From 2a234fabfd6e8e65c0be7d04b256351982c140eb Mon Sep 17 00:00:00 2001
From: Riyyi <riyyi3@gmail.com>
Date: Mon, 22 Aug 2022 13:12:27 +0200
Subject: [PATCH] Emulator: Add opcode LDH or LD 0xff00

---
 src/cpu.cpp | 31 +++++++++++++++++++++++++++++++
 src/cpu.h   |  4 ++++
 2 files changed, 35 insertions(+)

diff --git a/src/cpu.cpp b/src/cpu.cpp
index db42fa2..230e9cd 100644
--- a/src/cpu.cpp
+++ b/src/cpu.cpp
@@ -111,6 +111,27 @@ void CPU::ld8()
 	}
 }
 
+void CPU::ldh8()
+{
+	uint8_t opcode = consumeMemory();
+	switch (opcode) {
+	case 0xe0:
+		// LD ($ff00 + n),A == LDH (n),A
+		// Put value in A into address (0xff00 + next byte in memory):
+		m_wait_cycles += 12;
+		writeFf(m_a);
+		break;
+	case 0xf0:
+		// LD A,($ff00 + n) == LDH A,(n)
+		// Put value at address (0xff00 + next byte in memory) into A:
+		m_wait_cycles += 12;
+		m_a = readFf();
+		break;
+	default:
+		VERIFY_NOT_REACHED();
+	}
+}
+
 void CPU::ld16()
 {
 	uint8_t opcode = consumeMemory();
@@ -179,6 +200,16 @@ uint8_t CPU::consumeMemory()
 	return Emu::the().readMemory(m_pc++);
 }
 
+void CPU::writeFf(uint32_t value)
+{
+	Emu::the().writeMemory(immediate8() | (0xff << 8), value);
+}
+
+uint32_t CPU::readFf()
+{
+	return Emu::the().readMemory(immediate8() | (0xff << 8));
+}
+
 void CPU::setBc(uint32_t value)
 {
 	m_b = value >> 8;
diff --git a/src/cpu.h b/src/cpu.h
index 16b491c..835ffc2 100644
--- a/src/cpu.h
+++ b/src/cpu.h
@@ -39,6 +39,7 @@ public:
 
 	// 8-bit
 	void ld8();
+	void ldh8();
 
 	// 16-bit
 	void ld16();
@@ -61,6 +62,9 @@ private:
 	uint32_t immediate8() { return consumeMemory(); }
 	uint32_t immediate16() { return consumeMemory() | (consumeMemory() << 8); }
 
+	void writeFf(uint32_t value);
+	uint32_t readFf();
+
 	void setBc(uint32_t value);
 	void setDe(uint32_t value);
 	void setHl(uint32_t value);