1 files changed, 29 insertions, 0 deletions
diff --git a/cpu/flags.go b/cpu/flags.go
new file mode 100644
index 0000000..b6ede68
--- /dev/null
+++ b/cpu/flags.go
@@ -0,0 +1,29 @@
+package cpu
+
+const (
+	FlagC uint8 = 1 << 0
+	FlagZ uint8 = 1 << 1
+	FlagI uint8 = 1 << 2
+	FlagD uint8 = 1 << 3 // no-op on the NES's 2A03
+	FlagB uint8 = 1 << 4 // only meaningful in the byte pushed by brk/irq
+	FlagU uint8 = 1 << 5
+	FlagV uint8 = 1 << 6
+	FlagN uint8 = 1 << 7
+)
+
+func (c *CPU) setFlag(flag uint8, set bool) {
+	if set {
+		c.Status |= flag
+	} else {
+		c.Status &^= flag
+	}
+}
+
+func (c *CPU) flag(flag uint8) bool {
+	return c.Status&flag != 0
+}
+
+func (c *CPU) setZN(v uint8) {
+	c.setFlag(FlagZ, v == 0)
+	c.setFlag(FlagN, v&0x80 != 0)
+}