From c4dab4b15c2b5dca1b648b45c8154abc49d222b3 Mon Sep 17 00:00:00 2001
From: Aviii06 <architgosain0601@gmail.com>
Date: Tue, 3 Jan 2023 04:03:54 +0530
Subject: [PATCH] Write dec B and update flags

---
 src/cpu.cpp | 36 ++++++++++++++++++++++++++++++++++--
 src/cpu.h   |  8 ++++----
 2 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/src/cpu.cpp b/src/cpu.cpp
index 9f0c45c..0c2c817 100644
--- a/src/cpu.cpp
+++ b/src/cpu.cpp
@@ -58,9 +58,41 @@ int CPU::LD_BC_A()
 	return 8;
 }
 
-int CPU::INC_BC() { return 0; }
+int CPU::INC_BC()
+{
+	reg_BC.dat += 1;
+    reg_PC.dat += 1;
+    printf("INC BC\n");
+    return 8;
+}
 int CPU::INC_B() { return 0; }
-int CPU::DEC_B() { return 0; }
+int CPU::DEC_B()
+{
+	reg_BC.hi -= 1;
+	if (reg_BC.hi == 0)
+	{
+        reg_AF.lo |= FLAG_ZERO_z;
+    }
+    else
+    {
+        reg_AF.lo &= ~FLAG_ZERO_z;
+    }
+
+	reg_AF.lo |= FLAG_SUBTRACT_n;
+
+	if (reg_BC.hi == 0xFF)
+	{
+		reg_AF.lo |= FLAG_HALF_CARRY_h;
+    }
+    else
+    {
+        reg_AF.lo &= ~FLAG_HALF_CARRY_h;
+    }
+
+    reg_PC.dat += 1;
+    printf("DEC B\n");
+    return 4;
+}
 int CPU::LD_B_u8() { return 0; }
 int CPU::RLCA() { return 0; }
 int CPU::LD_u16_SP() { return 0; }
diff --git a/src/cpu.h b/src/cpu.h
index ca7edb9..0445abb 100644
--- a/src/cpu.h
+++ b/src/cpu.h
@@ -44,10 +44,10 @@ class CPU
 	// Bit 0-3 are not used
 	enum Flags
 	{
-		FLAG_CARRY_c = 4,
-		FLAG_HALF_CARRY_h = 5,
-		FLAG_SUBTRACT_n = 6,
-		FLAG_ZERO_z = 7
+		FLAG_CARRY_c = 0x10,
+		FLAG_HALF_CARRY_h = 0x20,
+		FLAG_SUBTRACT_n = 0x40,
+		FLAG_ZERO_z = 0x80
 	};
 
 	// Memory Map