Add random paging

hal/paging.go

@@ -1,7 +1,15 @@
 package hal
 
+import (
+	"fmt"
+	"math/rand"
+	"time"
+)
+
 const PageSize = 1024
 
+var seed = rand.NewSource(time.Now().UnixNano())
+
 var defaultRegister uint16 = 0
 
 type Page struct {
@@ -100,21 +108,15 @@ func (mmu *MMU) Write(address Address, content float64) {
 //
 func (mmu *MMU) Load(page *Page) {
 	if len(mmu.LoadedPages) >= 4 {
-		for index, loadedPage := range mmu.LoadedPages {
-			if loadedPage.Referenced {
-				loadedPage.Referenced = false
-				continue
-			}
-			mmu.movePageToDrive(loadedPage)
-			mmu.LoadedPages = append(mmu.LoadedPages[:index], mmu.LoadedPages[index+1:]...)
-			break
-		}
-
 		// Everything is referenced, we need to remove one
-		if len(mmu.LoadedPages) == 4 {
-			mmu.movePageToDrive(mmu.LoadedPages[3])
-			mmu.LoadedPages = mmu.LoadedPages[:3]
-		}
+		index := rand.New(seed).Intn(4)
+		removedPage := mmu.LoadedPages[index]
+		mmu.movePageToDrive(removedPage)
+
+		mmu.loadPageFromDrive(page)
+
+		mmu.LoadedPages[index] = page
+		return
 	}
 
 	mmu.loadPageFromDrive(page)
@@ -127,7 +129,7 @@ func (mmu *MMU) findEmptyRegisterAddress() *uint16 {
 	for i = 0; i < uint16(len(mmu.module.register)/PageSize); i++ {
 		var isTaken bool
 		for _, loadedPage := range mmu.LoadedPages {
-			if *loadedPage.RegisterAddress == i {
+			if loadedPage.RegisterAddress != nil && *loadedPage.RegisterAddress == i {
 				isTaken = true
 				break
 			}
@@ -142,7 +144,9 @@ func (mmu *MMU) findEmptyRegisterAddress() *uint16 {
 }
 
 func (mmu *MMU) movePageToDrive(page *Page) {
-
+	if page.RegisterAddress == nil {
+		fmt.Printf("PAGE NOT IN MEMORY\n")
+	}
 	for i := 0; i < PageSize-1; i++ {
 		mmu.drive[page.PageNumber][i] = mmu.module.register[i+page.RegisterOffset()]
 	}