From 43f3d06988c1c025feb4f88a949ad96e6dc829e3 Mon Sep 17 00:00:00 2001
From: Marco Peereboom <marco@conformal.com>
Date: Wed, 8 Apr 2015 16:56:35 -0500
Subject: [PATCH] Iterate over pointers instead of copies.

Modify addressable to become a pointer because Go's range does not
provide a pointer to the element but a copy of the element (urgh).

Go's range operator really can be considered broken.  In this case it
copies the addressable all the time which significantly slows things
down.  To boot, it isn't writing in the memory you think it is (it ends
up in the copy of memory).

Before the change:
$ go test -v -test.run Klaus
=== RUN TestKlausDormann6502
Running Klaus Dormann' 6502 functional tests. This may take some time...
Klaus Dormann's 6502 functional tests passed.
--- PASS: TestKlausDormann6502 (13.51s)
PASS
ok      github.com/ariejan/i6502        13.522s

After the change:
$ go test -v -test.run Klaus
=== RUN TestKlausDormann6502
Running Klaus Dormann' 6502 functional tests. This may take some time...
Klaus Dormann's 6502 functional tests passed.
--- PASS: TestKlausDormann6502 (4.87s)
PASS
ok      github.com/ariejan/i6502        4.877s
---
 address_bus.go | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/address_bus.go b/address_bus.go
index 01b632f..40bb942 100644
--- a/address_bus.go
+++ b/address_bus.go
@@ -11,7 +11,7 @@ address space of the Cpu to the relative memory addressing of
 each component.
 */
 type AddressBus struct {
-	addressables []addressable // Different components
+	addressables []*addressable // Different components
 }
 
 type addressable struct {
@@ -26,7 +26,7 @@ func (a *addressable) String() string {
 
 // Creates a new, empty 16-bit AddressBus
 func NewAddressBus() (*AddressBus, error) {
-	return &AddressBus{addressables: make([]addressable, 0)}, nil
+	return &AddressBus{addressables: make([]*addressable, 0)}, nil
 }
 
 // Returns a string with details about the AddressBus and attached memory
@@ -54,7 +54,7 @@ func (a *AddressBus) Attach(memory Memory, offset uint16) {
 	end := offset + memory.Size() - 1
 	addressable := addressable{memory: memory, start: start, end: end}
 
-	a.addressables = append(a.addressables, addressable)
+	a.addressables = append(a.addressables, &addressable)
 }
 
 /*
@@ -112,7 +112,7 @@ func (a *AddressBus) Write16(address uint16, data uint16) {
 func (a *AddressBus) addressableForAddress(address uint16) (*addressable, error) {
 	for _, addressable := range a.addressables {
 		if addressable.start <= address && addressable.end >= address {
-			return &addressable, nil
+			return addressable, nil
 		}
 	}