From 5adc7cf997d481a6afb3ed95573d6eff44cbdd5b Mon Sep 17 00:00:00 2001
From: Xander <xander@icth.xyz>
Date: Mon, 3 Jul 2023 15:27:49 +0200
Subject: Added clear screen function

---
 arch/x86_64/boot/long_mode_init.asm |  3 ---
 kernel/main.dats                    |  3 ++-
 kernel/writer.dats                  | 17 +++++++++++++++--
 kernel/writer.sats                  |  1 +
 4 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/arch/x86_64/boot/long_mode_init.asm b/arch/x86_64/boot/long_mode_init.asm
index c3167f9..22e7fd4 100644
--- a/arch/x86_64/boot/long_mode_init.asm
+++ b/arch/x86_64/boot/long_mode_init.asm
@@ -14,7 +14,4 @@ long_mode_start:
     extern main
     call main
 
-    ; print `OKAY` to screen
-    mov rax, 0x2f592f412f4b2f4f
-    mov qword [0xb8000], rax
     hlt
diff --git a/kernel/main.dats b/kernel/main.dats
index dfbaa49..bbd201a 100644
--- a/kernel/main.dats
+++ b/kernel/main.dats
@@ -4,6 +4,7 @@ staload "kernel/writer.sats"
 dynload "kernel/writer.dats"
 
 implement main0 () = (
-  put_string("         Hello world\n");
+  clear_screen();
+  put_string("Hello world\n");
   put_string("GOEIENDSG\n");
   put_string("GOEIENDSG"))
diff --git a/kernel/writer.dats b/kernel/writer.dats
index cd6f5d7..3e75a90 100644
--- a/kernel/writer.dats
+++ b/kernel/writer.dats
@@ -51,7 +51,6 @@ staload WRITER = {
   end
 }
 
-
 fun put_char (c : char, writer: &writer) : void = let
   val buf = get_buffer()
   val pos = writer.position
@@ -62,12 +61,16 @@ in
     in
       if (new_pos < N) then
         writer.position := new_pos
+      else
+        clear_screen()
     end
   else (
     buf.1->[writer.position] := @{ ascii_character = c, color_code = writer.color_code};
 
     if (pos < N - 1) then
-      writer.position := succ(pos));
+      writer.position := succ(pos)
+    else
+      clear_screen());
 
   let prval() = eat_buffer buf in () end
 end
@@ -80,3 +83,13 @@ implement put_string (str : string) : void = let
   prval() = fpf(pf)
 in  end
 
+implement clear_screen() : void = let
+  val (pf, fpf | p_val) = $WRITER.getref()
+  fun loop {n : nat | n < N - 1} .<N-n>. (i : int n, wr : &writer) : void = 
+    (put_char('\0', wr); if (i < N - 2) then loop(i+1,wr))
+in
+  !p_val.position := 0;
+  loop(0,!p_val);
+  !p_val.position := 0;
+  let prval() = fpf(pf) in () end
+end
diff --git a/kernel/writer.sats b/kernel/writer.sats
index 3ccfd7b..65a2ea9 100644
--- a/kernel/writer.sats
+++ b/kernel/writer.sats
@@ -29,3 +29,4 @@ typedef writer  = @{position = [a:int | a >= 0 && a < N] int (a), color_code = u
 castfn i2u8 {n: nat} (i: int n): uint8 n
 
 fun put_string (str : string) : void
+fun clear_screen() : void
-- 
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