basic memory and cpu

README.md

@@ -1,2 +1,7 @@
-# goboy
-Gameboy emulator in go
+# GoBoy
+As an effort to improve my technical abilities and a challenge to myself
+I've decided to start writing a GameBoy emulator in go.
+This is the first time I've ever written an emulator \(outside of university
+classes on FPGA emulation\). This is also my first project written in go.
+I will be documenting everything in a series of blogs on my
+[Personal Website](https://radu.macocian.me/GoBoy/)

cpu/cpu.go

@@ -0,0 +1,29 @@
+package cpu
+
+import (
+	"radu.macocian.me/goboy/memory"
+)
+
+type cpu_struct struct {
+	A  int8
+	F  int8
+	B  int8
+	C  int8
+	D  int8
+	E  int8
+	H  int8
+	L  int8
+	IR int8
+	IE int8
+
+	PC int16
+	SP int16
+}
+
+var cpu = new(cpu_struct)
+
+func Execute(addr int) {
+	instr := memory.Read(addr + int(cpu.PC))
+	cpu.PC++
+	print(string(instr))
+}

errorHandling/exceptions.go

@@ -0,0 +1,5 @@
+package errorHandling
+
+const InvalidRomError = "Critical Error. Invalid ROM file. Please make sure you input a valid .gb file. Exiting..."
+
+const OutOfMemoryBoundsError = "Critical Error. Trying to access data outside memory bounds. Exiting..."

gameboy.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"radu.macocian.me/goboy/cpu"
+	"radu.macocian.me/goboy/errorHandling"
+	"radu.macocian.me/goboy/memory"
+	"strings"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Println("Missing rom, please provide a rom")
+		return
+	}
+
+	checkExtension(os.Args[1])
+
+	data, err := os.ReadFile(os.Args[1])
+	check(err)
+
+	startMem := 1000
+	memory.WriteAll(startMem, data)
+	cpu.Execute(startMem)
+}
+
+func checkExtension(file string) {
+	splits := strings.Split(file, ".")
+	if splits[len(splits)-1] != "gb" {
+		panic(errorHandling.InvalidRomError)
+	}
+}
+
+func check(e error) {
+	if e != nil {
+		panic(e)
+	}
+}

journal/Day 1 - 2025.04.17.md

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+# First wrote a brief overview of the first milestone of the project:
+- load files form the os
+- create the memory struct with read/write functions on the memory
+- create a cpu state with registers 
+
+# For the day:
+- Setup goland
+- Disable autocomplete on space because it doesn't work
+- Find ways to store memory state in go
+- Write memory module with read, write, writeall functions
+- Reading or writing outside of memory bounds will close app
+- Write cpu module with registers, PC, SP
+- Are registers only 8bits?
+- Where are instructions stored?
+
+# Conclusion
+- Can read roms from external files
+- Have a 64kb memory with functions to read and write to it
+- Have a cpu which reads instructions from the memory and increments the PC
+
+# References:
+[Game Boy: Complete Technical Reference](https://gekkio.fi/files/gb-docs/gbctr.pdf)

memory/memory.go

@@ -0,0 +1,35 @@
+package memory
+
+import (
+	"radu.macocian.me/goboy/errorHandling"
+)
+
+var memory = new([64000]byte)
+
+func Read(addr int) []byte {
+	checkInside(addr)
+	checkInside(addr + 8)
+
+	return memory[addr : addr+9]
+}
+
+func Write(addr int, val [8]byte) {
+	checkInside(addr)
+	for i := 0; i < 8; i++ {
+		memory[addr+i] = val[i]
+	}
+}
+
+func WriteAll(addr int, val []byte) {
+	checkInside(addr)
+	checkInside(addr + len(val))
+	for b := 0; b < len(val); b++ {
+		memory[addr+b] = val[b]
+	}
+}
+
+func checkInside(addr int) {
+	if addr < 0 || addr >= len(memory) {
+		panic(errorHandling.OutOfMemoryBoundsError)
+	}
+}

roms/rom.gb

@@ -0,0 +1 @@
+noop