init project structure

lib

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+Subproject commit f6da8f15242c6e5c96d79a2e150db383cd8b23dc

src/kernel.c

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+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+/* Check if the compiler thinks you are targeting the wrong operating system. */
+#if defined(__linux__)
+#error                                                                         \
+    "You are not using a cross-compiler, you will most certainly run into trouble"
+#endif
+
+/* This tutorial will only work for the 32-bit ix86 targets. */
+#if !defined(__i386__)
+#error "This tutorial needs to be compiled with a ix86-elf compiler"
+#endif
+
+/* 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;
+}
+
+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_setcolor(uint8_t color) { terminal_color = color; }
+
+void terminal_putentryat(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_putchar(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_writestring(const char *data) {
+  terminal_write(data, strlen(data));
+}
+
+void kernel_main(void) {
+  /* Initialize terminal interface */
+  terminal_initialize();
+
+  /* Newline support is left as an exercise. */
+  terminal_writestring("Hello, kernel World!\n");
+}