Made heap a vector of pages

Instead of using a linked list, which is incredibly fragmented, a
vector keeps all pointers together.  Keeps all our stuff together and
in theory we should have less cache misses when deleting pages.

It does introduce the issue of fragmenting, where if we allocate and
then delete many times a lot of the heap vector will be empty so
traversal will be over a ton of useless stuff.

lib/heap.c

@@ -12,17 +12,19 @@
 
 #include "./heap.h"
 
+#include <lib/darr.h>
+
+#include <malloc.h>
 #include <stdio.h>
 #include <string.h>
 
-page_t *page_create(size_t max, page_t *next)
+page_t *page_create(size_t max)
 {
   if (max == 0)
     max = PAGE_DEFAULT_SIZE;
 
   page_t *page    = calloc(1, sizeof(*page) + max);
   page->available = max;
-  page->next      = next;
   return page;
 }
 
@@ -38,13 +40,8 @@ void heap_create(heap_t *heap)
 
 page_t *heap_allocate(heap_t *heap, size_t requested)
 {
-  page_t *cur = page_create(requested, NULL);
-  if (heap->end)
-    heap->end->next = cur;
-  else
-    heap->beg = cur;
-  heap->end = cur;
-  heap->pages++;
+  page_t *cur = page_create(requested);
+  darr_append_bytes(&heap->page_vec, (byte_t *)cur, sizeof(cur));
   return cur;
 }
 
@@ -53,52 +50,30 @@ bool heap_free(heap_t *heap, page_t *page)
   if (!page || !heap)
     return false;
 
-  if (page == heap->beg)
+  for (size_t i = 0; i < (heap->page_vec.used / sizeof(page)); ++i)
   {
-    heap->beg = heap->beg->next;
-    page_delete(page);
-    --heap->pages;
-    if (heap->pages == 0)
-      heap->end = NULL;
-    return true;
-  }
-
-  page_t *prev = NULL, *next = NULL, *cur = NULL;
-  for (cur = heap->beg; cur; cur = cur->next)
-  {
-    next = cur->next;
+    page_t *cur = DARR_AT(page_t *, heap->page_vec.data, i);
     if (cur == page)
-      break;
-    prev = cur;
+    {
+      page_delete(cur);
+      // TODO: When does this fragmentation become a performance
+      // issue?
+      DARR_AT(page_t *, heap->page_vec.data, i) = NULL;
+      return true;
+    }
   }
 
-  if (!cur)
-    // Couldn't find the page
-    return false;
-  // Page was found
-  prev->next = next;
-  if (!next)
-    // This means page == heap->end
-    heap->end = prev;
-  page_delete(page);
-  --heap->pages;
-  if (heap->pages == 0)
-    heap->beg = NULL;
-
-  return true;
+  return false;
 }
 
 void heap_stop(heap_t *heap)
 {
-  page_t *ptr = heap->beg;
-  for (size_t i = 0; i < heap->pages; ++i)
+  for (size_t i = 0; i < (heap->page_vec.used / sizeof(page_t *)); i++)
   {
-    page_t *cur  = ptr;
-    page_t *next = ptr->next;
-    page_delete(cur);
-    ptr = next;
+    page_t *ptr = DARR_AT(page_t *, heap->page_vec.data, i);
+    if (ptr)
+      page_delete(ptr);
   }
-  heap->beg   = NULL;
-  heap->end   = NULL;
-  heap->pages = 0;
+  free(heap->page_vec.data);
+  heap->page_vec = (darr_t){0};
 }