improve removeal code

src/data/entry.rs

@@ -59,6 +59,12 @@ impl Entry
 	    ..self
 	}
     }
+
+    /// Clone the data needed for a refresh of this entry in a store before it is mutated.
+    #[inline(always)] pub(super) fn prepare_for_refresh(&self) -> (EntryKey, Box<[String]>)
+    {
+	(self.hash().clone(), self.tags.clone().into_boxed_slice())
+    }
 }
 
 impl Borrow<sha256::Sha256Hash> for Entry

src/data/mutation.rs

@@ -1,5 +1,6 @@
 //! Handling store mutation
 use super::*;
+use std::borrow::Borrow;
 
 impl Store
 {
@@ -10,16 +11,8 @@ impl Store
 
 	let hash_idx = self.data_hashes.insert(*ent.hash());
 	for tag in ent.tags.iter() {
-	    if let Some(&ti) = self.tags.get(tag) {
-		// This tag has an entry already, append to it
-		self.tag_mappings.get_mut(ti).unwrap().insert(hash_idx);
-	    } else {
-		// This tag has no entry, create it
-		let ti = self.tag_mappings.insert(iter![hash_idx].collect());
-		self.tags.insert(tag.clone(), ti);
-	    }
+	    self.insert_tag_for_idx(tag, hash_idx);
 	}
-	
 	self.data.insert(ent);
 	old
     }
@@ -39,51 +32,62 @@ impl Store
     where F: FnOnce(&mut Entry) -> T
     {
 	if let Some(mut ent) = self.data.take(ent_id) {
-	    let ohash = ent.hash().clone();
-	    let otags = ent.tags.clone();
+	    let update = ent.prepare_for_refresh();
+	    
 	    let out = f(&mut ent);
 	    let new = ent;
 
-	    let iidx = if new.hash() != &ohash {
-		// We need to update `data_hashes`.
-		for (_, hash) in self.data_hashes.iter_mut()
-		{
-		    if hash == &ohash {
-			*hash = *new.hash();
-			break;
-		    }
-		}
-		self.reverse_index_lookup(new.hash()).unwrap()
-	    } else {
-		self.reverse_index_lookup(&ohash).unwrap()
-	    };
+	    self.refresh_for_entry(update, &new);
 	    
-	    if &new.tags[..] != &otags[..] {
-		// We need to update tag mappings
-
-		
-		let ntags: HashSet<_> = new.tags.iter().collect();
-		let otags: HashSet<_> = otags.iter().collect();
-		// Find the ones that were removed and added in parallel.
-		for (t, u) in ntags.iter().zip(otags.iter())
-		{
-		    if !otags.contains(t) {
-			// It was added
-			self.insert_tag_for_idx(t, iidx);
-		    }
-		    if !ntags.contains(u) {
-			// It was removed
-			self.remove_tag_for_idx(t, iidx);
-		    }
-		}
-		
-	    }
 	    self.data.insert(new);
 	    Some(out)
 	} else {
 	    None
 	}
     }
+
+    /// Update an entry that may have been modified.
+    ///
+    /// The entries old hash and tags are passed, and it updates the store to reflect the new entry mutation.
+    /// You must still insert the new entry after this.
+    fn refresh_for_entry(&mut self, (ohash, otags): (impl Borrow<EntryKey>, impl AsRef<[String]>), new: &Entry)
+    {
+	let ohash = ohash.borrow();
+	let iidx = if new.hash() != ohash {
+	    // We need to update `data_hashes`.
+	    for (_, hash) in self.data_hashes.iter_mut()
+	    {
+		if hash == ohash {
+		    *hash = *new.hash();
+		    break;
+		}
+	    }
+	    self.reverse_index_lookup(new.hash()).unwrap()
+	} else {
+	    self.reverse_index_lookup(ohash).unwrap()
+	};
+
+	let otags =otags.as_ref();
+	if &new.tags[..] != &otags[..] {
+	    // We need to update tag mappings
+	    
+	    let ntags: HashSet<_> = new.tags.iter().collect();
+	    let otags: HashSet<_> = otags.iter().collect();
+	    // Find the ones that were removed and added in parallel.
+	    for (t, u) in ntags.iter().zip(otags.iter())
+	    {
+		if !otags.contains(t) {
+		    // It was added
+		    self.insert_tag_for_idx(t, iidx);
+		}
+		if !ntags.contains(u) {
+		    // It was removed
+		    self.remove_tag_for_idx(t, iidx);
+		}
+	    }
+	    
+	}
+    }
     
     /// Map the entry with this function, updating references to it if needed.
     ///
@@ -92,18 +96,11 @@ impl Store
     where F: FnOnce(Entry) -> Entry
     {
 	if let Some(ent) = self.data.take(ent_id) {
-	    let ohash = ent.hash().clone();
+	    let update = ent.prepare_for_refresh();
 	    let new = f(ent);
-	    if new.hash() != &ohash {
-		// We need to update `data_hashes`.
-		for (_, hash) in self.data_hashes.iter_mut()
-		{
-		    if hash == &ohash {
-			*hash = *new.hash();
-			break;
-		    }
-		}
-	    }
+	    
+	    self.refresh_for_entry(update, &new);
+	    
 	    self.data.insert(new); 
 	}
     }
@@ -113,7 +110,7 @@ impl Store
     pub fn remove(&mut self, key: &EntryKey) -> Option<Entry>
     {
 	if let Some(entry) = self.data.take(key) {
-	    Some(self.cleanup_remove_entry(entry))
+	    Some(self.cleanup_remove_entry(entry.with_no_cache()))
 	} else {
 	    None
 	}
@@ -122,37 +119,19 @@ impl Store
     /// Preform cleanup on an entry *already removed* from `data`.
     fn cleanup_remove_entry(&mut self, ent: Entry) -> Entry
     {
-	let ent = ent.with_no_cache();
 	// Remove any unused tags
-	for (nm, ti) in precollect!(self.tag_index_lookup(&ent.tags[..]).map(|(nm, idx)| ({
-	    ent.tags.iter().filter(|y| y.as_str() == nm).next().unwrap() // swap the `nm` reference to the owned reference in `ent`'s tags... There should be a better way that this eh
-	}, idx))) {
-	    if self.purge_tag_index(ti, ent.hash()) {
-		// No more mappings, remove this tag 
-		self.tags.remove(nm);
-		// And its mapping
-		self.tag_mappings.remove(ti);
+	if let Some(hash_idx) = self.reverse_index_lookup(ent.hash()) {   
+	    for tag in ent.tags.iter()
+	    {
+		self.remove_tag_for_idx(tag, hash_idx);
 	    }
 	}
+	
 	// Remove from data hashes can be deferred
 	self.purge_if_needed();
 	ent
     }
 
-    /// Purge this tag index from the mappings for the entry `to_remove`.
-    /// Returns true if there are no more references to this tag and it can be removed.
-    #[inline] fn purge_tag_index(&mut self, idx: ArenaIndex, to_remove: &EntryKey) -> bool
-    {
-	let data_hashes = &mut self.data_hashes;
-	if let Some(map) = self.tag_mappings.get_mut(idx) {
-	    map.retain(move |&hash_idx| data_hashes.get(hash_idx).map(|x| x != to_remove).unwrap_or(false));
-	    map.len() == 0
-	} else {
-	    // There is no reference in the tag mapping itself.
-	    false
-	}
-    }
-
     /// Remove dead mappings from `data_hashes` to `data`.
     #[inline] fn purge_data_hash_mappings(&mut self)
     {