Implement cartridge SRAM save/restore

README.md

@@ -1,6 +1,8 @@
 # gogo-gb
 a gameboy emulator for funsies
 
+Current status: Games are playable, but slow. Graphics are buggy. No audio.
+
 ## TODO
 
 - [X] Pass all of Blargg's `cpu_instrs` ROMs via `gameboy-doctor` (expect `02-interrupts.gb`, which isn't verifyable via `gameboy-doctor`)
@@ -15,9 +17,10 @@ a gameboy emulator for funsies
 - [ ] Pass all of Blargg's `mem_timing-2` ROMs (manually verified)
 - [X] Implement Joypad
 - [ ] Implement RTC for MBC3
-- [ ] Implement SRAM save & restore
+- [X] Implement SRAM save & restore
 - [ ] Pass `dmg-acid2` test ROM
 - [ ] Implement Sound/APU
+- [ ] Implement GBC
 
 ## Maybe Never?
 
@@ -26,6 +29,7 @@ Just being realistic about my likelihood of getting to these:
 - [ ] FIFO-based rendering PPU (currently scanline)
 - [ ] Implement emulation for every known DMG bug
 - [ ] Implement SGB mode
+- [ ] Implement MBC2
 - [ ] Implement MBC6
 - [ ] Implement MBC7
 - [ ] Implement any multicarts or Hudson carts

cart/cartridge.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"errors"
 	"fmt"
+	"io"
 	"log"
 
 	"github.com/maxfierke/gogo-gb/cart/mbc"
@@ -17,7 +18,7 @@ var (
 
 type Cartridge struct {
 	Header Header
-	mbc    mem.MemHandler
+	mbc    mbc.MBC
 }
 
 func NewCartridge() *Cartridge {
@@ -81,6 +82,14 @@ func (c *Cartridge) LoadCartridge(r *Reader) error {
 	return nil
 }
 
+func (c *Cartridge) Save(w io.Writer) error {
+	return c.mbc.Save(w)
+}
+
+func (c *Cartridge) LoadSave(r io.Reader) error {
+	return c.mbc.LoadSave(r)
+}
+
 func (c *Cartridge) OnRead(mmu *mem.MMU, addr uint16) mem.MemRead {
 	if c.mbc == nil {
 		return mem.ReadPassthrough()

cart/header.go

@@ -238,6 +238,10 @@ func (hdr *Header) RamSizeBytes() uint {
 	}
 }
 
+func (hdr *Header) SupportsSaving() bool {
+	return hdr.RamSizeBytes() > 0
+}
+
 func (hdr *Header) DebugPrint(logger *log.Logger) {
 	logger.Printf("== Cartridge Info ==\n")
 	logger.Printf("\n")

cart/mbc/common.go

@@ -1,6 +1,10 @@
 package mbc
 
-import "github.com/maxfierke/gogo-gb/mem"
+import (
+	"io"
+
+	"github.com/maxfierke/gogo-gb/mem"
+)
 
 const (
 	RAM_BANK_SIZE = 0x2000
@@ -18,3 +22,9 @@ func writeBankAddr(memory []byte, banksRegion mem.MemRegion, bankSize uint16, cu
 	bankSlotAddr := uint(addr) - uint(banksRegion.Start)
 	memory[bankBaseAddr+bankSlotAddr] = value
 }
+
+type MBC interface {
+	mem.MemHandler
+	Save(w io.Writer) error
+	LoadSave(r io.Reader) error
+}

cart/mbc/mbc0.go

@@ -2,6 +2,7 @@ package mbc
 
 import (
 	"fmt"
+	"io"
 
 	"github.com/maxfierke/gogo-gb/mem"
 )
@@ -15,6 +16,8 @@ type MBC0 struct {
 	rom []byte
 }
 
+var _ MBC = (*MBC0)(nil)
+
 func NewMBC0(rom []byte) *MBC0 {
 	return &MBC0{rom: rom}
 }
@@ -40,3 +43,11 @@ func (m *MBC0) OnWrite(mmu *mem.MMU, addr uint16, value byte) mem.MemWrite {
 
 	panic(fmt.Sprintf("Attempting to write 0x%02X @ 0x%04X, which is out-of-bounds for MBC0", value, addr))
 }
+
+func (m *MBC0) Save(w io.Writer) error {
+	return nil
+}
+
+func (m *MBC0) LoadSave(r io.Reader) error {
+	return nil
+}

cart/mbc/mbc1.go

@@ -2,6 +2,7 @@ package mbc
 
 import (
 	"fmt"
+	"io"
 
 	"github.com/maxfierke/gogo-gb/mem"
 )
@@ -34,6 +35,8 @@ type MBC1 struct {
 	rom         []byte
 }
 
+var _ MBC = (*MBC1)(nil)
+
 func NewMBC1(rom []byte, ram []byte) *MBC1 {
 	return &MBC1{
 		curRamBank:  0,
@@ -128,3 +131,29 @@ func (m *MBC1) OnWrite(mmu *mem.MMU, addr uint16, value byte) mem.MemWrite {
 
 	panic(fmt.Sprintf("Attempting to write 0x%02X @ 0x%04X, which is out-of-bounds for MBC1", value, addr))
 }
+
+func (m *MBC1) Save(w io.Writer) error {
+	if len(m.ram) == 0 {
+		return nil
+	}
+
+	n, err := w.Write(m.ram)
+	if err != nil {
+		return fmt.Errorf("mbc1: saving SRAM: %w. wrote %d bytes", err, n)
+	}
+
+	return nil
+}
+
+func (m *MBC1) LoadSave(r io.Reader) error {
+	if len(m.ram) == 0 {
+		return nil
+	}
+
+	n, err := io.ReadFull(r, m.ram)
+	if err != nil {
+		return fmt.Errorf("mbc1: loading save into SRAM: %w. read %d bytes", err, n)
+	}
+
+	return nil
+}

cart/mbc/mbc3.go

@@ -2,6 +2,7 @@ package mbc
 
 import (
 	"fmt"
+	"io"
 
 	"github.com/maxfierke/gogo-gb/mem"
 )
@@ -60,6 +61,8 @@ type MBC3 struct {
 	rtcDaysOverflow   bool
 }
 
+var _ MBC = (*MBC3)(nil)
+
 func NewMBC3(rom []byte, ram []byte, rtcAvailable bool) *MBC3 {
 	return &MBC3{
 		ram:          ram,
@@ -210,6 +213,36 @@ func (m *MBC3) writeRtcReg(reg mbc3RtcReg, value byte) {
 	}
 }
 
+func (m *MBC3) Save(w io.Writer) error {
+	if len(m.ram) == 0 {
+		return nil
+	}
+
+	n, err := w.Write(m.ram)
+	if err != nil {
+		return fmt.Errorf("mbc3: saving SRAM: %w. wrote %d bytes", err, n)
+	}
+
+	// TODO: Write RTC registers
+
+	return nil
+}
+
+func (m *MBC3) LoadSave(r io.Reader) error {
+	if len(m.ram) == 0 {
+		return nil
+	}
+
+	n, err := io.ReadFull(r, m.ram)
+	if err != nil {
+		return fmt.Errorf("mbc3: loading save into SRAM: %w. read %d bytes", err, n)
+	}
+
+	// TODO: Read RTC registers
+
+	return nil
+}
+
 var (
 	MBC30_ROM_BANKS = mem.MemRegion{Start: 0x4000, End: 0x7FFF}
 
@@ -269,3 +302,11 @@ func (m *MBC30) OnWrite(mmu *mem.MMU, addr uint16, value byte) mem.MemWrite {
 
 	return m.MBC3.OnWrite(mmu, addr, value)
 }
+
+func (m *MBC30) Save(w io.Writer) error {
+	return m.MBC3.Save(w)
+}
+
+func (m *MBC30) LoadSave(r io.Reader) error {
+	return m.MBC3.LoadSave(r)
+}

cart/mbc/mbc5.go

@@ -2,6 +2,7 @@ package mbc
 
 import (
 	"fmt"
+	"io"
 
 	"github.com/maxfierke/gogo-gb/mem"
 )
@@ -34,6 +35,8 @@ type MBC5 struct {
 	rom        []byte
 }
 
+var _ MBC = (*MBC5)(nil)
+
 func NewMBC5(rom []byte, ram []byte) *MBC5 {
 	return &MBC5{
 		curRamBank: 0,
@@ -114,3 +117,29 @@ func (m *MBC5) OnWrite(mmu *mem.MMU, addr uint16, value byte) mem.MemWrite {
 
 	panic(fmt.Sprintf("Attempting to write 0x%02X @ 0x%04X, which is out-of-bounds for MBC5", value, addr))
 }
+
+func (m *MBC5) Save(w io.Writer) error {
+	if len(m.ram) == 0 {
+		return nil
+	}
+
+	n, err := w.Write(m.ram)
+	if err != nil {
+		return fmt.Errorf("mbc5: saving SRAM: %w. wrote %d bytes", err, n)
+	}
+
+	return nil
+}
+
+func (m *MBC5) LoadSave(r io.Reader) error {
+	if len(m.ram) == 0 {
+		return nil
+	}
+
+	n, err := io.ReadFull(r, m.ram)
+	if err != nil {
+		return fmt.Errorf("mbc5: loading save into SRAM: %w. read %d bytes", err, n)
+	}
+
+	return nil
+}

hardware/console.go

@@ -1,6 +1,8 @@
 package hardware
 
 import (
+	"io"
+
 	"github.com/maxfierke/gogo-gb/cart"
 	"github.com/maxfierke/gogo-gb/debug"
 	"github.com/maxfierke/gogo-gb/devices"
@@ -9,7 +11,10 @@ import (
 type Console interface {
 	AttachDebugger(debugger debug.Debugger)
 	DetachDebugger()
+	CartridgeHeader() cart.Header
 	LoadCartridge(r *cart.Reader) error
+	Save(w io.Writer) error
+	LoadSave(r io.Reader) error
 	Step() error
 	Run(host devices.HostInterface) error
 }

hardware/dmg.go

@@ -138,8 +138,39 @@ func (dmg *DMG) DetachDebugger() {
 	dmg.debugger = debug.NewNullDebugger()
 }
 
+func (dmg *DMG) CartridgeHeader() cart.Header {
+	if dmg.cartridge == nil {
+		return cart.Header{}
+	}
+
+	return dmg.cartridge.Header
+}
+
 func (dmg *DMG) LoadCartridge(r *cart.Reader) error {
-	return dmg.cartridge.LoadCartridge(r)
+	err := dmg.cartridge.LoadCartridge(r)
+	if err != nil {
+		return fmt.Errorf("dmg: loading cartridge: %w", err)
+	}
+
+	return nil
+}
+
+func (dmg *DMG) LoadSave(r io.Reader) error {
+	err := dmg.cartridge.LoadSave(r)
+	if err != nil {
+		return fmt.Errorf("dmg: loading save: %w", err)
+	}
+
+	return nil
+}
+
+func (dmg *DMG) Save(w io.Writer) error {
+	err := dmg.cartridge.Save(w)
+	if err != nil {
+		return fmt.Errorf("dmg: writing save: %w", err)
+	}
+
+	return nil
 }
 
 func (dmg *DMG) DebugPrint(logger *log.Logger) {