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| 1 | +const std = @import("std"); |
| 2 | +const builtin = @import("builtin"); |
| 3 | +const mem = std.mem; |
| 4 | +const meta = std.meta; |
| 5 | + |
| 6 | +/// Provides generic hashing for any eligible type. |
| 7 | +/// Only hashes `key` itself, pointers are not followed. |
| 8 | +pub fn autoHash(hasher: var, key: var) void { |
| 9 | + const Key = @typeOf(key); |
| 10 | + switch (@typeInfo(Key)) { |
| 11 | + builtin.TypeId.NoReturn, |
| 12 | + builtin.TypeId.Opaque, |
| 13 | + builtin.TypeId.Undefined, |
| 14 | + builtin.TypeId.ArgTuple, |
| 15 | + builtin.TypeId.Void, |
| 16 | + builtin.TypeId.Null, |
| 17 | + builtin.TypeId.BoundFn, |
| 18 | + builtin.TypeId.ComptimeFloat, |
| 19 | + builtin.TypeId.ComptimeInt, |
| 20 | + builtin.TypeId.Type, |
| 21 | + builtin.TypeId.EnumLiteral, |
| 22 | + => @compileError("cannot hash this type"), |
| 23 | + |
| 24 | + // Help the optimizer see that hashing an int is easy by inlining! |
| 25 | + // TODO Check if the situation is better after #561 is resolved. |
| 26 | + builtin.TypeId.Int => @inlineCall(hasher.update, std.mem.asBytes(&key)), |
| 27 | + |
| 28 | + builtin.TypeId.Float => |info| autoHash(hasher, @bitCast(@IntType(false, info.bits), key)), |
| 29 | + |
| 30 | + builtin.TypeId.Bool => autoHash(hasher, @boolToInt(key)), |
| 31 | + builtin.TypeId.Enum => autoHash(hasher, @enumToInt(key)), |
| 32 | + builtin.TypeId.ErrorSet => autoHash(hasher, @errorToInt(key)), |
| 33 | + builtin.TypeId.Promise, builtin.TypeId.Fn => autoHash(hasher, @ptrToInt(key)), |
| 34 | + |
| 35 | + builtin.TypeId.Pointer => |info| switch (info.size) { |
| 36 | + builtin.TypeInfo.Pointer.Size.One, |
| 37 | + builtin.TypeInfo.Pointer.Size.Many, |
| 38 | + builtin.TypeInfo.Pointer.Size.C, |
| 39 | + => autoHash(hasher, @ptrToInt(key)), |
| 40 | + |
| 41 | + builtin.TypeInfo.Pointer.Size.Slice => { |
| 42 | + autoHash(hasher, key.ptr); |
| 43 | + autoHash(hasher, key.len); |
| 44 | + }, |
| 45 | + }, |
| 46 | + |
| 47 | + builtin.TypeId.Optional => if (key) |k| autoHash(hasher, k), |
| 48 | + |
| 49 | + builtin.TypeId.Array => { |
| 50 | + // TODO detect via a trait when Key has no padding bits to |
| 51 | + // hash it as an array of bytes. |
| 52 | + // Otherwise, hash every element. |
| 53 | + for (key) |element| { |
| 54 | + autoHash(hasher, element); |
| 55 | + } |
| 56 | + }, |
| 57 | + |
| 58 | + builtin.TypeId.Vector => |info| { |
| 59 | + if (info.child.bit_count % 8 == 0) { |
| 60 | + // If there's no unused bits in the child type, we can just hash |
| 61 | + // this as an array of bytes. |
| 62 | + hasher.update(mem.asBytes(&key)); |
| 63 | + } else { |
| 64 | + // Otherwise, hash every element. |
| 65 | + // TODO remove the copy to an array once field access is done. |
| 66 | + const array: [info.len]info.child = key; |
| 67 | + comptime var i: u32 = 0; |
| 68 | + inline while (i < info.len) : (i += 1) { |
| 69 | + autoHash(hasher, array[i]); |
| 70 | + } |
| 71 | + } |
| 72 | + }, |
| 73 | + |
| 74 | + builtin.TypeId.Struct => |info| { |
| 75 | + // TODO detect via a trait when Key has no padding bits to |
| 76 | + // hash it as an array of bytes. |
| 77 | + // Otherwise, hash every field. |
| 78 | + inline for (info.fields) |field| { |
| 79 | + // We reuse the hash of the previous field as the seed for the |
| 80 | + // next one so that they're dependant. |
| 81 | + autoHash(hasher, @field(key, field.name)); |
| 82 | + } |
| 83 | + }, |
| 84 | + |
| 85 | + builtin.TypeId.Union => |info| blk: { |
| 86 | + if (info.tag_type) |tag_type| { |
| 87 | + const tag = meta.activeTag(key); |
| 88 | + const s = autoHash(hasher, tag); |
| 89 | + inline for (info.fields) |field| { |
| 90 | + const enum_field = field.enum_field.?; |
| 91 | + if (enum_field.value == @enumToInt(tag)) { |
| 92 | + autoHash(hasher, @field(key, enum_field.name)); |
| 93 | + // TODO use a labelled break when it does not crash the compiler. |
| 94 | + // break :blk; |
| 95 | + return; |
| 96 | + } |
| 97 | + } |
| 98 | + unreachable; |
| 99 | + } else @compileError("cannot hash untagged union type: " ++ @typeName(Key) ++ ", provide your own hash function"); |
| 100 | + }, |
| 101 | + |
| 102 | + builtin.TypeId.ErrorUnion => blk: { |
| 103 | + const payload = key catch |err| { |
| 104 | + autoHash(hasher, err); |
| 105 | + break :blk; |
| 106 | + }; |
| 107 | + autoHash(hasher, payload); |
| 108 | + }, |
| 109 | + } |
| 110 | +} |
| 111 | + |
| 112 | +const testing = std.testing; |
| 113 | +const Wyhash = std.hash.Wyhash; |
| 114 | + |
| 115 | +fn testAutoHash(key: var) u64 { |
| 116 | + // Any hash could be used here, for testing autoHash. |
| 117 | + var hasher = Wyhash.init(0); |
| 118 | + autoHash(&hasher, key); |
| 119 | + return hasher.final(); |
| 120 | +} |
| 121 | + |
| 122 | +test "autoHash slice" { |
| 123 | + // Allocate one array dynamically so that we're assured it is not merged |
| 124 | + // with the other by the optimization passes. |
| 125 | + const array1 = try std.heap.direct_allocator.create([6]u32); |
| 126 | + defer std.heap.direct_allocator.destroy(array1); |
| 127 | + array1.* = [_]u32{ 1, 2, 3, 4, 5, 6 }; |
| 128 | + const array2 = [_]u32{ 1, 2, 3, 4, 5, 6 }; |
| 129 | + const a = array1[0..]; |
| 130 | + const b = array2[0..]; |
| 131 | + const c = array1[0..3]; |
| 132 | + testing.expect(testAutoHash(a) == testAutoHash(a)); |
| 133 | + testing.expect(testAutoHash(a) != testAutoHash(array1)); |
| 134 | + testing.expect(testAutoHash(a) != testAutoHash(b)); |
| 135 | + testing.expect(testAutoHash(a) != testAutoHash(c)); |
| 136 | +} |
| 137 | + |
| 138 | +test "testAutoHash optional" { |
| 139 | + const a: ?u32 = 123; |
| 140 | + const b: ?u32 = null; |
| 141 | + testing.expectEqual(testAutoHash(a), testAutoHash(u32(123))); |
| 142 | + testing.expect(testAutoHash(a) != testAutoHash(b)); |
| 143 | + testing.expectEqual(testAutoHash(b), 0); |
| 144 | +} |
| 145 | + |
| 146 | +test "testAutoHash array" { |
| 147 | + const a = [_]u32{ 1, 2, 3 }; |
| 148 | + const h = testAutoHash(a); |
| 149 | + var hasher = Wyhash.init(0); |
| 150 | + autoHash(&hasher, u32(1)); |
| 151 | + autoHash(&hasher, u32(2)); |
| 152 | + autoHash(&hasher, u32(3)); |
| 153 | + testing.expectEqual(h, hasher.final()); |
| 154 | +} |
| 155 | + |
| 156 | +test "testAutoHash struct" { |
| 157 | + const Foo = struct { |
| 158 | + a: u32 = 1, |
| 159 | + b: u32 = 2, |
| 160 | + c: u32 = 3, |
| 161 | + }; |
| 162 | + const f = Foo{}; |
| 163 | + const h = testAutoHash(f); |
| 164 | + var hasher = Wyhash.init(0); |
| 165 | + autoHash(&hasher, u32(1)); |
| 166 | + autoHash(&hasher, u32(2)); |
| 167 | + autoHash(&hasher, u32(3)); |
| 168 | + testing.expectEqual(h, hasher.final()); |
| 169 | +} |
| 170 | + |
| 171 | +test "testAutoHash union" { |
| 172 | + const Foo = union(enum) { |
| 173 | + A: u32, |
| 174 | + B: f32, |
| 175 | + C: u32, |
| 176 | + }; |
| 177 | + |
| 178 | + const a = Foo{ .A = 18 }; |
| 179 | + var b = Foo{ .B = 12.34 }; |
| 180 | + const c = Foo{ .C = 18 }; |
| 181 | + testing.expect(testAutoHash(a) == testAutoHash(a)); |
| 182 | + testing.expect(testAutoHash(a) != testAutoHash(b)); |
| 183 | + testing.expect(testAutoHash(a) != testAutoHash(c)); |
| 184 | + |
| 185 | + b = Foo{ .A = 18 }; |
| 186 | + testing.expect(testAutoHash(a) == testAutoHash(b)); |
| 187 | +} |
| 188 | + |
| 189 | +test "testAutoHash vector" { |
| 190 | + const a: @Vector(4, u32) = [_]u32{ 1, 2, 3, 4 }; |
| 191 | + const b: @Vector(4, u32) = [_]u32{ 1, 2, 3, 5 }; |
| 192 | + const c: @Vector(4, u31) = [_]u31{ 1, 2, 3, 4 }; |
| 193 | + testing.expect(testAutoHash(a) == testAutoHash(a)); |
| 194 | + testing.expect(testAutoHash(a) != testAutoHash(b)); |
| 195 | + testing.expect(testAutoHash(a) != testAutoHash(c)); |
| 196 | +} |
| 197 | + |
| 198 | +test "testAutoHash error union" { |
| 199 | + const Errors = error{Test}; |
| 200 | + const Foo = struct { |
| 201 | + a: u32 = 1, |
| 202 | + b: u32 = 2, |
| 203 | + c: u32 = 3, |
| 204 | + }; |
| 205 | + const f = Foo{}; |
| 206 | + const g: Errors!Foo = Errors.Test; |
| 207 | + testing.expect(testAutoHash(f) != testAutoHash(g)); |
| 208 | + testing.expect(testAutoHash(f) == testAutoHash(Foo{})); |
| 209 | + testing.expect(testAutoHash(g) == testAutoHash(Errors.Test)); |
| 210 | +} |
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