lt;CoinType&gt;&gt;(@TreasuryCompliance) } </code></pre> </details>

<a name="0x1_TransactionFee_is_initialized"></a>

Function is_initialized

<pre><code><b>fun</b> <a href="TransactionFee.md#0x1_TransactionFee_is_initialized">is_initialized</a>(): bool </code></pre> <details> <summary>Implementation</summary> <pre><code><b>fun</b> <a href="TransactionFee.md#0x1_TransactionFee_is_initialized">is_initialized</a>(): bool { <a href="TransactionFee.md#0x1_TransactionFee_is_coin_initialized">is_coin_initialized</a>&lt;<a href="XUS.md#0x1_XUS">XUS</a>&gt;() } </code></pre> </details>

<a name="0x1_TransactionFee_add_txn_fee_currency"></a>

Function add_txn_fee_currency

Sets up the needed transaction fee state for a given <code>CoinType</code> currency by (1) configuring <code>tc_account</code> to accept <code>CoinType</code> (2) publishing a wrapper of the <code>Preburn<CoinType></code> resource under <code>tc_account</code>

<pre><code><b>public</b> <b>fun</b> <a href="TransactionFee.md#0x1_TransactionFee_add_txn_fee_currency">add_txn_fee_currency</a>&lt;CoinType&gt;(tc_account: &signer) </code></pre> <details> <summary>Implementation</summary> <pre><code><b>public</b> <b>fun</b> <a href="TransactionFee.md#0x1_TransactionFee_add_txn_fee_currency">add_txn_fee_currency</a>&lt;CoinType&gt;(tc_account: &signer) { <a href="Roles.md#0x1_Roles_assert_treasury_compliance">Roles::assert_treasury_compliance</a>(tc_account); <a href="Diem.md#0x1_Diem_assert_is_currency">Diem::assert_is_currency</a>&lt;CoinType&gt;(); <b>assert</b>( !<a href="TransactionFee.md#0x1_TransactionFee_is_coin_initialized">is_coin_initialized</a>&lt;CoinType&gt;(), <a href="../../../../../../move-stdlib/docs/Errors.md#0x1_Errors_already_published">Errors::already_published</a>(<a href="TransactionFee.md#0x1_TransactionFee_ETRANSACTION_FEE">ETRANSACTION_FEE</a>) ); move_to( tc_account, <a href="TransactionFee.md#0x1_TransactionFee">TransactionFee</a>&lt;CoinType&gt; { balance: <a href="Diem.md#0x1_Diem_zero">Diem::zero</a>(), preburn: <a href="Diem.md#0x1_Diem_create_preburn">Diem::create_preburn</a>(tc_account) } ) } </code></pre> </details>

<a name="0x1_TransactionFee_pay_fee"></a>

Function pay_fee

Deposit <code>coin</code> into the transaction fees bucket

<pre><code><b>public</b> <b>fun</b> <a href="TransactionFee.md#0x1_TransactionFee_pay_fee">pay_fee</a>&lt;CoinType&gt;(coin: <a href="Diem.md#0x1_Diem_Diem">Diem::Diem</a>&lt;CoinType&gt;) </code></pre> <details> <summary>Implementation</summary> <pre><code><b>public</b> <b>fun</b> <a href="TransactionFee.md#0x1_TransactionFee_pay_fee">pay_fee</a>&lt;CoinType&gt;(coin: <a href="Diem.md#0x1_Diem">Diem</a>&lt;CoinType&gt;) <b>acquires</b> <a href="TransactionFee.md#0x1_TransactionFee">TransactionFee</a> { <a href="DiemTimestamp.md#0x1_DiemTimestamp_assert_operating">DiemTimestamp::assert_operating</a>(); <b>assert</b>(<a href="TransactionFee.md#0x1_TransactionFee_is_coin_initialized">is_coin_initialized</a>&lt;CoinType&gt;(), <a href="../../../../../../move-stdlib/docs/Errors.md#0x1_Errors_not_published">Errors::not_published</a>(<a href="TransactionFee.md#0x1_TransactionFee_ETRANSACTION_FEE">ETRANSACTION_FEE</a>)); <b>let</b> fees = borrow_global_mut&lt;<a href="TransactionFee.md#0x1_TransactionFee">TransactionFee</a>&lt;CoinType&gt;&gt;(@TreasuryCompliance); <a href="Diem.md#0x1_Diem_deposit">Diem::deposit</a>(&<b>mut</b> fees.balance, coin) } </code></pre> </details> <details> <summary>Specification</summary> <pre><code><b>include</b> <a href="DiemTimestamp.md#0x1_DiemTimestamp_AbortsIfNotOperating">DiemTimestamp::AbortsIfNotOperating</a>; <b>aborts_if</b> !<a href="TransactionFee.md#0x1_TransactionFee_is_coin_initialized">is_coin_initialized</a>&lt;CoinType&gt;() <b>with</b> <a href="../../../../../../move-stdlib/docs/Errors.md#0x1_Errors_NOT_PUBLISHED">Errors::NOT_PUBLISHED</a>; <b>let</b> fees = <a href="TransactionFee.md#0x1_TransactionFee_spec_transaction_fee">spec_transaction_fee</a>&lt;CoinType&gt;().balance; <b>let</b> post post_fees = <a href="TransactionFee.md#0x1_TransactionFee_spec_transaction_fee">spec_transaction_fee</a>&lt;CoinType&gt;().balance; <b>include</b> <a href="Diem.md#0x1_Diem_DepositAbortsIf">Diem::DepositAbortsIf</a>&lt;CoinType&gt;{coin: fees, check: coin}; <b>ensures</b> post_fees.value == fees.value + coin.value; </code></pre> </details>

<a name="0x1_TransactionFee_burn_fees"></a>

Function burn_fees

Preburns the transaction fees collected in the <code>CoinType</code> currency. If the <code>CoinType</code> is XDX, it unpacks the coin and preburns the underlying fiat.

<pre><code><b>public</b> <b>fun</b> <a href="TransactionFee.md#0x1_TransactionFee_burn_fees">burn_fees</a>&lt;CoinType&gt;(tc_account: &signer) </code></pre> <details> <summary>Implementation</summary> <pre><code><b>public</b> <b>fun</b> <a href="TransactionFee.md#0x1_TransactionFee_burn_fees">burn_fees</a>&lt;CoinType&gt;( tc_account: &signer, ) <b>acquires</b> <a href="TransactionFee.md#0x1_TransactionFee">TransactionFee</a> { <a href="DiemTimestamp.md#0x1_DiemTimestamp_assert_operating">DiemTimestamp::assert_operating</a>(); <a href="Roles.md#0x1_Roles_assert_treasury_compliance">Roles::assert_treasury_compliance</a>(tc_account); <b>assert</b>(<a href="TransactionFee.md#0x1_TransactionFee_is_coin_initialized">is_coin_initialized</a>&lt;CoinType&gt;(), <a href="../../../../../../move-stdlib/docs/Errors.md#0x1_Errors_not_published">Errors::not_published</a>(<a href="TransactionFee.md#0x1_TransactionFee_ETRANSACTION_FEE">ETRANSACTION_FEE</a>)); <b>if</b> (<a href="XDX.md#0x1_XDX_is_xdx">XDX::is_xdx</a>&lt;CoinType&gt;()) { // TODO: Once the composition of <a href="XDX.md#0x1_XDX">XDX</a> is determined fill this in <b>to</b> // <b>unpack</b> and burn the backing coins of the <a href="XDX.md#0x1_XDX">XDX</a> coin. <b>abort</b> <a href="../../../../../../move-stdlib/docs/Errors.md#0x1_Errors_invalid_state">Errors::invalid_state</a>(<a href="TransactionFee.md#0x1_TransactionFee_ETRANSACTION_FEE">ETRANSACTION_FEE</a>) } <b>else</b> { // extract fees <b>let</b> fees = borrow_global_mut&lt;<a href="TransactionFee.md#0x1_TransactionFee">TransactionFee</a>&lt;CoinType&gt;&gt;(@TreasuryCompliance); <b>let</b> coin = <a href="Diem.md#0x1_Diem_withdraw_all">Diem::withdraw_all</a>(&<b>mut</b> fees.balance); <b>let</b> burn_cap = <a href="Diem.md#0x1_Diem_remove_burn_capability">Diem::remove_burn_capability</a>&lt;CoinType&gt;(tc_account); // burn <a href="Diem.md#0x1_Diem_burn_now">Diem::burn_now</a>( coin, &<b>mut</b> fees.preburn, @TreasuryCompliance, &burn_cap ); <a href="Diem.md#0x1_Diem_publish_burn_capability">Diem::publish_burn_capability</a>(tc_account, burn_cap); } } </code></pre> </details> <details> <summary>Specification</summary>

Must abort if the account does not have the TreasuryCompliance role [H3].

<pre><code><b>include</b> <a href="Roles.md#0x1_Roles_AbortsIfNotTreasuryCompliance">Roles::AbortsIfNotTreasuryCompliance</a>{account: tc_account}; <b>include</b> <a href="DiemTimestamp.md#0x1_DiemTimestamp_AbortsIfNotOperating">DiemTimestamp::AbortsIfNotOperating</a>; <b>aborts_if</b> !<a href="TransactionFee.md#0x1_TransactionFee_is_coin_initialized">is_coin_initialized</a>&lt;CoinType&gt;() <b>with</b> <a href="../../../../../../move-stdlib/docs/Errors.md#0x1_Errors_NOT_PUBLISHED">Errors::NOT_PUBLISHED</a>; <b>include</b> <b>if</b> (<a href="XDX.md#0x1_XDX_spec_is_xdx">XDX::spec_is_xdx</a>&lt;CoinType&gt;()) <a href="TransactionFee.md#0x1_TransactionFee_BurnFeesXDX">BurnFeesXDX</a> <b>else</b> <a href="TransactionFee.md#0x1_TransactionFee_BurnFeesNotXDX">BurnFeesNotXDX</a>&lt;CoinType&gt;; </code></pre>

The correct amount of fees is burnt and subtracted from market cap.

<pre><code><b>ensures</b> <a href="Diem.md#0x1_Diem_spec_market_cap">Diem::spec_market_cap</a>&lt;CoinType&gt;() == <b>old</b>(<a href="Diem.md#0x1_Diem_spec_market_cap">Diem::spec_market_cap</a>&lt;CoinType&gt;()) - <b>old</b>(<a href="TransactionFee.md#0x1_TransactionFee_spec_transaction_fee">spec_transaction_fee</a>&lt;CoinType&gt;().balance.value); </code></pre>

All the fees is burnt so the balance becomes 0.

<pre><code><b>ensures</b> <a href="TransactionFee.md#0x1_TransactionFee_spec_transaction_fee">spec_transaction_fee</a>&lt;CoinType&gt;().balance.value == 0; </code></pre>

STUB: To be filled in at a later date once the makeup of the XDX has been determined.

<a name="@Specification_of_the_case_where_burn_type_is_XDX._1"></a>

Specification of the case where burn type is XDX.

<a name="0x1_TransactionFee_BurnFeesXDX"></a>

<pre><code><b>schema</b> <a href="TransactionFee.md#0x1_TransactionFee_BurnFeesXDX">BurnFeesXDX</a> { tc_account: signer; <b>aborts_if</b> <b>true</b> <b>with</b> <a href="../../../../../../move-stdlib/docs/Errors.md#0x1_Errors_INVALID_STATE">Errors::INVALID_STATE</a>; } </code></pre>

<a name="@Specification_of_the_case_where_burn_type_is_not_XDX._2"></a>

Specification of the case where burn type is not XDX.

<a name="0x1_TransactionFee_BurnFeesNotXDX"></a>

<pre><code><b>schema</b> <a href="TransactionFee.md#0x1_TransactionFee_BurnFeesNotXDX">BurnFeesNotXDX</a>&lt;CoinType&gt; { tc_account: signer; } </code></pre>

Must abort if the account does not have BurnCapability [H3].

<pre><code><b>schema</b> <a href="TransactionFee.md#0x1_TransactionFee_BurnFeesNotXDX">BurnFeesNotXDX</a>&lt;CoinType&gt; { <b>include</b> <a href="Diem.md#0x1_Diem_AbortsIfNoBurnCapability">Diem::AbortsIfNoBurnCapability</a>&lt;CoinType&gt;{account: tc_account}; <b>let</b> fees = <a href="TransactionFee.md#0x1_TransactionFee_spec_transaction_fee">spec_transaction_fee</a>&lt;CoinType&gt;(); <b>include</b> <a href="Diem.md#0x1_Diem_BurnNowAbortsIf">Diem::BurnNowAbortsIf</a>&lt;CoinType&gt;{coin: fees.balance, preburn: fees.preburn}; } </code></pre>

tc_account retrieves BurnCapability [H3]. BurnCapability is not transferrable [J3].

<pre><code><b>schema</b> <a href="TransactionFee.md#0x1_TransactionFee_BurnFeesNotXDX">BurnFeesNotXDX</a>&lt;CoinType&gt; { <b>ensures</b> <b>exists</b>&lt;<a href="Diem.md#0x1_Diem_BurnCapability">Diem::BurnCapability</a>&lt;CoinType&gt;&gt;(<a href="../../../../../../move-stdlib/docs/Signer.md#0x1_Signer_spec_address_of">Signer::spec_address_of</a>(tc_account)); } </code></pre> </details>

<a name="@Module_Specification_3"></a>

Module Specification

<a name="@Initialization_4"></a>

Initialization

If time has started ticking, then <code><a href="TransactionFee.md#0x1_TransactionFee">TransactionFee</a></code> resources have been initialized.

<pre><code><b>invariant</b> [suspendable] <a href="DiemTimestamp.md#0x1_DiemTimestamp_is_operating">DiemTimestamp::is_operating</a>() ==&gt; <a href="TransactionFee.md#0x1_TransactionFee_is_initialized">is_initialized</a>(); </code></pre>

<a name="@Helper_Function_5"></a>

Helper Function

<a name="0x1_TransactionFee_spec_transaction_fee"></a>

<pre><code><b>fun</b> <a href="TransactionFee.md#0x1_TransactionFee_spec_transaction_fee">spec_transaction_fee</a>&lt;CoinType&gt;(): <a href="TransactionFee.md#0x1_TransactionFee">TransactionFee</a>&lt;CoinType&gt; { borrow_global&lt;<a href="TransactionFee.md#0x1_TransactionFee">TransactionFee</a>&lt;CoinType&gt;&gt;(@TreasuryCompliance) } </code></pre>