Commit 5bd407b278
Changed files (1)
std
std/hash_map.zig
@@ -4,6 +4,8 @@ const assert = debug.assert;
const testing = std.testing;
const math = std.math;
const mem = std.mem;
+const meta = std.meta;
+const wyhash = std.hash.wyhash;
const Allocator = mem.Allocator;
const builtin = @import("builtin");
@@ -448,15 +450,17 @@ test "iterator hash map" {
try reset_map.putNoClobber(2, 22);
try reset_map.putNoClobber(3, 33);
+ // TODO this test depends on the hashing algorithm, because it assumes the
+ // order of the elements in the hashmap. This should not be the case.
var keys = [_]i32{
+ 1,
3,
2,
- 1,
};
var values = [_]i32{
+ 11,
33,
22,
- 11,
};
var it = reset_map.iterator();
@@ -518,8 +522,8 @@ pub fn getTrivialEqlFn(comptime K: type) (fn (K, K) bool) {
pub fn getAutoHashFn(comptime K: type) (fn (K) u32) {
return struct {
fn hash(key: K) u32 {
- comptime var rng = comptime std.rand.DefaultPrng.init(0);
- return autoHash(key, &rng.random, u32);
+ const h = autoHash(key, 0);
+ return @truncate(u32, h);
}
}.hash;
}
@@ -527,114 +531,192 @@ pub fn getAutoHashFn(comptime K: type) (fn (K) u32) {
pub fn getAutoEqlFn(comptime K: type) (fn (K, K) bool) {
return struct {
fn eql(a: K, b: K) bool {
- return autoEql(a, b);
+ return meta.eql(a, b);
}
}.eql;
}
-// TODO improve these hash functions
-pub fn autoHash(key: var, comptime rng: *std.rand.Random, comptime HashInt: type) HashInt {
- switch (@typeInfo(@typeOf(key))) {
+/// Provides generic hashing for any eligible type.
+/// Only hashes `key` itself, pointers are not followed.
+/// The underlying hashing algorithm is wyhash.
+pub fn autoHash(key: var, seed: u64) u64 {
+ // We use the fact that wyhash takes an input seed to "chain" hasing when the
+ // key has multiple parts that are not necessarily contiguous in memory.
+ const Key = @typeOf(key);
+ switch (@typeInfo(Key)) {
builtin.TypeId.NoReturn,
builtin.TypeId.Opaque,
builtin.TypeId.Undefined,
builtin.TypeId.ArgTuple,
- => @compileError("cannot hash this type"),
-
builtin.TypeId.Void,
builtin.TypeId.Null,
- => return 0,
-
- builtin.TypeId.Int => |info| {
- const unsigned_x = @bitCast(@IntType(false, info.bits), key);
- if (info.bits <= HashInt.bit_count) {
- return HashInt(unsigned_x) ^ comptime rng.scalar(HashInt);
- } else {
- return @truncate(HashInt, unsigned_x ^ comptime rng.scalar(@typeOf(unsigned_x)));
- }
- },
-
- builtin.TypeId.Float => |info| {
- return autoHash(@bitCast(@IntType(false, info.bits), key), rng, HashInt);
- },
- builtin.TypeId.Bool => return autoHash(@boolToInt(key), rng, HashInt),
- builtin.TypeId.Enum => return autoHash(@enumToInt(key), rng, HashInt),
- builtin.TypeId.ErrorSet => return autoHash(@errorToInt(key), rng, HashInt),
- builtin.TypeId.Promise, builtin.TypeId.Fn => return autoHash(@ptrToInt(key), rng, HashInt),
-
builtin.TypeId.BoundFn,
builtin.TypeId.ComptimeFloat,
builtin.TypeId.ComptimeInt,
builtin.TypeId.Type,
builtin.TypeId.EnumLiteral,
- => return 0,
-
- builtin.TypeId.Pointer => |info| switch (info.size) {
- builtin.TypeInfo.Pointer.Size.One => @compileError("TODO auto hash for single item pointers"),
- builtin.TypeInfo.Pointer.Size.Many => @compileError("TODO auto hash for many item pointers"),
- builtin.TypeInfo.Pointer.Size.C => @compileError("TODO auto hash C pointers"),
- builtin.TypeInfo.Pointer.Size.Slice => {
- const interval = std.math.max(1, key.len / 256);
- var i: usize = 0;
- var h = comptime rng.scalar(HashInt);
- while (i < key.len) : (i += interval) {
- h ^= autoHash(key[i], rng, HashInt);
- }
- return h;
- },
+ => @compileError("cannot hash this type"),
+
+ builtin.TypeId.Int => return wyhash(std.mem.asBytes(&key), seed),
+
+ builtin.TypeId.Float => |info| return autoHash(@bitCast(@IntType(false, info.bits), key), seed),
+
+ builtin.TypeId.Bool => return autoHash(@boolToInt(key), seed),
+ builtin.TypeId.Enum => return autoHash(@enumToInt(key), seed),
+ builtin.TypeId.ErrorSet => return autoHash(@errorToInt(key), seed),
+ builtin.TypeId.Promise, builtin.TypeId.Fn => return autoHash(@ptrToInt(key), seed),
+
+ builtin.TypeId.Pointer => |info| return switch (info.size) {
+ builtin.TypeInfo.Pointer.Size.One,
+ builtin.TypeInfo.Pointer.Size.Many,
+ builtin.TypeInfo.Pointer.Size.C,
+ => return autoHash(@ptrToInt(key), seed),
+
+ builtin.TypeInfo.Pointer.Size.Slice => return autoHash(key.len, autoHash(key.ptr, seed)),
},
- builtin.TypeId.Optional => @compileError("TODO auto hash for optionals"),
- builtin.TypeId.Array => @compileError("TODO auto hash for arrays"),
- builtin.TypeId.Vector => @compileError("TODO auto hash for vectors"),
- builtin.TypeId.Struct => @compileError("TODO auto hash for structs"),
- builtin.TypeId.Union => @compileError("TODO auto hash for unions"),
- builtin.TypeId.ErrorUnion => @compileError("TODO auto hash for unions"),
- }
-}
+ builtin.TypeId.Optional => return if (key) |k| autoHash(k, seed) else 0,
+
+ builtin.TypeId.Array => {
+ // TODO detect via a trait when Key has no padding bits to
+ // hash it as an array of bytes.
+ // Otherwise, hash every element.
+ var s = seed;
+ for (key) |element| {
+ // We reuse the hash of the previous element as the seed for the
+ // next one so that they're dependant.
+ s = autoHash(element, s);
+ }
+ return s;
+ },
-pub fn autoEql(a: var, b: @typeOf(a)) bool {
- switch (@typeInfo(@typeOf(a))) {
- builtin.TypeId.NoReturn,
- builtin.TypeId.Opaque,
- builtin.TypeId.Undefined,
- builtin.TypeId.ArgTuple,
- => @compileError("cannot test equality of this type"),
- builtin.TypeId.Void,
- builtin.TypeId.Null,
- => return true,
- builtin.TypeId.Bool,
- builtin.TypeId.Int,
- builtin.TypeId.Float,
- builtin.TypeId.ComptimeFloat,
- builtin.TypeId.ComptimeInt,
- builtin.TypeId.EnumLiteral,
- builtin.TypeId.Promise,
- builtin.TypeId.Enum,
- builtin.TypeId.BoundFn,
- builtin.TypeId.Fn,
- builtin.TypeId.ErrorSet,
- builtin.TypeId.Type,
- => return a == b,
-
- builtin.TypeId.Pointer => |info| switch (info.size) {
- builtin.TypeInfo.Pointer.Size.One => @compileError("TODO auto eql for single item pointers"),
- builtin.TypeInfo.Pointer.Size.Many => @compileError("TODO auto eql for many item pointers"),
- builtin.TypeInfo.Pointer.Size.C => @compileError("TODO auto eql for C pointers"),
- builtin.TypeInfo.Pointer.Size.Slice => {
- if (a.len != b.len) return false;
- for (a) |a_item, i| {
- if (!autoEql(a_item, b[i])) return false;
+ builtin.TypeId.Vector => |info| {
+ // If there's no unused bits in the child type, we can just hash
+ // this as an array of bytes.
+ if (info.child.bit_count % 8 == 0) {
+ return wyhash(mem.asBytes(&key), seed);
+ }
+
+ // Otherwise, hash every element.
+ var s = seed;
+ // TODO remove the copy to an array once field access is done.
+ const array: [info.len]info.child = key;
+ comptime var i: u32 = 0;
+ inline while (i < info.len) : (i += 1) {
+ s = autoHash(array[i], s);
+ }
+ return s;
+ },
+
+ builtin.TypeId.Struct => |info| {
+ // TODO detect via a trait when Key has no padding bits to
+ // hash it as an array of bytes.
+ // Otherwise, hash every field.
+ var s = seed;
+ inline for (info.fields) |field| {
+ // We reuse the hash of the previous field as the seed for the
+ // next one so that they're dependant.
+ s = autoHash(@field(key, field.name), s);
+ }
+ return s;
+ },
+
+ builtin.TypeId.Union => |info| {
+ if (info.tag_type) |tag_type| {
+ const tag = meta.activeTag(key);
+ const s = autoHash(tag, seed);
+ inline for (info.fields) |field| {
+ const enum_field = field.enum_field.?;
+ if (enum_field.value == @enumToInt(tag)) {
+ return autoHash(@field(key, enum_field.name), s);
+ }
}
- return true;
- },
+ unreachable;
+ } else @compileError("cannot hash untagged union type: " ++ @typeName(Key) ++ ", provide your own hash function");
},
- builtin.TypeId.Optional => @compileError("TODO auto eql for optionals"),
- builtin.TypeId.Array => @compileError("TODO auto eql for arrays"),
- builtin.TypeId.Struct => @compileError("TODO auto eql for structs"),
- builtin.TypeId.Union => @compileError("TODO auto eql for unions"),
- builtin.TypeId.ErrorUnion => @compileError("TODO auto eql for unions"),
- builtin.TypeId.Vector => @compileError("TODO auto eql for vectors"),
+ builtin.TypeId.ErrorUnion => {
+ return autoHash(key catch |err| return autoHash(err, seed), seed);
+ },
}
}
+
+test "autoHash slice" {
+ const array1 = try std.heap.direct_allocator.create([6]u32);
+ defer std.heap.direct_allocator.destroy(array1);
+ array1.* = [_]u32{ 1, 2, 3, 4, 5, 6 };
+ const array2 = [_]u32{ 1, 2, 3, 4, 5, 6 };
+ const a = array1[0..];
+ const b = array2[0..];
+ const c = array1[0..3];
+ testing.expect(autoHash(a, 0) == autoHash(a, 0));
+ testing.expect(autoHash(a, 0) != autoHash(array1, 0));
+ testing.expect(autoHash(a, 0) != autoHash(b, 0));
+ testing.expect(autoHash(a, 0) != autoHash(c, 0));
+}
+
+test "autoHash optional" {
+ const a: ?u32 = 123;
+ const b: ?u32 = null;
+ testing.expectEqual(autoHash(a, 0), autoHash(u32(123), 0));
+ testing.expect(autoHash(a, 0) != autoHash(b, 0));
+ testing.expectEqual(autoHash(b, 0), 0);
+}
+
+test "autoHash array" {
+ const a = [_]u32{ 1, 2, 3 };
+ const h = autoHash(a, 0);
+ testing.expectEqual(h, autoHash(u32(3), autoHash(u32(2), autoHash(u32(1), 0))));
+}
+
+test "autoHash struct" {
+ const Foo = struct {
+ a: u32 = 1,
+ b: u32 = 2,
+ c: u32 = 3,
+ };
+ const f = Foo{};
+ const h = autoHash(f, 0);
+ testing.expectEqual(h, autoHash(u32(3), autoHash(u32(2), autoHash(u32(1), 0))));
+}
+
+test "autoHash union" {
+ const Foo = union(enum) {
+ A: u32,
+ B: f32,
+ C: u32,
+ };
+
+ const a = Foo{ .A = 18 };
+ var b = Foo{ .B = 12.34 };
+ const c = Foo{ .C = 18 };
+ testing.expect(autoHash(a, 0) == autoHash(a, 0));
+ testing.expect(autoHash(a, 0) != autoHash(b, 0));
+ testing.expect(autoHash(a, 0) != autoHash(c, 0));
+
+ b = Foo{ .A = 18 };
+ testing.expect(autoHash(a, 0) == autoHash(b, 0));
+}
+
+test "autoHash vector" {
+ const a: @Vector(4, u32) = [_]u32{ 1, 2, 3, 4 };
+ const b: @Vector(4, u32) = [_]u32{ 1, 2, 3, 5 };
+ const c: @Vector(4, u31) = [_]u31{ 1, 2, 3, 4 };
+ testing.expect(autoHash(a, 0) == autoHash(a, 0));
+ testing.expect(autoHash(a, 0) != autoHash(b, 0));
+ testing.expect(autoHash(a, 0) != autoHash(c, 0));
+}
+
+test "autoHash error union" {
+ const Errors = error{Test};
+ const Foo = struct {
+ a: u32 = 1,
+ b: u32 = 2,
+ c: u32 = 3,
+ };
+ const f = Foo{};
+ const g: Errors!Foo = Errors.Test;
+ testing.expect(autoHash(f, 0) != autoHash(g, 0));
+ testing.expect(autoHash(f, 0) == autoHash(Foo{}, 0));
+ testing.expect(autoHash(g, 0) == autoHash(Errors.Test, 0));
+}