# TraceLogging for Rust
The `tracelogging` crate provides a simple and efficient system for
logging TraceLogging events when the event schema is known at compile time.
This is similar to the C/C++
[TraceLoggingProvider.h](https://docs.microsoft.com/windows/win32/api/traceloggingprovider/)
implementation in the Windows SDK.
```rust
use tracelogging as tlg;
// Define a static variable for the "MyCompany.MyComponent" provider.
tlg::define_provider!(
MY_PROVIDER, // The static symbol to use for this provider.
"MyCompany.MyComponent"); // The provider's name (string literal).
// Register the provider at module initialization. If you don't register (or if
// register fails) then MY_PROVIDER.enabled() will always return false, the
// write_event macro will be a no-op, and MY_PROVIDER.unregister() will be a no-op.
// Safety: MUST call MY_PROVIDER.unregister() before module unload.
unsafe { MY_PROVIDER.register(); }
// As necessary, call write_event to send events to ETW.
let field1_value = "String Value";
let field2_value = 42u32;
tlg::write_event!(
MY_PROVIDER, // The provider to use for the event.
"MyEventName", // The event's name (string literal).
level(Warning), // Event's severity level.
keyword(0x23), // Event category bits.
str8("Field1", field1_value), // Add a string field to the event.
u32("Field2", &field2_value), // Add an integer field to the event.
);
// Before module unload, unregister the provider.
MY_PROVIDER.unregister();
```
## Configuration
This crate supports the following configurable features:
- `etw`: Use
[Windows ETW](https://docs.microsoft.com/windows/win32/etw/about-event-tracing) APIs to
log events. If not enabled, all logging operations will be no-ops.
**Enabled by default.**
- `macros`: Re-export the `define_provider!` and `write_event!` macros from the
`tracelogging_macros` crate. **Enabled by default.**
In addition, this crate will log events only if compiled for a Windows operating system.
If compiled for a non-Windows operating system, all logging operations will be no-ops.