1 files changed, 329 insertions, 0 deletions

diff --git a/src/ps2.rs b/src/ps2.rs
new file mode 100644
index 0000000..e972658
--- /dev/null
+++ b/src/ps2.rs
@@ -0,0 +1,329 @@
+/// PS/2 keyboard driver — polling, scancode set 1, US QWERTY layout.
+// Port addresses
+const DATA_PORT: u16 = 0x60;
+const STATUS_PORT: u16 = 0x64;
+
+// Status register bits
+const STAT_OUTPUT_FULL: u8 = 0x01;
+
+// Modifier bit constants
+const MOD_LSHIFT: u8 = 0x01;
+const MOD_RSHIFT: u8 = 0x02;
+const MOD_LCTRL: u8 = 0x04;
+const MOD_RCTRL: u8 = 0x08;
+const MOD_LALT: u8 = 0x10;
+const MOD_RALT: u8 = 0x20;
+const MOD_CAPS: u8 = 0x40;
+
+/// A decoded key event.
+pub enum KeyEvent {
+    Char(char),
+    Enter,
+    Backspace,
+    Tab,
+    Escape,
+    ArrowUp,
+    ArrowDown,
+    ArrowLeft,
+    ArrowRight,
+    Home,
+    End,
+    PageUp,
+    PageDown,
+    Delete,
+    F(u8),
+    Unknown(u8),
+}
+
+// ----- scancode-set-1 translation tables (US QWERTY) -----
+
+/// Normal (unshifted) scancode → ASCII mapping.  0 = unmapped.
+static SCAN_NORMAL: [u8; 128] = {
+    let mut t = [0u8; 128];
+    t[0x02] = b'1';
+    t[0x03] = b'2';
+    t[0x04] = b'3';
+    t[0x05] = b'4';
+    t[0x06] = b'5';
+    t[0x07] = b'6';
+    t[0x08] = b'7';
+    t[0x09] = b'8';
+    t[0x0A] = b'9';
+    t[0x0B] = b'0';
+    t[0x0C] = b'-';
+    t[0x0D] = b'=';
+    t[0x10] = b'q';
+    t[0x11] = b'w';
+    t[0x12] = b'e';
+    t[0x13] = b'r';
+    t[0x14] = b't';
+    t[0x15] = b'y';
+    t[0x16] = b'u';
+    t[0x17] = b'i';
+    t[0x18] = b'o';
+    t[0x19] = b'p';
+    t[0x1A] = b'[';
+    t[0x1B] = b']';
+    t[0x1E] = b'a';
+    t[0x1F] = b's';
+    t[0x20] = b'd';
+    t[0x21] = b'f';
+    t[0x22] = b'g';
+    t[0x23] = b'h';
+    t[0x24] = b'j';
+    t[0x25] = b'k';
+    t[0x26] = b'l';
+    t[0x27] = b';';
+    t[0x28] = b'\'';
+    t[0x29] = b'`';
+    t[0x2B] = b'\\';
+    t[0x2C] = b'z';
+    t[0x2D] = b'x';
+    t[0x2E] = b'c';
+    t[0x2F] = b'v';
+    t[0x30] = b'b';
+    t[0x31] = b'n';
+    t[0x32] = b'm';
+    t[0x33] = b',';
+    t[0x34] = b'.';
+    t[0x35] = b'/';
+    t[0x37] = b'*';
+    t[0x39] = b' ';
+    t
+};
+
+/// Shifted scancode → ASCII.
+static SCAN_SHIFT: [u8; 128] = {
+    let mut t = [0u8; 128];
+    t[0x02] = b'!';
+    t[0x03] = b'@';
+    t[0x04] = b'#';
+    t[0x05] = b'$';
+    t[0x06] = b'%';
+    t[0x07] = b'^';
+    t[0x08] = b'&';
+    t[0x09] = b'*';
+    t[0x0A] = b'(';
+    t[0x0B] = b')';
+    t[0x0C] = b'_';
+    t[0x0D] = b'+';
+    t[0x10] = b'Q';
+    t[0x11] = b'W';
+    t[0x12] = b'E';
+    t[0x13] = b'R';
+    t[0x14] = b'T';
+    t[0x15] = b'Y';
+    t[0x16] = b'U';
+    t[0x17] = b'I';
+    t[0x18] = b'O';
+    t[0x19] = b'P';
+    t[0x1A] = b'{';
+    t[0x1B] = b'}';
+    t[0x1E] = b'A';
+    t[0x1F] = b'S';
+    t[0x20] = b'D';
+    t[0x21] = b'F';
+    t[0x22] = b'G';
+    t[0x23] = b'H';
+    t[0x24] = b'J';
+    t[0x25] = b'K';
+    t[0x26] = b'L';
+    t[0x27] = b':';
+    t[0x28] = b'"';
+    t[0x29] = b'~';
+    t[0x2B] = b'|';
+    t[0x2C] = b'Z';
+    t[0x2D] = b'X';
+    t[0x2E] = b'C';
+    t[0x2F] = b'V';
+    t[0x30] = b'B';
+    t[0x31] = b'N';
+    t[0x32] = b'M';
+    t[0x33] = b'<';
+    t[0x34] = b'>';
+    t[0x35] = b'?';
+    t[0x37] = b'*';
+    t[0x39] = b' ';
+    t
+};
+
+/// Internal keyboard state
+struct KbdState {
+    modifiers: u8,
+    got_e0: bool,
+}
+
+static mut KBD: KbdState = KbdState {
+    modifiers: 0,
+    got_e0: false,
+};
+
+/// Initialise the PS/2 port for the keyboard — just drain stale bytes.
+pub fn init() {
+    drain_input();
+}
+
+fn drain_input() {
+    unsafe {
+        loop {
+            let status: u8;
+            core::arch::asm!("in al, dx", out("al") status, in("dx") STATUS_PORT,
+                options(nostack, preserves_flags));
+            if status & STAT_OUTPUT_FULL == 0 {
+                break;
+            }
+            let _data: u8;
+            core::arch::asm!("in al, dx", out("al") _data, in("dx") DATA_PORT,
+                options(nostack, preserves_flags));
+        }
+    }
+}
+
+/// Poll for a key event. Blocks until a key is pressed.
+pub fn poll_key() -> KeyEvent {
+    loop {
+        let byte = read_data();
+        if let Some(ev) = process_byte(byte) {
+            return ev;
+        }
+    }
+}
+
+/// Non-blocking poll.
+pub fn try_poll_key() -> Option<KeyEvent> {
+    unsafe {
+        let status: u8;
+        core::arch::asm!("in al, dx", out("al") status, in("dx") STATUS_PORT,
+            options(nostack, preserves_flags));
+        if status & STAT_OUTPUT_FULL == 0 {
+            return None;
+        }
+        let data: u8;
+        core::arch::asm!("in al, dx", out("al") data, in("dx") DATA_PORT,
+            options(nostack, preserves_flags));
+        process_byte(data)
+    }
+}
+
+/// Read a byte from the keyboard data port (blocking).
+fn read_data() -> u8 {
+    unsafe {
+        loop {
+            let status: u8;
+            core::arch::asm!("in al, dx", out("al") status, in("dx") STATUS_PORT,
+                options(nostack, preserves_flags));
+            if status & STAT_OUTPUT_FULL != 0 {
+                let data: u8;
+                core::arch::asm!("in al, dx", out("al") data, in("dx") DATA_PORT,
+                    options(nostack, preserves_flags));
+                return data;
+            }
+        }
+    }
+}
+
+/// Process a single scancode byte. Returns Some(KeyEvent) when a visible
+/// event happens; returns None for modifier changes, releases, and prefixes.
+fn process_byte(byte: u8) -> Option<KeyEvent> {
+    let state = unsafe { &mut KBD };
+
+    if byte == 0xE0 {
+        state.got_e0 = true;
+        return None;
+    }
+
+    if state.got_e0 {
+        state.got_e0 = false;
+        return process_e0(byte);
+    }
+
+    // Break code (key release) — bit 7 set
+    if byte & 0x80 != 0 {
+        update_modifiers(byte & 0x7F, false, false);
+        return None;
+    }
+
+    // Make code (key press)
+    update_modifiers(byte, true, false);
+
+    match byte {
+        0x01 => Some(KeyEvent::Escape),
+        0x0E => Some(KeyEvent::Backspace),
+        0x0F => Some(KeyEvent::Tab),
+        0x1C => Some(KeyEvent::Enter),
+        0x37 => Some(KeyEvent::Char('*')),
+        0x3B..=0x44 => Some(KeyEvent::F(byte - 0x3B + 1)),
+        _ => {
+            let shifted = (state.modifiers & (MOD_LSHIFT | MOD_RSHIFT)) != 0;
+            // CapsLock inverts case for letters
+            let caps = state.modifiers & MOD_CAPS != 0;
+            let table = if shifted { SCAN_SHIFT } else { SCAN_NORMAL };
+            let mut ch = table[byte as usize];
+            // Handle CapsLock for letters
+            if caps && ch.is_ascii_alphabetic() {
+                // Swap case: if table gives lowercase, make uppercase; etc.
+                // Since normal table has lowercase, shift table has uppercase:
+                ch = if shifted {
+                    ch.to_ascii_lowercase()
+                } else {
+                    ch.to_ascii_uppercase()
+                };
+            }
+            if ch != 0 {
+                Some(KeyEvent::Char(ch as char))
+            } else {
+                Some(KeyEvent::Unknown(byte))
+            }
+        }
+    }
+}
+
+/// Process an E0-prefixed scancode.
+fn process_e0(byte: u8) -> Option<KeyEvent> {
+    if byte & 0x80 != 0 {
+        update_modifiers(byte & 0x7F, false, true);
+        return None;
+    }
+
+    update_modifiers(byte, true, true);
+
+    match byte {
+        0x48 => Some(KeyEvent::ArrowUp),
+        0x50 => Some(KeyEvent::ArrowDown),
+        0x4B => Some(KeyEvent::ArrowLeft),
+        0x4D => Some(KeyEvent::ArrowRight),
+        0x47 => Some(KeyEvent::Home),
+        0x4F => Some(KeyEvent::End),
+        0x49 => Some(KeyEvent::PageUp),
+        0x51 => Some(KeyEvent::PageDown),
+        0x53 => Some(KeyEvent::Delete),
+        0x35 => Some(KeyEvent::Char('/')),
+        _ => Some(KeyEvent::Unknown(byte)),
+    }
+}
+
+fn update_modifiers(scancode: u8, pressed: bool, e0: bool) {
+    let state = unsafe { &mut KBD };
+    match (scancode, e0) {
+        (0x2A, false) => set_mod(state, MOD_LSHIFT, pressed),
+        (0x36, false) => set_mod(state, MOD_RSHIFT, pressed),
+        (0x1D, false) => set_mod(state, MOD_LCTRL, pressed),
+        (0x1D, true) => set_mod(state, MOD_RCTRL, pressed),
+        (0x38, false) => set_mod(state, MOD_LALT, pressed),
+        (0x38, true) => set_mod(state, MOD_RALT, pressed),
+        (0x3A, false) => {
+            if pressed {
+                state.modifiers ^= MOD_CAPS;
+            }
+        }
+        _ => {}
+    }
+}
+
+fn set_mod(state: &mut KbdState, bit: u8, pressed: bool) {
+    if pressed {
+        state.modifiers |= bit;
+    } else {
+        state.modifiers &= !bit;
+    }
+}