emu: factor out operations and operands into own module

src/emu/operations.rs

@@ -0,0 +1,48 @@
+use emu::byteorder::{ByteOrder, LittleEndian};
+use emu::dos;
+use emu::i8088::{i8088, segoff_to_addr};
+use emu::operands::{Address, LValue, Reg, RValue};
+use emu::pc::Bus;
+
+pub fn show(cpu: &mut i8088) {
+  println!("{:#X?}", cpu);
+}
+
+pub fn peek(addr: &(impl Address + RValue<u8>)) {
+  println!("PEEK: @{:#X} = {:#X} ({})", addr.addr(), addr.read(), addr.read());
+}
+
+pub fn call(ip: &mut Reg, ss: u16, sp: &mut Reg, mem: &mut [u8], addr: i16) {
+  let target = ip.read().wrapping_add(addr as u16);
+  push16(ss, sp, mem, ip.read());
+  ip.write(target);
+}
+
+pub fn int(cpu: &mut i8088, bus: &mut Bus, num: &u8) {
+  match num {
+    0x21 => dos::interrupt(cpu, bus),
+    _ => unimplemented!("interrupt: {:02X}\ncpu: {:#X?}", num, cpu)
+  }
+}
+
+pub fn mov<T>(dst: &mut impl LValue<T>, src: &impl RValue<T>) {
+  dst.write(src.read());
+}
+
+pub fn nop() {}
+
+pub fn pop16(ss: u16, sp: &mut Reg, mem: &[u8]) -> u16 {
+  let val = LittleEndian::read_u16(&mem[segoff_to_addr(ss.read(), sp.read())..]);
+  sp.write(sp.read() + 2);
+  val
+}
+
+pub fn push16(ss: u16, sp: &mut Reg, mem: &mut [u8], val: u16) {
+  // XXX: Not checking for stack faults or anything
+  sp.write(sp.read() - 2);
+  LittleEndian::write_u16(&mut mem[segoff_to_addr(ss.read(), sp.read())..], val);
+}
+
+pub fn ret(ip: &mut Reg, ss: u16, sp: &mut Reg, mem: &[u8]) {
+  ip.write(pop16(ss, sp, mem));
+}