1 files changed, 83 insertions, 0 deletions
diff --git a/kernel/tty.c b/kernel/tty.c
new file mode 100644
index 0000000..4cb2cf1
--- /dev/null
+++ b/kernel/tty.c
@@ -0,0 +1,83 @@
+#include "tty.h"
+
+/* Hardware text mode color constants. */
+enum vga_color {
+    COLOR_BLACK         = 0,
+    COLOR_BLUE          = 1,
+    COLOR_GREEN         = 2,
+    COLOR_CYAN          = 3,
+    COLOR_RED           = 4,
+    COLOR_MAGENTA       = 5,
+    COLOR_BROWN         = 6,
+    COLOR_LIGHT_GREY    = 7,
+    COLOR_DARK_GREY     = 8,
+    COLOR_LIGHT_BLUE    = 9,
+    COLOR_LIGHT_GREEN   = 10,
+    COLOR_LIGHT_CYAN    = 11,
+    COLOR_LIGHT_RED     = 12,
+    COLOR_LIGHT_MAGENTA = 13,
+    COLOR_LIGHT_BROWN   = 14,
+    COLOR_WHITE         = 15,
+};
+
+#define VGA_WIDTH   80
+#define VGA_HEIGHT  25
+#define VGA_TEXT_BUFFER 0xB8000
+#define VGA_COLOR_SHIFT 8
+
+static size_t tty_row;
+static size_t tty_col;
+static uint8_t tty_color;
+static uint16_t* tty_buffer;
+
+static inline uint8_t make_color(enum vga_color fg, enum vga_color bg)
+{
+    return fg | bg << 4;
+}
+
+static inline uint16_t make_vgaentry(char c, uint8_t color)
+{
+    return ((uint16_t) c) | (((uint16_t) color) << VGA_COLOR_SHIFT);
+}
+
+static inline void tty_putentryat(char c, uint8_t color, size_t x, size_t y)
+{
+    const size_t i = y * VGA_WIDTH + x;
+    tty_buffer[i] = make_vgaentry(c, color);
+}
+
+void tty_setcolor(uint8_t color)
+{
+    tty_color = color;
+}
+
+void tty_putchar(char c)
+{
+    tty_putentryat(c, tty_color, tty_col, tty_row);
+    if (++tty_col == VGA_WIDTH) {
+        tty_col = 0;
+        if (++tty_row == VGA_HEIGHT) {
+            tty_row = 0;
+        }
+    }
+}
+
+void tty_writestring(const char* data)
+{
+    for (const char* p = data; *p != 0; p++)
+        tty_putchar(*p);
+}
+
+void tty_init()
+{
+    tty_row = 0;
+    tty_col = 0;
+    tty_buffer = (uint16_t*) VGA_TEXT_BUFFER;
+    tty_setcolor(make_color(COLOR_LIGHT_GREY, COLOR_BLACK));
+    for (size_t y = 0; y < VGA_HEIGHT; y++) {
+        for (size_t x = 0; x < VGA_WIDTH; x++) {
+            const size_t i = y * VGA_WIDTH + x;
+            tty_buffer[i] = make_vgaentry(' ', tty_color);
+        }
+    }
+}