refactor arena code

1 files changed, 35 insertions, 0 deletions

diff --git a/src/mixed_arena.h b/src/mixed_arena.h
new file mode 100644
index 000000000..a92026580
--- /dev/null
+++ b/src/mixed_arena.h
@@ -0,0 +1,35 @@
+
+#include <vector>
+
+// Arena allocation for mixed-type data.
+struct MixedArena {
+  std::vector<char*> chunks;
+  int index; // in last chunk
+
+  template<class T>
+  T* alloc() {
+    const size_t CHUNK = 10000;
+    size_t currSize = (sizeof(T) + 7) & (-8); // same alignment as malloc TODO optimize?
+    assert(currSize < CHUNK);
+    if (chunks.size() == 0 || index + currSize >= CHUNK) {
+      chunks.push_back(new char[CHUNK]);
+      index = 0;
+    }
+    T* ret = (T*)(chunks.back() + index);
+    index += currSize;
+    new (ret) T();
+    return ret;
+  }
+
+  void clear() {
+    for (char* chunk : chunks) {
+      delete[] chunk;
+    }
+    chunks.clear();
+  }
+
+  ~MixedArena() {
+    clear();
+  }
+};
+