Stack stuff

Author: josh-perry

gbboi-emu/Opcodes/0xC5.cs

@@ -3,13 +3,12 @@
 namespace gbboi_emu.Opcodes
 {
     /// <summary>
-    /// PUSH
-    ///
+    /// PUSH BC
     /// </summary>
     [OneByteOpcode]
     public class _0xC5 : IOpcode
     {
-        public string Mnemonic { get; set; } = "PUSH";
+        public string Mnemonic { get; set; } = "PUSH BC";
 
         public ushort Length { get; set; } = 1;
 
@@ -19,7 +18,7 @@ public class _0xC5 : IOpcode
 
         public void Execute(Instruction instruction, ICpu cpu, IMmu mmu)
         {
-            throw new NotImplementedException(Mnemonic);
+            cpu.Stack.Push(cpu.Registers.BC.Value, cpu.Registers, mmu);
         }
     }
 }

gbboi-emu/Stack.cs

@@ -1,12 +1,12 @@
-namespace gbboi_emu
+using System;
+
+namespace gbboi_emu
 {
     public class Stack
     {
         public void Call(ushort address, Registers registers, IMmu mmu)
         {
-            // Decrement the SP
-            // TODO: Stop skipping the first 2 bytes of the stack
-            //registers.SP.Value -= 2;
+            registers.SP.Value -= 2;
 
             // Add current PC to the stack
             mmu.WriteByte(registers.SP.Value, registers.PC.Registers[0].Value);
@@ -16,6 +16,20 @@ public void Call(ushort address, Registers registers, IMmu mmu)
             registers.PC.Value = address;
         }
 
+        public void Push(ushort value, Registers registers, IMmu mmu)
+        {
+            registers.SP.Value -= 2;
+
+            Push((byte)(value >> 8), registers, mmu);
+            Push((byte)(value & 0x00FF), registers, mmu);
+        }
+
+        public void Push(byte value, Registers registers, IMmu mmu)
+        {
+            mmu.WriteByte(registers.SP.Value, value);
+            mmu.WriteByte((ushort)(registers.SP.Value + 1), value);
+        }
+
         public void Return(Registers registers, IMmu mmu)
         {
             // Decrement stack pointer