authorgravatar for hi@whatisaph.onewhatisaphone <hi@whatisaph.one> 2026-06-20 09:45:17-04:00
committergravatar for andrew@ziglang.orgAndrew Kelley <andrew@ziglang.org> 2026-06-26 23:30:13+02:00
logb636906fb640a12107cd21637c2af67b8e9d6ebd
treeccce4bfafa7324b82b59c72580b012c488ac430a
parentc150a66bfe2010be86e38f40573ffc8bdf5c2326

std.math: Add signExtend

1 files changed, 36 insertions(+), 0 deletions(-)

lib/std/math.zig+36
......@@ -1875,3 +1875,39 @@ test sign {
18751875 try testSign();
18761876 try comptime testSign();
18771877}
1878
1879/// Increases the bit width of an integer by copying the most significant bit.
1880/// This results in the input and output having the same arithmetic value, when
1881/// interpreted as two's complement integers.
1882fn signExtend(To: type, n: anytype) To {
1883 const From = @TypeOf(n);
1884 if (From == u0) return 0;
1885 const FromSigned = @Int(.signed, @typeInfo(From).int.bits);
1886 const ToSigned = @Int(.signed, @typeInfo(To).int.bits);
1887
1888 return @bitCast(@as(ToSigned, @as(FromSigned, @bitCast(n))));
1889}
1890
1891test signExtend {
1892 const number: u8 = 0x86;
1893 try testing.expectEqual(0xff86, signExtend(u16, number));
1894
1895 try testing.expectEqual(0, signExtend(u1, @as(u0, 0)));
1896 try testing.expectEqual(0, signExtend(u16, @as(u0, 0)));
1897
1898 try testing.expectEqual(0x0000, signExtend(u16, @as(u1, 0b0)));
1899 try testing.expectEqual(0xffff, signExtend(u16, @as(u1, 0b1)));
1900
1901 try testing.expectEqual(0b000, signExtend(u3, @as(u2, 0b00)));
1902 try testing.expectEqual(0b001, signExtend(u3, @as(u2, 0b01)));
1903 try testing.expectEqual(0b110, signExtend(u3, @as(u2, 0b10)));
1904 try testing.expectEqual(0b111, signExtend(u3, @as(u2, 0b11)));
1905 try testing.expectEqual(0b0000_0001, signExtend(u8, @as(u2, 0b01)));
1906 try testing.expectEqual(0b1111_1110, signExtend(u8, @as(u2, 0b10)));
1907
1908 try testing.expectEqual(0x0039, signExtend(u16, @as(u8, 0x39)));
1909 try testing.expectEqual(0xff93, signExtend(u16, @as(u8, 0x93)));
1910
1911 try testing.expectEqual(5, signExtend(i32, @as(i8, 5)));
1912 try testing.expectEqual(-123, signExtend(i16, @as(i8, -123)));
1913}