Intial commit: No free list management yet

1 files changed, 87 insertions, 0 deletions

diff --git a/src/alloc.c b/src/alloc.c
new file mode 100644
index 0000000..c13b1e8
--- /dev/null
+++ b/src/alloc.c
@@ -0,0 +1,87 @@
+/*
+ * src/alloc.c
+ *
+ * Primary implementation of allocator logic for liballoc
+ * CISC 301 -- Operating Systems, Project 3
+ *
+ * Copyright (C) 2025  Douglas B. Rumbaugh <dbrumbaugh@harrisburgu.edu>
+ * 
+ * Distributed under the Modified BSD License
+ *
+ */
+#include "alloc.h"
+#include "constants.h"
+#include "free_list.h"
+
+typedef struct header {
+  size_t size;
+  size_t magic_number;
+} header;
+
+static_assert(sizeof(header) % ALIGNMENT == 0, "Header improperly aligned");
+
+static void *heap_start = 0;
+static void *heap_end = 0;
+free_nd *free_list = NULL;
+
+static void initialize() {
+  heap_start = sbrk(0);
+
+  if (heap_start == (void *)-1) {
+    perror("liballoc initialization:");
+    exit(EXIT_FAILURE);
+  }
+
+  size_t padding = (size_t)heap_start % ALIGNMENT;
+  if (padding) {
+    heap_start = sbrk(padding);
+    if (heap_start == (void *)-1) {
+      perror("liballoc initialization:");
+      exit(EXIT_FAILURE);
+    }
+  }
+
+  assert((size_t)heap_start % ALIGNMENT == 0);
+  heap_end = heap_start;
+}
+
+void *allocate(size_t size) {
+  if (!heap_start) {
+    initialize();
+  }
+
+  /*
+   * pad the requested size to ensure alignment using
+   * the alignment one-liner we discussed in class
+   */
+  size = (size + ALIGNMENT - 1) & ~(ALIGNMENT - 1);
+
+  /* first check for a suitable memory block on the free list */
+  free_nd *nd = fl_find_first_fit(free_list, size);
+  if (nd) {
+    void *return_region = fl_split_node(free_list, nd, size);
+  }
+
+  /*
+   * if there aren't any blocks on the free list, we need to allocate
+   * from scratch
+   */
+  void *new_region = sbrk(size + sizeof(header));
+
+  /* out of memory */
+  if (new_region == (void *)-1) {
+    return NULL;
+  }
+
+  heap_end = new_region + size + sizeof(header);
+
+  ((header *)new_region)->size = size;
+  ((header *)new_region)->magic_number = MAGIC_NUMBER;
+
+  return new_region + sizeof(header);
+}
+
+void release(void *ptr) {
+  fl_add_node(free_list, ptr);
+  fl_coalesce_nodes(free_list);
+}