comments: add precondition comments

Add `/// Preconditiion:` comments replacing the `#[pre()]` macros
since we are no longer using the `pre` crate.

Signed-off-by: Dan Cross <cross@oxidecomputer.com>

Author: dancrossnyc

src/group.rs

@@ -392,6 +392,8 @@ impl GroupMutIter<'_> {
         }
     }
     /// Inserts the given entry data at the right spot.
+    /// Precondition: The caller already grew the group by
+    /// `payload_size + size_of::<ENTRY_HEADER>()`
     #[allow(clippy::too_many_arguments)]
     pub(crate) fn insert_entry(
         &mut self,
@@ -566,6 +568,9 @@ impl GroupMutItem<'_> {
         Ok(entry_size as u32)
     }
     /// Resizes the given entry by SIZE_DIFF.
+    /// Precondition: If `size_diff > 0`, the caller must have already
+    /// expanded the group `size_diff`.  If `size_diff < 0`, the caller
+    /// must call `resize_entry_by` before resizing the group.
     pub(crate) fn resize_entry_by(
         &mut self,
         entry_id: EntryId,
@@ -634,6 +639,8 @@ impl GroupMutItem<'_> {
         }
     }
     /// Inserts the given token.
+    /// Precondition: Caller already increased the group size by
+    /// `size_of::<TOKEN_ENTRY>()`.
     pub(crate) fn insert_token(
         &mut self,
         entry_id: EntryId,

src/tokens_entry.rs

@@ -203,6 +203,8 @@ impl<'a> TokensEntryIter<&'a mut [u8]> {
     }
 
     /// Inserts the given entry data at the right spot.
+    /// Precondition: Caller must have already increased the group size
+    /// by `size_of::<TOKEN_ENTRY>()`.
     pub(crate) fn insert_token(
         &mut self,
         token_id: u32,
@@ -602,6 +604,8 @@ impl TokensEntryBodyItem<&mut [u8]> {
         (self.iter_mut().ok()?).find(|entry| entry.id() == token_id)
     }
 
+    /// Precondition: Caller already increased the group size by
+    /// `size_of::<TOKEN_ENTRY>()`.
     pub(crate) fn insert_token(
         &mut self,
         token_id: u32,