1 files changed, 94 insertions, 0 deletions
diff --git a/common/memorypool.cpp b/common/memorypool.cpp
new file mode 100644
index 0000000000..8bd7f802ca
--- /dev/null
+++ b/common/memorypool.cpp
@@ -0,0 +1,94 @@
+#include "common/memorypool.h"
+#include <algorithm>
+
+namespace Common
+{
+
+static const size_t CHUNK_PAGE_SIZE = 32;
+
+void* MemoryPool::allocPage() {
+  void* result = ::malloc(CHUNK_PAGE_SIZE * _chunkSize);
+  _pages.push_back(result);
+  void* current = result;
+  for(size_t i=1; i<CHUNK_PAGE_SIZE; ++i)
+  {
+    void* next    = ((char*)current + _chunkSize);
+    *(void**)current = next;
+    
+    current = next;
+  }
+  *(void**)current = NULL;
+  return result;
+}
+
+MemoryPool::MemoryPool(size_t chunkSize) {
+   // You must at least fit the pointer in the node (technically unneeded considering the next rounding statement)
+  _chunkSize = std::max(chunkSize, sizeof(void*));
+  // There might be an alignment problem on some platforms when trying to load a void* on a non natural boundary
+  // so we round to the next sizeof(void*)
+  _chunkSize = (_chunkSize + sizeof(void*) - 1) & (~(sizeof(void*) - 1));
+
+  _next = NULL;
+}
+
+MemoryPool::~MemoryPool() {
+  for(size_t i=0; i<_pages.size(); ++i)
+    free(_pages[i]);
+}
+
+void* MemoryPool::malloc() {
+#if 1
+  if(!_next)
+    _next = allocPage();
+
+  void* result = _next;
+  _next = *(void**)result;
+  return result;
+#else
+  return ::malloc(_chunkSize);
+#endif
+}
+
+void MemoryPool::free(void* ptr) {
+#if 1
+  *(void**)ptr = _next;
+  _next = ptr;
+#else
+  ::free(ptr);
+#endif
+}
+
+// Technically not compliant C++ to compare unrelated pointers. In practice...
+bool MemoryPool::isPointerInPage(void* ptr, void* page) {
+    return (ptr >= page) && (ptr < (char*)page + CHUNK_PAGE_SIZE * _chunkSize);
+}
+
+void MemoryPool::freeUnusedPages() {
+  //std::sort(_pages.begin(), _pages.end());
+  Array<int> numberOfFreeChunksPerPage;
+  numberOfFreeChunksPerPage.resize(_pages.size());
+  for(size_t i=0; i<numberOfFreeChunksPerPage.size(); ++i) {
+      numberOfFreeChunksPerPage[i] = 0;
+  }
+  
+  void* iterator = _next;
+  while(iterator) {
+    // This should be a binary search
+    for(size_t i=0; i<_pages.size(); ++i) {
+      if(isPointerInPage(iterator, _pages[i])) {
+	++numberOfFreeChunksPerPage[i];
+	break;
+      }
+    }
+    iterator = *(void**)iterator;
+  }
+
+  for(size_t i=0; i<_pages.size(); ++i) {
+    if(numberOfFreeChunksPerPage[i] == CHUNK_PAGE_SIZE) {
+      free(_pages[i]);
+      _pages[i] = NULL; // TODO : Remove NULL values
+    }
+  }
+}
+
+}