版权声明:本文为博主原创文章,未经博主允许不得转载。 https://blog.csdn.net/zong596568821xp/article/details/82185537
什么是protobuf
Google Protocol Buffer(简称 Protobuf)是一种轻便高效的结构化数据存储格式,平台无关、语言无关、可扩展,可用于通讯协议和数据存储等领域。
优点
- 平台无关,语言无关,可扩展;
- 提供了友好的动态库,使用简单;
- 解析速度快,比对应的XML快约20-100倍;
- 序列化数据非常简洁、紧凑,与XML相比,其序列化之后的数据量约为1/3到1/10。
使用步骤
1 编写proto文件
首先需要一个proto文件,其中定义了我们程序中需要处理的结构化数据:
// Filename: addressbook.proto
syntax="proto2"; //表明使用protobuf的编译器版本为v2,目前最新的版本为v3
package addressbook;//声明一个包名,用来防止不同的消息类型命名冲突,类似于namespace
import "src/help.proto"; //举例用,编译时去掉 导入一个外部proto文件中的定义,
//类似于C++中的include
message Person { //message是Protobuf中的结构化数据,类似于C++中的类
//可以在其中定义需要处理的数据
required string name = 1; //声明一个名为name,数据类型为string的required字段
//字段的标识号为1
required int32 id = 2;
optional string email = 3;
enum PhoneType {
MOBILE = 0;
HOME = 1;
WORK = 2;
}
message PhoneNumber {
required string number = 1;
optional PhoneType type = 2 [default = HOME];
}
repeated PhoneNumber phone = 4;
}
message AddressBook {
repeated Person person_info = 1;
}
2 生成C++文件
protoc是proto文件的编译器,可以将proto文件编译成C++、Java、Python三种代码文件,编译格式如下
protoc -I=$SRC_DIR --cpp_out=$DST_DIR /path/to/file.proto
上面的命令会生成xxx.pb.h 和 xxx.pb.cc两个C++文件。
protoc的具体使用可执行protoc -help,输出内容如下
Usage: protoc [OPTION] PROTO_FILES
Parse PROTO_FILES and generate output based on the options given:
-IPATH, --proto_path=PATH Specify the directory in which to search for
imports. May be specified multiple times;
directories will be searched in order. If not
given, the current working directory is used.
--version Show version info and exit.
-h, --help Show this text and exit.
--encode=MESSAGE_TYPE Read a text-format message of the given type
from standard input and write it in binary
to standard output. The message type must
be defined in PROTO_FILES or their imports.
--decode=MESSAGE_TYPE Read a binary message of the given type from
standard input and write it in text format
to standard output. The message type must
be defined in PROTO_FILES or their imports.
--decode_raw Read an arbitrary protocol message from
standard input and write the raw tag/value
pairs in text format to standard output. No
PROTO_FILES should be given when using this
flag.
--descriptor_set_in=FILES Specifies a delimited list of FILES
each containing a FileDescriptorSet (a
protocol buffer defined in descriptor.proto).
The FileDescriptor for each of the PROTO_FILES
provided will be loaded from these
FileDescriptorSets. If a FileDescriptor
appears multiple times, the first occurrence
will be used.
-oFILE, Writes a FileDescriptorSet (a protocol buffer,
--descriptor_set_out=FILE defined in descriptor.proto) containing all of
the input files to FILE.
--include_imports When using --descriptor_set_out, also include
all dependencies of the input files in the
set, so that the set is self-contained.
--include_source_info When using --descriptor_set_out, do not strip
SourceCodeInfo from the FileDescriptorProto.
This results in vastly larger descriptors that
include information about the original
location of each decl in the source file as
well as surrounding comments.
--dependency_out=FILE Write a dependency output file in the format
expected by make. This writes the transitive
set of input file paths to FILE
--error_format=FORMAT Set the format in which to print errors.
FORMAT may be 'gcc' (the default) or 'msvs'
(Microsoft Visual Studio format).
--print_free_field_numbers Print the free field numbers of the messages
defined in the given proto files. Groups share
the same field number space with the parent
message. Extension ranges are counted as
occupied fields numbers.
--plugin=EXECUTABLE Specifies a plugin executable to use.
Normally, protoc searches the PATH for
plugins, but you may specify additional
executables not in the path using this flag.
Additionally, EXECUTABLE may be of the form
NAME=PATH, in which case the given plugin name
is mapped to the given executable even if
the executable's own name differs.
--cpp_out=OUT_DIR Generate C++ header and source.
--csharp_out=OUT_DIR Generate C# source file.
--java_out=OUT_DIR Generate Java source file.
--javanano_out=OUT_DIR Generate Java Nano source file.
--js_out=OUT_DIR Generate JavaScript source.
--objc_out=OUT_DIR Generate Objective C header and source.
--php_out=OUT_DIR Generate PHP source file.
--python_out=OUT_DIR Generate Python source file.
--ruby_out=OUT_DIR Generate Ruby source file.
3 使用C++文件
现在编写一个main.cc文件
#include <iostream>
#include "addressbook.pb.h"
int main(int argc, const char* argv[])
{
addressbook::AddressBook person;
addressbook::Person* pi = person.add_person_info();
pi->set_name("aut");
pi->set_id(1219);
std::cout << "before clear(), id = " << pi->id() << std::endl;
pi->clear_id();
std::cout << "after clear(), id = " << pi->id() << std::endl;
pi->set_id(1087);
if (!pi->has_email())
pi->set_email("[email protected]");
addressbook::Person::PhoneNumber* pn = pi->add_phone();
pn->set_number("021-8888-8888");
pn = pi->add_phone();
pn->set_number("138-8888-8888");
pn->set_type(addressbook::Person::MOBILE);
uint32_t size = person.ByteSize();
unsigned char byteArray[size];
person.SerializeToArray(byteArray, size);
addressbook::AddressBook help_person;
help_person.ParseFromArray(byteArray, size);
addressbook::Person help_pi = help_person.person_info(0);
std::cout << "*****************************" << std::endl;
std::cout << "id: " << help_pi.id() << std::endl;
std::cout << "name: " << help_pi.name() << std::endl;
std::cout << "email: " << help_pi.email() << std::endl;
for (int i = 0; i < help_pi.phone_size(); ++i)
{
auto help_pn = help_pi.mutable_phone(i);
std::cout << "phone_type: " << help_pn->type() << std::endl;
std::cout << "phone_number: " << help_pn->number() << std::endl;
}
std::cout << "*****************************" << std::endl;
return 0;
}
4 编译生成可执行文件
编译格式和普通的C++代码一样,但是要加上 -lprotobuf -pthread
g++ main.cc xxx.pb.cc -I $INCLUDE_PATH -L $LIB_PATH -lprotobuf -pthread
5 输出结果
before clear(), id = 1219
after clear(), id = 0
*****************************
id: 1087
name: aut
email: [email protected]
phone_type: 1
phone_number: 021-8888-8888
phone_type: 0
phone_number: 138-8888-8888
*****************************