From 4955030f13c1d79aef005bb3d292224302afcdfa Mon Sep 17 00:00:00 2001
From: Oxore <oxore@protonmail.com>
Date: Tue, 19 Nov 2019 02:47:35 +0300
Subject: Implement Push and Pop instructions

---
 src/core.rs | 37 +++++++++++++++++++++++++++++++++----
 1 file changed, 33 insertions(+), 4 deletions(-)

diff --git a/src/core.rs b/src/core.rs
index 37886c5..74f79b0 100644
--- a/src/core.rs
+++ b/src/core.rs
@@ -73,6 +73,7 @@ pub struct Core {
 }
 
 const RAM_OFFSET_ACC: u8 = 0xE0;
+const RAM_OFFSET_SP: u8 = 0x80;
 const RAM_OFFSET_R0: u8 = 0x00;
 const RAM_OFFSET_R1: u8 = 0x01;
 const RAM_OFFSET_R2: u8 = 0x02;
@@ -82,6 +83,9 @@ const RAM_OFFSET_R5: u8 = 0x05;
 const RAM_OFFSET_R6: u8 = 0x06;
 const RAM_OFFSET_R7: u8 = 0x07;
 
+const RESET_VALUE_ACC: u8 = 0x00;
+const RESET_VALUE_SP: u8 = 0x07;
+
 const OPCODE_NOP: u8 = 0x00;
 const OPCODE_AJMP_P0: u8 = 0x01;
 const OPCODE_LJMP: u8 = 0x02;
@@ -321,7 +325,9 @@ impl IncompleteOp {
 impl Core {
     /// Constructor
     pub fn new_with_rom_from_hex(hex: String) -> Result<Self, String> {
-        let ram: [u8; u8::max_value() as usize + 1] = [0; u8::max_value() as usize + 1];
+        let mut ram: [u8; u8::max_value() as usize + 1] = [0; u8::max_value() as usize + 1];
+        ram[RAM_OFFSET_SP as usize] = RESET_VALUE_SP;
+        ram[RAM_OFFSET_ACC as usize] = RESET_VALUE_ACC;
         let rom = match Rom::from_hex(hex) {
             Ok(value) => value,
             Err(err_string) => return Err(err_string),
@@ -377,10 +383,13 @@ impl Core {
     fn exec(&mut self, op: Op) {
         match op.opname {
             Opname::Nop => (),
-            Opname::Mov => (self.mov(op.operand1.unwrap(), op.operand2.unwrap())),
+            Opname::Mov => self.mov(
+                op.operand1.expect("MOV has no first operand given"),
+                op.operand2.expect("MOV has no second operand given"),
+            ),
             Opname::Illegal => (),
-            Opname::Push => (),
-            Opname::Pop => (),
+            Opname::Push => self.push(op.operand1.expect("PUSH has no operand given")),
+            Opname::Pop => self.pop(op.operand1.expect("POP has no operand given")),
             Opname::Sjmp => {
                 if let Some(operand) = op.operand1 {
                     match operand {
@@ -466,6 +475,26 @@ impl Core {
         self.ram[dest as usize] = value;
     }
 
+    fn push(&mut self, o: Operand) {
+        match o {
+            Operand::Direct(offset) => {
+                self.ram[RAM_OFFSET_SP as usize] += 1;
+                self.ram[self.ram[RAM_OFFSET_SP as usize] as usize] = self.ram[offset as usize];
+            }
+            other => panic!("PUSH got incompatible operand \"{:?}\"", other),
+        }
+    }
+
+    fn pop(&mut self, o: Operand) {
+        match o {
+            Operand::Direct(offset) => {
+                self.ram[offset as usize] = self.ram[self.ram[RAM_OFFSET_SP as usize] as usize];
+                self.ram[RAM_OFFSET_SP as usize] -= 1;
+            }
+            other => panic!("POP got incompatible operand \"{:?}\"", other),
+        }
+    }
+
     fn sjmp(&mut self, reladdr: i8) {
         self.pc = (self.pc as i16 + i16::from(reladdr)) as u16;
     }
-- 
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