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|
package cpu
import (
"bufio"
"os"
"regexp"
"strconv"
"testing"
)
type nestestBus struct {
ram [0x0800]uint8
prg []uint8
}
func (b *nestestBus) Read(addr uint16) uint8 {
switch {
case addr < 0x2000:
return b.ram[addr%0x0800]
case addr >= 0x8000:
return b.prg[int(addr-0x8000)%len(b.prg)]
default:
return 0
}
}
func (b *nestestBus) Write(addr uint16, v uint8) {
if addr < 0x2000 {
b.ram[addr%0x0800] = v
}
}
func loadNestestPRG(path string) ([]uint8, error) {
data, err := os.ReadFile(path)
if err != nil {
return nil, err
}
prgBanks := int(data[4])
prgSize := prgBanks * 16 * 1024
hasTrainer := data[6]&0x04 != 0
offset := 16
if hasTrainer {
offset += 512
}
return data[offset : offset+prgSize], nil
}
type cpuState struct {
pc uint16
a, x, y, p, sp uint8
cyc uint64
}
var nestestLogRE = regexp.MustCompile(
`^([0-9A-F]{4}).*A:([0-9A-F]{2}) X:([0-9A-F]{2}) Y:([0-9A-F]{2}) P:([0-9A-F]{2}) SP:([0-9A-F]{2}).*CYC:\s*(\d+)`)
func loadNestestLog(path string) ([]cpuState, error) {
f, err := os.Open(path)
if err != nil {
return nil, err
}
defer f.Close()
var lines []cpuState
scanner := bufio.NewScanner(f)
for scanner.Scan() {
m := nestestLogRE.FindStringSubmatch(scanner.Text())
if m == nil {
continue
}
parseHex8 := func(s string) uint8 {
v, _ := strconv.ParseUint(s, 16, 8)
return uint8(v)
}
pc, _ := strconv.ParseUint(m[1], 16, 16)
cyc, _ := strconv.ParseUint(m[7], 10, 64)
lines = append(lines, cpuState{
pc: uint16(pc),
a: parseHex8(m[2]),
x: parseHex8(m[3]),
y: parseHex8(m[4]),
p: parseHex8(m[5]),
sp: parseHex8(m[6]),
cyc: cyc,
})
}
return lines, scanner.Err()
}
// TestNestest runs nestest.nes and diffs the state against a known good log before each instruction
func TestNestest(t *testing.T) {
const romPath = "testdata/nestest.nes"
const logPath = "testdata/nestest.log"
if _, err := os.Stat(romPath); err != nil {
t.Skip("testdata/nestest.nes not present; add it and testdata/nestest.log to run this test")
}
prg, err := loadNestestPRG(romPath)
if err != nil {
t.Fatalf("loading ROM: %v", err)
}
want, err := loadNestestLog(logPath)
if err != nil {
t.Fatalf("loading log: %v", err)
}
if len(want) == 0 {
t.Fatal("no log lines parsed")
}
bus := &nestestBus{prg: prg}
c := NewCPU(bus)
c.PC = 0xC000
c.SP = 0xFD
c.Status = 0x24
c.Cycles = want[0].cyc
for i, w := range want {
got := cpuState{c.PC, c.A, c.X, c.Y, c.Status, c.SP, c.Cycles}
if got != w {
t.Fatalf("line %d: got %+v, want %+v", i+1, got, w)
}
stopped := func() (panicked bool) {
defer func() {
if r := recover(); r != nil {
t.Logf("stopped at line %d: %v", i+1, r)
panicked = true
}
}()
c.Step()
return false
}()
if stopped {
t.Logf("matched %d instructions before stopping", i+1)
return
}
}
}
|