lib/src/protobuf/field_set.dart - protobuf - Git at Google

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // 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.

 part of protobuf;

 typedef void FrozenMessageErrorHandler(String messageName, [String methodName]);

 void defaultFrozenMessageModificationHandler(String messageName,
     [String methodName]) {
   if (methodName != null) {
     throw new UnsupportedError(
         "Attempted to call $methodName on a read-only message ($messageName)");
   }
   throw new UnsupportedError(
       "Attempted to change a read-only message ($messageName)");
 }

 /// Invoked when an attempt is made to modify a frozen message.
 ///
 /// This handler can log the attempt, throw an exception, or ignore the attempt
 /// altogether.
 ///
 /// If the handler returns normally, the modification is allowed, and execution
 /// proceeds as if the message was writable.
 FrozenMessageErrorHandler frozenMessageModificationHandler =
     defaultFrozenMessageModificationHandler;

 /// All the data in a GeneratedMessage.
 ///
 /// These fields and methods are in a separate class to avoid
 /// polymorphic access due to inheritance. This turns out to
 /// be faster when compiled to JavaScript.
 class _FieldSet {
   final GeneratedMessage _message;
   final BuilderInfo _meta;
   final EventPlugin _eventPlugin;
   bool _isReadOnly = false;

   /// The value of each non-extension field in a fixed-length array.
   /// The index of a field can be found in [FieldInfo.index].
   /// A null entry indicates that the field has no value.
   final List _values;

   /// Contains all the extension fields, or null if there aren't any.
   _ExtensionFieldSet _extensions;

   /// Contains all the unknown fields, or null if there aren't any.
   UnknownFieldSet _unknownFields;

   _FieldSet(this._message, BuilderInfo meta, this._eventPlugin)
       : this._meta = meta,
         _values = _makeValueList(meta.byIndex.length);

   static _makeValueList(int length) {
     if (length == 0) return _zeroList;
     return new List(length);
   }

   // Use a fixed length list and not a constant list to ensure that _values
   // always has the same implementation type.
   static List _zeroList = new List(0);

   // Metadata about multiple fields

   String get _messageName => _meta.messageName;
   bool get _hasRequiredFields => _meta.hasRequiredFields;

   /// The FieldInfo for each non-extension field.
   Iterable<FieldInfo> get _infos => _meta.fieldInfo.values;

   /// The FieldInfo for each non-extension field in tag order.
   Iterable<FieldInfo> get _infosSortedByTag => _meta.sortedByTag;

   /// Returns true if we should send events to the plugin.
   bool get _hasObservers => _eventPlugin != null && _eventPlugin.hasObservers;

   bool get _hasExtensions => _extensions != null;
   bool get hasUnknownFields => _unknownFields != null;

   _ExtensionFieldSet _ensureExtensions() {
     assert(!_isReadOnly);
     if (!_hasExtensions) _extensions = new _ExtensionFieldSet(this);
     return _extensions;
   }

   UnknownFieldSet _ensureUnknownFields() {
     if (_isReadOnly) return _ReadonlyUnknownFieldSet._empty;
     if (_unknownFields == null) _unknownFields = new UnknownFieldSet();
     return _unknownFields;
   }

   // Metadata about single fields

   /// Returns FieldInfo for a non-extension field, or null if not found.
   FieldInfo _nonExtensionInfo(int tagNumber) => _meta.fieldInfo[tagNumber];

   /// Returns FieldInfo for a non-extension field.
   FieldInfo _nonExtensionInfoByIndex(int index) => _meta.byIndex[index];

   /// Returns the FieldInfo for a regular or extension field.
   /// throws ArgumentException if no info is found.
   FieldInfo _ensureInfo(int tagNumber) {
     var fi = _getFieldInfoOrNull(tagNumber);
     if (fi != null) return fi;
     throw new ArgumentError("tag $tagNumber not defined in $_messageName");
   }

   /// Returns the FieldInfo for a regular or extension field.
   FieldInfo _getFieldInfoOrNull(int tagNumber) {
     var fi = _nonExtensionInfo(tagNumber);
     if (fi != null) return fi;
     if (!_hasExtensions) return null;
     return _extensions._getInfoOrNull(tagNumber);
   }

   void _markReadOnly() {
     if (_isReadOnly) return;
     _isReadOnly = true;
     for (var field in _meta.sortedByTag) {
       if (field.isRepeated) {
         final entries = _values[field.index];
         if (entries == null) continue;
         if (field.isGroupOrMessage) {
           for (var subMessage in entries as List<GeneratedMessage>) {
             subMessage.freeze();
           }
         }
         _values[field.index] = entries.toFrozenPbList();
       } else if (field.isGroupOrMessage) {
         final entry = _values[field.index];
         if (entry != null) {
           (entry as GeneratedMessage).freeze();
         }
       }
     }
   }

   void _ensureWritable() {
     if (_isReadOnly) frozenMessageModificationHandler(_messageName);
   }

   // Single-field operations

   /// Gets a field with full error-checking.
   ///
   /// Works for both extended and non-extended fields.
   /// Creates repeated fields (unless read-only).
   /// Suitable for public API.
   _getField(int tagNumber) {
     var fi = _nonExtensionInfo(tagNumber);
     if (fi != null) {
       var value = _values[fi.index];
       if (value != null) return value;
       return _getDefault(fi);
     }
     if (_hasExtensions) {
       var fi = _extensions._getInfoOrNull(tagNumber);
       if (fi != null) {
         return _extensions._getFieldOrDefault(fi);
       }
     }
     throw new ArgumentError("tag $tagNumber not defined in $_messageName");
   }

   _getDefault(FieldInfo fi) {
     if (!fi.isRepeated) return fi.makeDefault();
     if (_isReadOnly) return fi.readonlyDefault;

     // TODO(skybrian) we could avoid this by generating another
     // method for repeated fields:
     //   msg.mutableFoo().add(123);
     var value = fi._createRepeatedField(_message);
     _setNonExtensionFieldUnchecked(fi, value);
     return value;
   }

   List<T> _getDefaultList<T>(FieldInfo<T> fi) {
     assert(fi.isRepeated);
     if (_isReadOnly) return new List.unmodifiable(const []);

     // TODO(skybrian) we could avoid this by generating another
     // method for repeated fields:
     //   msg.mutableFoo().add(123);
     var value = fi._createRepeatedFieldWithType<T>(_message);
     _setNonExtensionFieldUnchecked(fi, value);
     return value;
   }

   _getFieldOrNullByTag(int tagNumber) {
     var fi = _getFieldInfoOrNull(tagNumber);
     if (fi == null) return null;
     return _getFieldOrNull(fi);
   }

   /// Returns the field's value or null if not set.
   ///
   /// Works for both extended and non-extend fields.
   /// Works for both repeated and non-repeated fields.
   _getFieldOrNull(FieldInfo fi) {
     if (fi.index != null) return _values[fi.index];
     if (!_hasExtensions) return null;
     return _extensions._getFieldOrNull(fi);
   }

   bool _hasField(int tagNumber) {
     var fi = _nonExtensionInfo(tagNumber);
     if (fi != null) return _$has(fi.index);
     if (!_hasExtensions) return false;
     return _extensions._hasField(tagNumber);
   }

   void _clearField(int tagNumber) {
     _ensureWritable();
     var fi = _nonExtensionInfo(tagNumber);
     if (fi != null) {
       // clear a non-extension field
       if (_hasObservers) _eventPlugin.beforeClearField(fi);
       _values[fi.index] = null;
       return;
     }

     if (_hasExtensions) {
       var fi = _extensions._getInfoOrNull(tagNumber);
       if (fi != null) {
         _extensions._clearField(fi);
         return;
       }
     }

     // neither a regular field nor an extension.
     // TODO(skybrian) throw?
   }

   /// Sets a non-repeated field with error-checking.
   ///
   /// Works for both extended and non-extended fields.
   /// Suitable for public API.
   void _setField(int tagNumber, value) {
     if (value == null) throw new ArgumentError('value is null');

     var fi = _nonExtensionInfo(tagNumber);
     if (fi == null) {
       if (!_hasExtensions) {
         throw new ArgumentError("tag $tagNumber not defined in $_messageName");
       }
       _extensions._setField(tagNumber, value);
       return;
     }

     if (fi.isRepeated) {
       throw new ArgumentError(_setFieldFailedMessage(
           fi, value, 'repeating field (use get + .add())'));
     }
     _validateField(fi, value);
     _setNonExtensionFieldUnchecked(fi, value);
   }

   /// Sets a non-repeated field without validating it.
   ///
   /// Works for both extended and non-extended fields.
   /// Suitable for decoders that do their own validation.
   void _setFieldUnchecked(FieldInfo fi, value) {
     assert(fi != null);
     assert(!fi.isRepeated);
     if (fi.index == null) {
       _ensureExtensions()
         .._addInfoUnchecked(fi)
         .._setFieldUnchecked(fi, value);
     } else {
       _setNonExtensionFieldUnchecked(fi, value);
     }
   }

   /// Returns the list to use for adding to a repeated field.
   ///
   /// Works for both extended and non-extended fields.
   /// Creates and stores the repeated field if it doesn't exist.
   /// If it's an extension and the list doesn't exist, validates and stores it.
   /// Suitable for decoders.
   List<T> _ensureRepeatedField<T>(FieldInfo<T> fi) {
     assert(!_isReadOnly);
     assert(fi.isRepeated);
     if (fi.index == null) {
       return _ensureExtensions()._ensureRepeatedField(fi);
     }
     var value = _getFieldOrNull(fi);
     if (value != null) return value as List<T>;

     var newValue = fi._createRepeatedField(_message);
     _setNonExtensionFieldUnchecked(fi, newValue);
     return newValue;
   }

   /// Sets a non-extended field and fires events.
   void _setNonExtensionFieldUnchecked(FieldInfo fi, value) {
     if (_hasObservers) {
       _eventPlugin.beforeSetField(fi, value);
     }
     _values[fi.index] = value;
   }

   // Generated method implementations

   /// The implementation of a generated getter.
   T _$get<T>(int index, T defaultValue) {
     var value = _values[index];
     if (value != null) return value as T;
     if (defaultValue != null) return defaultValue;
     return _getDefault(_nonExtensionInfoByIndex(index)) as T;
   }

   /// The implementation of a generated getter. Common case for submessages.
   T _$getN<T>(int index) {
     var value = _values[index];
     if (value != null) return value as T;
     return _getDefault(_nonExtensionInfoByIndex(index)) as T;
   }

   /// The implementation of a generated getter for repeated fields.
   List<T> _$getList<T>(int index) {
     var value = _values[index];
     if (value != null) return value as List<T>;
     return _getDefaultList<T>(_nonExtensionInfoByIndex(index));
   }

   /// The implementation of a generated getter for String fields.
   String _$getS(int index, String defaultValue) {
     var value = _values[index];
     if (value == null) {
       if (defaultValue != null) return defaultValue;
       value = _getDefault(_nonExtensionInfoByIndex(index));
     }
     String result = value;
     return result;
   }

   /// The implementation of a generated getter for Int64 fields.
   Int64 _$getI64(int index) {
     var value = _values[index];
     if (value == null) {
       value = _getDefault(_nonExtensionInfoByIndex(index));
     }
     Int64 result = value;
     return result;
   }

   /// The implementation of a generated 'has' method.
   bool _$has(int index) {
     var value = _values[index];
     if (value == null) return false;
     if (value is List) return value.isNotEmpty;
     return true;
   }

   /// The implementation of a generated setter.
   ///
   /// In production, does no validation other than a null check.
   /// Only handles non-repeated, non-extension fields.
   /// Also, doesn't handle enums or messages which need per-type validation.
   void _$set(int index, value) {
     assert(!_nonExtensionInfoByIndex(index).isRepeated);
     assert(_$check(index, value));
     _ensureWritable();
     if (value == null) {
       _$check(index, value); // throw exception for null value
     }
     if (_hasObservers) {
       _eventPlugin.beforeSetField(_nonExtensionInfoByIndex(index), value);
     }
     _values[index] = value;
   }

   bool _$check(int index, var newValue) {
     _validateField(_nonExtensionInfoByIndex(index), newValue);
     return true; // Allows use in an assertion.
   }

   // Bulk operations reading or writing multiple fields

   void _clear() {
     _ensureWritable();
     if (_unknownFields != null) {
       _unknownFields.clear();
     }

     if (_hasObservers) {
       for (var fi in _infos) {
         if (_values[fi.index] != null) {
           _eventPlugin.beforeClearField(fi);
         }
       }
       if (_hasExtensions) {
         for (int key in _extensions._tagNumbers) {
           var fi = _extensions._getInfoOrNull(key);
           _eventPlugin.beforeClearField(fi);
         }
       }
     }
     if (_values.isNotEmpty) _values.fillRange(0, _values.length, null);
     if (_hasExtensions) _extensions._clearValues();
   }

   bool _equals(_FieldSet o) {
     if (_meta != o._meta) return false;
     for (var i = 0; i < _values.length; i++) {
       if (!_equalFieldValues(_values[i], o._values[i])) return false;
     }

     if (!_hasExtensions || !_extensions._hasValues) {
       // Check if other extensions are logically empty.
       // (Don't create them unnecessarily.)
       if (o._hasExtensions && o._extensions._hasValues) {
         return false;
       }
     } else {
       if (!_extensions._equalValues(o._extensions)) return false;
     }

     if (_unknownFields == null || _unknownFields.isEmpty) {
       // Check if other unknown fields is logically empty.
       // (Don't create them unnecessarily.)
       if (o._unknownFields != null && o._unknownFields.isNotEmpty) return false;
     } else {
       // Check if the other unknown fields has the same fields.
       if (_unknownFields != o._unknownFields) return false;
     }

     return true;
   }

   bool _equalFieldValues(left, right) {
     if (left != null && right != null) return _deepEquals(left, right);

     var val = left ?? right;

     // Two uninitialized fields are equal.
     if (val == null) return true;

     // One field is null. We are comparing an initialized field
     // with its default value.

     // An empty repeated field is the same as uninitialized.
     // This is because accessing a repeated field automatically creates it.
     // We don't want reading a field to change equality comparisons.
     if (val is List && val.isEmpty) return true;

     // For now, initialized and uninitialized fields are different.
     // TODO(skybrian) consider other cases; should we compare with the
     // default value or not?
     return false;
   }

   /// Calculates a hash code based on the contents of the protobuf.
   ///
   /// The hash may change when any field changes (recursively).
   /// Therefore, protobufs used as map keys shouldn't be changed.
   int get _hashCode {
     int hash;

     void hashEnumList(PbListBase enums) {
       for (ProtobufEnum enm in enums) {
         hash = 0x1fffffff & ((31 * hash) + enm.value);
       }
     }

     // Hashes the value of one field (recursively).
     void hashField(FieldInfo fi, value) {
       if (value is List && value.isEmpty) {
         return; // It's either repeated or an empty byte array.
       }
       hash = 0x1fffffff & ((37 * hash) + fi.tagNumber);
       if (!_isEnum(fi.type)) {
         hash = 0x1fffffff & ((53 * hash) + value.hashCode);
       } else if (fi.isRepeated) {
         hashEnumList(value);
       } else {
         ProtobufEnum enm = value;
         hash = 0x1fffffff & ((53 * hash) + enm.value);
       }
     }

     void hashEachField() {
       for (var fi in _infosSortedByTag) {
         var v = _values[fi.index];
         if (v != null) hashField(fi, v);
       }
       if (!_hasExtensions) return;
       for (int tagNumber in sorted(_extensions._tagNumbers)) {
         var fi = _extensions._getInfoOrNull(tagNumber);
         hashField(fi, _extensions._getFieldOrNull(fi));
       }
     }

     // Generate hash.
     hash = 41;
     // Hash with descriptor.
     hash = 0x1fffffff & ((19 * hash) + _meta.hashCode);
     // Hash with fields.
     hashEachField();
     // Hash with unknown fields.
     if (hasUnknownFields) {
       hash = 0x1fffffff & ((29 * hash) + _unknownFields.hashCode);
     }
     return hash;
   }

   void writeString(StringBuffer out, String indent) {
     void renderValue(key, value) {
       if (value is GeneratedMessage) {
         out.write('$indent$key: {\n');
         value._fieldSet.writeString(out, '$indent  ');
         out.write('$indent}\n');
       } else {
         out.write('$indent$key: $value\n');
       }
     }

     for (FieldInfo fi in _infosSortedByTag) {
       var fieldValue = _values[fi.index];
       if (fieldValue == null) continue;
       if (fieldValue is ByteData) {
         // TODO(skybrian): possibly unused. Delete?
         final value = fieldValue.getUint64(0, Endian.little);
         renderValue(fi.name, value);
       } else if (fieldValue is List) {
         for (var value in fieldValue) {
           renderValue(fi.name, value);
         }
       } else {
         renderValue(fi.name, fieldValue);
       }
     }
     // TODO(skybrian) write extension fields? So far we haven't.
     if (hasUnknownFields) {
       out.write(_unknownFields.toString());
     } else {
       out.write(new UnknownFieldSet().toString());
     }
   }

   /// Merges the contents of the [other] into this message.
   ///
   /// Singular fields that are set in [other] overwrite the corresponding fields
   /// in this message. Repeated fields are appended. Singular sub-messages are
   /// recursively merged.
   void _mergeFromMessage(_FieldSet other) {
     // TODO(https://github.com/dart-lang/protobuf/issues/60): Recognize
     // when [this] and [other] are the same protobuf (e.g. from cloning). In
     // this case, we can merge the non-extension fields without field lookups or
     // validation checks.

     for (FieldInfo fi in other._infosSortedByTag) {
       var value = other._values[fi.index];
       if (value != null) _mergeField(fi, value);
     }
     if (other._hasExtensions) {
       var others = other._extensions;
       for (int tagNumber in others._tagNumbers) {
         var extension = others._getInfoOrNull(tagNumber);
         var value = others._getFieldOrNull(extension);
         _mergeField(extension, value);
       }
     }

     if (other.hasUnknownFields) {
       _ensureUnknownFields().mergeFromUnknownFieldSet(other._unknownFields);
     }
   }

   void _mergeField(FieldInfo otherFi, fieldValue) {
     int tagNumber = otherFi.tagNumber;

     // Determine the FieldInfo to use.
     // Don't allow regular fields to be overwritten by extensions.
     var fi = _nonExtensionInfo(tagNumber);
     if (fi == null && otherFi is Extension) {
       // This will overwrite any existing extension field info.
       fi = otherFi;
     }

     bool mustClone = _isGroupOrMessage(otherFi.type);

     if (fi.isRepeated) {
       if (mustClone) {
         // fieldValue must be a PbListBase of GeneratedMessage.
         PbListBase<GeneratedMessage> pbList = fieldValue;
         var repeatedFields = fi._ensureRepeatedField(this);
         for (int i = 0; i < pbList.length; ++i) {
           repeatedFields.add(_cloneMessage(pbList[i]));
         }
       } else {
         // fieldValue must be at least a PbListBase.
         PbListBase pbList = fieldValue;
         fi._ensureRepeatedField(this).addAll(pbList);
       }
       return;
     }

     if (mustClone) {
       fieldValue = _cloneMessage(fieldValue);
     }
     if (fi.index == null) {
       _ensureExtensions()._setFieldAndInfo(fi, fieldValue);
     } else {
       _validateField(fi, fieldValue);
       _setNonExtensionFieldUnchecked(fi, fieldValue);
     }
   }

   // This function is declared as a static method rather than an in-place
   // closure since dart2js does not currently hoist closures with no captured
   // variables (See http://dartbug.com/26932), and dart2js will inline this
   // version at the direct call site.
   static GeneratedMessage _cloneMessage(GeneratedMessage message) =>
       message.clone();

   // Error-checking

   /// Checks the value for a field that's about to be set.
   void _validateField(FieldInfo fi, var newValue) {
     _ensureWritable();
     var message = _getFieldError(fi.type, newValue);
     if (message != null) {
       throw new ArgumentError(_setFieldFailedMessage(fi, newValue, message));
     }
   }

   String _setFieldFailedMessage(FieldInfo fi, var value, String detail) {
     return 'Illegal to set field ${fi.name} (${fi.tagNumber}) of $_messageName'
         ' to value ($value): $detail';
   }

   bool _hasRequiredValues() {
     if (!_hasRequiredFields) return true;
     for (var fi in _infos) {
       var value = _values[fi.index];
       if (!fi._hasRequiredValues(value)) return false;
     }
     return _hasRequiredExtensionValues();
   }

   bool _hasRequiredExtensionValues() {
     if (!_hasExtensions) return true;
     for (var fi in _extensions._infos) {
       var value = _extensions._getFieldOrNull(fi);
       if (!fi._hasRequiredValues(value)) return false;
     }
     return true; // No problems found.
   }

   /// Adds the path to each uninitialized field to the list.
   void _appendInvalidFields(List<String> problems, String prefix) {
     if (!_hasRequiredFields) return;
     for (var fi in _infos) {
       var value = _values[fi.index];
       fi._appendInvalidFields(problems, value, prefix);
     }
     // TODO(skybrian): search extensions as well
     // https://github.com/dart-lang/protobuf/issues/46
   }
 }
	// Copyright (c) 2015, the Dart project authors. Please see the AUTHORS file
	// 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.

	part of protobuf;

	typedef void FrozenMessageErrorHandler(String messageName, [String methodName]);

	void defaultFrozenMessageModificationHandler(String messageName,
	[String methodName]) {
	if (methodName != null) {
	throw new UnsupportedError(
	"Attempted to call $methodName on a read-only message ($messageName)");
	}
	throw new UnsupportedError(
	"Attempted to change a read-only message ($messageName)");
	}

	/// Invoked when an attempt is made to modify a frozen message.
	///
	/// This handler can log the attempt, throw an exception, or ignore the attempt
	/// altogether.
	///
	/// If the handler returns normally, the modification is allowed, and execution
	/// proceeds as if the message was writable.
	FrozenMessageErrorHandler frozenMessageModificationHandler =
	defaultFrozenMessageModificationHandler;

	/// All the data in a GeneratedMessage.
	///
	/// These fields and methods are in a separate class to avoid
	/// polymorphic access due to inheritance. This turns out to
	/// be faster when compiled to JavaScript.
	class _FieldSet {
	final GeneratedMessage _message;
	final BuilderInfo _meta;
	final EventPlugin _eventPlugin;
	bool _isReadOnly = false;

	/// The value of each non-extension field in a fixed-length array.
	/// The index of a field can be found in [FieldInfo.index].
	/// A null entry indicates that the field has no value.
	final List _values;

	/// Contains all the extension fields, or null if there aren't any.
	_ExtensionFieldSet _extensions;

	/// Contains all the unknown fields, or null if there aren't any.
	UnknownFieldSet _unknownFields;

	_FieldSet(this._message, BuilderInfo meta, this._eventPlugin)
	: this._meta = meta,
	_values = _makeValueList(meta.byIndex.length);

	static _makeValueList(int length) {
	if (length == 0) return _zeroList;
	return new List(length);
	}

	// Use a fixed length list and not a constant list to ensure that _values
	// always has the same implementation type.
	static List _zeroList = new List(0);

	// Metadata about multiple fields

	String get _messageName => _meta.messageName;
	bool get _hasRequiredFields => _meta.hasRequiredFields;

	/// The FieldInfo for each non-extension field.
	Iterable<FieldInfo> get _infos => _meta.fieldInfo.values;

	/// The FieldInfo for each non-extension field in tag order.
	Iterable<FieldInfo> get _infosSortedByTag => _meta.sortedByTag;

	/// Returns true if we should send events to the plugin.
	bool get _hasObservers => _eventPlugin != null && _eventPlugin.hasObservers;

	bool get _hasExtensions => _extensions != null;
	bool get hasUnknownFields => _unknownFields != null;

	_ExtensionFieldSet _ensureExtensions() {
	assert(!_isReadOnly);
	if (!_hasExtensions) _extensions = new _ExtensionFieldSet(this);
	return _extensions;
	}

	UnknownFieldSet _ensureUnknownFields() {
	if (_isReadOnly) return _ReadonlyUnknownFieldSet._empty;
	if (_unknownFields == null) _unknownFields = new UnknownFieldSet();
	return _unknownFields;
	}

	// Metadata about single fields

	/// Returns FieldInfo for a non-extension field, or null if not found.
	FieldInfo _nonExtensionInfo(int tagNumber) => _meta.fieldInfo[tagNumber];

	/// Returns FieldInfo for a non-extension field.
	FieldInfo _nonExtensionInfoByIndex(int index) => _meta.byIndex[index];

	/// Returns the FieldInfo for a regular or extension field.
	/// throws ArgumentException if no info is found.
	FieldInfo _ensureInfo(int tagNumber) {
	var fi = _getFieldInfoOrNull(tagNumber);
	if (fi != null) return fi;
	throw new ArgumentError("tag $tagNumber not defined in $_messageName");
	}

	/// Returns the FieldInfo for a regular or extension field.
	FieldInfo _getFieldInfoOrNull(int tagNumber) {
	var fi = _nonExtensionInfo(tagNumber);
	if (fi != null) return fi;
	if (!_hasExtensions) return null;
	return _extensions._getInfoOrNull(tagNumber);
	}

	void _markReadOnly() {
	if (_isReadOnly) return;
	_isReadOnly = true;
	for (var field in _meta.sortedByTag) {
	if (field.isRepeated) {
	final entries = _values[field.index];
	if (entries == null) continue;
	if (field.isGroupOrMessage) {
	for (var subMessage in entries as List<GeneratedMessage>) {
	subMessage.freeze();
	}
	}
	_values[field.index] = entries.toFrozenPbList();
	} else if (field.isGroupOrMessage) {
	final entry = _values[field.index];
	if (entry != null) {
	(entry as GeneratedMessage).freeze();
	}
	}
	}
	}

	void _ensureWritable() {
	if (_isReadOnly) frozenMessageModificationHandler(_messageName);
	}

	// Single-field operations

	/// Gets a field with full error-checking.
	///
	/// Works for both extended and non-extended fields.
	/// Creates repeated fields (unless read-only).
	/// Suitable for public API.
	_getField(int tagNumber) {
	var fi = _nonExtensionInfo(tagNumber);
	if (fi != null) {
	var value = _values[fi.index];
	if (value != null) return value;
	return _getDefault(fi);
	}
	if (_hasExtensions) {
	var fi = _extensions._getInfoOrNull(tagNumber);
	if (fi != null) {
	return _extensions._getFieldOrDefault(fi);
	}
	}
	throw new ArgumentError("tag $tagNumber not defined in $_messageName");
	}

	_getDefault(FieldInfo fi) {
	if (!fi.isRepeated) return fi.makeDefault();
	if (_isReadOnly) return fi.readonlyDefault;

	// TODO(skybrian) we could avoid this by generating another
	// method for repeated fields:
	// msg.mutableFoo().add(123);
	var value = fi._createRepeatedField(_message);
	_setNonExtensionFieldUnchecked(fi, value);
	return value;
	}

	List<T> _getDefaultList<T>(FieldInfo<T> fi) {
	assert(fi.isRepeated);
	if (_isReadOnly) return new List.unmodifiable(const []);

	// TODO(skybrian) we could avoid this by generating another
	// method for repeated fields:
	// msg.mutableFoo().add(123);
	var value = fi._createRepeatedFieldWithType<T>(_message);
	_setNonExtensionFieldUnchecked(fi, value);
	return value;
	}

	_getFieldOrNullByTag(int tagNumber) {
	var fi = _getFieldInfoOrNull(tagNumber);
	if (fi == null) return null;
	return _getFieldOrNull(fi);
	}

	/// Returns the field's value or null if not set.
	///
	/// Works for both extended and non-extend fields.
	/// Works for both repeated and non-repeated fields.
	_getFieldOrNull(FieldInfo fi) {
	if (fi.index != null) return _values[fi.index];
	if (!_hasExtensions) return null;
	return _extensions._getFieldOrNull(fi);
	}

	bool _hasField(int tagNumber) {
	var fi = _nonExtensionInfo(tagNumber);
	if (fi != null) return _$has(fi.index);
	if (!_hasExtensions) return false;
	return _extensions._hasField(tagNumber);
	}

	void _clearField(int tagNumber) {
	_ensureWritable();
	var fi = _nonExtensionInfo(tagNumber);
	if (fi != null) {
	// clear a non-extension field
	if (_hasObservers) _eventPlugin.beforeClearField(fi);
	_values[fi.index] = null;
	return;
	}

	if (_hasExtensions) {
	var fi = _extensions._getInfoOrNull(tagNumber);
	if (fi != null) {
	_extensions._clearField(fi);
	return;
	}
	}

	// neither a regular field nor an extension.
	// TODO(skybrian) throw?
	}

	/// Sets a non-repeated field with error-checking.
	///
	/// Works for both extended and non-extended fields.
	/// Suitable for public API.
	void _setField(int tagNumber, value) {
	if (value == null) throw new ArgumentError('value is null');

	var fi = _nonExtensionInfo(tagNumber);
	if (fi == null) {
	if (!_hasExtensions) {
	throw new ArgumentError("tag $tagNumber not defined in $_messageName");
	}
	_extensions._setField(tagNumber, value);
	return;
	}

	if (fi.isRepeated) {
	throw new ArgumentError(_setFieldFailedMessage(
	fi, value, 'repeating field (use get + .add())'));
	}
	_validateField(fi, value);
	_setNonExtensionFieldUnchecked(fi, value);
	}

	/// Sets a non-repeated field without validating it.
	///
	/// Works for both extended and non-extended fields.
	/// Suitable for decoders that do their own validation.
	void _setFieldUnchecked(FieldInfo fi, value) {
	assert(fi != null);
	assert(!fi.isRepeated);
	if (fi.index == null) {
	_ensureExtensions()
	.._addInfoUnchecked(fi)
	.._setFieldUnchecked(fi, value);
	} else {
	_setNonExtensionFieldUnchecked(fi, value);
	}
	}

	/// Returns the list to use for adding to a repeated field.
	///
	/// Works for both extended and non-extended fields.
	/// Creates and stores the repeated field if it doesn't exist.
	/// If it's an extension and the list doesn't exist, validates and stores it.
	/// Suitable for decoders.
	List<T> _ensureRepeatedField<T>(FieldInfo<T> fi) {
	assert(!_isReadOnly);
	assert(fi.isRepeated);
	if (fi.index == null) {
	return _ensureExtensions()._ensureRepeatedField(fi);
	}
	var value = _getFieldOrNull(fi);
	if (value != null) return value as List<T>;

	var newValue = fi._createRepeatedField(_message);
	_setNonExtensionFieldUnchecked(fi, newValue);
	return newValue;
	}

	/// Sets a non-extended field and fires events.
	void _setNonExtensionFieldUnchecked(FieldInfo fi, value) {
	if (_hasObservers) {
	_eventPlugin.beforeSetField(fi, value);
	}
	_values[fi.index] = value;
	}

	// Generated method implementations

	/// The implementation of a generated getter.
	T _$get<T>(int index, T defaultValue) {
	var value = _values[index];
	if (value != null) return value as T;
	if (defaultValue != null) return defaultValue;
	return _getDefault(_nonExtensionInfoByIndex(index)) as T;
	}

	/// The implementation of a generated getter. Common case for submessages.
	T _$getN<T>(int index) {
	var value = _values[index];
	if (value != null) return value as T;
	return _getDefault(_nonExtensionInfoByIndex(index)) as T;
	}

	/// The implementation of a generated getter for repeated fields.
	List<T> _$getList<T>(int index) {
	var value = _values[index];
	if (value != null) return value as List<T>;
	return _getDefaultList<T>(_nonExtensionInfoByIndex(index));
	}

	/// The implementation of a generated getter for String fields.
	String _$getS(int index, String defaultValue) {
	var value = _values[index];
	if (value == null) {
	if (defaultValue != null) return defaultValue;
	value = _getDefault(_nonExtensionInfoByIndex(index));
	}
	String result = value;
	return result;
	}

	/// The implementation of a generated getter for Int64 fields.
	Int64 _$getI64(int index) {
	var value = _values[index];
	if (value == null) {
	value = _getDefault(_nonExtensionInfoByIndex(index));
	}
	Int64 result = value;
	return result;
	}

	/// The implementation of a generated 'has' method.
	bool _$has(int index) {
	var value = _values[index];
	if (value == null) return false;
	if (value is List) return value.isNotEmpty;
	return true;
	}

	/// The implementation of a generated setter.
	///
	/// In production, does no validation other than a null check.
	/// Only handles non-repeated, non-extension fields.
	/// Also, doesn't handle enums or messages which need per-type validation.
	void _$set(int index, value) {
	assert(!_nonExtensionInfoByIndex(index).isRepeated);
	assert(_$check(index, value));
	_ensureWritable();
	if (value == null) {
	_$check(index, value); // throw exception for null value
	}
	if (_hasObservers) {
	_eventPlugin.beforeSetField(_nonExtensionInfoByIndex(index), value);
	}
	_values[index] = value;
	}

	bool _$check(int index, var newValue) {
	_validateField(_nonExtensionInfoByIndex(index), newValue);
	return true; // Allows use in an assertion.
	}

	// Bulk operations reading or writing multiple fields

	void _clear() {
	_ensureWritable();
	if (_unknownFields != null) {
	_unknownFields.clear();
	}

	if (_hasObservers) {
	for (var fi in _infos) {
	if (_values[fi.index] != null) {
	_eventPlugin.beforeClearField(fi);
	}
	}
	if (_hasExtensions) {
	for (int key in _extensions._tagNumbers) {
	var fi = _extensions._getInfoOrNull(key);
	_eventPlugin.beforeClearField(fi);
	}
	}
	}
	if (_values.isNotEmpty) _values.fillRange(0, _values.length, null);
	if (_hasExtensions) _extensions._clearValues();
	}

	bool _equals(_FieldSet o) {
	if (_meta != o._meta) return false;
	for (var i = 0; i < _values.length; i++) {
	if (!_equalFieldValues(_values[i], o._values[i])) return false;
	}

	if (!_hasExtensions \|\| !_extensions._hasValues) {
	// Check if other extensions are logically empty.
	// (Don't create them unnecessarily.)
	if (o._hasExtensions && o._extensions._hasValues) {
	return false;
	}
	} else {
	if (!_extensions._equalValues(o._extensions)) return false;
	}

	if (_unknownFields == null \|\| _unknownFields.isEmpty) {
	// Check if other unknown fields is logically empty.
	// (Don't create them unnecessarily.)
	if (o._unknownFields != null && o._unknownFields.isNotEmpty) return false;
	} else {
	// Check if the other unknown fields has the same fields.
	if (_unknownFields != o._unknownFields) return false;
	}

	return true;
	}

	bool _equalFieldValues(left, right) {
	if (left != null && right != null) return _deepEquals(left, right);

	var val = left ?? right;

	// Two uninitialized fields are equal.
	if (val == null) return true;

	// One field is null. We are comparing an initialized field
	// with its default value.

	// An empty repeated field is the same as uninitialized.
	// This is because accessing a repeated field automatically creates it.
	// We don't want reading a field to change equality comparisons.
	if (val is List && val.isEmpty) return true;

	// For now, initialized and uninitialized fields are different.
	// TODO(skybrian) consider other cases; should we compare with the
	// default value or not?
	return false;
	}

	/// Calculates a hash code based on the contents of the protobuf.
	///
	/// The hash may change when any field changes (recursively).
	/// Therefore, protobufs used as map keys shouldn't be changed.
	int get _hashCode {
	int hash;

	void hashEnumList(PbListBase enums) {
	for (ProtobufEnum enm in enums) {
	hash = 0x1fffffff & ((31 * hash) + enm.value);
	}
	}

	// Hashes the value of one field (recursively).
	void hashField(FieldInfo fi, value) {
	if (value is List && value.isEmpty) {
	return; // It's either repeated or an empty byte array.
	}
	hash = 0x1fffffff & ((37 * hash) + fi.tagNumber);
	if (!_isEnum(fi.type)) {
	hash = 0x1fffffff & ((53 * hash) + value.hashCode);
	} else if (fi.isRepeated) {
	hashEnumList(value);
	} else {
	ProtobufEnum enm = value;
	hash = 0x1fffffff & ((53 * hash) + enm.value);
	}
	}

	void hashEachField() {
	for (var fi in _infosSortedByTag) {
	var v = _values[fi.index];
	if (v != null) hashField(fi, v);
	}
	if (!_hasExtensions) return;
	for (int tagNumber in sorted(_extensions._tagNumbers)) {
	var fi = _extensions._getInfoOrNull(tagNumber);
	hashField(fi, _extensions._getFieldOrNull(fi));
	}
	}

	// Generate hash.
	hash = 41;
	// Hash with descriptor.
	hash = 0x1fffffff & ((19 * hash) + _meta.hashCode);
	// Hash with fields.
	hashEachField();
	// Hash with unknown fields.
	if (hasUnknownFields) {
	hash = 0x1fffffff & ((29 * hash) + _unknownFields.hashCode);
	}
	return hash;
	}

	void writeString(StringBuffer out, String indent) {
	void renderValue(key, value) {
	if (value is GeneratedMessage) {
	out.write('$indent$key: {\n');
	value._fieldSet.writeString(out, '$indent ');
	out.write('$indent}\n');
	} else {
	out.write('$indent$key: $value\n');
	}
	}

	for (FieldInfo fi in _infosSortedByTag) {
	var fieldValue = _values[fi.index];
	if (fieldValue == null) continue;
	if (fieldValue is ByteData) {
	// TODO(skybrian): possibly unused. Delete?
	final value = fieldValue.getUint64(0, Endian.little);
	renderValue(fi.name, value);
	} else if (fieldValue is List) {
	for (var value in fieldValue) {
	renderValue(fi.name, value);
	}
	} else {
	renderValue(fi.name, fieldValue);
	}
	}
	// TODO(skybrian) write extension fields? So far we haven't.
	if (hasUnknownFields) {
	out.write(_unknownFields.toString());
	} else {
	out.write(new UnknownFieldSet().toString());
	}
	}

	/// Merges the contents of the [other] into this message.
	///
	/// Singular fields that are set in [other] overwrite the corresponding fields
	/// in this message. Repeated fields are appended. Singular sub-messages are
	/// recursively merged.
	void _mergeFromMessage(_FieldSet other) {
	// TODO(https://github.com/dart-lang/protobuf/issues/60): Recognize
	// when [this] and [other] are the same protobuf (e.g. from cloning). In
	// this case, we can merge the non-extension fields without field lookups or
	// validation checks.

	for (FieldInfo fi in other._infosSortedByTag) {
	var value = other._values[fi.index];
	if (value != null) _mergeField(fi, value);
	}
	if (other._hasExtensions) {
	var others = other._extensions;
	for (int tagNumber in others._tagNumbers) {
	var extension = others._getInfoOrNull(tagNumber);
	var value = others._getFieldOrNull(extension);
	_mergeField(extension, value);
	}
	}

	if (other.hasUnknownFields) {
	_ensureUnknownFields().mergeFromUnknownFieldSet(other._unknownFields);
	}
	}

	void _mergeField(FieldInfo otherFi, fieldValue) {
	int tagNumber = otherFi.tagNumber;

	// Determine the FieldInfo to use.
	// Don't allow regular fields to be overwritten by extensions.
	var fi = _nonExtensionInfo(tagNumber);
	if (fi == null && otherFi is Extension) {
	// This will overwrite any existing extension field info.
	fi = otherFi;
	}

	bool mustClone = _isGroupOrMessage(otherFi.type);

	if (fi.isRepeated) {
	if (mustClone) {
	// fieldValue must be a PbListBase of GeneratedMessage.
	PbListBase<GeneratedMessage> pbList = fieldValue;
	var repeatedFields = fi._ensureRepeatedField(this);
	for (int i = 0; i < pbList.length; ++i) {
	repeatedFields.add(_cloneMessage(pbList[i]));
	}
	} else {
	// fieldValue must be at least a PbListBase.
	PbListBase pbList = fieldValue;
	fi._ensureRepeatedField(this).addAll(pbList);
	}
	return;
	}

	if (mustClone) {
	fieldValue = _cloneMessage(fieldValue);
	}
	if (fi.index == null) {
	_ensureExtensions()._setFieldAndInfo(fi, fieldValue);
	} else {
	_validateField(fi, fieldValue);
	_setNonExtensionFieldUnchecked(fi, fieldValue);
	}
	}

	// This function is declared as a static method rather than an in-place
	// closure since dart2js does not currently hoist closures with no captured
	// variables (See http://dartbug.com/26932), and dart2js will inline this
	// version at the direct call site.
	static GeneratedMessage _cloneMessage(GeneratedMessage message) =>
	message.clone();

	// Error-checking

	/// Checks the value for a field that's about to be set.
	void _validateField(FieldInfo fi, var newValue) {
	_ensureWritable();
	var message = _getFieldError(fi.type, newValue);
	if (message != null) {
	throw new ArgumentError(_setFieldFailedMessage(fi, newValue, message));
	}
	}

	String _setFieldFailedMessage(FieldInfo fi, var value, String detail) {
	return 'Illegal to set field ${fi.name} (${fi.tagNumber}) of $_messageName'
	' to value ($value): $detail';
	}

	bool _hasRequiredValues() {
	if (!_hasRequiredFields) return true;
	for (var fi in _infos) {
	var value = _values[fi.index];
	if (!fi._hasRequiredValues(value)) return false;
	}
	return _hasRequiredExtensionValues();
	}

	bool _hasRequiredExtensionValues() {
	if (!_hasExtensions) return true;
	for (var fi in _extensions._infos) {
	var value = _extensions._getFieldOrNull(fi);
	if (!fi._hasRequiredValues(value)) return false;
	}
	return true; // No problems found.
	}

	/// Adds the path to each uninitialized field to the list.
	void _appendInvalidFields(List<String> problems, String prefix) {
	if (!_hasRequiredFields) return;
	for (var fi in _infos) {
	var value = _values[fi.index];
	fi._appendInvalidFields(problems, value, prefix);
	}
	// TODO(skybrian): search extensions as well
	// https://github.com/dart-lang/protobuf/issues/46
	}
	}