1 files changed, 143 insertions, 0 deletions
diff --git a/mubios/services/int16.c b/mubios/services/int16.c
new file mode 100644
index 0000000..7acccfb
--- /dev/null
+++ b/mubios/services/int16.c
@@ -0,0 +1,143 @@
+/*
+ RCC-Project
+
+ Copyright (C) 2026 Richard Qin
+
+ This file is part of RCC-Project.
+
+ RCC-Project is free software; you can redistribute it and/or modify it under
+ the terms of the GNU General Public License as published by the Free
+ Software Foundation; either version 3 of the License, or (at your option)
+ any later version.
+
+ RCC-Project is distributed in the hope that it will be useful, but WITHOUT
+ ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ more details.
+ */
+
+#include "bios.h"
+#include "regs.h"
+
+#define BIOS_ZF 0x0040u
+#define BDA_KBD_HEAD 0x041Au
+#define BDA_KBD_TAIL 0x041Cu
+#define BDA_KBD_BUFFER 0x041Eu
+#define BDA_KBD_BUFFER_END 0x043Eu
+
+static u8
+scancode_to_ascii (u8 scancode)
+{
+  switch (scancode)
+    {
+    case 0x1Eu:
+      return 'a';
+    case 0x30u:
+      return 'b';
+    case 0x2Eu:
+      return 'c';
+    case 0x20u:
+      return 'd';
+    case 0x12u:
+      return 'e';
+    case 0x21u:
+      return 'f';
+    case 0x22u:
+      return 'g';
+    case 0x23u:
+      return 'h';
+    case 0x17u:
+      return 'i';
+    case 0x24u:
+      return 'j';
+    case 0x25u:
+      return 'k';
+    case 0x26u:
+      return 'l';
+    case 0x32u:
+      return 'm';
+    case 0x31u:
+      return 'n';
+    case 0x18u:
+      return 'o';
+    case 0x19u:
+      return 'p';
+    case 0x10u:
+      return 'q';
+    case 0x13u:
+      return 'r';
+    case 0x1Fu:
+      return 's';
+    case 0x14u:
+      return 't';
+    case 0x16u:
+      return 'u';
+    case 0x2Fu:
+      return 'v';
+    case 0x11u:
+      return 'w';
+    case 0x2Du:
+      return 'x';
+    case 0x15u:
+      return 'y';
+    case 0x2Cu:
+      return 'z';
+    case 0x39u:
+      return ' ';
+    case 0x1Cu:
+      return '\r';
+    default:
+      return 0;
+    }
+}
+
+void
+int16_service (struct bios_regs *regs)
+{
+  volatile u16 *head;
+  volatile u16 *tail;
+  volatile u16 *buffer;
+  u8 function;
+  u16 position;
+  u16 value;
+  u8 scancode;
+  u8 ascii;
+
+  function = (u8)(regs->eax >> 8);
+
+  if (function != 0x00u && function != 0x01u)
+    {
+      regs->eax = 0;
+      regs->flags |= BIOS_ZF;
+      return;
+    }
+
+  head = (volatile u16 *)BDA_KBD_HEAD;
+  tail = (volatile u16 *)BDA_KBD_TAIL;
+  buffer = (volatile u16 *)BDA_KBD_BUFFER;
+
+  if (*head == *tail)
+    {
+      regs->eax = 0;
+      regs->flags |= BIOS_ZF;
+      return;
+    }
+
+  position = *head;
+  value = buffer[(position - BDA_KBD_BUFFER) >> 1];
+  scancode = (u8)(value >> 8);
+  ascii = scancode_to_ascii (scancode);
+
+  regs->eax = ((u32)scancode << 8) | ascii;
+  regs->flags &= (u16)~BIOS_ZF;
+
+  if (function == 0x00u)
+    {
+      position += 2;
+
+      if (position >= BDA_KBD_BUFFER_END)
+        position = BDA_KBD_BUFFER;
+
+      *head = position;
+    }
+}