From 4ee37711afd0de98bc757ed4853a81d66a6a1533 Mon Sep 17 00:00:00 2001
From: Brian Norris <banorris@uci.edu>
Date: Mon, 8 Oct 2012 13:36:11 -0700
Subject: [PATCH 1/1] mymemory: add SnapshotAlloc STL allocator

Now, we just need to go through the tedious process of rewriting all our
STL definitions
---
 mymemory.cc |  4 +--
 mymemory.h  | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 93 insertions(+), 3 deletions(-)

diff --git a/mymemory.cc b/mymemory.cc
index 08bd4e43..5922a32d 100644
--- a/mymemory.cc
+++ b/mymemory.cc
@@ -149,9 +149,7 @@ mspace model_snapshot_space = NULL;
 
 #if USE_MPROTECT_SNAPSHOT
 
-/** @brief Global mspace reference for the user's snapshotting heap
- *  @todo use this ONLY for user's allocations, not for internal snapshotting
- *  state */
+/** @brief Global mspace reference for the user's snapshotting heap */
 mspace user_snapshot_space = NULL;
 
 /** Check whether this is bootstrapped memory that we should not free */
diff --git a/mymemory.h b/mymemory.h
index d7c4f995..a2a9096d 100644
--- a/mymemory.h
+++ b/mymemory.h
@@ -142,6 +142,98 @@ bool operator!= (const ModelAlloc<T1>&,
 	return false;
 }
 
+/** @brief Provides a snapshotting allocator for use in STL classes.
+ *
+ * The code was adapted from a code example from the book The C++
+ * Standard Library - A Tutorial and Reference by Nicolai M. Josuttis,
+ * Addison-Wesley, 1999 © Copyright Nicolai M. Josuttis 1999
+ * Permission to copy, use, modify, sell and distribute this software
+ * is granted provided this copyright notice appears in all copies.
+ * This software is provided "as is" without express or implied
+ * warranty, and with no claim as to its suitability for any purpose.
+ */
+template <class T>
+class SnapshotAlloc {
+ public:
+	// type definitions
+	typedef T        value_type;
+	typedef T*       pointer;
+	typedef const T* const_pointer;
+	typedef T&       reference;
+	typedef const T& const_reference;
+	typedef size_t   size_type;
+	typedef size_t   difference_type;
+
+	// rebind allocator to type U
+	template <class U>
+	struct rebind {
+		typedef SnapshotAlloc<U> other;
+	};
+
+	// return address of values
+	pointer address(reference value) const {
+		return &value;
+	}
+	const_pointer address(const_reference value) const {
+		return &value;
+	}
+
+	/* constructors and destructor
+	 * - nothing to do because the allocator has no state
+	 */
+	SnapshotAlloc() throw() {
+	}
+	SnapshotAlloc(const SnapshotAlloc&) throw() {
+	}
+	template <class U>
+	SnapshotAlloc(const SnapshotAlloc<U>&) throw() {
+	}
+	~SnapshotAlloc() throw() {
+	}
+
+	// return maximum number of elements that can be allocated
+	size_type max_size() const throw() {
+		return std::numeric_limits<size_t>::max() / sizeof(T);
+	}
+
+	// allocate but don't initialize num elements of type T
+	pointer allocate(size_type num, const void * = 0) {
+		pointer p = (pointer)snapshot_malloc(num * sizeof(T));
+		return p;
+	}
+
+	// initialize elements of allocated storage p with value value
+	void construct(pointer p, const T& value) {
+		// initialize memory with placement new
+		new((void*)p)T(value);
+	}
+
+	// destroy elements of initialized storage p
+	void destroy(pointer p) {
+		// destroy objects by calling their destructor
+		p->~T();
+	}
+
+	// deallocate storage p of deleted elements
+	void deallocate(pointer p, size_type num) {
+		snapshot_free((void*)p);
+	}
+};
+
+/** Return that all specializations of this allocator are interchangeable. */
+template <class T1, class T2>
+bool operator ==(const SnapshotAlloc<T1>&,
+		const SnapshotAlloc<T2>&) throw() {
+	return true;
+}
+
+/** Return that all specializations of this allocator are interchangeable. */
+template <class T1, class T2>
+bool operator!= (const SnapshotAlloc<T1>&,
+		const SnapshotAlloc<T2>&) throw() {
+	return false;
+}
+
 #ifdef __cplusplus
 extern "C" {
 #endif
-- 
2.34.1