Use Object.hash to hash raw bytes (#134)

Avoids decoding values during hashing just to re-encode them as bytes to hash, when stored as raw bytes. Ultimately this mostly just applies to Strings, but that is still impactful. We also avoid a lot of type checks, instead doing switches based on the known or encoded types.

For now I am just using Object.hash and Object.hashAll but we could explore alternatives later on as well, although it would mean passing a byte sink around.

This drops the total time for the large benchmark another 10% ish on my machine.

Author: jakemac53

pkgs/_macro_host/lib/src/macro_cache.dart

@@ -36,7 +36,7 @@ class MacroResultsCache {
           .skip(1)
           .fold(queryResults.first.response,
               (model, next) => model.mergeWith(next.response))
-          .identityHash,
+          .fingerprint,
       response: response
     );
   }
@@ -61,7 +61,7 @@ class MacroResultsCache {
         .skip(1)
         .fold(queryResults.first.model,
             (model, next) => model.mergeWith(next.model))
-        .identityHash;
+        .fingerprint;
     if (newResultsHash != cached.resultsHash) {
       _cache.remove(cacheKey);
       return null;

pkgs/dart_model/lib/src/dart_model.dart

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:collection/collection.dart';
-
 import 'dart_model.g.dart';
 import 'json_buffer/json_buffer_builder.dart';
 import 'lazy_merged_map.dart';
@@ -33,7 +31,12 @@ extension ModelExtension on Model {
   /// An identity hash for `this`, used for comparing query results.
   ///
   /// TODO: A faster/better implementation?
-  int get identityHash => const DeepCollectionEquality().hash(node);
+  int get fingerprint {
+    // TODO: Implementation for non-buffer maps?
+    var node = this.node as MapInBuffer;
+    return node.buffer.fingerprint(node.pointer,
+        type: Type.typedMapPointer, alreadyDereferenced: true);
+  }
 
   /// Looks up [name] in `this`.
   ///

pkgs/dart_model/lib/src/json_buffer/closed_list.dart

@@ -77,10 +77,19 @@ class _ClosedList with ListMixin<Object?> {
   set length(int length) {
     throw UnsupportedError('This JsonBufferBuilder list is read-only.');
   }
+
+  int get fingerprint {
+    var iterator = _ClosedListHashIterator(_buffer, _pointer, length);
+    var hash = 0;
+    while (iterator.moveNext()) {
+      hash = Object.hash(hash, iterator.current);
+    }
+    return hash;
+  }
 }
 
 /// `Iterator` that reads a "closed list" in a [JsonBufferBuilder].
-class _ClosedListIterator implements Iterator<Object?> {
+class _ClosedListIterator<T extends Object?> implements Iterator<T> {
   final JsonBufferBuilder _buffer;
   final _Pointer _last;
   _Pointer _pointer;
@@ -91,7 +100,7 @@ class _ClosedListIterator implements Iterator<Object?> {
         _pointer = pointer + _lengthSize - ClosedLists._valueSize;
 
   @override
-  Object? get current => _buffer._readAny(_pointer);
+  T get current => _buffer._readAny(_pointer) as T;
 
   @override
   bool moveNext() {
@@ -101,3 +110,10 @@ class _ClosedListIterator implements Iterator<Object?> {
     return _pointer != _last;
   }
 }
+
+class _ClosedListHashIterator extends _ClosedListIterator<int> {
+  _ClosedListHashIterator(super.buffer, super.pointer, super.length);
+
+  @override
+  int get current => _buffer.fingerprint(_pointer);
+}

pkgs/dart_model/lib/src/json_buffer/closed_map.dart

@@ -55,14 +55,15 @@ class _ClosedMap
     implements MapInBuffer {
   @override
   final JsonBufferBuilder buffer;
-  final _Pointer _pointer;
+  @override
+  final _Pointer pointer;
   @override
   final Map<String, Object?>? parent;
   @override
   final int length;
 
-  _ClosedMap(this.buffer, this._pointer, this.parent)
-      : length = buffer._readLength(_pointer);
+  _ClosedMap(this.buffer, this.pointer, this.parent)
+      : length = buffer._readLength(pointer);
 
   @override
   Object? operator [](Object? key) {
@@ -75,18 +76,18 @@ class _ClosedMap
 
   @override
   late final Iterable<String> keys = _IteratorFunctionIterable(
-      () => _ClosedMapKeyIterator(buffer, this, _pointer, length),
+      () => _ClosedMapKeyIterator(buffer, this, pointer, length),
       length: length);
 
   @override
   late final Iterable<Object?> values = _IteratorFunctionIterable(
-      () => _ClosedMapValueIterator(buffer, this, _pointer, length),
+      () => _ClosedMapValueIterator(buffer, this, pointer, length),
       length: length);
 
   @override
   late final Iterable<MapEntry<String, Object?>> entries =
       _IteratorFunctionIterable(
-          () => _ClosedMapEntryIterator(buffer, this, _pointer, length),
+          () => _ClosedMapEntryIterator(buffer, this, pointer, length),
           length: length);
 
   @override
@@ -109,18 +110,25 @@ class _ClosedMap
 
   @override
   bool operator ==(Object other) =>
-      other is _ClosedMap &&
-      other.buffer == buffer &&
-      other._pointer == _pointer;
+      other is _ClosedMap && other.buffer == buffer && other.pointer == pointer;
 
   @override
-  int get hashCode => Object.hash(buffer, _pointer);
+  int get hashCode => Object.hash(buffer, pointer);
+
+  int get fingerprint {
+    var iterator = _ClosedMapHashIterator(buffer, null, pointer, length);
+    var hash = 0;
+    while (iterator.moveNext()) {
+      hash = Object.hash(hash, iterator.current);
+    }
+    return hash;
+  }
 }
 
 /// `Iterator` that reads a "closed map" in a [JsonBufferBuilder].
 abstract class _ClosedMapIterator<T> implements Iterator<T> {
   final JsonBufferBuilder _buffer;
-  final _ClosedMap _parent;
+  final _ClosedMap? _parent;
   final _Pointer _last;
 
   _Pointer _pointer;
@@ -148,15 +156,15 @@ abstract class _ClosedMapIterator<T> implements Iterator<T> {
 
 class _ClosedMapKeyIterator extends _ClosedMapIterator<String> {
   _ClosedMapKeyIterator(
-      super._buffer, super._porent, super.pointer, super.length);
+      super._buffer, super._parent, super.pointer, super.length);
 
   @override
   String get current => _currentKey;
 }
 
 class _ClosedMapValueIterator extends _ClosedMapIterator<Object?> {
   _ClosedMapValueIterator(
-      super._buffer, super._porent, super.pointer, super.length);
+      super._buffer, super._parent, super.pointer, super.length);
 
   @override
   Object? get current => _currentValue;
@@ -165,8 +173,19 @@ class _ClosedMapValueIterator extends _ClosedMapIterator<Object?> {
 class _ClosedMapEntryIterator
     extends _ClosedMapIterator<MapEntry<String, Object?>> {
   _ClosedMapEntryIterator(
-      super._buffer, super._porent, super.pointer, super.length);
+      super._buffer, super._parent, super.pointer, super.length);
 
   @override
   MapEntry<String, Object?> get current => MapEntry(_currentKey, _currentValue);
 }
+
+class _ClosedMapHashIterator extends _ClosedMapIterator<int> {
+  _ClosedMapHashIterator(
+      super._buffer, super._parent, super.pointer, super.length);
+
+  @override
+  int get current => Object.hash(
+        _buffer._fingerprint(_pointer, Type.stringPointer),
+        _buffer.fingerprint(_pointer + ClosedMaps._keySize),
+      );
+}

pkgs/dart_model/lib/src/json_buffer/growable_map.dart

@@ -52,7 +52,7 @@ extension GrowableMaps on JsonBufferBuilder {
   /// [createGrowableMap]. Otherwise, [UnsupportedError] is thrown.
   _Pointer _pointerToGrowableMap(_GrowableMap<Object?> map) {
     _checkGrowableMapOwnership(map);
-    return map._pointer;
+    return map.pointer;
   }
 
   /// Throws if [map is backed by a different buffer to `this`.
@@ -75,14 +75,15 @@ class _GrowableMap<V>
     implements MapInBuffer {
   @override
   final JsonBufferBuilder buffer;
-  final _Pointer _pointer;
+  @override
+  final _Pointer pointer;
   @override
   final Map<String, Object?>? parent;
   int _length;
   _Pointer? _lastPointer;
 
-  _GrowableMap(this.buffer, this._pointer, this.parent)
-      : _length = buffer._readLength(_pointer + _pointerSize);
+  _GrowableMap(this.buffer, this.pointer, this.parent)
+      : _length = buffer._readLength(pointer + _pointerSize);
 
   @override
   int get length => _length;
@@ -100,17 +101,17 @@ class _GrowableMap<V>
 
   @override
   late final Iterable<String> keys = _IteratorFunctionIterable(
-      () => _GrowableMapKeyIterator(buffer, this, _pointer),
+      () => _GrowableMapKeyIterator(buffer, this, pointer),
       length: length);
 
   @override
   late final Iterable<V> values = _IteratorFunctionIterable(
-      () => _GrowableMapValueIterator<V>(buffer, this, _pointer),
+      () => _GrowableMapValueIterator<V>(buffer, this, pointer),
       length: length);
 
   @override
   late final Iterable<MapEntry<String, V>> entries = _IteratorFunctionIterable(
-      () => _GrowableMapEntryIterator(buffer, this, _pointer),
+      () => _GrowableMapEntryIterator(buffer, this, pointer),
       length: length);
 
   /// Add [value] to the map with key [key].
@@ -125,27 +126,27 @@ class _GrowableMap<V>
 
     // If `_lastPointer` is not set yet, walk the map to find the end of it.
     if (_lastPointer == null) {
-      final iterator = _GrowableMapEntryIterator<V>(buffer, this, _pointer);
-      _lastPointer = _pointer;
+      final iterator = _GrowableMapEntryIterator<V>(buffer, this, pointer);
+      _lastPointer = pointer;
       while (iterator.moveNext()) {
         _lastPointer = iterator._pointer;
       }
     }
 
     // Reserve and write the new node.
-    final pointer = buffer._reserve(GrowableMaps._entrySize);
-    final entryPointer = pointer + _pointerSize;
+    final newPointer = buffer._reserve(GrowableMaps._entrySize);
+    final entryPointer = newPointer + _pointerSize;
     buffer._writePointer(entryPointer, buffer._pointerToString(key));
     buffer._writeAny(entryPointer + _pointerSize, value);
 
     // Point to the new node in the previous node.
-    buffer._writePointer(_lastPointer!, pointer);
+    buffer._writePointer(_lastPointer!, newPointer);
     // Update `_lastPointer` to the new node.
-    _lastPointer = pointer;
+    _lastPointer = newPointer;
 
     // Update length.
     ++_length;
-    buffer._writeLength(_pointer + _pointerSize, length, allowOverwrite: true);
+    buffer._writeLength(pointer + _pointerSize, length, allowOverwrite: true);
     buffer._explanations?.pop();
   }
 
@@ -163,16 +164,25 @@ class _GrowableMap<V>
   bool operator ==(Object other) =>
       other is _GrowableMap &&
       other.buffer == buffer &&
-      other._pointer == _pointer;
+      other.pointer == pointer;
 
   @override
-  int get hashCode => Object.hash(buffer, _pointer);
+  int get hashCode => Object.hash(buffer, pointer);
+
+  int get fingerprint {
+    var iterator = _GrowableMapHashIterator(buffer, null, pointer);
+    var hash = 0;
+    while (iterator.moveNext()) {
+      hash = Object.hash(hash, iterator.current);
+    }
+    return hash;
+  }
 }
 
 /// `Iterator` that reads a "growable map" in a [JsonBufferBuilder].
 abstract class _GrowableMapIterator<T> implements Iterator<T> {
   final JsonBufferBuilder _buffer;
-  final _GrowableMap _parent;
+  final _GrowableMap? _parent;
   _Pointer _pointer;
 
   _GrowableMapIterator(this._buffer, this._parent, this._pointer);
@@ -214,3 +224,13 @@ class _GrowableMapEntryIterator<V>
   @override
   MapEntry<String, V> get current => MapEntry(_currentKey, _currentValue as V);
 }
+
+class _GrowableMapHashIterator extends _GrowableMapIterator<int> {
+  _GrowableMapHashIterator(super._buffer, super._parent, super._pointer);
+
+  @override
+  int get current => Object.hash(
+        _buffer._fingerprint(_pointer + _pointerSize, Type.stringPointer),
+        _buffer.fingerprint(_pointer + _pointerSize + GrowableMaps._keySize),
+      );
+}

pkgs/dart_model/lib/src/json_buffer/iterables.dart

@@ -48,4 +48,7 @@ abstract interface class MapInBuffer {
   /// The `Map` that contains this value, or `null` if this value has not been
   /// added to a `Map` or is itself the root `Map`.
   Map<String, Object?>? get parent;
+
+  /// A pointer to the start of this object in [buffer].
+  int get pointer;
 }

pkgs/dart_model/lib/src/json_buffer/json_buffer_builder.dart

@@ -52,6 +52,67 @@ class JsonBufferBuilder {
     map = createGrowableMap<Object?>();
   }
 
+  /// Computes the identity hash of the object at [pointer] from its raw bytes.
+  ///
+  /// Any nested pointers use the hash of the values they point to.
+  ///
+  /// If [type] is provided, [pointer] should point directly at the object.
+  /// Otherwise a [Type] will be read first, followed by the value.
+  ///
+  /// If [alreadyDereferenced] is `true`, then for types which are pointers,
+  /// [pointer] already points at the top of the object, and should not be
+  /// followed before reading the object.
+  int fingerprint(int pointer, {Type? type, bool alreadyDereferenced = false}) {
+    if (type == null) {
+      type = _readType(pointer);
+      pointer += _typeSize;
+    }
+    return _fingerprint(pointer, type,
+        alreadyDereferenced: alreadyDereferenced);
+  }
+
+  /// Computes the identity hash of the object at [pointer] with a known [type]
+  /// from its raw bytes.
+  ///
+  /// If [alreadyDereferenced] is `true`, then for types which are pointers,
+  /// [pointer] already points at the top of the object, and should not be
+  /// followed before reading the object.
+  int _fingerprint(_Pointer pointer, Type type,
+      {bool alreadyDereferenced = false}) {
+    // Dereference [pointer] if it is a pointer type, and hasn't already been
+    // dereferenced.
+    if (type.isPointer && !alreadyDereferenced) {
+      pointer = _readPointer(pointer);
+    }
+
+    switch (type) {
+      case Type.nil:
+        return null.hashCode;
+      case Type.type:
+        return _buffer[pointer];
+      case Type.pointer:
+        return fingerprint(pointer);
+      case Type.uint32:
+        return _readUint32(pointer);
+      case Type.boolean:
+        return _buffer[pointer];
+      case Type.anyPointer:
+        return fingerprint(pointer);
+      case Type.stringPointer:
+        final length = _readLength(pointer);
+        pointer += _lengthSize;
+        return Object.hashAll(_buffer.sublist(pointer, pointer + length));
+      case Type.closedListPointer:
+        return _ClosedList(this, pointer).fingerprint;
+      case Type.closedMapPointer:
+        return _ClosedMap(this, pointer, null).fingerprint;
+      case Type.growableMapPointer:
+        return _GrowableMap<Object?>(this, pointer, null).fingerprint;
+      case Type.typedMapPointer:
+        return _TypedMap(this, pointer, null).fingerprint;
+    }
+  }
+
   /// The JSON data.
   ///
   /// The buffer is _not_ copied, unpredictable behavior will result if it is