1 files changed, 42 insertions, 0 deletions
diff --git a/src/memory.c b/src/memory.c
new file mode 100644
index 0000000..970ba29
--- /dev/null
+++ b/src/memory.c
@@ -0,0 +1,42 @@
+
+#include <stdint.h>
+#include <limits.h>
+#include <stddef.h>
+#include "memory.h"
+#include "multiboot.h"
+
+struct memory_area {
+	uint32_t len;
+	struct memory_area *next;
+};
+
+struct memory_area *first = NULL;
+
+void init_memory(multiboot_info_t *mb) {
+	struct memory_area *prev = NULL;
+	for (
+		multiboot_memory_map_t *e = (multiboot_memory_map_t *) mb->mmap_addr;
+		(unsigned int) e < mb->mmap_addr + mb->mmap_length; 
+		e += 1
+	) {
+		if (e->type != MULTIBOOT_MEMORY_AVAILABLE) continue;
+		// memory below 1MB is not safe to use.
+		if (e->addr < 1000000) continue;
+		// memory above UINT_MAX is unusable.
+		if (e->addr > UINT_MAX) continue;
+
+		uint32_t length;
+		// if the memory reaches outside of UINT_MAX, truncate length value
+		if (e->addr + e->len > UINT_MAX)
+			length = UINT_MAX - e->addr;
+		else length = e->len;
+
+		struct memory_area *cur = (struct memory_area *) e->addr;
+		cur->len = length;
+
+		if (prev != NULL)
+			prev->next = (struct memory_area *) e->addr;
+
+		prev = cur;
+	}
+}