Add benchmark for hashing. Improve hashing performance.

Author: davidmorgan

CHANGELOG.md

@@ -6,6 +6,7 @@
 - Generate empty constructor with semicolon instead of {}.
 - Use ArgumentError.notNull for null errors.
 - Reject dynamic fields.
+- Add simple benchmark for hashing. Improve hashing performance.
 
 ## 0.1.5
 

built_value/lib/built_value.dart

@@ -4,8 +4,6 @@
 
 library built_value;
 
-export 'package:quiver/core.dart' show hashObjects;
-
 /// Implement this for a Built Value.
 ///
 /// Then use built_value_generator.dart code generation functionality to
@@ -59,3 +57,19 @@ abstract class Builder<V extends Built<V, B>, B extends Builder<V, B>> {
 //
 // Fields marked with this annotation are allowed to be null.
 const String nullable = 'nullable';
+
+/// For use by generated code in calculating hash codes. Do not use directly.
+int $jc(int hash, int value) {
+  // Jenkins hash "combine".
+  hash = 0x1fffffff & (hash + value);
+  hash = 0x1fffffff & (hash + ((0x0007ffff & hash) << 10));
+  return hash ^ (hash >> 6);
+}
+
+/// For use by generated code in calculating hash codes. Do not use directly.
+int $jf(int hash) {
+  // Jenkins hash "finish".
+  hash = 0x1fffffff & (hash + ((0x03ffffff & hash) << 3));
+  hash = hash ^ (hash >> 11);
+  return 0x1fffffff & (hash + ((0x00003fff & hash) << 15));
+}

built_value/pubspec.yaml

@@ -8,6 +8,3 @@ homepage: https://github.com/google/built_value.dart
 
 environment:
   sdk: '>=1.8.0 <2.0.0'
-
-dependencies:
-  quiver: '>=0.21.0 <0.24.0'

built_value_generator/lib/src/source_class.dart

@@ -259,9 +259,11 @@ abstract class SourceClass implements Built<SourceClass, SourceClassBuilder> {
     if (fields.length == 0) {
       result.writeln('return ${name.hashCode};');
     } else {
-      result.writeln('return hashObjects([');
-      result.write(fields.map((field) => field.name).join(', '));
-      result.writeln(']);');
+      result.writeln(r'return $jf(');
+      result.writeln(r'$jc(' * fields.length);
+      result.writeln('0, ');
+      result.write(fields.map((field) => '${field.name}.hashCode').join('), '));
+      result.writeln('));');
     }
     result.writeln('}');
     result.writeln();