1 files changed, 94 insertions, 3 deletions

diff --git a/src/std/mem.c b/src/std/mem.c
index 00f9c39..a5321fb 100644
--- a/src/std/mem.c
+++ b/src/std/mem.c
@@ -1,13 +1,17 @@
-#include "mem.h"
+#include <assert.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <string.h>
+
 #include "log.h"
+#include "mem.h"
 
 #ifndef DEFAULT_ALIGNMENT
 #define DEFAULT_ALIGNMENT (2 * sizeof(void*))
 #endif
 
+// --- Arena
+
 void* arena_alloc_align(arena* a, size_t size, size_t align) {
   ptrdiff_t padding = -(uintptr_t)a->curr & (align - 1);
   ptrdiff_t available = a->end - a->curr - padding;
@@ -15,7 +19,7 @@ void* arena_alloc_align(arena* a, size_t size, size_t align) {
   if (available < 0 || (ptrdiff_t)size > available) {
     ERROR_EXIT("Arena ran out of memory\n");
   }
-  void* p = a->begin + padding;
+  void* p = a->curr + padding;
   a->curr += padding + size;
   return memset(p, 0, size);
 }
@@ -31,4 +35,91 @@ void arena_free_all(arena* a) {
   a->curr = a->begin;  // pop everything at once and reset to the start.
 }
 
-void arena_free_storage(arena* a) { free(a->begin); }
\ No newline at end of file
+void arena_free_storage(arena* a) { free(a->begin); }
+
+arena_save arena_savepoint(arena* a) {
+  arena_save savept = { .arena = a, .savepoint = a->curr };
+  return savept;
+}
+
+void arena_rewind(arena_save savepoint) { savepoint.arena->curr = savepoint.savepoint; }
+
+// --- Pool
+
+void_pool void_pool_create(arena* a, u64 capacity, u64 entry_size) {
+  size_t memory_requirements = capacity * entry_size;
+  void* backing_buf = arena_alloc(a, memory_requirements);
+
+  void_pool pool = { .capacity = capacity,
+                     .entry_size = entry_size,
+                     .count = 0,
+                     .backing_buffer = backing_buf,
+                     .free_list_head = NULL };
+
+  void_pool_free_all(&pool);
+
+  return pool;
+}
+
+void void_pool_free_all(void_pool* pool) {
+  // set all entries to be free
+  for (u64 i = 0; i < pool->capacity; i++) {
+    void* ptr = &pool->backing_buffer[i * pool->entry_size];
+    void_pool_header* free_node =
+        (void_pool_header*)ptr;  // we reuse the actual entry itself to hold the header
+    if (i == (pool->capacity - 1)) {
+      // if the last one we make its next pointer NULL indicating its full
+      free_node->next = NULL;
+    }
+    free_node->next = pool->free_list_head;
+    // now the head points to this entry
+    pool->free_list_head = free_node;
+  }
+}
+
+void* void_pool_get(void_pool* pool, u32 raw_handle) {
+  // An handle is an index into the array essentially
+  void* ptr = pool->backing_buffer + (raw_handle * pool->entry_size);
+  return ptr;
+}
+
+void* void_pool_alloc(void_pool* pool, u32* out_raw_handle) {
+  // get the next free node
+  if (pool->count == pool->capacity) {
+    WARN("Pool is full!");
+    return NULL;
+  }
+  if (pool->free_list_head == NULL) {
+    ERROR("Pool is full (head = null)");
+    return NULL;
+  }
+  void_pool_header* free_node = pool->free_list_head;
+
+  // What index does this become?
+  uintptr_t start = (uintptr_t)pool->backing_buffer;
+  uintptr_t cur = (uintptr_t)free_node;
+  TRACE("%ld %ld ", start, cur);
+  /* assert(cur > start); */
+  u32 index = (u32)((cur - start) / pool->entry_size);
+  printf("Index %d\n", index);
+  if (out_raw_handle != NULL) {
+    *out_raw_handle = index;
+  }
+
+  pool->free_list_head = free_node->next;
+
+  memset(free_node, 0, pool->entry_size);
+  pool->count++;
+  return (void*)free_node;
+}
+
+void void_pool_dealloc(void_pool* pool, u32 raw_handle) {
+  // push free node back onto the free list
+  void* ptr = void_pool_get(pool, raw_handle);
+  void_pool_header* freed_node = (void_pool_header*)ptr;
+
+  freed_node->next = pool->free_list_head;
+  pool->free_list_head = freed_node;
+
+  pool->count--;
+}