From eddfb7a0c6b193312d1e50dcbb94110ebf921b8c Mon Sep 17 00:00:00 2001
From: radumacocian <rmacocian@yahoo.com>
Date: Mon, 30 Jun 2025 15:08:25 +0200
Subject: [PATCH] added helper function for flag setting on addition

---
 cpu/flags.go     | 19 +++++++++++++++++++
 cpu/functions.go | 32 +++++++++++++++++++-------------
 2 files changed, 38 insertions(+), 13 deletions(-)
 create mode 100644 cpu/flags.go

diff --git a/cpu/flags.go b/cpu/flags.go
new file mode 100644
index 0000000..de184c6
--- /dev/null
+++ b/cpu/flags.go
@@ -0,0 +1,19 @@
+package cpu
+
+func Set8BitAddFlags(context op_context, byte1 byte, byte2 byte) byte {
+	result := uint16(byte1) + uint16(byte2)
+	halfcarry := (byte1&0x0F)+(byte2&0x0F) > 0x0F
+	context.cpu.SetNF(false)
+	context.cpu.SetHF(halfcarry)
+	context.cpu.SetCF(result > 0xFFFF)
+	return byte(result)
+}
+
+func Add16BitsAndSetFlags(context op_context, op1 uint16, op2 uint16) uint16 {
+	result := uint32(op1) + uint32(op2)
+	halfcarry := (op1&0x0FFF)+(op2&0x0FFF) > 0x0FFF
+	context.cpu.SetNF(false)
+	context.cpu.SetHF(halfcarry)
+	context.cpu.SetCF(result > 0xFFFF)
+	return uint16(result)
+}
diff --git a/cpu/functions.go b/cpu/functions.go
index 8031f6a..162d5bb 100644
--- a/cpu/functions.go
+++ b/cpu/functions.go
@@ -7,32 +7,32 @@ import (
 
 type op_context struct {
 	cpu       CPU_struct
-	immediate byte
+	immediate uint16
 }
 
+// 0x00 NOOP function
 func Noop(context op_context) {
 	return
 }
 
-// LDBCd16 Load the 2 bytes of immediate data into register pair BC.
+// 0x01 LDBCd16 Load the 2 bytes of immediate data into register pair BC.
 func LDBCd16(context op_context) {
-	operations.LD(&context.cpu.C, memory.Read8(uint(context.immediate)))
-	operations.LD(&context.cpu.B, memory.Read8(uint(context.immediate)+8))
+	context.cpu.SetBC(context.immediate)
 }
 
-// LDBCa Store the contents of register A in the memory location specified by register pair BC.
+// 0x02 LDBCa Store the contents of register A in the memory location specified by register pair BC.
 func LDBCa(context op_context) {
 	operations.LDInMemory8(context.cpu.BC(), context.cpu.A)
 	return
 }
 
-// INCBC Increment the contents of register pair BC by 1.
+// 0x03 INCBC Increment the contents of register pair BC by 1.
 func INCBC(context op_context) {
 	operations.INC16(&context.cpu.B, &context.cpu.C)
 	return
 }
 
-// INCB Increment the contents of register B by 1.
+// 0x04 INCB Increment the contents of register B by 1.
 func INCB(context op_context) {
 	if context.cpu.B&0x0F == 0x0F {
 		context.cpu.SetHF(true)
@@ -45,7 +45,7 @@ func INCB(context op_context) {
 	context.cpu.SetNF(false)
 }
 
-// DECB Decrement the contents of register B by 1.
+// 0x05 DECB Decrement the contents of register B by 1.
 func DECB(context op_context) {
 	if context.cpu.B&0x0F == 0x00 {
 		context.cpu.SetHF(true)
@@ -58,12 +58,12 @@ func DECB(context op_context) {
 	context.cpu.SetNF(true)
 }
 
-// LD8B Load the 8-bit immediate operand d8 into register B.
+// 0x06 LD8B Load the 8-bit immediate operand d8 into register B.
 func LD8B(context op_context) {
 	operations.LD(&context.cpu.B, memory.Read8(uint(context.immediate)))
 }
 
-// RLCA Rotate the contents of register A to the left. The contents of bit 7 are placed in both the CY flag and bit 0 of register A.
+// 0x07 RLCA Rotate the contents of register A to the left. The contents of bit 7 are placed in both the CY flag and bit 0 of register A.
 func RLCA(context op_context) {
 	a7 := context.cpu.A>>7 == 1
 	operations.Shift(&context.cpu.A)
@@ -74,8 +74,14 @@ func RLCA(context op_context) {
 	context.cpu.SetCF(a7)
 }
 
-// LDA16 Store the lower byte of stack pointer SP at the address specified by the 16-bit immediate operand a16, and store the upper byte of SP at address a16 + 1.
+// 0x08 LDA16 Store the lower byte of stack pointer SP at the address specified by the 16-bit immediate operand a16, and store the upper byte of SP at address a16 + 1.
 func LDA16(context op_context) {
-	operations.LDInMemory8(uint16(context.immediate), operations.GetLowerByte(context.cpu.SP))
-	operations.LDInMemory8(uint16(context.immediate+1), operations.GetHigherByte(context.cpu.SP))
+	operations.LDInMemory8(context.immediate, operations.GetLowerByte(context.cpu.SP))
+	operations.LDInMemory8(context.immediate+1, operations.GetHigherByte(context.cpu.SP))
+}
+
+// 0x09 ADDHLBC Add the contents of register pair BC to the contents of register pair HL, and store the results in register pair HL.
+func ADDHLBC(context op_context) {
+	result := Add16BitsAndSetFlags(context, context.cpu.HL(), context.cpu.BC())
+	context.cpu.SetHL(result)
 }