From 0e1d9eaa8f3c9dc78b3118d69cb4abf9a3deae2e Mon Sep 17 00:00:00 2001
From: Ariejan de Vroom <ariejan@ariejan.net>
Date: Sun, 17 Aug 2014 16:20:30 +0200
Subject: [PATCH] Add ROM Memory

---
 ram_test.go   |   9 +++------
 rom.go        |  38 ++++++++++++++++++++++++++++++++++++++
 rom_test.go   |  39 +++++++++++++++++++++++++++++++++++++++
 test/16kb.rom | Bin 0 -> 16384 bytes
 test/8kb.rom  | Bin 0 -> 8192 bytes
 5 files changed, 80 insertions(+), 6 deletions(-)
 create mode 100644 rom.go
 create mode 100644 rom_test.go
 create mode 100644 test/16kb.rom
 create mode 100644 test/8kb.rom

diff --git a/ram_test.go b/ram_test.go
index 6890621..f958986 100644
--- a/ram_test.go
+++ b/ram_test.go
@@ -6,21 +6,18 @@ import (
 )
 
 func TestRamSize(t *testing.T) {
-	assert := assert.New(t)
-
 	ram, _ := NewRam(0x8000) // 32 kB
-	assert.Equal(0x8000, ram.Size())
+	assert.Equal(t, 0x8000, ram.Size())
 }
 
 func TestRamReadWrite(t *testing.T) {
-	assert := assert.New(t)
 	ram, _ := NewRam(0x8000) // 32 kB
 
 	// Ram zeroed out initially
 	for i := 0; i < 0x8000; i++ {
-		assert.Equal(0x00, ram.data[i])
+		assert.Equal(t, 0x00, ram.data[i])
 	}
 
 	ram.Write(0x1000, 0x42)
-	assert.Equal(0x42, ram.Read(0x1000))
+	assert.Equal(t, 0x42, ram.Read(0x1000))
 }
diff --git a/rom.go b/rom.go
new file mode 100644
index 0000000..9c8e248
--- /dev/null
+++ b/rom.go
@@ -0,0 +1,38 @@
+package i6502
+
+import (
+	"fmt"
+	"io/ioutil"
+)
+
+/*
+Read-Only Memory
+*/
+type Rom struct {
+	data []byte
+}
+
+/*
+Create a new Rom component, using the content of `path`. The file automatically
+specifies the size of Rom.
+*/
+func NewRom(path string) (*Rom, error) {
+	data, err := ioutil.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Rom{data: data}, nil
+}
+
+func (r *Rom) Size() uint16 {
+	return uint16(len(r.data))
+}
+
+func (r *Rom) Read(address uint16) byte {
+	return r.data[address]
+}
+
+func (r *Rom) Write(address uint16, data byte) {
+	panic(fmt.Errorf("Trying to write to ROM at 0x%04X", address))
+}
diff --git a/rom_test.go b/rom_test.go
new file mode 100644
index 0000000..58a24b3
--- /dev/null
+++ b/rom_test.go
@@ -0,0 +1,39 @@
+package i6502
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func Test8kRoms(t *testing.T) {
+	rom, err := NewRom("test/8kb.rom")
+
+	assert.Nil(t, err)
+	assert.Equal(t, 0x2000, rom.Size())
+	assert.Equal(t, 0x01, rom.Read(0x0000))
+	assert.Equal(t, 0xFF, rom.Read(0x2000-1))
+}
+
+func TestRomWritePanic(t *testing.T) {
+	rom, _ := NewRom("test/8kb.rom")
+
+	// Writing to rom should panic
+	assert.Panics(t, func() {
+		rom.Write(0x1337, 0x42)
+	}, "Writing to Rom should panic")
+}
+
+func Test16kRom(t *testing.T) {
+	rom, err := NewRom("test/16kb.rom")
+
+	assert.Nil(t, err)
+	assert.Equal(t, 0x4000, rom.Size())
+	assert.Equal(t, 0x01, rom.Read(0x0000))
+	assert.Equal(t, 0xFF, rom.Read(0x4000-1))
+}
+
+func TestRomNotFound(t *testing.T) {
+	rom, err := NewRom("test/does-not-exists.rom")
+	assert.NotNil(t, err)
+	assert.Nil(t, rom)
+}
diff --git a/test/16kb.rom b/test/16kb.rom
new file mode 100644
index 0000000000000000000000000000000000000000..7f395904e9d0b1ba70b9ffba4e525e50a7744745
GIT binary patch
literal 16384
zcmeIuK>+|j1OTve^pA`fK3jyv&w3azV8DO@0|pEjFkrxd0RsjM7%*VKfB^#r3>YwA
vz<>b*1`HT5V8DO@0|pEjFkrxd0RsjM7%*VKfB^#r3>YwAz<>b*hXXwe!vz8e

literal 0
HcmV?d00001

diff --git a/test/8kb.rom b/test/8kb.rom
new file mode 100644
index 0000000000000000000000000000000000000000..c138c62cf51eea12ac731bb72e9b612524fc6f7c
GIT binary patch
literal 8192
zcmeIu0Sy2!2mqja?H^gq;RX?ipY<?cz<>b*1`HT5V8DO@0|pEjFkrxd0RsjM7%*VK
LfB^#r4iEG!V)g<E

literal 0
HcmV?d00001