Separate ETW into low-level and high-level API

internal/etw/eventopt.go

@@ -0,0 +1,29 @@
+package etw
+
+// EventOpt defines the option function type that can be passed to
+// Provider.WriteEvent to specify general event options, such as level and
+// keyword.
+type EventOpt func(*EventDescriptor, *uint32)
+
+// WithLevel specifies the level of the event to be written.
+func WithLevel(level Level) EventOpt {
+	return func(descriptor *EventDescriptor, tags *uint32) {
+		descriptor.Level = level
+	}
+}
+
+// WithKeyword specifies the keywords of the event to be written. Multiple uses
+// of this option are OR'd together.
+func WithKeyword(keyword uint64) EventOpt {
+	return func(descriptor *EventDescriptor, tags *uint32) {
+		descriptor.Keyword |= keyword
+	}
+}
+
+// WithTags specifies the tags of the event to be written. Tags is a 28-bit
+// value (top 4 bits are ignored) which are interpreted by the event consumer.
+func WithTags(newTags uint32) EventOpt {
+	return func(descriptor *EventDescriptor, tags *uint32) {
+		*tags |= newTags
+	}
+}