unknown_field_set.h

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本文介绍了一个用于跟踪协议消息中未定义字段的UnknownFieldSet类及其子类UnknownField。UnknownFieldSet能够保存解析过程中遇到但类型定义中不存在的字段，便于后续处理或重新序列化。

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unknown_field_set.h

#include <google/protobuf/unknown_field_set.h> namespace google::protobuf

Contains classes used to keep track of unrecognized fields seen while parsing a protocol message.

Classes in this file
`UnknownFieldSet` An UnknownFieldSet contains fields that were encountered while parsing a message but were not defined by its type.
`UnknownField` Represents one field in an UnknownFieldSet.

class UnknownFieldSet

#include <google/protobuf/unknown_field_set.h> namespace google::protobuf

An UnknownFieldSet contains fields that were encountered while parsing a message but were not defined by its type.

Keeping track of these can be useful, especially in that they may be written if the message is serialized again without being cleared in between. This means that software which simply receives messages and forwards them to other servers does not need to be updated every time a new field is added to the message definition.

To get the UnknownFieldSet attached to any message, call Reflection::GetUnknownFields().

This class is necessarily tied to the protocol buffer wire format, unlike the Reflection interface which is independent of any serialization scheme.

Members
	`UnknownFieldSet()`
	`~UnknownFieldSet()`
`void`	`Clear()` Remove all fields.
`void`	`ClearAndFreeMemory()` Remove all fields and deallocate internal data objects.
`bool`	`empty() const` Is this set empty?
`void`	`MergeFrom(const UnknownFieldSet & other)` Merge the contents of some other UnknownFieldSet with this one.
`void`	`Swap(UnknownFieldSet * x)` Swaps the contents of some other UnknownFieldSet with this one.
`int`	`SpaceUsedExcludingSelf() const` Computes (an estimate of) the total number of bytes currently used for storing the unknown fields in memory. more...
`int`	`SpaceUsed() const` Version of SpaceUsed() including sizeof(*this).
`int`	`field_count() const` Returns the number of fields present in the UnknownFieldSet.
`const UnknownField &`	`field(int index) const` Get a field in the set, where 0 <= index < field_count(). more...
`UnknownField *`	`mutable_field(int index)` Get a mutable pointer to a field in the set, where 0 <= index < field_count(). more...
`bool`	`MergeFromCodedStream(io::CodedInputStream * input)`
`bool`	`ParseFromCodedStream(io::CodedInputStream * input)`
`bool`	`ParseFromZeroCopyStream(io::ZeroCopyInputStream * input)`
`bool`	`ParseFromArray(const void * data, int size)`
`bool`	`ParseFromString(const string & data)`
Adding fields
`void`	`AddVarint(int number, uint64 value)`
`void`	`AddFixed32(int number, uint32 value)`
`void`	`AddFixed64(int number, uint64 value)`
`void`	`AddLengthDelimited(int number, const string & value)`
`string *`	`AddLengthDelimited(int number)`
`UnknownFieldSet *`	`AddGroup(int number)`
`void`	`AddField(const UnknownField & field)` Adds an unknown field from another set.
`void`	`DeleteSubrange(int start, int num)` Delete fields with indices in the range [[]start . more...
`void`	`DeleteByNumber(int number)` Delete all fields with a specific field number. more...

`int UnknownFieldSet::SpaceUsedExcludingSelf() const`

Computes (an estimate of) the total number of bytes currently used for storing the unknown fields in memory.

Does NOT include sizeof(*this) in the calculation.

`const UnknownField & UnknownFieldSet::field( int index) const`

Get a field in the set, where 0 <= index < field_count().

The fields appear in the order in which they were added.

`UnknownField * UnknownFieldSet::mutable_field( int index)`

Get a mutable pointer to a field in the set, where 0 <= index < field_count().

The fields appear in the order in which they were added.

`void UnknownFieldSet::DeleteSubrange( int start, int num)`

Delete fields with indices in the range [[]start .

. start+num-1]. Caution: implementation moves all fields with indices [[]start+num .. ].

`void UnknownFieldSet::DeleteByNumber( int number)`

Delete all fields with a specific field number.

The order of left fields is preserved. Caution: implementation moves all fields after the first deleted field.

class UnknownField

#include <google/protobuf/unknown_field_set.h> namespace google::protobuf

Represents one field in an UnknownFieldSet.

Members
`enum`	`Type` more...
`uint64`	`varint_`
`uint32`	`fixed32_`
`uint64`	`fixed64_`
`string *`	`string_value_`
`union google::protobuf::UnknownField::@2::@4`	`length_delimited_`
`UnknownFieldSet *`	`group_`
`int`	`number() const` The field's tag number, as seen on the wire.
`Type`	`type() const` The field type.
Accessors Each method works only for UnknownFields of the corresponding type.
`uint64`	`varint() const`
`uint32`	`fixed32() const`
`uint64`	`fixed64() const`
`const string &`	`length_delimited() const`
`const UnknownFieldSet &`	`group() const`
`void`	`set_varint(uint64 value)`
`void`	`set_fixed32(uint32 value)`
`void`	`set_fixed64(uint64 value)`
`void`	`set_length_delimited(const string & value)`
`string *`	`mutable_length_delimited()`
`UnknownFieldSet *`	`mutable_group()`
`void`	`SerializeLengthDelimitedNoTag(io::CodedOutputStream * output) const` Serialization API. more...
`uint8 *`	`SerializeLengthDelimitedNoTagToArray(uint8 * target) const`
`int`	`GetLengthDelimitedSize() const`

`enum UnknownField::Type { TYPE_VARINT, TYPE_FIXED32, TYPE_FIXED64, TYPE_LENGTH_DELIMITED, TYPE_GROUP }`

TYPE_VARINT
TYPE_FIXED32
TYPE_FIXED64
TYPE_LENGTH_DELIMITED
TYPE_GROUP

`void UnknownField::SerializeLengthDelimitedNoTag( io::CodedOutputStream * output) const`

Serialization API.

These methods can take advantage of the underlying implementation and may archieve a better performance than using getters to retrieve the data and do the serialization yourself.