use wyhash in std's hashmap, and improve autoHash to handle more types and behave more correctly
Sahnvour
parent
6150da3df9
commit
5bd407b278
264
std/hash_map.zig
264
std/hash_map.zig
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@ -4,6 +4,8 @@ const assert = debug.assert;
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const testing = std.testing;
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const math = std.math;
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const mem = std.mem;
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const meta = std.meta;
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const wyhash = std.hash.wyhash;
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const Allocator = mem.Allocator;
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const builtin = @import("builtin");
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@ -448,15 +450,17 @@ test "iterator hash map" {
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try reset_map.putNoClobber(2, 22);
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try reset_map.putNoClobber(3, 33);
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// TODO this test depends on the hashing algorithm, because it assumes the
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// order of the elements in the hashmap. This should not be the case.
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var keys = [_]i32{
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1,
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3,
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2,
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1,
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};
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var values = [_]i32{
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11,
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33,
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22,
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11,
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};
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var it = reset_map.iterator();
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@ -518,8 +522,8 @@ pub fn getTrivialEqlFn(comptime K: type) (fn (K, K) bool) {
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pub fn getAutoHashFn(comptime K: type) (fn (K) u32) {
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return struct {
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fn hash(key: K) u32 {
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comptime var rng = comptime std.rand.DefaultPrng.init(0);
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return autoHash(key, &rng.random, u32);
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const h = autoHash(key, 0);
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return @truncate(u32, h);
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}
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}.hash;
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}
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@ -527,114 +531,192 @@ pub fn getAutoHashFn(comptime K: type) (fn (K) u32) {
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pub fn getAutoEqlFn(comptime K: type) (fn (K, K) bool) {
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return struct {
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fn eql(a: K, b: K) bool {
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return autoEql(a, b);
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return meta.eql(a, b);
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}
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}.eql;
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}
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// TODO improve these hash functions
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pub fn autoHash(key: var, comptime rng: *std.rand.Random, comptime HashInt: type) HashInt {
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switch (@typeInfo(@typeOf(key))) {
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/// Provides generic hashing for any eligible type.
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/// Only hashes `key` itself, pointers are not followed.
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/// The underlying hashing algorithm is wyhash.
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pub fn autoHash(key: var, seed: u64) u64 {
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// We use the fact that wyhash takes an input seed to "chain" hasing when the
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// key has multiple parts that are not necessarily contiguous in memory.
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const Key = @typeOf(key);
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switch (@typeInfo(Key)) {
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builtin.TypeId.NoReturn,
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builtin.TypeId.Opaque,
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builtin.TypeId.Undefined,
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builtin.TypeId.ArgTuple,
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builtin.TypeId.Void,
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builtin.TypeId.Null,
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builtin.TypeId.BoundFn,
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builtin.TypeId.ComptimeFloat,
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builtin.TypeId.ComptimeInt,
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builtin.TypeId.Type,
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builtin.TypeId.EnumLiteral,
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=> @compileError("cannot hash this type"),
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builtin.TypeId.Void,
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builtin.TypeId.Null,
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=> return 0,
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builtin.TypeId.Int => return wyhash(std.mem.asBytes(&key), seed),
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builtin.TypeId.Int => |info| {
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const unsigned_x = @bitCast(@IntType(false, info.bits), key);
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if (info.bits <= HashInt.bit_count) {
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return HashInt(unsigned_x) ^ comptime rng.scalar(HashInt);
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} else {
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return @truncate(HashInt, unsigned_x ^ comptime rng.scalar(@typeOf(unsigned_x)));
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builtin.TypeId.Float => |info| return autoHash(@bitCast(@IntType(false, info.bits), key), seed),
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builtin.TypeId.Bool => return autoHash(@boolToInt(key), seed),
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builtin.TypeId.Enum => return autoHash(@enumToInt(key), seed),
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builtin.TypeId.ErrorSet => return autoHash(@errorToInt(key), seed),
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builtin.TypeId.Promise, builtin.TypeId.Fn => return autoHash(@ptrToInt(key), seed),
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builtin.TypeId.Pointer => |info| return switch (info.size) {
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builtin.TypeInfo.Pointer.Size.One,
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builtin.TypeInfo.Pointer.Size.Many,
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builtin.TypeInfo.Pointer.Size.C,
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=> return autoHash(@ptrToInt(key), seed),
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builtin.TypeInfo.Pointer.Size.Slice => return autoHash(key.len, autoHash(key.ptr, seed)),
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},
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builtin.TypeId.Optional => return if (key) |k| autoHash(k, seed) else 0,
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builtin.TypeId.Array => {
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// TODO detect via a trait when Key has no padding bits to
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// hash it as an array of bytes.
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// Otherwise, hash every element.
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var s = seed;
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for (key) |element| {
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// We reuse the hash of the previous element as the seed for the
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// next one so that they're dependant.
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s = autoHash(element, s);
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}
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return s;
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},
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builtin.TypeId.Float => |info| {
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return autoHash(@bitCast(@IntType(false, info.bits), key), rng, HashInt);
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builtin.TypeId.Vector => |info| {
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// If there's no unused bits in the child type, we can just hash
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// this as an array of bytes.
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if (info.child.bit_count % 8 == 0) {
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return wyhash(mem.asBytes(&key), seed);
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}
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// Otherwise, hash every element.
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var s = seed;
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// TODO remove the copy to an array once field access is done.
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const array: [info.len]info.child = key;
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comptime var i: u32 = 0;
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inline while (i < info.len) : (i += 1) {
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s = autoHash(array[i], s);
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}
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return s;
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},
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builtin.TypeId.Bool => return autoHash(@boolToInt(key), rng, HashInt),
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builtin.TypeId.Enum => return autoHash(@enumToInt(key), rng, HashInt),
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builtin.TypeId.ErrorSet => return autoHash(@errorToInt(key), rng, HashInt),
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builtin.TypeId.Promise, builtin.TypeId.Fn => return autoHash(@ptrToInt(key), rng, HashInt),
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builtin.TypeId.BoundFn,
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builtin.TypeId.ComptimeFloat,
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builtin.TypeId.ComptimeInt,
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builtin.TypeId.Type,
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builtin.TypeId.EnumLiteral,
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=> return 0,
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builtin.TypeId.Struct => |info| {
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// TODO detect via a trait when Key has no padding bits to
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// hash it as an array of bytes.
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// Otherwise, hash every field.
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var s = seed;
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inline for (info.fields) |field| {
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// We reuse the hash of the previous field as the seed for the
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// next one so that they're dependant.
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s = autoHash(@field(key, field.name), s);
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}
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return s;
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},
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builtin.TypeId.Pointer => |info| switch (info.size) {
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builtin.TypeInfo.Pointer.Size.One => @compileError("TODO auto hash for single item pointers"),
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builtin.TypeInfo.Pointer.Size.Many => @compileError("TODO auto hash for many item pointers"),
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builtin.TypeInfo.Pointer.Size.C => @compileError("TODO auto hash C pointers"),
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builtin.TypeInfo.Pointer.Size.Slice => {
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const interval = std.math.max(1, key.len / 256);
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var i: usize = 0;
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var h = comptime rng.scalar(HashInt);
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while (i < key.len) : (i += interval) {
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h ^= autoHash(key[i], rng, HashInt);
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builtin.TypeId.Union => |info| {
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if (info.tag_type) |tag_type| {
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const tag = meta.activeTag(key);
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const s = autoHash(tag, seed);
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inline for (info.fields) |field| {
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const enum_field = field.enum_field.?;
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if (enum_field.value == @enumToInt(tag)) {
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return autoHash(@field(key, enum_field.name), s);
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}
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}
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return h;
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},
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unreachable;
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} else @compileError("cannot hash untagged union type: " ++ @typeName(Key) ++ ", provide your own hash function");
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},
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builtin.TypeId.Optional => @compileError("TODO auto hash for optionals"),
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builtin.TypeId.Array => @compileError("TODO auto hash for arrays"),
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builtin.TypeId.Vector => @compileError("TODO auto hash for vectors"),
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builtin.TypeId.Struct => @compileError("TODO auto hash for structs"),
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builtin.TypeId.Union => @compileError("TODO auto hash for unions"),
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builtin.TypeId.ErrorUnion => @compileError("TODO auto hash for unions"),
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builtin.TypeId.ErrorUnion => {
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return autoHash(key catch |err| return autoHash(err, seed), seed);
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},
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}
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}
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pub fn autoEql(a: var, b: @typeOf(a)) bool {
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switch (@typeInfo(@typeOf(a))) {
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builtin.TypeId.NoReturn,
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builtin.TypeId.Opaque,
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builtin.TypeId.Undefined,
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builtin.TypeId.ArgTuple,
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=> @compileError("cannot test equality of this type"),
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builtin.TypeId.Void,
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builtin.TypeId.Null,
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=> return true,
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builtin.TypeId.Bool,
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builtin.TypeId.Int,
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builtin.TypeId.Float,
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builtin.TypeId.ComptimeFloat,
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builtin.TypeId.ComptimeInt,
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builtin.TypeId.EnumLiteral,
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builtin.TypeId.Promise,
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builtin.TypeId.Enum,
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builtin.TypeId.BoundFn,
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builtin.TypeId.Fn,
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builtin.TypeId.ErrorSet,
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builtin.TypeId.Type,
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=> return a == b,
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builtin.TypeId.Pointer => |info| switch (info.size) {
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builtin.TypeInfo.Pointer.Size.One => @compileError("TODO auto eql for single item pointers"),
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builtin.TypeInfo.Pointer.Size.Many => @compileError("TODO auto eql for many item pointers"),
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builtin.TypeInfo.Pointer.Size.C => @compileError("TODO auto eql for C pointers"),
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builtin.TypeInfo.Pointer.Size.Slice => {
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if (a.len != b.len) return false;
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for (a) |a_item, i| {
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if (!autoEql(a_item, b[i])) return false;
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}
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return true;
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},
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},
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builtin.TypeId.Optional => @compileError("TODO auto eql for optionals"),
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builtin.TypeId.Array => @compileError("TODO auto eql for arrays"),
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builtin.TypeId.Struct => @compileError("TODO auto eql for structs"),
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builtin.TypeId.Union => @compileError("TODO auto eql for unions"),
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builtin.TypeId.ErrorUnion => @compileError("TODO auto eql for unions"),
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builtin.TypeId.Vector => @compileError("TODO auto eql for vectors"),
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}
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test "autoHash slice" {
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const array1 = try std.heap.direct_allocator.create([6]u32);
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defer std.heap.direct_allocator.destroy(array1);
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array1.* = [_]u32{ 1, 2, 3, 4, 5, 6 };
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const array2 = [_]u32{ 1, 2, 3, 4, 5, 6 };
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const a = array1[0..];
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const b = array2[0..];
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const c = array1[0..3];
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testing.expect(autoHash(a, 0) == autoHash(a, 0));
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testing.expect(autoHash(a, 0) != autoHash(array1, 0));
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testing.expect(autoHash(a, 0) != autoHash(b, 0));
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testing.expect(autoHash(a, 0) != autoHash(c, 0));
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}
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test "autoHash optional" {
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const a: ?u32 = 123;
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const b: ?u32 = null;
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testing.expectEqual(autoHash(a, 0), autoHash(u32(123), 0));
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testing.expect(autoHash(a, 0) != autoHash(b, 0));
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testing.expectEqual(autoHash(b, 0), 0);
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}
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test "autoHash array" {
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const a = [_]u32{ 1, 2, 3 };
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const h = autoHash(a, 0);
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testing.expectEqual(h, autoHash(u32(3), autoHash(u32(2), autoHash(u32(1), 0))));
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}
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test "autoHash struct" {
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const Foo = struct {
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a: u32 = 1,
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b: u32 = 2,
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c: u32 = 3,
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};
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const f = Foo{};
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const h = autoHash(f, 0);
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testing.expectEqual(h, autoHash(u32(3), autoHash(u32(2), autoHash(u32(1), 0))));
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}
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test "autoHash union" {
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const Foo = union(enum) {
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A: u32,
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B: f32,
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C: u32,
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};
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const a = Foo{ .A = 18 };
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var b = Foo{ .B = 12.34 };
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const c = Foo{ .C = 18 };
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testing.expect(autoHash(a, 0) == autoHash(a, 0));
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testing.expect(autoHash(a, 0) != autoHash(b, 0));
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testing.expect(autoHash(a, 0) != autoHash(c, 0));
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b = Foo{ .A = 18 };
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testing.expect(autoHash(a, 0) == autoHash(b, 0));
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}
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test "autoHash vector" {
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const a: @Vector(4, u32) = [_]u32{ 1, 2, 3, 4 };
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const b: @Vector(4, u32) = [_]u32{ 1, 2, 3, 5 };
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const c: @Vector(4, u31) = [_]u31{ 1, 2, 3, 4 };
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testing.expect(autoHash(a, 0) == autoHash(a, 0));
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testing.expect(autoHash(a, 0) != autoHash(b, 0));
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testing.expect(autoHash(a, 0) != autoHash(c, 0));
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}
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test "autoHash error union" {
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const Errors = error{Test};
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const Foo = struct {
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a: u32 = 1,
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b: u32 = 2,
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c: u32 = 3,
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};
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const f = Foo{};
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const g: Errors!Foo = Errors.Test;
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testing.expect(autoHash(f, 0) != autoHash(g, 0));
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testing.expect(autoHash(f, 0) == autoHash(Foo{}, 0));
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testing.expect(autoHash(g, 0) == autoHash(Errors.Test, 0));
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}
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