CMake基础第15节使用Protobuf生成源文件

转载

mob604757042166 2021-07-28 11:33:00

文章标签 c++ ios #include 源文件编译器 文章分类 C/C++ 后端开发

介绍

这个例子展示了如何使用Protobuf生成源文件。Protocol Buffers是Google提供的一种数据序列化格式。用户提供带有数据描述的.proto文件。然后使用Protobuf编译器，可以将该原始文件翻译成包括C++在内的多种语言的源代码。

本教程中的文件如下：

$ tree
.
├── AddressBook.proto
├── CMakeLists.txt
├── main.cpp

[AddressBook.proto] - 来自main protocol buffer示例的proto文件

package tutorial;

message Person {
  required string name = 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 = 1;
}

[CMakeLists.txt] - 包含要运行的CMake命令

cmake_minimum_required(VERSION 3.5)

# Set the project name
project (protobuf_example)

# find the protobuf compiler and libraries
find_package(Protobuf REQUIRED)

# check if protobuf was found
if(PROTOBUF_FOUND)
    message ("protobuf found")
else()
    message (FATAL_ERROR "Cannot find Protobuf")
endif()

# Generate the .h and .cxx files
PROTOBUF_GENERATE_CPP(PROTO_SRCS PROTO_HDRS AddressBook.proto)

# Print path to generated files
message ("PROTO_SRCS = ${PROTO_SRCS}")
message ("PROTO_HDRS = ${PROTO_HDRS}")

# Add an executable
add_executable(protobuf_example
    main.cpp
    ${PROTO_SRCS}
    ${PROTO_HDRS})

target_include_directories(protobuf_example
    PUBLIC
    ${PROTOBUF_INCLUDE_DIRS}
    ${CMAKE_CURRENT_BINARY_DIR}
)

# link the exe against the libraries
target_link_libraries(protobuf_example
    PUBLIC
    ${PROTOBUF_LIBRARIES}
)

[main.cpp] - protobuf示例的源文件.

#include <iostream>
#include <fstream>
#include <string>
#include "AddressBook.pb.h"
using namespace std;

// This function fills in a Person message based on user input.
void PromptForAddress(tutorial::Person* person) {
  cout << "Enter person ID number: ";
  int id;
  cin >> id;
  person->set_id(id);
  cin.ignore(256, '\n');

  cout << "Enter name: ";
  getline(cin, *person->mutable_name());

  cout << "Enter email address (blank for none): ";
  string email;
  getline(cin, email);
  if (!email.empty()) {
    person->set_email(email);
  }

  while (true) {
    cout << "Enter a phone number (or leave blank to finish): ";
    string number;
    getline(cin, number);
    if (number.empty()) {
      break;
    }

    tutorial::Person::PhoneNumber* phone_number = person->add_phone();
    phone_number->set_number(number);

    cout << "Is this a mobile, home, or work phone? ";
    string type;
    getline(cin, type);
    if (type == "mobile") {
      phone_number->set_type(tutorial::Person::MOBILE);
    } else if (type == "home") {
      phone_number->set_type(tutorial::Person::HOME);
    } else if (type == "work") {
      phone_number->set_type(tutorial::Person::WORK);
    } else {
      cout << "Unknown phone type.  Using default." << endl;
    }
  }
}

// Main function:  Reads the entire address book from a file,
//   adds one person based on user input, then writes it back out to the same
//   file.
int main(int argc, char* argv[]) {
  // Verify that the version of the library that we linked against is
  // compatible with the version of the headers we compiled against.
  GOOGLE_PROTOBUF_VERIFY_VERSION;

  if (argc != 2) {
    cerr << "Usage:  " << argv[0] << " ADDRESS_BOOK_FILE" << endl;
    return -1;
  }

  tutorial::AddressBook address_book;

  {
    // Read the existing address book.
    fstream input(argv[1], ios::in | ios::binary);
    if (!input) {
      cout << argv[1] << ": File not found.  Creating a new file." << endl;
    } else if (!address_book.ParseFromIstream(&input)) {
      cerr << "Failed to parse address book." << endl;
      return -1;
    }
  }

  // Add an address.
  PromptForAddress(address_book.add_person());

  {
    // Write the new address book back to disk.
    fstream output(argv[1], ios::out | ios::trunc | ios::binary);
    if (!address_book.SerializeToOstream(&output)) {
      cerr << "Failed to write address book." << endl;
      return -1;
    }
  }

  // Optional:  Delete all global objects allocated by libprotobuf.
  google::protobuf::ShutdownProtobufLibrary();

  return 0;
}

要求

此示例需要安装protocol buffers二进制文件和库。可以使用以下命令将其安装在Ubuntu上。

sudo apt-get install protobuf-compiler libprotobuf-dev

概念

导出变量

由CMake Protobuf包导出并在此示例中使用的变量包括:

PROTOBUF_FOUND - 如果安装了Protocol Buffers
PROTOBUF_INCLUDE_DIRS - protobuf的头文件
PROTOBUF_LIBRARIES - protobuf库

此外，还可以通过查看FindProtobuf.cmake文件顶部的内容找到定义的更多变量。

生成源代码

Protobuf CMake包包含许多帮助函数，以简化代码生成。在本例中，我们生成的是C++源代码，使用以下代码：

PROTOBUF_GENERATE_CPP(PROTO_SRCS PROTO_HDRS AddressBook.proto)

这些参数包括:

PROTO_SRCS - 存储.pb.cc文件的变量名称
PROTO_HDRS- 存储.pb.h文件的变量名称
AddressBook.proto - 从中生成代码的.proto文件

生成文件

在调用PROTOBUF_GENERATE_CPP函数之后，你将拥有上面提到的变量。这些将被标记为自定义命令的输出，该命令将调用Protobuf编译器来生成它们。

要生成这些文件，你应该将它们添加到库或可执行文件中。

例如：

add_executable(protobuf_example
    main.cpp
    ${PROTO_SRCS}
    ${PROTO_HDRS})

这将导致在对该可执行文件目标调用make时调用protocol buf编译器。

对.proto文件进行更改后，将再次自动生成关联的源文件。但是，如果没有对.proto文件进行任何更改，并且你重新运行make，则不会执行任何操作。

构建示例

$ mkdir build

$ cd build/

$ cmake ..
-- The C compiler identification is GNU 4.8.4
-- The CXX compiler identification is GNU 4.8.4
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Looking for include file pthread.h
-- Looking for include file pthread.h - found
-- Looking for pthread_create
-- Looking for pthread_create - not found
-- Looking for pthread_create in pthreads
-- Looking for pthread_create in pthreads - not found
-- Looking for pthread_create in pthread
-- Looking for pthread_create in pthread - found
-- Found Threads: TRUE
-- Found PROTOBUF: /usr/lib/x86_64-linux-gnu/libprotobuf.so
protobuf found
PROTO_SRCS = /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/AddressBook.pb.cc
PROTO_HDRS = /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/AddressBook.pb.h
-- Configuring done
-- Generating done
-- Build files have been written to: /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build

$ ls
CMakeCache.txt  CMakeFiles  cmake_install.cmake  Makefile

$ make VERBOSE=1
/usr/bin/cmake -H/home/matrim/workspace/cmake-examples/03-code-generation/protobuf -B/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build --check-build-system CMakeFiles/Makefile.cmake 0
/usr/bin/cmake -E cmake_progress_start /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles/progress.marks
make -f CMakeFiles/Makefile2 all
make[1]: Entering directory `/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build'
make -f CMakeFiles/protobuf_example.dir/build.make CMakeFiles/protobuf_example.dir/depend
make[2]: Entering directory `/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build'
/usr/bin/cmake -E cmake_progress_report /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles 1
[ 33%] Running C++ protocol buffer compiler on AddressBook.proto
/usr/bin/protoc --cpp_out /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build -I /home/matrim/workspace/cmake-examples/03-code-generation/protobuf /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/AddressBook.proto
cd /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build && /usr/bin/cmake -E cmake_depends "Unix Makefiles" /home/matrim/workspace/cmake-examples/03-code-generation/protobuf /home/matrim/workspace/cmake-examples/03-code-generation/protobuf /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles/protobuf_example.dir/DependInfo.cmake --color=
Dependee "/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles/protobuf_example.dir/DependInfo.cmake" is newer than depender "/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles/protobuf_example.dir/depend.internal".
Dependee "/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles/CMakeDirectoryInformation.cmake" is newer than depender "/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles/protobuf_example.dir/depend.internal".
Scanning dependencies of target protobuf_example
make[2]: Leaving directory `/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build'
make -f CMakeFiles/protobuf_example.dir/build.make CMakeFiles/protobuf_example.dir/build
make[2]: Entering directory `/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build'
/usr/bin/cmake -E cmake_progress_report /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles 2
[ 66%] Building CXX object CMakeFiles/protobuf_example.dir/main.cpp.o
/usr/bin/c++    -I/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build    -o CMakeFiles/protobuf_example.dir/main.cpp.o -c /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/main.cpp
/usr/bin/cmake -E cmake_progress_report /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles 3
[100%] Building CXX object CMakeFiles/protobuf_example.dir/AddressBook.pb.cc.o
/usr/bin/c++    -I/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build    -o CMakeFiles/protobuf_example.dir/AddressBook.pb.cc.o -c /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/AddressBook.pb.cc
Linking CXX executable protobuf_example
/usr/bin/cmake -E cmake_link_script CMakeFiles/protobuf_example.dir/link.txt --verbose=1
/usr/bin/c++       CMakeFiles/protobuf_example.dir/main.cpp.o CMakeFiles/protobuf_example.dir/AddressBook.pb.cc.o  -o protobuf_example -rdynamic -lprotobuf -lpthread
make[2]: Leaving directory `/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build'
/usr/bin/cmake -E cmake_progress_report /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles  1 2 3
[100%] Built target protobuf_example
make[1]: Leaving directory `/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build'
/usr/bin/cmake -E cmake_progress_start /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles 0
$ make VERBOSE=1
/usr/bin/cmake -H/home/matrim/workspace/cmake-examples/03-code-generation/protobuf -B/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build --check-build-system CMakeFiles/Makefile.cmake 0
/usr/bin/cmake -E cmake_progress_start /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles/progress.marks
make -f CMakeFiles/Makefile2 all
make[1]: Entering directory `/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build'
make -f CMakeFiles/protobuf_example.dir/build.make CMakeFiles/protobuf_example.dir/depend
make[2]: Entering directory `/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build'
/usr/bin/cmake -E cmake_progress_report /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles 1
[ 33%] Running C++ protocol buffer compiler on AddressBook.proto
/usr/bin/protoc --cpp_out /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build -I /home/matrim/workspace/cmake-examples/03-code-generation/protobuf /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/AddressBook.proto
cd /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build && /usr/bin/cmake -E cmake_depends "Unix Makefiles" /home/matrim/workspace/cmake-examples/03-code-generation/protobuf /home/matrim/workspace/cmake-examples/03-code-generation/protobuf /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles/protobuf_example.dir/DependInfo.cmake --color=
Dependee "/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles/protobuf_example.dir/DependInfo.cmake" is newer than depender "/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles/protobuf_example.dir/depend.internal".
Dependee "/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles/CMakeDirectoryInformation.cmake" is newer than depender "/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles/protobuf_example.dir/depend.internal".
Scanning dependencies of target protobuf_example
make[2]: Leaving directory `/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build'
make -f CMakeFiles/protobuf_example.dir/build.make CMakeFiles/protobuf_example.dir/build
make[2]: Entering directory `/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build'
/usr/bin/cmake -E cmake_progress_report /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles 2
[ 66%] Building CXX object CMakeFiles/protobuf_example.dir/main.cpp.o
/usr/bin/c++    -I/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build    -o CMakeFiles/protobuf_example.dir/main.cpp.o -c /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/main.cpp
/usr/bin/cmake -E cmake_progress_report /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles 3
[100%] Building CXX object CMakeFiles/protobuf_example.dir/AddressBook.pb.cc.o
/usr/bin/c++    -I/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build    -o CMakeFiles/protobuf_example.dir/AddressBook.pb.cc.o -c /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/AddressBook.pb.cc
Linking CXX executable protobuf_example
/usr/bin/cmake -E cmake_link_script CMakeFiles/protobuf_example.dir/link.txt --verbose=1
/usr/bin/c++       CMakeFiles/protobuf_example.dir/main.cpp.o CMakeFiles/protobuf_example.dir/AddressBook.pb.cc.o  -o protobuf_example -rdynamic -lprotobuf -lpthread
make[2]: Leaving directory `/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build'
/usr/bin/cmake -E cmake_progress_report /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles  1 2 3
[100%] Built target protobuf_example
make[1]: Leaving directory `/home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build'
/usr/bin/cmake -E cmake_progress_start /home/matrim/workspace/cmake-examples/03-code-generation/protobuf/build/CMakeFiles 0

$ ls
AddressBook.pb.cc  CMakeCache.txt  cmake_install.cmake  protobuf_example
AddressBook.pb.h   CMakeFiles      Makefile

$ ./protobuf_example test.db
test.db: File not found.  Creating a new file.
Enter person ID number: 11
Enter name: John Doe
Enter email address (blank for none): wolly@sheep.ie
Enter a phone number (or leave blank to finish):

$ ls
AddressBook.pb.cc  CMakeCache.txt  cmake_install.cmake  protobuf_example
AddressBook.pb.h   CMakeFiles      Makefile             test.db

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