mymemory: add SnapshotAlloc STL allocator

Now, we just need to go through the tedious process of rewriting all our
STL definitions

diff --git a/mymemory.cc b/mymemory.cc
index 08bd4e437c897967830d5dc760d0d4f27f351b50..5922a32d19f63491d556a275cb2d25be5bf510da 100644 (file)
--- 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 d7c4f99599ac785f9abdb9845c00bc563db0b747..a2a9096dcded46bc8a955269d4468084cea059df 100644 (file)
--- 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