Revert "Death to C++"

This reverts commit 066ac22605.

src/base/base_arena.cpp

@@ -0,0 +1,53 @@
+#include "base/base_arena.h"
+#include <stdlib.h>
+
+Arena *arena_alloc(U64 cap) {
+    U8 *mem = (U8 *)malloc(sizeof(Arena) + cap);
+    if (!mem) return nullptr;
+    Arena *arena = (Arena *)mem;
+    arena->base = mem + sizeof(Arena);
+    arena->pos = 0;
+    arena->cap = cap;
+    return arena;
+}
+
+void arena_release(Arena *arena) {
+    if (arena) free(arena);
+}
+
+void *arena_push(Arena *arena, U64 size) {
+    U64 aligned = AlignPow2(size, 8);
+    if (arena->pos + aligned > arena->cap) {
+        Assert(!"Arena overflow");
+        return nullptr;
+    }
+    void *result = arena->base + arena->pos;
+    arena->pos += aligned;
+    MemoryZero(result, aligned);
+    return result;
+}
+
+void *arena_push_no_zero(Arena *arena, U64 size) {
+    U64 aligned = AlignPow2(size, 8);
+    if (arena->pos + aligned > arena->cap) {
+        Assert(!"Arena overflow");
+        return nullptr;
+    }
+    void *result = arena->base + arena->pos;
+    arena->pos += aligned;
+    return result;
+}
+
+U64 arena_pos(Arena *arena) {
+    return arena->pos;
+}
+
+void arena_pop_to(Arena *arena, U64 pos) {
+    if (pos < arena->pos) {
+        arena->pos = pos;
+    }
+}
+
+void arena_clear(Arena *arena) {
+    arena->pos = 0;
+}