Initial commit

src/screen.c

@@ -0,0 +1,73 @@
+// screen.c
+#include "../include/screen.h"
+
+static size_t terminal_row;
+static size_t terminal_column;
+static uint8_t terminal_color;
+static uint16_t* terminal_buffer;
+
+uint8_t vga_entry_color(enum vga_color fg, enum vga_color bg) 
+{
+        return fg | bg << 4;
+}
+
+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;
+}
+
+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));
+	terminal_row++;
+	terminal_column = 0;
+}