add basic CPU visualization function

Also add a sample program which **screams**
for assembler and disassembler.
With no assembler one cannot write programs for this
CPU without pulling out their hear.

src/cpu.rs

@@ -18,6 +18,7 @@ pub struct Cpu {
     data: [u8; 0x10],
     port_in: VecDeque<u8>,
     port_out: VecDeque<u8>,
+    num_cycles: u64,
 }
 
 impl Cpu {
@@ -34,6 +35,7 @@ impl Cpu {
             data: [0u8; 0x10],
             port_in: VecDeque::<u8>::new(),
             port_out: VecDeque::<u8>::new(),
+            num_cycles: 0,
         }
     }
 
@@ -329,6 +331,7 @@ impl Cpu {
     }
 
     pub fn step(&mut self) -> bool {
+        self.num_cycles += 1;
         let insn = decode(self.code[self.IP.0 as usize]);
         match insn {
             Instruction::Load { reg, addr } => self.load(reg, addr),
@@ -376,6 +379,32 @@ impl Cpu {
         }
         false
     }
+
+    pub fn visualize(&self) {
+        println!("+--+----+----------+");
+        println!("|IP|{:#04X}|{:#010b}|", self.IP, self.IP);
+        println!("|R0|{:#04X}|{:#010b}|", self.R0, self.R0);
+        println!("|R1|{:#04X}|{:#010b}|", self.R1, self.R1);
+        println!("+--+----+----------+");
+        println!("|FLAGS:{}           |", if self.C { "C" } else { " " });
+        println!("+------------------+");
+        println!("|CYCLES:{:11}|", self.num_cycles);
+        println!("|PORTIN:{:11}|", self.port_in.len());
+        println!("|PORTOUT:{:10}|", self.port_out.len());
+        println!("+------------------+");
+        println!("| MEM  +0|+1|+2|+3 |");
+        for i in 0..4 {
+            println!(
+                "| 0x{:X}  {:02X}|{:02X}|{:02X}|{:02X} |",
+                i * 4,
+                self.data[i * 4 + 0],
+                self.data[i * 4 + 1],
+                self.data[i * 4 + 2],
+                self.data[i * 4 + 3]
+            );
+        }
+        println!("+------------------+");
+    }
 }
 
 #[cfg(test)]

src/main.rs

@@ -7,10 +7,18 @@ mod instruction;
 use cpu::*;
 
 fn main() {
-    let mut cpu = Cpu::new(&[]);
+    let mut cpu = Cpu::new(&[
+                           0b01001111, // R0 = 0xF
+                           0b01010011, // R1.l = 0x3
+                           0b11100100, // ADD
+                           0b00100000, // [0] = R0
+                           0b11111000, // R0 = 0
+                           0b11110101, // HALT
+    ]);
     loop {
         if cpu.step() {
             break;
         }
     }
+    cpu.visualize();
 }