Module `0x1::Event`

The Event module defines an <code><a href="Event.md#0x1_Event_EventHandleGenerator">EventHandleGenerator</a></code> that is used to create <code><a href="Event.md#0x1_Event_EventHandle">EventHandle</a></code>s with unique GUIDs. It contains a counter for the number of <code><a href="Event.md#0x1_Event_EventHandle">EventHandle</a></code>s it generates. An <code><a href="Event.md#0x1_Event_EventHandle">EventHandle</a></code> is used to count the number of events emitted to a handle and emit events to the event store.

Resource EventHandleGenerator
Struct EventHandle
Constants
Function publish_generator
Function fresh_guid
Function new_event_handle
Function emit_event
Function write_to_event_store
Function destroy_handle
Module Specification

<pre><code>use <a href="BCS.md#0x1_BCS">0x1::BCS</a>; use <a href="Errors.md#0x1_Errors">0x1::Errors</a>; use <a href="Signer.md#0x1_Signer">0x1::Signer</a>; use <a href="Vector.md#0x1_Vector">0x1::Vector</a>; </code></pre>

Resource `EventHandleGenerator`

A resource representing the counter used to generate uniqueness under each account. There won't be destructor for this resource to guarantee the uniqueness of the generated handle.

<pre><code>struct <a href="Event.md#0x1_Event_EventHandleGenerator">EventHandleGenerator</a> has key </code></pre> <details> <summary>Fields</summary> <dl> <dt> <code>counter: u64</code> </dt> <dd> </dd> <dt> <code>addr: address</code> </dt> <dd> </dd> </dl> </details>

Struct `EventHandle`

A handle for an event such that:

Other modules can emit events to this handle.
Storage can use this handle to prove the total number of events that happened in the past.

<pre><code>struct <a href="Event.md#0x1_Event_EventHandle">EventHandle</a><T: drop, store> has store </code></pre> <details> <summary>Fields</summary> <dl> <dt> <code>counter: u64</code> </dt> <dd> Total number of events emitted to this event stream. </dd> <dt> <code>guid: vector<u8></code> </dt> <dd> A globally unique ID for this event stream. </dd> </dl> </details>

Constants

The event generator resource was in an invalid state

<pre><code>const <a href="Event.md#0x1_Event_EEVENT_GENERATOR">EEVENT_GENERATOR</a>: u64 = 0; </code></pre>

Function `publish_generator`

Publishs a new event handle generator.

<pre><code>public fun <a href="Event.md#0x1_Event_publish_generator">publish_generator</a>(account: &signer) </code></pre> <details> <summary>Implementation</summary> <pre><code>public fun <a href="Event.md#0x1_Event_publish_generator">publish_generator</a>(account: &signer) { let addr = <a href="Signer.md#0x1_Signer_address_of">Signer::address_of</a>(account); assert(!exists<<a href="Event.md#0x1_Event_EventHandleGenerator">EventHandleGenerator</a>>(addr), <a href="Errors.md#0x1_Errors_already_published">Errors::already_published</a>(<a href="Event.md#0x1_Event_EEVENT_GENERATOR">EEVENT_GENERATOR</a>)); move_to(account, <a href="Event.md#0x1_Event_EventHandleGenerator">EventHandleGenerator</a>{ counter: 0, addr }) } </code></pre> </details>

Function `fresh_guid`

Derive a fresh unique id by using sender's EventHandleGenerator. The generated vector<u8> is indeed unique because it was derived from the hash(sender's EventHandleGenerator || sender_address). This module guarantees that the EventHandleGenerator is only going to be monotonically increased and there's no way to revert it or destroy it. Thus such counter is going to give distinct value for each of the new event stream under each sender. And since we hash it with the sender's address, the result is guaranteed to be globally unique.

<pre><code>fun <a href="Event.md#0x1_Event_fresh_guid">fresh_guid</a>(counter: &mut <a href="Event.md#0x1_Event_EventHandleGenerator">Event::EventHandleGenerator</a>): vector<u8> </code></pre> <details> <summary>Implementation</summary> <pre><code>fun <a href="Event.md#0x1_Event_fresh_guid">fresh_guid</a>(counter: &mut <a href="Event.md#0x1_Event_EventHandleGenerator">EventHandleGenerator</a>): vector<u8> { let sender_bytes = <a href="BCS.md#0x1_BCS_to_bytes">BCS::to_bytes</a>(&counter.addr); let count_bytes = <a href="BCS.md#0x1_BCS_to_bytes">BCS::to_bytes</a>(&counter.counter); counter.counter = counter.counter + 1; // <a href="Event.md#0x1_Event_EventHandleGenerator">EventHandleGenerator</a> goes first just in case we want to extend address in the future. <a href="Vector.md#0x1_Vector_append">Vector::append</a>(&mut count_bytes, sender_bytes); count_bytes } </code></pre> </details>

Function `new_event_handle`

Use EventHandleGenerator to generate a unique event handle for <code>sig</code>

<pre><code>public fun <a href="Event.md#0x1_Event_new_event_handle">new_event_handle</a><T: drop, store>(account: &signer): <a href="Event.md#0x1_Event_EventHandle">Event::EventHandle</a><T> </code></pre> <details> <summary>Implementation</summary> <pre><code>public fun <a href="Event.md#0x1_Event_new_event_handle">new_event_handle</a><T: drop + store>(account: &signer): <a href="Event.md#0x1_Event_EventHandle">EventHandle</a><T> acquires <a href="Event.md#0x1_Event_EventHandleGenerator">EventHandleGenerator</a> { let addr = <a href="Signer.md#0x1_Signer_address_of">Signer::address_of</a>(account); assert(exists<<a href="Event.md#0x1_Event_EventHandleGenerator">EventHandleGenerator</a>>(addr), <a href="Errors.md#0x1_Errors_not_published">Errors::not_published</a>(<a href="Event.md#0x1_Event_EEVENT_GENERATOR">EEVENT_GENERATOR</a>)); <a href="Event.md#0x1_Event_EventHandle">EventHandle</a><T> { counter: 0, guid: <a href="Event.md#0x1_Event_fresh_guid">fresh_guid</a>(borrow_global_mut<<a href="Event.md#0x1_Event_EventHandleGenerator">EventHandleGenerator</a>>(addr)) } } </code></pre> </details>

Function `emit_event`

Emit an event with payload <code>msg</code> by using <code>handle_ref</code>'s key and counter.

<pre><code>public fun <a href="Event.md#0x1_Event_emit_event">emit_event</a><T: drop, store>(handle_ref: &mut <a href="Event.md#0x1_Event_EventHandle">Event::EventHandle</a><T>, msg: T) </code></pre> <details> <summary>Implementation</summary> <pre><code>public fun <a href="Event.md#0x1_Event_emit_event">emit_event</a><T: drop + store>(handle_ref: &mut <a href="Event.md#0x1_Event_EventHandle">EventHandle</a><T>, msg: T) { let guid = *&handle_ref.guid; <a href="Event.md#0x1_Event_write_to_event_store">write_to_event_store</a><T>(guid, handle_ref.counter, msg); handle_ref.counter = handle_ref.counter + 1; } </code></pre> </details>

Function `write_to_event_store`

Native procedure that writes to the actual event stream in Event store This will replace the "native" portion of EmitEvent bytecode

<pre><code>fun <a href="Event.md#0x1_Event_write_to_event_store">write_to_event_store</a><T: drop, store>(guid: vector<u8>, count: u64, msg: T) </code></pre> <details> <summary>Implementation</summary> <pre><code>native fun <a href="Event.md#0x1_Event_write_to_event_store">write_to_event_store</a><T: drop + store>(guid: vector<u8>, count: u64, msg: T); </code></pre> </details>

Function `destroy_handle`

Destroy a unique handle.

<pre><code>public fun <a href="Event.md#0x1_Event_destroy_handle">destroy_handle</a><T: drop, store>(handle: <a href="Event.md#0x1_Event_EventHandle">Event::EventHandle</a><T>) </code></pre> <details> <summary>Implementation</summary> <pre><code>public fun <a href="Event.md#0x1_Event_destroy_handle">destroy_handle</a><T: drop + store>(handle: <a href="Event.md#0x1_Event_EventHandle">EventHandle</a><T>) { <a href="Event.md#0x1_Event_EventHandle">EventHandle</a><T> { counter: _, guid: _ } = handle; } </code></pre> </details>

Module Specification

Functions of the event module are mocked out using the intrinsic pragma. They are implemented in the prover's prelude.

<pre><code>pragma intrinsic = true; </code></pre>

Determines equality between the guids of two event handles. Since fields of intrinsic structs cannot be accessed, this function is provided.

<pre><code>fun <a href="Event.md#0x1_Event_spec_guid_eq">spec_guid_eq</a><T>(h1: <a href="Event.md#0x1_Event_EventHandle">EventHandle</a><T>, h2: <a href="Event.md#0x1_Event_EventHandle">EventHandle</a><T>): bool { // The implementation currently can just use native equality since the mocked prover // representation does not have the `counter` field. h1 == h2 } </code></pre>

Module `0x1::Event`

Module 0x1::Event

Resource EventHandleGenerator

Struct EventHandle

Constants

Function publish_generator

Function fresh_guid

Function new_event_handle

Function emit_event

Function write_to_event_store

Function destroy_handle

Module Specification

Module `0x1::Event`

Resource `EventHandleGenerator`

Struct `EventHandle`

Function `publish_generator`

Function `fresh_guid`

Function `new_event_handle`

Function `emit_event`

Function `write_to_event_store`

Function `destroy_handle`