add flag operating utility functions

flag.go

@@ -0,0 +1,35 @@
+package z80
+
+// Flag is the flag value used for GetFlag etc.
+// Each value can be combined with the OR (|) operator.
+type Flag uint8
+
+const (
+	FlagC  Flag = 0x01 // FlagC is carry flag.
+	FlagN  Flag = 0x02 // FlagN is subtract flag.
+	FlagPV Flag = 0x04 // FlagPV is parity/overflow flag.
+	FlagH  Flag = 0x10 // FlagH is half carry flag.
+	FlagZ  Flag = 0x40 // FlagZ is zero flag.
+	FlagS  Flag = 0x80 // FlagS is sign flag.
+
+	Flag3 Flag = 0x08 // Flag3 is undefined flag, at 3rd from LSB.
+	Flag5 Flag = 0x20 // Flag5 is undefined flag, at 5th from LSB.
+)
+
+// GetFlag gets a flag status.  For available flags, see Flag type.  When
+// multiple flags are combined, if any one of them is true, this returns true.
+func (gpr GPR) GetFlag(f Flag) bool {
+	return gpr.AF.Lo&uint8(f) != 0
+}
+
+// SetFlag sets the specified flag to true.  For available flags, see Flag
+// type.  When multiple flags are combined, all flags are set to true.
+func (gpr *GPR) SetFlag(f Flag) {
+	gpr.AF.Lo |= uint8(f)
+}
+
+// ResetFlag resets the specified flag to false. Fo available flags, see Flag
+// type. When multiple flags are combined, all flags are set to false.
+func (gpr *GPR) ResetFlag(f Flag) {
+	gpr.AF.Lo &= ^uint8(f)
+}

flag_test.go

@@ -0,0 +1,126 @@
+package z80_test
+
+import (
+	"testing"
+
+	"github.com/koron-go/z80"
+)
+
+func TestGetFlag(t *testing.T) {
+	for i, c := range []struct {
+		lo   uint8
+		flag z80.Flag
+		want bool
+	}{
+		{0b00000001, z80.FlagC, true},
+		{0b00000000, z80.FlagC, false},
+		{0b11111110, z80.FlagC, false},
+
+		{0b00000010, z80.FlagN, true},
+		{0b00000000, z80.FlagN, false},
+		{0b11111101, z80.FlagN, false},
+
+		{0b00000100, z80.FlagPV, true},
+		{0b00000000, z80.FlagPV, false},
+		{0b11111011, z80.FlagPV, false},
+
+		{0b00010000, z80.FlagH, true},
+		{0b00000000, z80.FlagH, false},
+		{0b11100111, z80.FlagH, false},
+
+		{0b01000000, z80.FlagZ, true},
+		{0b00000000, z80.FlagZ, false},
+		{0b10111111, z80.FlagZ, false},
+
+		{0b10000000, z80.FlagS, true},
+		{0b00000000, z80.FlagS, false},
+		{0b01111111, z80.FlagS, false},
+	} {
+		var cpu z80.CPU
+		cpu.AF.Lo = c.lo
+		got := cpu.GetFlag(c.flag)
+		if got != c.want {
+			t.Errorf("unexpected value: %d %+v: got=%t", i, c, got)
+		}
+	}
+}
+
+func TestSetFlag(t *testing.T) {
+	for i, c := range []struct {
+		prev uint8
+		flag z80.Flag
+		want uint8
+	}{
+		{0b00000000, z80.FlagC, 0b00000001},
+		{0b00000001, z80.FlagC, 0b00000001},
+		{0b11111110, z80.FlagC, 0b11111111},
+
+		{0b00000000, z80.FlagN, 0b00000010},
+		{0b00000010, z80.FlagN, 0b00000010},
+		{0b11111101, z80.FlagN, 0b11111111},
+
+		{0b00000000, z80.FlagPV, 0b00000100},
+		{0b00000100, z80.FlagPV, 0b00000100},
+		{0b11111011, z80.FlagPV, 0b11111111},
+
+		{0b00000000, z80.FlagH, 0b00010000},
+		{0b00010000, z80.FlagH, 0b00010000},
+		{0b11101111, z80.FlagH, 0b11111111},
+
+		{0b00000000, z80.FlagZ, 0b01000000},
+		{0b01000000, z80.FlagZ, 0b01000000},
+		{0b10111111, z80.FlagZ, 0b11111111},
+
+		{0b00000000, z80.FlagS, 0b10000000},
+		{0b10000000, z80.FlagS, 0b10000000},
+		{0b01111111, z80.FlagS, 0b11111111},
+	} {
+		var cpu z80.CPU
+		cpu.AF.Lo = c.prev
+		cpu.SetFlag(c.flag)
+		got := cpu.AF.Lo
+		if got != c.want {
+			t.Errorf("unexpected value: %d {prev:%08b flag:0x%02x want:%08b}: got=%08b", i, c.prev, c.flag, c.want, got)
+		}
+	}
+}
+
+func TestResetFlag(t *testing.T) {
+	for i, c := range []struct {
+		prev uint8
+		flag z80.Flag
+		want uint8
+	}{
+		{0b00000001, z80.FlagC, 0b00000000},
+		{0b00000000, z80.FlagC, 0b00000000},
+		{0b11111111, z80.FlagC, 0b11111110},
+
+		{0b00000010, z80.FlagN, 0b00000000},
+		{0b00000000, z80.FlagN, 0b00000000},
+		{0b11111111, z80.FlagN, 0b11111101},
+
+		{0b00000100, z80.FlagPV, 0b00000000},
+		{0b00000000, z80.FlagPV, 0b00000000},
+		{0b11111111, z80.FlagPV, 0b11111011},
+
+		{0b00010000, z80.FlagH, 0b00000000},
+		{0b00000000, z80.FlagH, 0b00000000},
+		{0b11111111, z80.FlagH, 0b11101111},
+
+		{0b01000000, z80.FlagZ, 0b00000000},
+		{0b00000000, z80.FlagZ, 0b00000000},
+		{0b10111111, z80.FlagZ, 0b10111111},
+
+		{0b10000000, z80.FlagS, 0b00000000},
+		{0b00000000, z80.FlagS, 0b00000000},
+		{0b11111111, z80.FlagS, 0b01111111},
+	} {
+		var cpu z80.CPU
+		cpu.AF.Lo = c.prev
+		cpu.ResetFlag(c.flag)
+		got := cpu.AF.Lo
+		if got != c.want {
+			t.Errorf("unexpected value: %d {prev:%08b flag:0x%02x want:%08b}: got=%08b", i, c.prev, c.flag, c.want, got)
+		}
+	}
+}