...

src/kernel/kernel.c

@@ -1,52 +1,6 @@
 #include "print.h"
 
-/**
- * C++ version 0.4 char* style "itoa":
- * Written by Lukás Chmela
- * Released under GPLv3.
- */
-char* itoa(int value, char* result, int base)
-{
-    // check that the base if valid
-    if (base < 2 || base > 36)
-    {
-        *result = '\0';
-        return result;
-    }
-
-    char *ptr = result, *ptr1 = result, tmp_char;
-    int tmp_value;
-
-    do
-    {
-        tmp_value = value;
-        value /= base;
-        *ptr++ =
-            "zyxwvutsrqponmlkjihgfedcba9876543210123456789abcdefghijklmnopqrstuvwxyz"[35 + (tmp_value - value * base)];
-    } while (value);
-
-    // Apply negative sign
-    if (tmp_value < 0)
-        *ptr++ = '-';
-    *ptr-- = '\0';
-
-    // Reverse the string
-    while (ptr1 < ptr)
-    {
-        tmp_char = *ptr;
-        *ptr-- = *ptr1;
-        *ptr1++ = tmp_char;
-    }
-    return result;
-}
-
 void kernel_init(void)
 {
-    for (int i = 0; i < 100; i++)
+    print("Starting nub-os\n");
-    {
-        // char buf[10];
-        // itoa(i, buf, 10);
-        // kernel_print(buf);
-        kernel_print("Starting nub-osStarting");
-    }
 }

src/kernel/print.c

@@ -1,6 +1,5 @@
 #include "print.h"
 #include <stdint.h>
-#include <string.h>
 
 #define ROWS 25
 #define COLUMNS 80
@@ -47,14 +46,80 @@ typedef struct
     uint8_t color;
 } vga_char;
 
-static vga_char* print_buf = (vga_char*)BUF_START;
+static vga_char* vga_buffer = (vga_char*)BUF_START;
+static int cursor_row = 0;
+static int cursor_col = 0;
 
-void kernel_print(const char* string)
+void scroll(void)
 {
+    for (int row = 1; row < ROWS; row++)
+    {
+        for (int col = 0; col < COLUMNS; col++)
+        {
+            vga_buffer[(row - 1) * COLUMNS + col] = vga_buffer[row * COLUMNS + col];
+        }
+    }
+
+    for (int col = 0; col < COLUMNS; col++)
+    {
+        vga_buffer[(ROWS - 1) * COLUMNS + col] = (vga_char){ ' ', FG_WHITE | BG_BLACK << 4 };
+    }
+}
+
+void put_char(char c, uint8_t color)
+{
+    if (c == '\n')
+    {
+        cursor_col = 0;
+        cursor_row++;
+    }
+    else
+    {
+        vga_buffer[cursor_row * COLUMNS + cursor_col] = (vga_char){ c, color };
+        cursor_col++;
+    }
+
+    if (cursor_col >= COLUMNS)
+    {
+        cursor_col = 0;
+        cursor_row++;
+    }
+
+    if (cursor_row >= ROWS)
+    {
+        scroll();
+        cursor_row = ROWS - 1;
+    }
+}
+
+void print(const char* string)
+{
+    uint8_t color = FG_WHITE | BG_BLACK << 4;
+
     for (int i = 0; string[i]; i++)
     {
-        // todo(nub): scroll if overflowing
+        put_char(string[i], color);
+    }
+}
 
-        *print_buf++ = (vga_char){ string[i], FG_WHITE | BG_BLACK << 4 };
+void clear_screen(void)
+{
+    uint8_t color = FG_WHITE | BG_BLACK << 4;
+
+    for (int i = 0; i < ROWS * COLUMNS; i++)
+    {
+        vga_buffer[i] = (vga_char){ ' ', color };
+    }
+
+    cursor_row = 0;
+    cursor_col = 0;
+}
+
+void set_cursor_position(int row, int col)
+{
+    if (row >= 0 && row < ROWS && col >= 0 && col < COLUMNS)
+    {
+        cursor_row = row;
+        cursor_col = col;
     }
 }

src/kernel/print.h

@@ -1 +1,8 @@
+#include <stdint.h>
+
 void kernel_print(const char* string);
+
+void put_char(char c, uint8_t color);
+void print(const char* string);
+void clear_screen(void);
+void set_cursor_position(int row, int col);