From 88b524543119a18297240a563cb8c08ff440dd53 Mon Sep 17 00:00:00 2001
From: the lemons <citrons@mondecitronne.com>
Date: Sun, 4 Apr 2021 02:53:05 -0500
Subject: memory bookkeeping

---
 kernel.bin     | Bin 87888 -> 89720 bytes
 os.iso         | Bin 19890176 -> 19892224 bytes
 src/main.c     |   7 ++++---
 src/memory.c   |  42 ++++++++++++++++++++++++++++++++++++++++++
 src/memory.h   |  35 +++++++++++++++++++++++++++++++++++
 src/redacted.h |  11 +++++++++++
 6 files changed, 92 insertions(+), 3 deletions(-)
 create mode 100644 src/memory.c
 create mode 100644 src/memory.h
 create mode 100644 src/redacted.h

diff --git a/kernel.bin b/kernel.bin
index a3d698f..1043589 100755
Binary files a/kernel.bin and b/kernel.bin differ
diff --git a/os.iso b/os.iso
index 9c9759f..a095b2f 100644
Binary files a/os.iso and b/os.iso differ
diff --git a/src/main.c b/src/main.c
index 0022a4c..a17db9a 100644
--- a/src/main.c
+++ b/src/main.c
@@ -3,8 +3,8 @@
 
 #include "vga.h"
 #include "interrupt.h"
-#include "string.h"
 #include "multiboot.h"
+#include "memory.h"
 #include "printf.h"
 
 extern void *gdt;
@@ -29,11 +29,12 @@ const char *pope =
 "by means of its diplomatic relations and political accords with many           \n"
 "independent states.\n";
 
-void kernel_main(multiboot_info_t *mbd) {
+void kernel_main(multiboot_info_t *mb) {
 	vsetcolor(vga_color(vga_black, vga_white));
 	vclear();
 	interrupt_init();
 	start_interrupts();
+	init_memory(mb);
 	
 	vprint("      _ _                                   \n");
 	vprint("  ___(_) |_ _ __ ___  _ __  ___    ___  ___ \n");
@@ -43,5 +44,5 @@ void kernel_main(multiboot_info_t *mbd) {
                                             
 	vprint(pope);
 
-	while (1) asm("hlt");
+	while (1) asm volatile("hlt");
 }
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;
+	}
+}
diff --git a/src/memory.h b/src/memory.h
new file mode 100644
index 0000000..3c38af7
--- /dev/null
+++ b/src/memory.h
@@ -0,0 +1,35 @@
+#ifndef __MEMORY_H
+#define __MEMORY_H
+
+#include <stdint.h>
+#include "redacted.h"
+#include "multiboot.h"
+
+enum cell_type {
+	FREE_CELL,
+	CONS_CELL,
+	INT_CELL,
+	CHAR_CELL,
+	FLOAT_CELL,
+	ARRAY_CELL,
+	ARRAY_MEMBER,
+	APIOFORM
+};
+
+struct cell {
+	uint8_t type;
+	union car {
+		struct cell *free;
+		struct cell *cons;
+		struct {int type : 8; int size : 24;} ARRAY_CELL;
+		uint32_t int_;
+		uint32_t char_;
+		float float_;
+		REDACTED_t apioform;
+	};
+	struct cell *cdr;
+};
+
+void init_memory(multiboot_info_t *mb);
+
+#endif
diff --git a/src/redacted.h b/src/redacted.h
new file mode 100644
index 0000000..5b5a667
--- /dev/null
+++ b/src/redacted.h
@@ -0,0 +1,11 @@
+#ifndef __REDACTED_H
+#define __REDACTED_H
+
+typedef struct {
+	unsigned int type : 8;
+	unsigned int apiocity : 4;
+	int communism_value : 4;
+	int rotational_velocity : 16;
+} REDACTED_t;
+
+#endif
-- 
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