1 files changed, 110 insertions, 0 deletions
diff --git a/utils/intern_pool.h b/utils/intern_pool.h
new file mode 100755
index 00000000..c85c9881
--- /dev/null
+++ b/utils/intern_pool.h
@@ -0,0 +1,110 @@
+#ifndef INTERN_POOL_H
+#define INTERN_POOL_H
+
+#define DEBUG_INTERN_POOL(x) x
+
+/* to "intern" a string in lisp is to make a symbol from it (a pointer to a canonical copy whose pointer can be equality-compared/hashed directly with other interned things).  we take an Item that has a key part and some mutable parts (that aren't in its identity), and we hash-by-value the key part to map to a canonical on-heap Item - and we use a boost object pool to allocate them */
+
+//FIXME: actually store function object state (assumed stateless so far)
+
+#include <boost/pool/object_pool.hpp>
+#include "hash.h"
+//#include "null_traits.h"
+#include <functional>
+
+template <class I>
+struct get_key { // default accessor for I = like pair<key,val>
+  typedef typename I::first_type const& return_type;
+  typedef I const& argument_type;
+  return_type operator()(I const& i) const {
+    return i.first;
+  }
+};
+
+template <class KeyF,class F,class Arg=typename KeyF::argument_type>
+struct compose_indirect {
+  typedef Arg *argument_type; // also Arg
+  KeyF kf;
+  F f;
+  typedef typename F::return_type return_type;
+  return_type operator()(Arg p) const {
+    return f(kf(p));
+  }
+  template <class V>
+  return_type operator()(Arg *p) const {
+    return f(kf(*p));
+  }
+
+};
+
+/*
+
+template <class F>
+struct indirect_function {
+  F f;
+  explicit indirect_function(F const& f=F()) : f(f) {}
+  typedef typename F::return_type return_type;
+  template <class V>
+  return_type operator()(V *p) const {
+    return f(*p);
+  }
+};
+*/
+
+template <class Item,class KeyF=get_key<Item>,class HashKey=boost::hash<typename KeyF::return_type>,class EqKey=std::equal_to<typename KeyF::return_type>, class Pool=boost::object_pool<Item> >
+struct intern_pool : Pool {
+  KeyF key;
+  typedef typename KeyF::return_type Key;
+  typedef Item *Handle;
+  typedef compose_indirect<KeyF,HashKey,Handle> HashDeep;
+  typedef compose_indirect<KeyF,EqKey,Handle> EqDeep;
+  typedef HASH_SET<Handle,HashDeep,EqDeep> Canonical;
+  typedef typename Canonical::iterator CFind;
+  typedef std::pair<CFind,bool> CInsert;
+  Canonical canonical;
+  void interneq(Handle &i) {
+    i=intern(i);
+  }
+// inherited: Handle construct(...)
+  Handle construct_fresh() { return Pool::construct(); }
+  Handle intern(Handle i) { // (maybe invalidating i, returning a valid canonical handle (pointer)
+    CInsert i_new=canonical.insert(i);
+    if (i_new.second)
+      return i;
+    else {
+      free(i);
+      return *i_new->first;
+    }
+  }
+  void destroy_interned(Handle i) {
+    DEBUG_INTERN_POOL(assert(canonical.find(i)!=canonical.end()));
+    canonical.erase(i);
+    destroy(i);
+  }
+  bool destroy_fresh(Handle i) {
+    DEBUG_INTERN_POOL(assert(canonical.find(i)!=canonical.end()||*canonical.find(i)!=i)); // i is a constructed item not yet interned.
+    destroy(i);
+  }
+  void destroy_both(Handle i) { // i must have come from this pool.  may be interned, or not.  destroy both the noninterned and interned.
+    if (!destroy_if_interned(i)) destroy(i);
+  }
+  // destroy intern(i) if it exists.  return true if it existed AND its address was i.  otherwise return false (whether or not a value-equal item existed and was destroyed)
+  bool destroy_if_interned(Handle i) {
+    CFind f=canonical.find(i);
+    if (f!=canonical.end()) {
+      Handle interned=*f;
+      canonical.erase(f);
+      destroy(f);
+      if (f==i) return true;
+    }
+    return false;
+  }
+
+  intern_pool() {
+    HASH_MAP_EMPTY(canonical,(Handle)0);
+  }
+};
+
+
+
+#endif