...

src/arch/x86_64/vga.c

@@ -0,0 +1,120 @@
+#include "vga.h"
+#include <stddef.h>
+
+#define ROWS 25
+#define COLUMNS 80
+
+typedef struct
+{
+    uint8_t character;
+    uint8_t color;
+} vga_char_t;
+
+static vga_char_t* vga_buffer = (vga_char_t*)0xb8000;
+static uint8_t cursor_row = 0;
+static uint8_t cursor_col = 0;
+
+void vga_put_char(char character, uint8_t color)
+{
+    switch (character)
+    {
+    case '\n':
+    {
+        cursor_row += 1;
+        cursor_col = 0;
+        break;
+    }
+    case '\r':
+    {
+        cursor_col = 0;
+        break;
+    }
+    case '\t':
+    {
+        uint8_t remainder = 4 - (cursor_col % 4);
+        cursor_col += remainder;
+        break;
+    }
+    case '\b':
+    {
+        if (cursor_col > 0)
+        {
+            cursor_col -= 1;
+        }
+        else if (cursor_row > 0)
+        {
+            cursor_row -= 1;
+
+            cursor_col = 0;
+            for (int col = COLUMNS - 1; col >= 0; col--)
+            {
+                vga_char_t cell = vga_buffer[cursor_row * COLUMNS + col];
+                if (cell.character != ' ')
+                {
+                    cursor_col = col;
+                    break;
+                }
+            }
+        }
+
+        vga_buffer[cursor_row * COLUMNS + cursor_col] = (vga_char_t){
+            .character = ' ',
+            .color = VGA_DEFAULT_COLOR,
+        };
+        break;
+    }
+    default:
+    {
+        vga_buffer[COLUMNS * cursor_row + cursor_col] = (vga_char_t){
+            .character = character,
+            .color = color,
+        };
+        cursor_col += 1;
+        break;
+    }
+    }
+
+    if (cursor_col >= COLUMNS)
+    {
+        cursor_col = 0;
+        cursor_row += 1;
+    }
+
+    if (cursor_row >= ROWS)
+    {
+        for (size_t row = 1; row < ROWS; row++)
+        {
+            for (size_t col = 0; col < COLUMNS; col++)
+            {
+                vga_buffer[COLUMNS * (row - 1) + col] = vga_buffer[COLUMNS * row + col];
+            }
+        }
+
+        for (size_t col = 0; col < COLUMNS; col++)
+        {
+            vga_buffer[COLUMNS * (ROWS - 1) + col] = (vga_char_t){
+                .character = ' ',
+                .color = VGA_DEFAULT_COLOR,
+            };
+        };
+
+        cursor_row = ROWS - 1;
+    }
+}
+
+void vga_clear()
+{
+    for (size_t row = 0; row < ROWS; row++)
+    {
+        for (size_t col = 0; col < COLUMNS; col++)
+        {
+            vga_buffer[COLUMNS * row + col] = (vga_char_t){
+                .character = ' ',
+                .color = VGA_DEFAULT_COLOR,
+            };
+        }
+    }
+
+    cursor_row = 0;
+    cursor_col = 0;
+}