make use of hashing streaming interface in autoHash
Sahnvour
parent
8805a7b509
commit
5bf63bfbf1
142
std/hash_map.zig
142
std/hash_map.zig
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@ -522,8 +522,9 @@ 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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const h = autoHash(key, 0);
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return @truncate(u32, h);
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var hasher = Wyhash.init(0);
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autoHash(&hasher, key);
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return @truncate(u32, hasher.final());
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}
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}.hash;
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}
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@ -538,10 +539,7 @@ pub fn getAutoEqlFn(comptime K: type) (fn (K, K) bool) {
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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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pub fn autoHash(hasher: var, key: var) void {
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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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@ -557,91 +555,101 @@ pub fn autoHash(key: var, seed: u64) u64 {
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builtin.TypeId.EnumLiteral,
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=> @compileError("cannot hash this type"),
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builtin.TypeId.Int => return Wyhash.hash(seed, std.mem.asBytes(&key)),
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builtin.TypeId.Int => hasher.update(std.mem.asBytes(&key)),
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builtin.TypeId.Float => |info| return autoHash(@bitCast(@IntType(false, info.bits), key), seed),
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builtin.TypeId.Float => |info| autoHash(hasher, @bitCast(@IntType(false, info.bits), key)),
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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.Bool => autoHash(hasher, @boolToInt(key)),
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builtin.TypeId.Enum => autoHash(hasher, @enumToInt(key)),
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builtin.TypeId.ErrorSet => autoHash(hasher, @errorToInt(key)),
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builtin.TypeId.Promise, builtin.TypeId.Fn => autoHash(hasher, @ptrToInt(key)),
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builtin.TypeId.Pointer => |info| return switch (info.size) {
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builtin.TypeId.Pointer => |info| 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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=> autoHash(hasher, @ptrToInt(key)),
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builtin.TypeInfo.Pointer.Size.Slice => return autoHash(key.len, autoHash(key.ptr, seed)),
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builtin.TypeInfo.Pointer.Size.Slice => {
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autoHash(hasher, key.ptr);
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autoHash(hasher, key.len);
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},
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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.Optional => if (key) |k| autoHash(hasher, k),
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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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autoHash(hasher, element);
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}
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return s;
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},
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builtin.TypeId.Vector => |info| {
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if (info.child.bit_count % 8 == 0) {
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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.hash(seed, mem.asBytes(&key));
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}
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hasher.update(mem.asBytes(&key));
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} else {
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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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autoHash(hasher, array[i]);
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}
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}
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return s;
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},
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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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autoHash(hasher, @field(key, field.name));
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}
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return s;
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},
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builtin.TypeId.Union => |info| {
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builtin.TypeId.Union => |info| blk: {
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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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const s = autoHash(hasher, tag);
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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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autoHash(hasher, @field(key, enum_field.name));
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// TODO use a labelled break when it does not crash the compiler.
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// break :blk;
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return;
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}
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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.ErrorUnion => {
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return autoHash(key catch |err| return autoHash(err, seed), seed);
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builtin.TypeId.ErrorUnion => blk: {
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const payload = key catch |err| {
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autoHash(hasher, err);
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break :blk;
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};
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autoHash(hasher, payload);
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},
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}
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}
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fn testAutoHash(key: var) u64 {
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var hasher = Wyhash.init(0);
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autoHash(&hasher, key);
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return hasher.final();
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}
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test "autoHash slice" {
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// Allocate one array dynamically so that we're assured it is not merged
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// with the other by the optimization passes.
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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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@ -649,38 +657,46 @@ test "autoHash slice" {
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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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testing.expect(testAutoHash(a) == testAutoHash(a));
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testing.expect(testAutoHash(a) != testAutoHash(array1));
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testing.expect(testAutoHash(a) != testAutoHash(b));
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testing.expect(testAutoHash(a) != testAutoHash(c));
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}
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test "autoHash optional" {
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test "testAutoHash 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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testing.expectEqual(testAutoHash(a), testAutoHash(u32(123)));
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testing.expect(testAutoHash(a) != testAutoHash(b));
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testing.expectEqual(testAutoHash(b), 0);
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}
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test "autoHash array" {
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test "testAutoHash 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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const h = testAutoHash(a);
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var hasher = Wyhash.init(0);
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autoHash(&hasher, u32(1));
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autoHash(&hasher, u32(2));
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autoHash(&hasher, u32(3));
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testing.expectEqual(h, hasher.final());
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}
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test "autoHash struct" {
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test "testAutoHash 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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const h = testAutoHash(f);
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var hasher = Wyhash.init(0);
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autoHash(&hasher, u32(1));
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autoHash(&hasher, u32(2));
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autoHash(&hasher, u32(3));
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testing.expectEqual(h, hasher.final());
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}
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test "autoHash union" {
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test "testAutoHash 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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@ -690,24 +706,24 @@ test "autoHash union" {
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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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testing.expect(testAutoHash(a) == testAutoHash(a));
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testing.expect(testAutoHash(a) != testAutoHash(b));
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testing.expect(testAutoHash(a) != testAutoHash(c));
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b = Foo{ .A = 18 };
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testing.expect(autoHash(a, 0) == autoHash(b, 0));
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testing.expect(testAutoHash(a) == testAutoHash(b));
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}
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test "autoHash vector" {
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test "testAutoHash 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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testing.expect(testAutoHash(a) == testAutoHash(a));
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testing.expect(testAutoHash(a) != testAutoHash(b));
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testing.expect(testAutoHash(a) != testAutoHash(c));
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}
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test "autoHash error union" {
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test "testAutoHash 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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@ -716,7 +732,7 @@ test "autoHash error union" {
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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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testing.expect(testAutoHash(f) != testAutoHash(g));
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testing.expect(testAutoHash(f) == testAutoHash(Foo{}));
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testing.expect(testAutoHash(g) == testAutoHash(Errors.Test));
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}
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