feat(core): add emulator save state snapshotting

src/GameBoy.Core/Emulator.State.cs

@@ -0,0 +1,73 @@
+using System;
+using System.IO;
+using GameBoy.Audio;
+
+namespace GameBoy
+{
+    public sealed partial class Emulator
+    {
+        private const uint SnapshotMagic = 0x31545347;
+
+        public Apu Apu => apu;
+
+        public bool HasBattery => Cartridge.HasBattery;
+        public bool HasRtc => Cartridge.HasRtc;
+
+        public byte ReadMemory(ushort address) => mmu.Read(address);
+
+        public void WriteMemory(ushort address, byte value) => mmu.Write(address, value);
+
+        public void AdvanceRtcSeconds(long seconds) => Cartridge.AdvanceRtc(seconds);
+
+        public byte[] SaveRam() => (byte[])Cartridge.Ram.Clone();
+
+        public void LoadRam(byte[] contents)
+        {
+            Array.Copy(contents, 0, Cartridge.Ram, 0, Math.Min(contents.Length, Cartridge.Ram.Length));
+        }
+
+        public byte[] SaveState()
+        {
+            using var stream = new MemoryStream();
+            using var writer = new BinaryWriter(stream);
+
+            writer.Write(SnapshotMagic);
+            writer.Write(TotalCycles);
+            cpu.SaveState(writer);
+            interrupts.SaveState(writer);
+            ppu.SaveState(writer);
+            timer.SaveState(writer);
+            joypad.SaveState(writer);
+            serial.SaveState(writer);
+            apu.SaveState(writer);
+            mmu.SaveState(writer);
+            dma.SaveState(writer);
+            Cartridge.SaveState(writer);
+
+            writer.Flush();
+            return stream.ToArray();
+        }
+
+        public void LoadState(byte[] snapshot)
+        {
+            using var stream = new MemoryStream(snapshot);
+            using var reader = new BinaryReader(stream);
+
+            uint magic = reader.ReadUInt32();
+            if (magic != SnapshotMagic)
+                throw new InvalidDataException("unrecognized save state header");
+
+            TotalCycles = reader.ReadInt64();
+            cpu.LoadState(reader);
+            interrupts.LoadState(reader);
+            ppu.LoadState(reader);
+            timer.LoadState(reader);
+            joypad.LoadState(reader);
+            serial.LoadState(reader);
+            apu.LoadState(reader);
+            mmu.LoadState(reader);
+            dma.LoadState(reader);
+            Cartridge.LoadState(reader);
+        }
+    }
+}