proxmox-rrd: improve developer docs

proxmox-rrd/src/lib.rs

@@ -1,5 +1,21 @@
-mod rrd;
-pub use rrd::*;
+//! # Simple Round Robin Database files with fixed format
+//!
+//! ## Features
+//!
+//! * One file stores a single data source
+//! * Small/constant file size (6008 bytes)
+//! * Stores avarage and maximum values
+//! * Stores data for different time resolution ([RRDTimeFrameResolution](proxmox_rrd_api_types::RRDTimeFrameResolution))
+
+pub mod rrd;
 
 mod cache;
 pub use cache::*;
+
+/// RRD data source tyoe
+pub enum DST {
+    /// Gauge values are stored unmodified.
+    Gauge,
+    /// Stores the difference to the previous value.
+    Derive,
+}