From 0e9bff7bffb42c7024fa91bfd2384b562ba01b61 Mon Sep 17 00:00:00 2001
From: greg <greg.shuflin@protonmail.com>
Date: Wed, 10 Jul 2019 02:25:12 -0700
Subject: [PATCH] Vga buffer + test for it

---
 src/main.rs       | 14 ++-----
 src/vga_buffer.rs | 96 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 100 insertions(+), 10 deletions(-)
 create mode 100644 src/vga_buffer.rs

diff --git a/src/main.rs b/src/main.rs
index 98ecf3e..11b1a71 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,6 +1,8 @@
 #![no_std]
 #![no_main]
 
+mod vga_buffer;
+
 use core::panic::PanicInfo;
 
 #[panic_handler]
@@ -8,19 +10,11 @@ fn panic(_info: &PanicInfo) -> !{
   loop {}
 }
 
-static GREETING: &[u8] = b"Gamarjoba, munde";
-
 #[no_mangle]
 pub extern "C" fn _start() -> ! {
 
-  let vga_buffer = 0xb8000 as *mut u8;
-
-  for (i, &byte) in GREETING.iter().enumerate() {
-    unsafe {
-      *vga_buffer.offset(i as isize * 2) = byte;
-      *vga_buffer.offset(i as isize * 2 + 1) = 0xb; //light cyan
-    }
-  }
+  vga_buffer::yolo();
 
   loop {}
 }
+
diff --git a/src/vga_buffer.rs b/src/vga_buffer.rs
new file mode 100644
index 0000000..34227e2
--- /dev/null
+++ b/src/vga_buffer.rs
@@ -0,0 +1,96 @@
+#[allow(dead_code)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[repr(u8)]
+pub enum Color {
+    Black = 0,
+    Blue = 1,
+    Green = 2,
+    Cyan = 3,
+    Red = 4,
+    Magenta = 5,
+    Brown = 6,
+    LightGray = 7,
+    DarkGray = 8,
+    LightBlue = 9,
+    LightGreen = 10,
+    LightCyan = 11,
+    LightRed = 12,
+    Pink = 13,
+    Yellow = 14,
+    White = 15,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[repr(transparent)]
+struct ColorCode(u8);
+
+impl ColorCode {
+  fn new(foreground: Color, background: Color) -> ColorCode {
+    ColorCode((background as u8) << 4 | (foreground as u8))
+  }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[repr(C)]
+struct ScreenChar {
+  ascii_char: u8,
+  color_code: ColorCode,
+}
+
+const BUFFER_WIDTH: usize = 80;
+const BUFFER_HEIGHT: usize = 25;
+
+#[repr(transparent)]
+struct Buffer {
+  chars: [[ScreenChar; BUFFER_WIDTH]; BUFFER_HEIGHT],
+}
+
+pub struct Writer {
+  column_position: usize,
+  color_code: ColorCode,
+  buffer: &'static mut Buffer,
+}
+
+impl Writer {
+  pub fn write_string(&mut self, s: &str) {
+    for byte in s.bytes() {
+      match byte {
+        0x20..=0x7e | b'\n' => self.write_byte(byte),
+        _ => self.write_byte(0xfe), // a ■
+      }
+    }
+  }
+
+  pub fn write_byte(&mut self, byte: u8) {
+    match byte {
+      b'\n' => self.new_line(),
+      byte => {
+        if self.column_position >= BUFFER_WIDTH {
+          self.new_line();
+        }
+        let row = BUFFER_HEIGHT - 1;
+        let col = self.column_position;
+        let color_code = self.color_code;
+        self.buffer.chars[row][col] = ScreenChar {
+          ascii_char: byte, color_code,
+        };
+        self.column_position += 1;
+      }
+    }
+  }
+
+  fn new_line(&mut self) {
+
+  }
+}
+
+pub fn yolo() {
+  let mut writer = Writer {
+    column_position: 0, color_code: ColorCode::new(Color::Yellow, Color::Black),
+    buffer: unsafe { &mut *(0xb8000 as *mut Buffer) },
+  };
+
+  writer.write_string("Gamarjoba, munde\n");
+  writer.write_string("Hella bro");
+  writer.write_string("sore は");
+}