From 36bbfd9184426576d38841bcabfa5ba2b59f726c Mon Sep 17 00:00:00 2001
From: Marvin Borner
Date: Sat, 14 Sep 2019 17:05:06 +0200
Subject: Added very basic kernel and vga driver

---
 src/kernel.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 src/kernel.c

(limited to 'src/kernel.c')

diff --git a/src/kernel.c b/src/kernel.c
new file mode 100644
index 0000000..a0c86ee
--- /dev/null
+++ b/src/kernel.c
@@ -0,0 +1,91 @@
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+// Hardware text mode color constants
+enum vga_color {
+    VGA_COLOR_BLACK = 0,
+    VGA_COLOR_BLUE = 1,
+    VGA_COLOR_GREEN = 2,
+    VGA_COLOR_CYAN = 3,
+    VGA_COLOR_RED = 4,
+    VGA_COLOR_MAGENTA = 5,
+    VGA_COLOR_BROWN = 6,
+    VGA_COLOR_LIGHT_GREY = 7,
+    VGA_COLOR_DARK_GREY = 8,
+    VGA_COLOR_LIGHT_BLUE = 9,
+    VGA_COLOR_LIGHT_GREEN = 10,
+    VGA_COLOR_LIGHT_CYAN = 11,
+    VGA_COLOR_LIGHT_RED = 12,
+    VGA_COLOR_LIGHT_MAGENTA = 13,
+    VGA_COLOR_LIGHT_BROWN = 14,
+    VGA_COLOR_WHITE = 15,
+};
+
+static inline uint8_t vga_entry_color(enum vga_color fg, enum vga_color bg) {
+    return fg | bg << 4;
+}
+
+static inline uint16_t vga_entry(unsigned char uc, uint8_t color) {
+    return (uint16_t) uc | (uint16_t) color << 8;
+}
+
+size_t strlen(const char *str) {
+    size_t len = 0;
+    while (str[len])
+        len++;
+    return len;
+}
+
+static const size_t VGA_WIDTH = 80;
+static const size_t VGA_HEIGHT = 25;
+
+size_t terminal_row;
+size_t terminal_column;
+uint8_t terminal_color;
+uint16_t *terminal_buffer;
+
+void terminal_initialize(void) {
+    terminal_row = 0;
+    terminal_column = 0;
+    terminal_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
+    terminal_buffer = (uint16_t *) 0xB8000;
+    for (size_t y = 0; y < VGA_HEIGHT; y++) {
+        for (size_t x = 0; x < VGA_WIDTH; x++) {
+            const size_t index = y * VGA_WIDTH + x;
+            terminal_buffer[index] = vga_entry(' ', terminal_color);
+        }
+    }
+}
+
+void terminal_set_color(uint8_t color) {
+    terminal_color = color;
+}
+
+void terminal_put_entry_at(char c, uint8_t color, size_t x, size_t y) {
+    const size_t index = y * VGA_WIDTH + x;
+    terminal_buffer[index] = vga_entry(c, color);
+}
+
+void terminal_put_char(char c) {
+    terminal_putentryat(c, terminal_color, terminal_column, terminal_row);
+    if (++terminal_column == VGA_WIDTH) {
+        terminal_column = 0;
+        if (++terminal_row == VGA_HEIGHT)
+            terminal_row = 0;
+    }
+}
+
+void terminal_write(const char *data, size_t size) {
+    for (size_t i = 0; i < size; i++)
+        terminal_putchar(data[i]);
+}
+
+void terminal_write(const char *data) {
+    terminal_write(data, strlen(data));
+}
+
+void kernel_main(void) {
+    terminal_initialize();
+    terminal_write("Melvix loaded successfully!");
+}
\ No newline at end of file
-- 
cgit v1.2.3