1 files changed, 55 insertions, 5 deletions

diff --git a/src/memory.c b/src/memory.c
index bc65311..e5e215c 100644
--- a/src/memory.c
+++ b/src/memory.c
@@ -4,19 +4,29 @@
 #include <stddef.h>
 #include "memory.h"
 #include "multiboot.h"
+#include "bees.h"
+#include "misc.h"
 #include "printf.h"
 
 struct memory_area {
 	uint32_t len;
 	struct memory_area *next;
+	struct memory_area *prev;
 };
 
-struct memory_area *first = NULL;
-
 uint32_t memory_available = 0;
+uint32_t total_memory = 0;
+struct memory_area *first_area = NULL;
+
+struct cell *first_free = NULL;
+
+extern mem_t __kernel_start;
+extern mem_t __kernel_end;
 
 void init_memory(multiboot_info_t *mb) {
 	struct memory_area *prev = NULL;
+	struct cell *prev_cell = NULL;
+
 	for (
 		multiboot_memory_map_t *e = (multiboot_memory_map_t *) mb->mmap_addr;
 		(unsigned int) e < mb->mmap_addr + mb->mmap_length; 
@@ -24,7 +34,7 @@ void init_memory(multiboot_info_t *mb) {
 	) {
 		if (e->type != MULTIBOOT_MEMORY_AVAILABLE) continue;
 		// memory below 1MB is not safe to use.
-		if (e->addr < 1000000) continue;
+		if (e->addr < __kernel_start) continue;
 		// memory above UINT_MAX is unusable.
 		if (e->addr > UINT_MAX) continue;
 
@@ -34,14 +44,54 @@ void init_memory(multiboot_info_t *mb) {
 			length = UINT_MAX - e->addr;
 		else length = e->len;
 
-		memory_available += length;
+		// free memory comes after the kernel
+		uint32_t addr = e->addr;
+		if (addr < (uint32_t) __kernel_end) {
+			addr = (uint32_t) __kernel_end;
+			length -= addr - e->addr;
+		}
+
+		memory_available += length - sizeof(struct memory_area);
 
-		struct memory_area *cur = (struct memory_area *) e->addr;
+		// join memory area to linked list
+		struct memory_area *cur = (struct memory_area *) addr;
 		cur->len = length;
+		cur->next = NULL;
+		cur->prev = prev;
 
 		if (prev != NULL)
 			prev->next = (struct memory_area *) e->addr;
 
 		prev = cur;
+
+		if (first_area == NULL) first_area = cur;
+
+		unsigned char *after = (unsigned char*) (cur + 1);
+
+		// link memory into free list
+		for (
+			// cells start after memory area struct; they must be aligned.
+			struct cell *c = (struct cell *) 
+				(after + ((uint32_t) after % sizeof(struct cell)));
+			// no part of the cell can be outside of the memory area
+			(uint32_t) (c + 1) < (uint32_t) cur + cur->len;
+			c++
+		) {
+			if (first_free == NULL) first_free = c;
+			c->type = FREE_CELL;
+			set_cdr(c, 0);
+			if (prev_cell != NULL) set_cdr(prev_cell, (uint32_t) c);
+			prev_cell = c;
+		}
 	}
+	total_memory = memory_available;
+}
+
+struct cell *alloc_cell(enum cell_type t) {
+	if (first_free == NULL) return NULL; // GC should be invoked here somehow
+	if (first_free->type != FREE_CELL) bees("heap corruption has occurred");
+	first_free = cdr_cell(first_free);
+	first_free->type = t;
+	memory_available -= sizeof(struct cell);
+	return first_free;
 }