More SlotMeta docs

src/blocktree.rs

@@ -123,20 +123,25 @@ pub trait LedgerColumnFamilyRaw {
 #[derive(Clone, Debug, Default, Deserialize, Serialize, Eq, PartialEq)]
 // The Meta column family
 pub struct SlotMeta {
+    // The number of slots above the root (the genesis block). The first
+    // slot has slot_height 0.
     pub slot_height: u64,
-    // The total number of consecutive blob starting from index 0
+    // The total number of consecutive blobs starting from index 0
     // we have received for this slot.
     pub consumed: u64,
-    // The entry height of the highest blob received for this slot.
+    // The index *plus one* of the highest blob received for this slot.  Useful
+    // for checking if the slot has received any blobs yet, and to calculate the
+    // range where there is one or more holes: `(consumed..received)`.
     pub received: u64,
-    // The index of the blob that is flagged as the last blob for this slot
+    // The index of the blob that is flagged as the last blob for this slot.
     pub last_index: u64,
-    // The parent slot of this slot
+    // The slot height of the block this one derives from.
     pub parent_slot: u64,
-    // The list of slots that chains to this slot
+    // The list of slot heights, each of which contains a block that derives
+    // from this one.
     pub next_slots: Vec<u64>,
-    // True if every block from 0..slot, where slot is the slot index of this slot
-    // is full
+    // True if this slot is full (consumed == last_index + 1) and if every
+    // slot from 0..slot_height is also rooted.
     pub is_rooted: bool,
 }