diff --git a/lib/std/hash.zig b/lib/std/hash.zig index 68adb1afdd..b768a85861 100644 --- a/lib/std/hash.zig +++ b/lib/std/hash.zig @@ -37,25 +37,31 @@ pub const XxHash3 = xxhash.XxHash3; pub const XxHash64 = xxhash.XxHash64; pub const XxHash32 = xxhash.XxHash32; -/// Deprecated: use std.hash.int(comptime T, input T) T where T is an unsigned integer type. -/// This is handy if you have a u32 and want a u32 and don't want to take a -/// detour through many layers of abstraction elsewhere in the std.hash -/// namespace. +/// Deprecated in favor of `int`. pub fn uint32(input: u32) u32 { - return int(u32, input); + return int(input); } /// Applies a bit-mangling transformation to an unsigned integer type `T`. /// Optimized per type: for `u16` and `u32`, Skeeto's xorshift-multiply; for `u64`, Maiga's mx3. -/// Falls back on an avalanche pattern for other unsigned types, ensuring high entropy. -/// Only unsigned types are accepted; signed types will raise a compile-time error. -pub fn int(comptime T: type, input: T) T { - const tInfo = @typeInfo(T).int; - if (tInfo.signedness != .unsigned) @compileError("type has to be unsigned integer"); +/// Falls back on an avalanche pattern for other integer types, ensuring high entropy. +pub fn int(input: anytype) @TypeOf(input) { + const info = @typeInfo(@TypeOf(input)).int; + if (info.signedness == .signed) { + const Unsigned = @Type(.{ .int = .{ .signedness = .unsigned, .bits = info.bits } }); + const casted: Unsigned = @bitCast(input); + return @bitCast(int(casted)); + } else if (info.bits < 16) { + return @truncate(int(@as(u16, input))); + } else if (info.bits < 32) { + return @truncate(int(@as(u32, input))); + } else if (info.bits < 64) { + return @truncate(int(@as(u64, input))); + } var x = input; - switch (T) { - u16 => { - //https://github.com/skeeto/hash-prospector + switch (info.bits) { + 16 => { + // https://github.com/skeeto/hash-prospector // 3-round xorshift-multiply (-Xn3) // bias = 0.0045976709018820602 x = (x ^ (x >> 7)) *% 0x2993; @@ -63,36 +69,34 @@ pub fn int(comptime T: type, input: T) T { x = (x ^ (x >> 9)) *% 0x0235; x = x ^ (x >> 10); }, - u32 => { + 32 => { // https://github.com/skeeto/hash-prospector x = (x ^ (x >> 17)) *% 0xed5ad4bb; x = (x ^ (x >> 11)) *% 0xac4c1b51; x = (x ^ (x >> 15)) *% 0x31848bab; x = x ^ (x >> 14); }, - u64 => { + 64 => { // https://github.com/jonmaiga/mx3 // https://github.com/jonmaiga/mx3/blob/48924ee743d724aea2cafd2b4249ef8df57fa8b9/mx3.h#L17 - const C = 0xbea225f9eb34556d; - x = (x ^ (x >> 32)) *% C; - x = (x ^ (x >> 29)) *% C; - x = (x ^ (x >> 32)) *% C; + const c = 0xbea225f9eb34556d; + x = (x ^ (x >> 32)) *% c; + x = (x ^ (x >> 29)) *% c; + x = (x ^ (x >> 32)) *% c; x = x ^ (x >> 29); }, else => { - // this construction provides robust avalanche properties, but it is not optimal for any given size. - const Tsize = @bitSizeOf(T); - if (Tsize < 4) @compileError("not implemented."); - const hsize = Tsize >> 1; - const C = comptime blk: { - const max = (1 << Tsize) - 1; + // This construction provides robust avalanche properties, but it is not optimal for any given size. + const hsize = info.bits >> 1; + const c = comptime blk: { + const max = (1 << info.bits) - 1; var mul = 1; while (mul * 3 < max) mul *= 3; break :blk ((mul ^ (mul >> hsize)) | 1); }; inline for (0..2) |_| { - x = (x ^ (x >> hsize + 1)) *% C; - x = (x ^ (x >> hsize - 1)) *% C; + x = (x ^ (x >> hsize + 1)) *% c; + x = (x ^ (x >> hsize - 1)) *% c; } x ^= (x >> hsize); }, @@ -100,14 +104,15 @@ pub fn int(comptime T: type, input: T) T { return x; } -test "bit manglers" { - const expect = @import("std").testing.expect; - try expect(int(u4, 1) == 0xC); - try expect(int(u8, 1) == 0x4F); - try expect(int(u16, 1) == 0x2880); - try expect(int(u32, 1) == 0x42741D6); - try expect(int(u64, 1) == 0x71894DE00D9981F); - try expect(int(u128, 1) == 0x50BC2BB18910C3DE0BAA2CE0D0C5B83E); +test int { + const expectEqual = @import("std").testing.expectEqual; + try expectEqual(0xC, int(@as(u4, 1))); + try expectEqual(0x4F, int(@as(u8, 1))); + try expectEqual(0x4F, int(@as(i8, 1))); + try expectEqual(0x2880, int(@as(u16, 1))); + try expectEqual(0x42741D6, int(@as(u32, 1))); + try expectEqual(0x71894DE00D9981F, int(@as(u64, 1))); + try expectEqual(0x50BC2BB18910C3DE0BAA2CE0D0C5B83E, int(@as(u128, 1))); } test {