Extend class comment for UniqueStoreStringAllocator.

1 files changed, 9 insertions, 3 deletions

diff --git a/vespalib/src/vespa/vespalib/datastore/unique_store_string_allocator.h b/vespalib/src/vespa/vespalib/datastore/unique_store_string_allocator.h
index e914c4c7f66..b4ceab4c804 100644
--- a/vespalib/src/vespa/vespalib/datastore/unique_store_string_allocator.h
+++ b/vespalib/src/vespa/vespalib/datastore/unique_store_string_allocator.h
@@ -75,7 +75,14 @@ public:
 
 /**
  * Allocator for unique NUL-terminated strings that is accessed via a
- * 32-bit EntryRef.
+ * 32-bit EntryRef. Multiple buffer types are used. Small strings use
+ * a common buffer type handler with different parameters for array
+ * size (which denotes number of bytes set aside for meta data
+ * (reference count), string and NUL byte. Large strings use a
+ * different buffer type handler where buffer contains meta data
+ * (reference count) and an std::string, while the string value is on
+ * the heap.  string_allocator::get_type_id() is used to map from
+ * string length to type id.
  */
 template <typename RefT = EntryRefT<22> >
 class UniqueStoreStringAllocator : public ICompactable
@@ -97,8 +104,7 @@ public:
     EntryRef allocate(const char *value);
     void hold(EntryRef ref);
     EntryRef move(EntryRef ref) override;
-    const UniqueStoreEntryBase& getWrapped(EntryRef ref) const
-    {
+    const UniqueStoreEntryBase& getWrapped(EntryRef ref) const {
         RefType iRef(ref);
         auto &state = _store.getBufferState(iRef.bufferId());
         auto type_id = state.getTypeId();