kernel print and mem

src/print.c

@@ -0,0 +1,94 @@
+#include "print.h"
+
+#define VGA_WIDTH 80
+#define VGA_HEIGHT 25
+
+char* vga_text_pos;
+
+void print_init(void)
+{
+    vga_text_pos = (char*)0xb8000;
+}
+
+void print(char* string, enum VGA_FG_COLOR fg_color, enum VGA_BG_COLOR bg_color)
+{
+    for (int i = 0; string[i]; i++)
+    {
+        char c = string[i];
+
+        switch (c)
+        {
+        case '\n':
+        {
+
+            vga_text_pos += 160 - ((vga_text_pos - (char*)0xb8000) % 160);
+            break;
+        }
+        case '\r':
+        {
+            vga_text_pos -= ((vga_text_pos - (char*)0xb8000) % 160);
+            break;
+        }
+        case '\t':
+        {
+            int offset = (vga_text_pos - (char*)0xb8000) % 160;
+            int next_tab = ((offset / 16) + 1) * 16;
+            vga_text_pos += next_tab - offset;
+            break;
+        }
+        case '\b':
+        {
+            if (vga_text_pos > (char*)0xb8000)
+            {
+                vga_text_pos -= 2;
+                *vga_text_pos = ' ';
+                *(vga_text_pos + 1) = (bg_color << 4) | fg_color;
+            }
+            break;
+        }
+        case '\f':
+        {
+            char* start = (char*)0xb8000;
+            for (int j = 0; j < 80 * 25 * 2; j += 2)
+            {
+                start[j] = ' ';
+                start[j + 1] = (bg_color << 4) | fg_color;
+            }
+            vga_text_pos = (char*)0xb8000;
+            break;
+        }
+        case '\a':
+        {
+            break;
+        }
+        default:
+        {
+            *vga_text_pos++ = c;
+            *vga_text_pos++ = (bg_color << 4) | fg_color;
+            break;
+        }
+        }
+
+        if (vga_text_pos >= (char*)0xb8000 + VGA_WIDTH * VGA_HEIGHT * 2)
+        {
+            char* start = (char*)0xb8000;
+
+            for (int row = 1; row < VGA_HEIGHT; row++)
+            {
+                for (int col = 0; col < VGA_WIDTH * 2; col++)
+                {
+                    start[(row - 1) * VGA_WIDTH * 2 + col] = start[row * VGA_WIDTH * 2 + col];
+                }
+            }
+
+            char* last_row = start + (VGA_HEIGHT - 1) * VGA_WIDTH * 2;
+            for (int col = 0; col < VGA_WIDTH * 2; col += 2)
+            {
+                last_row[col] = ' ';
+                last_row[col + 1] = (VGA_BG_BLACK << 4) | VGA_FG_WHITE;
+            }
+
+            vga_text_pos -= VGA_WIDTH * 2;
+        }
+    }
+}