src/arena_allocator.c

@@ -2,7 +2,6 @@
 #include <assert.h>
 #include <stddef.h>
 #include <stdlib.h>
-#include <string.h>
 
 #define DEFAUL_REGION_SIZE 1048576 /* 8 * 1024 * 1024 = 8MB */
 
@@ -12,60 +11,19 @@ Region *new_region(size_t capacity) {
   }
   Region *region = malloc(capacity + sizeof(Region));
   assert(region != NULL);
-  *region = (Region){.next = NULL, .capacity = capacity, .cursor = 0};
-
-  // Zero initialise memory
-  memset(region->data, 0, capacity);
-
+  *region = (Region){.next = NULL,
+                     .capacity = capacity,
+                     .cursor = 0};
   return region;
 }
 
-Arena *arena_init(Arena *parent, size_t capacity) {
+Arena arena_init(size_t capacity) {
   Region *region = new_region(capacity);
-
-  if (parent != NULL) {
-    // Allocate new arena in parent to reduce likelyhood of loss
-    Arena *current_arena = arena_alloc(parent, sizeof(Arena));
-    *current_arena = (Arena){.parent = parent,
-                             .begin = region,
-                             .end = region,
-                             .child = NULL,
-                             .sibling = NULL};
-
-    // if parent has no children this arena is now it's child
-    if (parent->child == NULL) {
-      parent->child = current_arena;
-      return current_arena;
-    }
-
-    // Push the arena onto the first childs sibling list
-    current_arena->sibling = parent->child;
-    parent->child = current_arena;
-    return current_arena;
-  }
-
-  // Create root of arena tree
-  Arena *arena = malloc(sizeof(Arena));
-  *arena = (Arena){.parent = NULL,
-                   .begin = region,
-                   .end = region,
-                   .child = NULL,
-                   .sibling = NULL};
+  Arena arena = {.begin = region, .end = region};
   return arena;
 }
 
 void arena_deinit(Arena *arena) {
-  if (arena == NULL) {
-    return;
-  }
-  // Recursively deinit children
-  while (arena->child != NULL) {
-    Arena *current_child = arena->child;
-    arena->child = current_child->sibling;
-    arena_deinit(current_child);
-  }
-
-  // actually free the data
   assert(arena->begin != NULL && arena->end != NULL);
   Region *region = arena->begin;
   while (region != NULL) {
@@ -73,34 +31,10 @@ void arena_deinit(Arena *arena) {
     free(region);
     region = next_region;
   }
-
-  arena->begin = NULL;
-  arena->end = NULL;
-
-  // If we're the tree root free us from malloc
-  if (arena->parent == NULL) {
-    free(arena);
-    return;
-  }
-
-  // Now that we have no descendants tell our parent and siblings of our death
-  if (arena->parent->child == arena) {
-    arena->parent->child = arena->sibling;
-    return;
-  }
-
-  Arena *previous_sibling = arena->parent->child;
-  while (previous_sibling != NULL && previous_sibling->sibling != arena) {
-    previous_sibling = previous_sibling->sibling;
-  }
-  if (previous_sibling != NULL) {
-    previous_sibling->sibling = arena->sibling;
-  }
+  *arena = (Arena){.begin = NULL, .end = NULL};
 }
 
 void *arena_alloc(Arena *arena, size_t size) {
-  // TODO: only align when needed
-  size = (size + 7) & ~7; // align size increase to multiple of 8
   Region *region = arena->end;
   assert(region != NULL);
 
@@ -112,8 +46,6 @@ void *arena_alloc(Arena *arena, size_t size) {
 
   void *result = &region->data[region->cursor];
   region->cursor += size;
-  // TODO: only align when needed
-  size = (size + 7) & ~7; // align size increase to multiple of 8
   return result;
 }
 

src/arena_allocator.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <stddef.h>
+#include <stdint.h>
 
 typedef struct Region_s Region;
 struct Region_s {
@@ -10,16 +11,12 @@ struct Region_s {
   unsigned char data[];
 };
 
-typedef struct Arena_s Arena;
-struct Arena_s {
-  Arena *parent;
-  Arena *child;
-  Arena *sibling;
+typedef struct {
   Region *begin;
   Region *end;
-};
+} Arena;
 
-Arena *arena_init(Arena *parent, size_t capacity);
+Arena arena_init(size_t capacity);
 void arena_deinit(Arena *arena);
 
 void *arena_alloc(Arena *arena, size_t size);

src/main.c

@@ -10,37 +10,14 @@
 
 #include "arena_allocator.h"
 
-/*
-int main(int argc, char *argv[]) {
-  // arena allocation test
-  printf("Allocation test\n");
-  Arena *global_arena = arena_init(NULL, 0);
+/*int main(int argc, char *argv[]) {
+  Arena global_arena = arena_init(0);
   for (int i = 0; i <= 1048576+100; i++) {
-    int *number = arena_alloc(global_arena, sizeof(int));
+    int *number = arena_alloc(&global_arena, sizeof(int));
     *number = 42;
   }
-
-  // arena children test
-  printf("children test\n");
-  Arena *child_arena = arena_init(global_arena, 0);
-  Arena *sibling_arena = arena_init(global_arena, 0);
-  Arena *grandchild_arena = arena_init(child_arena, 0);
-  Arena *greatgrandchild_arena = arena_init(grandchild_arena, 0);
-  Arena *greatgrandchildsibling_arena = arena_init(grandchild_arena, 0);
-  Arena *greatgrandchildsiblingsibling_arena = arena_init(grandchild_arena, 0);
-  Arena *greategreatgrandchild_arena =
-      arena_init(greatgrandchildsibling_arena, 0);
-  Arena *greatsiblinggreatgrandchild_arena =
-      arena_init(greatgrandchildsiblingsibling_arena, 0);
-
-  printf("deinit tests\n");
-  arena_deinit(greatgrandchild_arena);
-
-  arena_deinit(global_arena);
-
-  printf("tests complete\n");
-}
-*/
+  arena_deinit(&global_arena);
+}*/
 
 int main(int argc, char *argv[]) {
   wn_window window = {0};