{"7fffffffffffffff", 16, 1<<63 - 1, nil},

	// underscores
	{"-0x_1_2_3_4_5", 0, -0x12345, nil},
	{"0x_1_2_3_4_5", 0, 0x12345, nil},
	{"-_0x12345", 0, 0, ErrSyntax},
	{"_-0x12345", 0, 0, ErrSyntax},
	{"_0x12345", 0, 0, ErrSyntax},
	{"0x__12345", 0, 0, ErrSyntax},
	{"0x1__2345", 0, 0, ErrSyntax},
	{"0x1234__5", 0, 0, ErrSyntax},
	{"0x12345_", 0, 0, ErrSyntax},

	`0Xdeadcafep+1 = 0x1bd5b95fc`,
	`0x1234P-10 = 0x1234/1024`,

	`0x0.0p0 = 0.`,
	`0Xdead.cafep+1 = 0x1bd5b95fc/0x10000`,
	`0x12.34P-10 = 0x1234/0x40000`,

	`0Xdead_cafep+1 = 0xdeadcafep+1`,
	`0x_1234P-10 = 0x1234p-10`,

	`0X_dead_cafe.p-10 = 0xdeadcafe.p-10`,
	`0x12_34.P1_2_3 = 0x1234.p123`,
}

var imagTests = []string{
	`1_234i = 1234i`,
	`1_234_567i = 1234567i`,

	`0.i = 0i`,

		{"0MiB", 0, true},
		{"0GiB", 0, true},
		{"0TiB", 0, true},

		// Bad inputs.
		{"", 0, false},
		{"-1", 0, false},
		{"a12345", 0, false},
		{"a12345B", 0, false},
		{"12345x", 0, false},
		{"0x12345", 0, false},

		// Bad numeric inputs.
		{"9223372036854775808", 0, false},
		{"9223372036854775809", 0, false},
		{"18446744073709551615", 0, false},
		{"20496382327982653440", 0, false},

	}
	Output = int(s)
}

func TestReverseBytes(t *testing.T) {
	for _, test := range []struct {
		x, r uint64
	}{
		{0, 0},
		{0x01, 0x01 << 56},
		{0x0123, 0x2301 << 48},
		{0x012345, 0x452301 << 40},
		{0x01234567, 0x67452301 << 32},
		{0x0123456789, 0x8967452301 << 24},
		{0x0123456789ab, 0xab8967452301 << 16},
		{0x0123456789abcd, 0xcdab8967452301 << 8},