nall: fix various hashset issues

- Fix copy assignment operator
- Prevent reserve() from reallocating/rehashing unless capacity is increasing
- Prevent insert() from inserting duplicate entries
- Disable remove() as needs some work and is currently unused

nall/hashset.hpp

@@ -24,8 +24,8 @@ struct hashset {
     if(this == &source) return *this;
     reset();
     if(source.pool) {
-      for(u32 n : range(source.count)) {
-        insert(*source.pool[n]);
+      for(u32 n : range(source.length)) {
+        if(source.pool[n]) insert(*source.pool[n]);
       }
     }
     return *this;
@@ -63,6 +63,8 @@ struct hashset {
   }
 
   auto reserve(u32 size) -> void {
+    if(length >= size) return;
+
     //ensure all items will fit into pool (with <= 50% load) and amortize growth
     size = bit::round(max(size, count << 1));
     T** copy = new T*[size]();
@@ -100,15 +102,20 @@ struct hashset {
 
     //double pool size when load is >= 50%
     if(count >= (length >> 1)) reserve(length << 1);
-    count++;
 
     u32 hash = value.hash() & (length - 1);
-    while(pool[hash]) if(++hash >= length) hash = 0;
+    while(pool[hash]) {
+      if(value == *pool[hash]) return nothing;
+      if(++hash >= length) hash = 0;
+    }
+    count++;
     pool[hash] = new T(value);
 
     return *pool[hash];
   }
 
+#if 0
+  //does not work! todo: implement tombstones or rehashing to fill gaps.
   auto remove(const T& value) -> bool {
     if(!pool) return false;
 
@@ -125,6 +132,7 @@ struct hashset {
 
     return false;
   }
+#endif
 
 protected:
   T** pool = nullptr;