1 files changed, 142 insertions, 0 deletions

diff --git a/source/base/base_arena.c b/source/base/base_arena.c
new file mode 100755
index 0000000..76938bd
--- /dev/null
+++ b/source/base/base_arena.c
@@ -0,0 +1,142 @@
+internal mem_arena *
+arena_create(u64 capacity)
+{
+    mem_arena *arena = (mem_arena *)mmap(
+    /* kernel decides where to throw the arena */
+    NULL,
+    capacity + sizeof(mem_arena),
+    PROT_READ | PROT_WRITE,
+    MAP_SHARED | MAP_ANONYMOUS,
+    -1,
+    0);
+
+    if (arena == MAP_FAILED)
+    {
+        return NULL;
+    }
+
+    arena->capacity          = capacity;
+    arena->base_position     = (u8 *)arena + sizeof(mem_arena);
+    arena->current_position  = 0;
+    arena->previous_position = 0;
+
+    return arena;
+}
+
+internal void
+arena_destroy(mem_arena *arena)
+{
+    if (!arena)
+    {
+        return;
+    }
+
+    int code = munmap(arena, arena->capacity + sizeof(mem_arena));
+}
+
+internal void *
+arena_alloc(mem_arena *arena, u64 size)
+{
+    if (!arena)
+    {
+        return NULL;
+    }
+
+    u64 aligned = Align(arena->current_position, ARENA_ALIGN);
+    u64 new_pos = aligned + size;
+
+    if (new_pos > arena->capacity)
+    {
+        return NULL;
+    }
+
+    void *out = arena->base_position + aligned;
+
+    arena->previous_position = arena->current_position;
+    arena->current_position  = aligned + size;
+
+    MemSet(out, size);
+
+    return out;
+}
+
+internal void
+arena_pop(mem_arena *arena, u64 size)
+{
+    size = MIN(size, arena->current_position);
+    arena->current_position -= size;
+}
+
+internal void
+arena_pop_to(mem_arena *arena, u64 pos)
+{
+    u64 size = pos < arena->current_position ? arena->current_position - pos : 0;
+    arena_pop(arena, size);
+}
+
+internal void
+arena_clear(mem_arena *arena)
+{
+    arena->current_position = 0;
+}
+
+internal mem_arena *
+arena_resize_align(mem_arena *arena, void *old_memory, u64 new_size, u64 old_size, umm alignment)
+{
+    u8 *old_mem = (u8 *)old_memory;
+
+    if (!is_pow(alignment))
+    {
+        Align(arena->current_position, alignment);
+    }
+
+    if (old_memory == NULL || old_size == 0)
+    {
+        return (mem_arena *)arena_alloc(arena, new_size);
+    }
+    else if ((old_mem >= arena->base_position && old_mem < arena->base_position + arena->capacity))
+    {
+        if ((arena->base_position + arena->previous_position) == old_memory)
+        {
+            arena->current_position = arena->previous_position + new_size;
+            if (new_size > old_size)
+            {
+                MemSet(&arena->current_position, new_size - old_size);
+            }
+            return (mem_arena *)old_memory;
+        }
+        else
+        {
+            void *new_memory = arena_alloc(arena, new_size);
+            umm   copy_size  = old_size < new_size ? old_size : new_size;
+            memmove(new_memory, old_mem, copy_size);
+        }
+    }
+    else
+    {
+        check(0);
+    }
+    return NULL;
+}
+
+internal mem_arena *
+arena_resize(mem_arena *arena, void *old_memory, u64 new_size, u64 old_size)
+{
+    return arena_resize_align(arena, old_memory, new_size, old_size, ARENA_ALIGN);
+}
+
+internal temp_arena
+temp_arena_begin(mem_arena *arena)
+{
+    temp_arena t;
+    t.arena          = arena;
+    t.start_position = arena->current_position;
+
+    return t;
+}
+
+internal void
+temp_arena_end(temp_arena temp)
+{
+    temp.arena->current_position = temp.start_position;
+}