new OS

kernel/terminal.c

@@ -0,0 +1,63 @@
+#include <stdint.h>
+#include "io.h"
+
+#define VGA_ADDRESS 0xB8000
+#define VGA_WIDTH 80
+#define VGA_HEIGHT 25
+#define WHITE_ON_BLACK 0x0F
+
+static uint16_t* const vga_buffer = (uint16_t*) VGA_ADDRESS;
+static uint8_t cursor_x = 0;
+static uint8_t cursor_y = 0;
+
+static uint16_t vga_entry(char c, uint8_t color) {
+    return (uint16_t) color << 8 | (uint8_t) c;
+}
+
+void terminal_initialize(void) {
+    for (uint16_t y = 0; y < VGA_HEIGHT; y++) {
+        for (uint16_t x = 0; x < VGA_WIDTH; x++) {
+            const size_t index = y * VGA_WIDTH + x;
+            vga_buffer[index] = vga_entry(' ', WHITE_ON_BLACK);
+        }
+    }
+    cursor_x = 0;
+    cursor_y = 0;
+}
+
+void terminal_putchar(char c) {
+    if (c == '\n') {
+        cursor_x = 0;
+        cursor_y++;
+    } else {
+        const size_t index = cursor_y * VGA_WIDTH + cursor_x;
+        vga_buffer[index] = vga_entry(c, WHITE_ON_BLACK);
+        cursor_x++;
+        if (cursor_x >= VGA_WIDTH) {
+            cursor_x = 0;
+            cursor_y++;
+        }
+    }
+
+    // Scroll if needed
+    if (cursor_y >= VGA_HEIGHT) {
+        for (uint16_t y = 1; y < VGA_HEIGHT; y++) {
+            for (uint16_t x = 0; x < VGA_WIDTH; x++) {
+                vga_buffer[(y - 1) * VGA_WIDTH + x] = vga_buffer[y * VGA_WIDTH + x];
+            }
+        }
+
+        // Clear the last line
+        for (uint16_t x = 0; x < VGA_WIDTH; x++) {
+            vga_buffer[(VGA_HEIGHT - 1) * VGA_WIDTH + x] = vga_entry(' ', WHITE_ON_BLACK);
+        }
+
+        cursor_y = VGA_HEIGHT - 1;
+    }
+}
+
+void terminal_write(const char* str) {
+    for (size_t i = 0; str[i] != '\0'; i++) {
+        terminal_putchar(str[i]);
+    }
+}