org

kernel/drivers/vga/vga.c

@@ -0,0 +1,109 @@
+#pragma once
+
+#include "vga.h"
+#include "../../memory/memory.h"
+#include <stdint.h>
+
+#define WIDTH 80
+#define HEIGHT 25
+
+static char vga_buf[HEIGHT * (WIDTH * 2)];
+
+static uint8_t vgabuf_col = 0;
+static uint8_t vgabuf_row = 0;
+
+static uint8_t vgabuf_start_row = 0;
+static uint8_t vgabuf_move_row = 0;
+
+static uint8_t default_color_code = 10;
+static char   *vram = (char *)0xb8000;
+
+static inline int VGA_idx(int row, int col) {
+  return (row * WIDTH * 2) + (col * 2);
+}
+
+static inline void VGA_set(int row, int col, char c, int color_code) {
+  vga_buf[VGA_idx(row, col)] = c;
+  vga_buf[VGA_idx(row, col) + 1] = color_code;
+}
+
+void VGA_flush() {
+  int topwrite = ((HEIGHT - vgabuf_start_row) * WIDTH * 2);
+
+  // Fill the top of the display from the offsetted buffer
+  memcpy(vga_buf + (vgabuf_start_row * WIDTH * 2), vram, topwrite);
+
+  // Fill the bottom of the display from the offsetted buffer
+  memcpy(vga_buf, vram + topwrite, ((vgabuf_start_row)*WIDTH * 2));
+}
+
+void VGA_clear_screen() {
+  for (int r = 0; r < HEIGHT - 1; r++) {
+    for (int c = 0; c < WIDTH; c++) {
+      VGA_set(r, c, ' ', default_color_code);
+    }
+  }
+
+  vgabuf_start_row = 0;
+  vgabuf_col = 0;
+  vgabuf_row = 0;
+
+  VGA_flush();
+}
+
+void VGA_clear_line() {
+  for (int i = 0; i < WIDTH; ++i) {
+    VGA_set(vgabuf_start_row, i, ' ', default_color_code);
+  }
+}
+
+void VGA_putc(char c) {
+  if (vgabuf_col == WIDTH) {
+    vgabuf_row = (vgabuf_row + 1) % HEIGHT;
+    vgabuf_col = 0;
+
+    if (vgabuf_start_row > 0 || vgabuf_row == 0) {
+      if (vgabuf_move_row == vgabuf_start_row) {
+        vgabuf_start_row = (vgabuf_start_row + 1) % HEIGHT;
+        vgabuf_move_row = vgabuf_start_row;
+      } else {
+        vgabuf_move_row++;
+      }
+      VGA_clear_line();
+    }
+  }
+
+  if (c == '\n') {
+    for (int i = vgabuf_col; i < WIDTH; i++) {
+      VGA_set(vgabuf_row, i, ' ', default_color_code);
+    }
+    vgabuf_row = (vgabuf_row + 1) % HEIGHT;
+    vgabuf_col = 0;
+
+    if (vgabuf_start_row > 0 || vgabuf_row == 0) {
+      if (vgabuf_move_row == vgabuf_start_row) {
+        vgabuf_start_row = (vgabuf_start_row + 1) % HEIGHT;
+        vgabuf_move_row = vgabuf_start_row;
+      } else {
+        vgabuf_move_row++;
+      }
+      VGA_clear_line();
+    }
+    return;
+  }
+
+  if (c == '\b') {
+    if (vgabuf_col == 0) {
+      vgabuf_col = WIDTH - 1;
+      vgabuf_row--;
+      vgabuf_move_row--;
+    } else {
+      vgabuf_col--;
+    }
+    // VGA_set(vgabuf_row, vgabuf_col, ' ', default_color_code);
+    return;
+  }
+
+  VGA_set(vgabuf_row, vgabuf_col, c, default_color_code);
+  vgabuf_col++;
+}

kernel/drivers/vga/vga.h

@@ -0,0 +1,5 @@
+#pragma once
+
+void VGA_clear_screen();
+void VGA_putc(char);
+void VGA_flush();