1 files changed, 104 insertions, 8 deletions

diff --git a/devices/vga.c b/devices/vga.c
index 983e630..908bd5e 100644
--- a/devices/vga.c
+++ b/devices/vga.c
@@ -1,35 +1,131 @@
 #include "vga.h"
-#include <stddef.h>
 #include <stdint.h>
+#include <sys/io.h>
 
 struct __attribute__((packed)) VGAEntry {
   unsigned char text;
   uint8_t foreground : 4;
   uint8_t background : 4;
 };
+_Static_assert(sizeof(struct VGAEntry) == 2, "sizeof VGAEntry");
 
-_Static_assert(sizeof(struct VGAEntry) == 2);
-
-const size_t width = 80;
-const size_t height = 25;
+const int width = 80;
+const int height = 25;
 
 struct VGAEntry *buffer;
+int col = 0;
+int row = 0;
 
 void
 vga_init()
 {
   buffer = (struct VGAEntry *)0xc03ff000;
+  // vga_enable_cursor(0, 15);
   vga_clear(VGA_COLOR_LIGHT_BLUE, VGA_COLOR_LIGHT_GREY);
 }
 
 void
 vga_clear(enum vga_color foreground, enum vga_color background)
 {
-  for (size_t y = 0; y < height; ++y)
-    for (size_t x = 0; x < width; ++x) {
-      const size_t index = y * width + x;
+  for (int y = 0; y < height; ++y)
+    for (int x = 0; x < width; ++x) {
+      const int index = y * width + x;
       buffer[index].text = ' ';
       buffer[index].foreground = foreground;
       buffer[index].background = background;
     }
+  col = row = 0;
+  // vga_update_cursor();
+}
+
+void
+vga_putc(char a)
+{
+  switch (a) {
+  case '\n':
+    col = 0;
+    ++row;
+    break;
+  case '\r':
+    col = 0;
+    break;
+  case '\b':
+    --col;
+    if (col < 0) col = 0;
+    break;
+  default:
+    buffer[row * width + col].text = a;
+    ++col;
+  }
+
+  if (col == width) {
+    col = 0;
+    ++row;
+  }
+
+  if (row == height) {
+    // scroll up
+    for (int y = 1; y < height; ++y)
+      for (int x = 0; x < width; ++x) {
+        const int prev = (y - 1) * width + x;
+        const int curr = y * width + x;
+        buffer[prev] = buffer[curr];
+      }
+    // blank out last row
+    for (int i = (height - 1) * width; i < height * width; ++i) buffer[i].text = ' ';
+    --row;
+  }
+}
+
+void
+vga_puts(const char *string, int len)
+{
+
+  if (len == -1)
+    while (*string != '\0') {
+      vga_putc(*string);
+      ++string;
+    }
+
+  else
+    for (int i = 0; i < len; ++i) { vga_putc(string[i]); }
+}
+
+// Cursor
+const uint16_t cga_idx_port = 0x3d4;
+const uint16_t cga_dat_port = 0x3d5;
+
+const uint8_t cursor_start = 0xa;
+const uint8_t cursor_end = 0xb;
+const uint8_t cursor_addr_h = 0xe;
+const uint8_t cursor_addr_l = 0xf;
+const uint8_t cursor_hide = 0x20;
+
+void
+vga_enable_cursor(unsigned char start, unsigned char end)
+{
+  outb(cga_idx_port, cursor_start);
+  outb(cga_dat_port, (inb(cga_dat_port) & 0xc0) | start);
+
+  outb(cga_idx_port, cursor_end);
+  outb(cga_dat_port, (inb(cga_dat_port) & 0xe0) | end);
+}
+
+void
+vga_disable_cursor()
+{
+  outb(cga_idx_port, cursor_start);
+  outb(cga_dat_port, cursor_hide);
+}
+
+void
+vga_update_cursor()
+{
+  const uint16_t pos = row * width + col;
+
+  outb(cga_idx_port, cursor_addr_l);
+  outb(cga_dat_port, pos & 0xff);
+
+  outb(cga_idx_port, cursor_addr_h);
+  outb(cga_dat_port, (pos >> 8) & 0xff);
 }