Add arena allocator library

libarena/arena.c

@@ -0,0 +1,78 @@
+#include <arena.h>
+#include <liballoc.h>
+#include <stddef.h>
+
+static struct arena_chunk* arena_create_chunk (size_t capacity) {
+  size_t size = sizeof (struct arena_chunk) + sizeof (uintptr_t) * capacity;
+  struct arena_chunk* chunk = malloc (size);
+
+  if (chunk == NULL)
+    return NULL;
+
+  chunk->next = NULL;
+  chunk->size = 0;
+  chunk->capacity = capacity;
+  return chunk;
+}
+
+static void arena_destroy_chunk (struct arena_chunk* chunk) { free (chunk); }
+
+void arena_reset (struct arena* arena) {
+  for (struct arena_chunk* chunk = arena->begin; chunk != NULL; chunk = chunk->next) {
+    chunk->size = 0;
+  }
+
+  arena->end = arena->begin;
+}
+
+void arena_destroy (struct arena* arena) {
+  struct arena_chunk* chunk = arena->begin;
+
+  while (chunk) {
+    struct arena_chunk* chunk1 = chunk;
+    chunk = chunk->next;
+    arena_destroy_chunk (chunk1);
+  }
+
+  arena->begin = NULL;
+  arena->end = NULL;
+}
+
+void* arena_malloc (struct arena* arena, size_t size) {
+  size_t size1 = (size + sizeof (uintptr_t) - 1) / sizeof (uintptr_t);
+
+  if (arena->end == NULL) {
+    size_t capacity = ARENA_CHUNK_CAPACITY;
+
+    if (capacity < size1) {
+      capacity = size1;
+    }
+
+    arena->end = arena_create_chunk (capacity);
+
+    if (arena->end == NULL) {
+      return NULL;
+    }
+
+    arena->begin = arena->end;
+  }
+
+  while (arena->end->size + size1 > arena->end->capacity && arena->end->next != NULL) {
+    arena->end = arena->end->next;
+  }
+
+  if (arena->end->size + size1 > arena->end->capacity) {
+    size_t capacity = ARENA_CHUNK_CAPACITY;
+
+    if (capacity < size1) {
+      capacity = size1;
+    }
+
+    arena->end = arena_create_chunk (capacity);
+    arena->end = arena->end->next;
+  }
+
+  void* result = &arena->end->memory[arena->end->size];
+  arena->end->size += size1;
+  return result;
+}