<a name="0x1_ChainId"></a>

Module 0x1::ChainId

The chain id distinguishes between different chains (e.g., testnet and the main Diem network). One important role is to prevent transactions intended for one chain from being executed on another. This code provides a container for storing a chain id and functions to initialize and get it.

• Resource ChainId
• Constants
• Function initialize
• Function get
• Module Specification
  • Initialization
  • Helper Functions

<pre><code><b>use</b> <a href="CoreAddresses.md#0x1_CoreAddresses">0x1::CoreAddresses</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="../../../../../../move-stdlib/docs/Signer.md#0x1_Signer">0x1::Signer</a>; </code></pre>

<a name="0x1_ChainId_ChainId"></a>

Resource ChainId

<pre><code><b>struct</b> <a href="ChainId.md#0x1_ChainId">ChainId</a> has key </code></pre> <details> <summary>Fields</summary> <dl> <dt> <code>id: u8</code> </dt> <dd> </dd> </dl> </details>

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

Constants

<a name="0x1_ChainId_ECHAIN_ID"></a>

The <code><a href="ChainId.md#0x1_ChainId">ChainId</a></code> resource was not in the required state

<pre><code><b>const</b> <a href="ChainId.md#0x1_ChainId_ECHAIN_ID">ECHAIN_ID</a>: u64 = 0; </code></pre>

<a name="0x1_ChainId_initialize"></a>

Function initialize

Publish the chain ID <code>id</code> of this Diem instance under the DiemRoot account

<pre><code><b>public</b> <b>fun</b> <a href="ChainId.md#0x1_ChainId_initialize">initialize</a>(dr_account: &signer, id: u8) </code></pre> <details> <summary>Implementation</summary> <pre><code><b>public</b> <b>fun</b> <a href="ChainId.md#0x1_ChainId_initialize">initialize</a>(dr_account: &signer, id: u8) { <a href="DiemTimestamp.md#0x1_DiemTimestamp_assert_genesis">DiemTimestamp::assert_genesis</a>(); <a href="CoreAddresses.md#0x1_CoreAddresses_assert_diem_root">CoreAddresses::assert_diem_root</a>(dr_account); <b>assert</b>(!<b>exists</b>&lt;<a href="ChainId.md#0x1_ChainId">ChainId</a>&gt;(<a href="../../../../../../move-stdlib/docs/Signer.md#0x1_Signer_address_of">Signer::address_of</a>(dr_account)), <a href="../../../../../../move-stdlib/docs/Errors.md#0x1_Errors_already_published">Errors::already_published</a>(<a href="ChainId.md#0x1_ChainId_ECHAIN_ID">ECHAIN_ID</a>)); move_to(dr_account, <a href="ChainId.md#0x1_ChainId">ChainId</a> { id }) } </code></pre> </details> <details> <summary>Specification</summary> <pre><code><b>pragma</b> opaque; <b>let</b> dr_addr = <a href="../../../../../../move-stdlib/docs/Signer.md#0x1_Signer_address_of">Signer::address_of</a>(dr_account); <b>modifies</b> <b>global</b>&lt;<a href="ChainId.md#0x1_ChainId">ChainId</a>&gt;(dr_addr); <b>include</b> <a href="DiemTimestamp.md#0x1_DiemTimestamp_AbortsIfNotGenesis">DiemTimestamp::AbortsIfNotGenesis</a>; <b>include</b> <a href="CoreAddresses.md#0x1_CoreAddresses_AbortsIfNotDiemRoot">CoreAddresses::AbortsIfNotDiemRoot</a>{account: dr_account}; <b>aborts_if</b> <b>exists</b>&lt;<a href="ChainId.md#0x1_ChainId">ChainId</a>&gt;(dr_addr) <b>with</b> <a href="../../../../../../move-stdlib/docs/Errors.md#0x1_Errors_ALREADY_PUBLISHED">Errors::ALREADY_PUBLISHED</a>; <b>ensures</b> <b>exists</b>&lt;<a href="ChainId.md#0x1_ChainId">ChainId</a>&gt;(dr_addr); </code></pre> </details>

<a name="0x1_ChainId_get"></a>

Function get

Return the chain ID of this Diem instance

<pre><code><b>public</b> <b>fun</b> <a href="ChainId.md#0x1_ChainId_get">get</a>(): u8 </code></pre> <details> <summary>Implementation</summary> <pre><code><b>public</b> <b>fun</b> <a href="ChainId.md#0x1_ChainId_get">get</a>(): u8 <b>acquires</b> <a href="ChainId.md#0x1_ChainId">ChainId</a> { <a href="DiemTimestamp.md#0x1_DiemTimestamp_assert_operating">DiemTimestamp::assert_operating</a>(); borrow_global&lt;<a href="ChainId.md#0x1_ChainId">ChainId</a>&gt;(@DiemRoot).id } </code></pre> </details>

<a name="@Module_Specification_1"></a>

Module Specification

<a name="@Initialization_2"></a>

Initialization

When Diem is operating, the chain id is always available.

<pre><code><b>invariant</b> [suspendable] <a href="DiemTimestamp.md#0x1_DiemTimestamp_is_operating">DiemTimestamp::is_operating</a>() ==&gt; <b>exists</b>&lt;<a href="ChainId.md#0x1_ChainId">ChainId</a>&gt;(@DiemRoot); </code></pre>

<a name="@Helper_Functions_3"></a>

Helper Functions

<a name="0x1_ChainId_spec_get_chain_id"></a>

<pre><code><b>fun</b> <a href="ChainId.md#0x1_ChainId_spec_get_chain_id">spec_get_chain_id</a>(): u8 { <b>global</b>&lt;<a href="ChainId.md#0x1_ChainId">ChainId</a>&gt;(@DiemRoot).id } </code></pre>