message_lite.h

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

Defines MessageLite, the abstract interface implemented by all (lite and non-lite) protocol message objects.

Classes in this file

Interface to light weight protocol messages.

class MessageLite

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

Interface to light weight protocol messages.

This interface is implemented by all protocol message objects. Non-lite messages additionally implement the Message interface, which is a subclass of MessageLite. Use MessageLite instead when you only need the subset of features which it supports – namely, nothing that uses descriptors or reflection. You can instruct the protocol compiler to generate classes which implement only MessageLite, not the full Message interface, by adding the following line to the .proto file:

option optimize_for = LITE_RUNTIME;
This is particularly useful on resource-constrained systems where
the full protocol buffers runtime library is too big.

Note that on non-constrained systems (e.g. servers) when you need
to link in lots of protocol definitions, a better way to reduce
total code footprint is to use optimize_for = CODE_SIZE.  This
will make the generated code smaller while still supporting all the
same features (at the expense of speed).  optimize_for = LITE_RUNTIME
is best when you only have a small number of message types linked
into your binary, in which case the size of the protocol buffers
runtime itself is the biggest problem.

Known subclasses:

Members

MessageLite()
virtual
~MessageLite()

Basic Operations

virtual string
GetTypeName() const = 0
Get the name of this message type, e.g. "foo.bar.BazProto".
virtual MessageLite *
New() const = 0
Construct a new instance of the same type. more...
virtual MessageLite *
New(Arena * arena) const
Construct a new instance on the arena. more...
virtual Arena *
GetArena() const
Get the arena, if any, associated with this message. more...
virtual void *
GetMaybeArenaPointer() const
Get a pointer that may be equal to this message's arena, or may not be. more...
virtual void
Clear() = 0
Clear all fields of the message and set them to their default values. more...
virtual bool
IsInitialized() const = 0
Quickly check if all required fields have values set.
virtual string
InitializationErrorString() const
This is not implemented for Lite messages – it just returns "(cannot determine missing fields for lite message)". more...
virtual void
CheckTypeAndMergeFrom(const MessageLite & other) = 0
If |other| is the exact same class as this, calls MergeFrom(). more...

Parsing

Methods for parsing in protocol buffer format.

Most of these are just simple wrappers around MergeFromCodedStream(). Clear() will be called before merging the input.

bool
ParseFromCodedStream(io::CodedInputStream * input)
Fill the message with a protocol buffer parsed from the given input stream. more...
bool
ParsePartialFromCodedStream(io::CodedInputStream * input)
Like ParseFromCodedStream(), but accepts messages that are missing required fields.
bool
ParseFromZeroCopyStream(io::ZeroCopyInputStream * input)
Read a protocol buffer from the given zero-copy input stream. more...
bool
ParsePartialFromZeroCopyStream(io::ZeroCopyInputStream * input)
Like ParseFromZeroCopyStream(), but accepts messages that are missing required fields.
bool
ParseFromBoundedZeroCopyStream(io::ZeroCopyInputStream * input, int size)
Read a protocol buffer from the given zero-copy input stream, expecting the message to be exactly "size" bytes long. more...
bool
ParsePartialFromBoundedZeroCopyStream(io::ZeroCopyInputStream * input, int size)
Like ParseFromBoundedZeroCopyStream(), but accepts messages that are missing required fields.
bool
ParseFromString(const string & data)
Parses a protocol buffer contained in a string. more...
bool
ParsePartialFromString(const string & data)
Like ParseFromString(), but accepts messages that are missing required fields.
bool
ParseFromArray(const void * data, int size)
Parse a protocol buffer contained in an array of bytes.
bool
ParsePartialFromArray(const void * data, int size)
Like ParseFromArray(), but accepts messages that are missing required fields.
bool
MergeFromCodedStream(io::CodedInputStream * input)
Reads a protocol buffer from the stream and merges it into this Message. more...
virtual bool
MergePartialFromCodedStream(io::CodedInputStream * input) = 0
Like MergeFromCodedStream(), but succeeds even if required fields are missing in the input. more...

Serialization

Methods for serializing in protocol buffer format.

Most of these are just simple wrappers around ByteSize() and SerializeWithCachedSizes().

bool
SerializeToCodedStream(io::CodedOutputStream * output) const
Write a protocol buffer of this message to the given output. more...
bool
SerializePartialToCodedStream(io::CodedOutputStream * output) const
Like SerializeToCodedStream(), but allows missing required fields.
bool
SerializeToZeroCopyStream(io::ZeroCopyOutputStream * output) const
Write the message to the given zero-copy output stream. more...
bool
SerializePartialToZeroCopyStream(io::ZeroCopyOutputStream * output) const
Like SerializeToZeroCopyStream(), but allows missing required fields.
bool
SerializeToString(string * output) const
Serialize the message and store it in the given string. more...
bool
SerializePartialToString(string * output) const
Like SerializeToString(), but allows missing required fields.
bool
SerializeToArray(void * data, int size) const
Serialize the message and store it in the given byte array. more...
bool
SerializePartialToArray(void * data, int size) const
Like SerializeToArray(), but allows missing required fields.
string
SerializeAsString() const
Make a string encoding the message. more...
string
SerializePartialAsString() const
Like SerializeAsString(), but allows missing required fields.
bool
AppendToString(string * output) const
Like SerializeToString(), but appends to the data to the string's existing contents. more...
bool
AppendPartialToString(string * output) const
Like AppendToString(), but allows missing required fields.
virtual int
ByteSize() const = 0
Computes the serialized size of the message. more...
virtual void
SerializeWithCachedSizes(io::CodedOutputStream * output) const = 0
Serializes the message without recomputing the size. more...
virtual uint8 *
SerializeWithCachedSizesToArray(uint8 * target) const
A version of SerializeWithCachedSizesToArray, below, that does not guarantee deterministic serialization.
virtual int
GetCachedSize() const = 0
Returns the result of the last call to ByteSize(). more...
virtual uint8 *
InternalSerializeWithCachedSizesToArray(bool deterministic, uint8 * target) const
Like SerializeWithCachedSizes, but writes directly to *target, returning a pointer to the byte immediately after the last byte written. more...

virtual MessageLite * MessageLite::New() const = 0

Construct a new instance of the same type.

Ownership is passed to the caller.

virtual MessageLite * MessageLite::New(
        Arena * arena) const

Construct a new instance on the arena.

Ownership is passed to the caller if arena is a NULL. Default implementation for backwards compatibility.

virtual Arena * MessageLite::GetArena() const

Get the arena, if any, associated with this message.

Virtual method required for generic operations but most arena-related operations should use the GetArenaNoVirtual() generated-code method. Default implementation to reduce code size by avoiding the need for per-type implementations when types do not implement arena support.

virtual void * MessageLite::GetMaybeArenaPointer() const

Get a pointer that may be equal to this message's arena, or may not be.

If the value returned by this method is equal to some arena pointer, then this message is on that arena; however, if this message is on some arena, this method may or may not return that arena's pointer. As a tradeoff, this method may be more efficient than GetArena(). The intent is to allow underlying representations that use e.g. tagged pointers to sometimes store the arena pointer directly, and sometimes in a more indirect way, and allow a fastpath comparison against the arena pointer when it's easy to obtain.

virtual void MessageLite::Clear() = 0

Clear all fields of the message and set them to their default values.

Clear() avoids freeing memory, assuming that any memory allocated to hold parts of the message will be needed again to hold the next message. If you actually want to free the memory used by a Message, you must delete it.

virtual string MessageLite::InitializationErrorString() const

This is not implemented for Lite messages – it just returns "(cannot determine missing fields for lite message)".

However, it is implemented for full messages. See message.h.

virtual void MessageLite::CheckTypeAndMergeFrom(
        const MessageLite & other) = 0

If |other| is the exact same class as this, calls MergeFrom().

Otherwise, results are undefined (probably crash).

bool MessageLite::ParseFromCodedStream(
        io::CodedInputStream * input)

Fill the message with a protocol buffer parsed from the given input stream.

Returns false on a read error or if the input is in the wrong format. A successful return does not indicate the entire input is consumed, ensure you call ConsumedEntireMessage() to check that if applicable.

bool MessageLite::ParseFromZeroCopyStream(
        io::ZeroCopyInputStream * input)

Read a protocol buffer from the given zero-copy input stream.

If successful, the entire input will be consumed.

bool MessageLite::ParseFromBoundedZeroCopyStream(
        io::ZeroCopyInputStream * input,
        int size)

Read a protocol buffer from the given zero-copy input stream, expecting the message to be exactly "size" bytes long.

If successful, exactly this many bytes will have been consumed from the input.

bool MessageLite::ParseFromString(
        const string & data)

Parses a protocol buffer contained in a string.

Returns true on success. This function takes a string in the (non-human-readable) binary wire format, matching the encoding output by MessageLite::SerializeToString(). If you'd like to convert a human-readable string into a protocol buffer object, see google::protobuf::TextFormat::ParseFromString().

bool MessageLite::MergeFromCodedStream(
        io::CodedInputStream * input)

Reads a protocol buffer from the stream and merges it into this Message.

Singular fields read from the input overwrite what is already in the Message and repeated fields are appended to those already present.

It is the responsibility of the caller to call input->LastTagWas() (for groups) or input->ConsumedEntireMessage() (for non-groups) after this returns to verify that the message's end was delimited correctly.

ParsefromCodedStream() is implemented as Clear() followed by MergeFromCodedStream().

virtual bool MessageLite::MergePartialFromCodedStream(
        io::CodedInputStream * input) = 0

Like MergeFromCodedStream(), but succeeds even if required fields are missing in the input.

MergeFromCodedStream() is just implemented as MergePartialFromCodedStream() followed by IsInitialized().

bool MessageLite::SerializeToCodedStream(
        io::CodedOutputStream * output) const

Write a protocol buffer of this message to the given output.

Returns false on a write error. If the message is missing required fields, this may GOOGLE_CHECK-fail.

bool MessageLite::SerializeToZeroCopyStream(
        io::ZeroCopyOutputStream * output) const

Write the message to the given zero-copy output stream.

All required fields must be set.

bool MessageLite::SerializeToString(
        string * output) const

Serialize the message and store it in the given string.

All required fields must be set.

bool MessageLite::SerializeToArray(
        void * data,
        int size) const

Serialize the message and store it in the given byte array.

All required fields must be set.

string MessageLite::SerializeAsString() const

Make a string encoding the message.

Is equivalent to calling SerializeToString() on a string and using that. Returns the empty string if SerializeToString() would have returned an error. Note: If you intend to generate many such strings, you may reduce heap fragmentation by instead re-using the same string object with calls to SerializeToString().

bool MessageLite::AppendToString(
        string * output) const

Like SerializeToString(), but appends to the data to the string's existing contents.

All required fields must be set.

virtual int MessageLite::ByteSize() const = 0

Computes the serialized size of the message.

This recursively calls ByteSize() on all embedded messages. If a subclass does not override this, it MUST override SetCachedSize().

ByteSize() is generally linear in the number of fields defined for the proto.

virtual void MessageLite::SerializeWithCachedSizes(
        io::CodedOutputStream * output) const = 0

Serializes the message without recomputing the size.

The message must not have changed since the last call to ByteSize(); if it has, the results are undefined.

virtual int MessageLite::GetCachedSize() const = 0

Returns the result of the last call to ByteSize().

An embedded message's size is needed both to serialize it (because embedded messages are length-delimited) and to compute the outer message's size. Caching the size avoids computing it multiple times.

ByteSize() does not automatically use the cached size when available because this would require invalidating it every time the message was modified, which would be too hard and expensive. (E.g. if a deeply-nested sub-message is changed, all of its parents' cached sizes would need to be invalidated, which is too much work for an otherwise inlined setter method.)

virtual uint8 * MessageLite::InternalSerializeWithCachedSizesToArray(
        bool deterministic,
        uint8 * target) const

Like SerializeWithCachedSizes, but writes directly to *target, returning a pointer to the byte immediately after the last byte written.

"target" must point at a byte array of at least ByteSize() bytes. If deterministic is true then we use deterministic serialization, e.g., map keys are sorted. FOR INTERNAL USE ONLY!