self-hosted: watch files and trigger a rebuild

std/hash_map.zig

@@ -9,6 +9,10 @@ const builtin = @import("builtin");
 const want_modification_safety = builtin.mode != builtin.Mode.ReleaseFast;
 const debug_u32 = if (want_modification_safety) u32 else void;
 
+pub fn AutoHashMap(comptime K: type, comptime V: type) type {
+    return HashMap(K, V, getAutoHashFn(K), getAutoEqlFn(K));
+}
+
 pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u32, comptime eql: fn (a: K, b: K) bool) type {
     return struct {
         entries: []Entry,
@@ -20,13 +24,22 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
 
         const Self = this;
 
-        pub const Entry = struct {
-            used: bool,
-            distance_from_start_index: usize,
+        pub const KV = struct {
             key: K,
             value: V,
         };
 
+        const Entry = struct {
+            used: bool,
+            distance_from_start_index: usize,
+            kv: KV,
+        };
+
+        pub const GetOrPutResult = struct {
+            kv: *KV,
+            found_existing: bool,
+        };
+
         pub const Iterator = struct {
             hm: *const Self,
             // how many items have we returned
@@ -36,7 +49,7 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
             // used to detect concurrent modification
             initial_modification_count: debug_u32,
 
-            pub fn next(it: *Iterator) ?*Entry {
+            pub fn next(it: *Iterator) ?*KV {
                 if (want_modification_safety) {
                     assert(it.initial_modification_count == it.hm.modification_count); // concurrent modification
                 }
@@ -46,7 +59,7 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
                     if (entry.used) {
                         it.index += 1;
                         it.count += 1;
-                        return entry;
+                        return &entry.kv;
                     }
                 }
                 unreachable; // no next item
@@ -71,7 +84,7 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
             };
         }
 
-        pub fn deinit(hm: *const Self) void {
+        pub fn deinit(hm: Self) void {
             hm.allocator.free(hm.entries);
         }
 
@@ -84,34 +97,65 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
             hm.incrementModificationCount();
         }
 
-        pub fn count(hm: *const Self) usize {
-            return hm.size;
+        pub fn count(self: Self) usize {
+            return self.size;
         }
 
-        /// Returns the value that was already there.
-        pub fn put(hm: *Self, key: K, value: *const V) !?V {
-            if (hm.entries.len == 0) {
-                try hm.initCapacity(16);
+        /// If key exists this function cannot fail.
+        /// If there is an existing item with `key`, then the result
+        /// kv pointer points to it, and found_existing is true.
+        /// Otherwise, puts a new item with undefined value, and
+        /// the kv pointer points to it. Caller should then initialize
+        /// the data.
+        pub fn getOrPut(self: *Self, key: K) !GetOrPutResult {
+            // TODO this implementation can be improved - we should only
+            // have to hash once and find the entry once.
+            if (self.get(key)) |kv| {
+                return GetOrPutResult{
+                    .kv = kv,
+                    .found_existing = true,
+                };
+            }
+            self.incrementModificationCount();
+            try self.ensureCapacity();
+            const put_result = self.internalPut(key);
+            assert(put_result.old_kv == null);
+            return GetOrPutResult{
+                .kv = &put_result.new_entry.kv,
+                .found_existing = false,
+            };
+        }
+
+        fn ensureCapacity(self: *Self) !void {
+            if (self.entries.len == 0) {
+                return self.initCapacity(16);
             }
-            hm.incrementModificationCount();
 
             // if we get too full (60%), double the capacity
-            if (hm.size * 5 >= hm.entries.len * 3) {
-                const old_entries = hm.entries;
-                try hm.initCapacity(hm.entries.len * 2);
+            if (self.size * 5 >= self.entries.len * 3) {
+                const old_entries = self.entries;
+                try self.initCapacity(self.entries.len * 2);
                 // dump all of the old elements into the new table
                 for (old_entries) |*old_entry| {
                     if (old_entry.used) {
-                        _ = hm.internalPut(old_entry.key, old_entry.value);
+                        self.internalPut(old_entry.kv.key).new_entry.kv.value = old_entry.kv.value;
                     }
                 }
-                hm.allocator.free(old_entries);
+                self.allocator.free(old_entries);
             }
-
-            return hm.internalPut(key, value);
         }
 
-        pub fn get(hm: *const Self, key: K) ?*Entry {
+        /// Returns the kv pair that was already there.
+        pub fn put(self: *Self, key: K, value: V) !?KV {
+            self.incrementModificationCount();
+            try self.ensureCapacity();
+
+            const put_result = self.internalPut(key);
+            put_result.new_entry.kv.value = value;
+            return put_result.old_kv;
+        }
+
+        pub fn get(hm: *const Self, key: K) ?*KV {
             if (hm.entries.len == 0) {
                 return null;
             }
@@ -122,7 +166,7 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
             return hm.get(key) != null;
         }
 
-        pub fn remove(hm: *Self, key: K) ?*Entry {
+        pub fn remove(hm: *Self, key: K) ?*KV {
             if (hm.entries.len == 0) return null;
             hm.incrementModificationCount();
             const start_index = hm.keyToIndex(key);
@@ -134,7 +178,7 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
 
                     if (!entry.used) return null;
 
-                    if (!eql(entry.key, key)) continue;
+                    if (!eql(entry.kv.key, key)) continue;
 
                     while (roll_over < hm.entries.len) : (roll_over += 1) {
                         const next_index = (start_index + roll_over + 1) % hm.entries.len;
@@ -142,7 +186,7 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
                         if (!next_entry.used or next_entry.distance_from_start_index == 0) {
                             entry.used = false;
                             hm.size -= 1;
-                            return entry;
+                            return &entry.kv;
                         }
                         entry.* = next_entry.*;
                         entry.distance_from_start_index -= 1;
@@ -168,7 +212,7 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
             try other.initCapacity(self.entries.len);
             var it = self.iterator();
             while (it.next()) |entry| {
-                try other.put(entry.key, entry.value);
+                assert((try other.put(entry.key, entry.value)) == null);
             }
             return other;
         }
@@ -188,60 +232,81 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
             }
         }
 
-        /// Returns the value that was already there.
-        fn internalPut(hm: *Self, orig_key: K, orig_value: *const V) ?V {
+        const InternalPutResult = struct {
+            new_entry: *Entry,
+            old_kv: ?KV,
+        };
+
+        /// Returns a pointer to the new entry.
+        /// Asserts that there is enough space for the new item.
+        fn internalPut(self: *Self, orig_key: K) InternalPutResult {
             var key = orig_key;
-            var value = orig_value.*;
-            const start_index = hm.keyToIndex(key);
+            var value: V = undefined;
+            const start_index = self.keyToIndex(key);
             var roll_over: usize = 0;
             var distance_from_start_index: usize = 0;
-            while (roll_over < hm.entries.len) : ({
+            var got_result_entry = false;
+            var result = InternalPutResult{
+                .new_entry = undefined,
+                .old_kv = null,
+            };
+            while (roll_over < self.entries.len) : ({
                 roll_over += 1;
                 distance_from_start_index += 1;
             }) {
-                const index = (start_index + roll_over) % hm.entries.len;
-                const entry = &hm.entries[index];
+                const index = (start_index + roll_over) % self.entries.len;
+                const entry = &self.entries[index];
 
-                if (entry.used and !eql(entry.key, key)) {
+                if (entry.used and !eql(entry.kv.key, key)) {
                     if (entry.distance_from_start_index < distance_from_start_index) {
                         // robin hood to the rescue
                         const tmp = entry.*;
-                        hm.max_distance_from_start_index = math.max(hm.max_distance_from_start_index, distance_from_start_index);
+                        self.max_distance_from_start_index = math.max(self.max_distance_from_start_index, distance_from_start_index);
+                        if (!got_result_entry) {
+                            got_result_entry = true;
+                            result.new_entry = entry;
+                        }
                         entry.* = Entry{
                             .used = true,
                             .distance_from_start_index = distance_from_start_index,
-                            .key = key,
-                            .value = value,
+                            .kv = KV{
+                                .key = key,
+                                .value = value,
+                            },
                         };
-                        key = tmp.key;
-                        value = tmp.value;
+                        key = tmp.kv.key;
+                        value = tmp.kv.value;
                         distance_from_start_index = tmp.distance_from_start_index;
                     }
                     continue;
                 }
 
-                var result: ?V = null;
                 if (entry.used) {
-                    result = entry.value;
+                    result.old_kv = entry.kv;
                 } else {
                     // adding an entry. otherwise overwriting old value with
                     // same key
-                    hm.size += 1;
+                    self.size += 1;
                 }
 
-                hm.max_distance_from_start_index = math.max(distance_from_start_index, hm.max_distance_from_start_index);
+                self.max_distance_from_start_index = math.max(distance_from_start_index, self.max_distance_from_start_index);
+                if (!got_result_entry) {
+                    result.new_entry = entry;
+                }
                 entry.* = Entry{
                     .used = true,
                     .distance_from_start_index = distance_from_start_index,
-                    .key = key,
-                    .value = value,
+                    .kv = KV{
+                        .key = key,
+                        .value = value,
+                    },
                 };
                 return result;
             }
             unreachable; // put into a full map
         }
 
-        fn internalGet(hm: *const Self, key: K) ?*Entry {
+        fn internalGet(hm: Self, key: K) ?*KV {
             const start_index = hm.keyToIndex(key);
             {
                 var roll_over: usize = 0;
@@ -250,13 +315,13 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
                     const entry = &hm.entries[index];
 
                     if (!entry.used) return null;
-                    if (eql(entry.key, key)) return entry;
+                    if (eql(entry.kv.key, key)) return &entry.kv;
                 }
             }
             return null;
         }
 
-        fn keyToIndex(hm: *const Self, key: K) usize {
+        fn keyToIndex(hm: Self, key: K) usize {
             return usize(hash(key)) % hm.entries.len;
         }
     };
@@ -266,7 +331,7 @@ test "basic hash map usage" {
     var direct_allocator = std.heap.DirectAllocator.init();
     defer direct_allocator.deinit();
 
-    var map = HashMap(i32, i32, hash_i32, eql_i32).init(&direct_allocator.allocator);
+    var map = AutoHashMap(i32, i32).init(&direct_allocator.allocator);
     defer map.deinit();
 
     assert((try map.put(1, 11)) == null);
@@ -275,8 +340,19 @@ test "basic hash map usage" {
     assert((try map.put(4, 44)) == null);
     assert((try map.put(5, 55)) == null);
 
-    assert((try map.put(5, 66)).? == 55);
-    assert((try map.put(5, 55)).? == 66);
+    assert((try map.put(5, 66)).?.value == 55);
+    assert((try map.put(5, 55)).?.value == 66);
+
+    const gop1 = try map.getOrPut(5);
+    assert(gop1.found_existing == true);
+    assert(gop1.kv.value == 55);
+    gop1.kv.value = 77;
+    assert(map.get(5).?.value == 77);
+
+    const gop2 = try map.getOrPut(99);
+    assert(gop2.found_existing == false);
+    gop2.kv.value = 42;
+    assert(map.get(99).?.value == 42);
 
     assert(map.contains(2));
     assert(map.get(2).?.value == 22);
@@ -289,7 +365,7 @@ test "iterator hash map" {
     var direct_allocator = std.heap.DirectAllocator.init();
     defer direct_allocator.deinit();
 
-    var reset_map = HashMap(i32, i32, hash_i32, eql_i32).init(&direct_allocator.allocator);
+    var reset_map = AutoHashMap(i32, i32).init(&direct_allocator.allocator);
     defer reset_map.deinit();
 
     assert((try reset_map.put(1, 11)) == null);
@@ -332,10 +408,124 @@ test "iterator hash map" {
     assert(entry.value == values[0]);
 }
 
-fn hash_i32(x: i32) u32 {
-    return @bitCast(u32, x);
+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);
+        }
+    }.hash;
 }
 
-fn eql_i32(a: i32, b: i32) bool {
-    return a == b;
+pub fn getAutoEqlFn(comptime K: type) (fn (K, K) bool) {
+    return struct {
+        fn eql(a: K, b: K) bool {
+            return autoEql(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))) {
+        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);
+        },
+        builtin.TypeId.Bool => return autoHash(@boolToInt(key), rng),
+        builtin.TypeId.Enum => return autoHash(@enumToInt(key), rng),
+        builtin.TypeId.ErrorSet => return autoHash(@errorToInt(key), rng),
+        builtin.TypeId.Promise, builtin.TypeId.Fn => return autoHash(@ptrToInt(key), rng),
+
+        builtin.TypeId.Namespace,
+        builtin.TypeId.Block,
+        builtin.TypeId.BoundFn,
+        builtin.TypeId.ComptimeFloat,
+        builtin.TypeId.ComptimeInt,
+        builtin.TypeId.Type,
+        => 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.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;
+            },
+        },
+
+        builtin.TypeId.Optional => @compileError("TODO auto hash for optionals"),
+        builtin.TypeId.Array => @compileError("TODO auto hash for arrays"),
+        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"),
+    }
+}
+
+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.Namespace,
+        builtin.TypeId.Block,
+        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.Slice => {
+                if (a.len != b.len) return false;
+                for (a) |a_item, i| {
+                    if (!autoEql(a_item, b[i])) return false;
+                }
+                return true;
+            },
+        },
+
+        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"),
+    }
 }