Expose SRAM pointers for frontends that manage save data their own way (#1643)

* Add a clarifying comment

- In case it saves some poor bastard hours of fruitless work

* Expose GBA and NDS save memory

- Add GetSaveMemory and GetSaveMemoryLength functions
- Where unsupported, they return null and zero

src/GBACart.cpp

@@ -100,6 +100,15 @@ void CartCommon::SRAMWrite(u32 addr, u8 val)
 {
 }
 
+u8* CartCommon::GetSaveMemory() const
+{
+    return nullptr;
+}
+
+u32 CartCommon::GetSaveMemoryLength() const
+{
+    return 0;
+}
 
 CartGame::CartGame(u8* rom, u32 len) : CartCommon()
 {
@@ -334,6 +343,16 @@ void CartGame::SRAMWrite(u32 addr, u8 val)
     }
 }
 
+u8* CartGame::GetSaveMemory() const
+{
+    return SRAM;
+}
+
+u32 CartGame::GetSaveMemoryLength() const
+{
+    return SRAMLength;
+}
+
 void CartGame::ProcessGPIO()
 {
 }
@@ -878,4 +897,14 @@ void SRAMWrite(u32 addr, u8 val)
     if (Cart) Cart->SRAMWrite(addr, val);
 }
 
+u8* GetSaveMemory()
+{
+    return Cart ? Cart->GetSaveMemory() : nullptr;
+}
+
+u32 GetSaveMemoryLength()
+{
+    return Cart ? Cart->GetSaveMemoryLength() : 0;
+}
+
 }

src/GBACart.h

@@ -49,6 +49,9 @@ public:
 
     virtual u8 SRAMRead(u32 addr);
     virtual void SRAMWrite(u32 addr, u8 val);
+
+    virtual u8* GetSaveMemory() const;
+    virtual u32 GetSaveMemoryLength() const;
 };
 
 // CartGame -- regular retail game cart (ROM, SRAM)
@@ -74,6 +77,8 @@ public:
     virtual u8 SRAMRead(u32 addr) override;
     virtual void SRAMWrite(u32 addr, u8 val) override;
 
+    virtual u8* GetSaveMemory() const override;
+    virtual u32 GetSaveMemoryLength() const override;
 protected:
     virtual void ProcessGPIO();
 
@@ -207,6 +212,19 @@ void ROMWrite(u32 addr, u16 val);
 u8 SRAMRead(u32 addr);
 void SRAMWrite(u32 addr, u8 val);
 
+/// This function is intended to allow frontends to save and load SRAM
+/// without using melonDS APIs.
+/// Modifying the emulated SRAM for any other reason is strongly discouraged.
+/// The returned pointer may be invalidated if the emulator is reset,
+/// or when a new game is loaded.
+/// Consequently, don't store the returned pointer for any longer than necessary.
+/// @returns Pointer to this cart's SRAM if a cart is loaded and supports SRAM, otherwise \c nullptr.
+u8* GetSaveMemory();
+
+/// @returns The length of the buffer returned by ::GetSaveMemory()
+/// if a cart is loaded and supports SRAM, otherwise zero.
+u32 GetSaveMemoryLength();
+
 }
 
 #endif // GBACART_H

src/NDSCart.cpp

@@ -383,6 +383,16 @@ void CartCommon::SetIRQ()
     NDS::SetIRQ(1, NDS::IRQ_CartIREQMC);
 }
 
+u8 *CartCommon::GetSaveMemory() const
+{
+    return nullptr;
+}
+
+u32 CartCommon::GetSaveMemoryLength() const
+{
+    return 0;
+}
+
 void CartCommon::ReadROM(u32 addr, u32 len, u8* data, u32 offset)
 {
     if (addr >= ROMLength) return;
@@ -553,6 +563,16 @@ u8 CartRetail::SPIWrite(u8 val, u32 pos, bool last)
     }
 }
 
+u8 *CartRetail::GetSaveMemory() const
+{
+    return SRAM;
+}
+
+u32 CartRetail::GetSaveMemoryLength() const
+{
+    return SRAMLength;
+}
+
 void CartRetail::ReadROM_B7(u32 addr, u32 len, u8* data, u32 offset)
 {
     addr &= (ROMLength-1);
@@ -1732,6 +1752,16 @@ void SetupDirectBoot(std::string romname)
         Cart->SetupDirectBoot(romname);
 }
 
+u8* GetSaveMemory()
+{
+    return Cart ? Cart->GetSaveMemory() : nullptr;
+}
+
+u32 GetSaveMemoryLength()
+{
+    return Cart ? Cart->GetSaveMemoryLength() : 0;
+}
+
 void EjectCart()
 {
     if (!CartInserted) return;

src/NDSCart.h

@@ -52,6 +52,9 @@ public:
 
     virtual u8 SPIWrite(u8 val, u32 pos, bool last);
 
+    virtual u8* GetSaveMemory() const;
+    virtual u32 GetSaveMemoryLength() const;
+
 protected:
     void ReadROM(u32 addr, u32 len, u8* data, u32 offset);
 
@@ -88,6 +91,9 @@ public:
 
     virtual u8 SPIWrite(u8 val, u32 pos, bool last) override;
 
+    virtual u8* GetSaveMemory() const override;
+    virtual u32 GetSaveMemoryLength() const override;
+
 protected:
     void ReadROM_B7(u32 addr, u32 len, u8* data, u32 offset);
 
@@ -223,6 +229,19 @@ bool LoadROM(const u8* romdata, u32 romlen);
 void LoadSave(const u8* savedata, u32 savelen);
 void SetupDirectBoot(std::string romname);
 
+/// This function is intended to allow frontends to save and load SRAM
+/// without using melonDS APIs.
+/// Modifying the emulated SRAM for any other reason is strongly discouraged.
+/// The returned pointer may be invalidated if the emulator is reset,
+/// or when a new game is loaded.
+/// Consequently, don't store the returned pointer for any longer than necessary.
+/// @returns Pointer to this cart's SRAM if a cart is loaded and supports SRAM, otherwise \c nullptr.
+u8* GetSaveMemory();
+
+/// @returns The length of the buffer returned by ::GetSaveMemory()
+/// if a cart is loaded and supports SRAM, otherwise zero.
+u32 GetSaveMemoryLength();
+
 void EjectCart();
 
 void ResetCart();

src/RTC.cpp

@@ -30,6 +30,9 @@ using Platform::LogLevel;
 namespace RTC
 {
 
+/// This value represents the Nintendo DS IO register,
+/// \em not the value of the system's clock.
+/// The actual system time is taken directly from the host.
 u16 IO;
 
 u8 Input;