[C++知识库]c++与python共享内存

c++与python通信

步骤

0.c++编译带有使用共享内存函数的动态链接库
1.c++开内存，读内存
2.python写内存
注：二者的内存同一地址。

程序

#ifndef  __SHRMM_HPP_
#define  __SHRMM_HPP_

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include  <sys/types.h>
#include  <sys/ipc.h>
#include  <sys/shm.h>

class TestLib
{
 public:
  TestLib() {addr = NULL; shmid = 0; size = 0;};
  int open_shm(int share_memory_key, int share_feature);
  int close_shm();
  void* get_address();
  int get_maxsize();
 private:
  int shmid = 0;
  int size = 0;
  void* addr = NULL;
};

#endif // __SHRMM_HPP_

#include "shrmm.hpp"
#include "iostream"


int TestLib::open_shm(int share_memory_key, int share_memory_size)
{
  int id;
  if (share_memory_key <= 0) return 0;
  id = shmget(share_memory_key, share_memory_size, 0666 | IPC_CREAT);

  if (id == -1) return 0;
  shmid = id;
  size = share_memory_size;
  addr = shmat(shmid, (void *)0, 0);

  return 1;
}

/**
 * @brief  free the share memory
 * <long-description>
 *
 * @param
 * @return <ReturnValue>
 */
int TestLib:: close_shm()
{
  int rtn;
  rtn = shmdt(addr);
  return rtn;

}

/**
 * @brief get address of share memory
 * <long-description>
 *
 * @param
 * @return <ReturnValue>
 */
void* TestLib::get_address()
{
  if (addr == NULL) return NULL;
  return (void*) addr;
}

/**
 * @brief get the size of created share memory
 * <long-description>
 *
 * @param
 * @return <ReturnValue>
 */
int TestLib::get_maxsize()
{
  return size;
}

extern "C" {
  TestLib obj;
  int open_shm(int share_memory_key, int share_memory_size) {
    int id = obj.open_shm(share_memory_key, share_memory_size);
    return id;
  }
  int close_shm() {
    int rtn = obj.close_shm();
    return rtn;
  }
  void * get_address() {
    void * add1;
    add1 = obj.get_address();
    return add1;
  }
}

cmake_minimum_required(VERSION 3.1.0)                              
project (lib) 
set (CMAKE_CXX_STANDARD 14)

set(CMAKE_EXPORT_COMPILE_COMMANDS 1)
set(CMAKE_BUILD_TYPE "Release")
set(BOOST_LIBS date_time system)

include_directories("../include/"
)
                                                                   
add_library(m_sharmMem  SHARED ../shrmm.cpp)


set(libso m_sharmMem )
set(includeFile ../include/shrmm.hpp )
target_link_libraries(${libso}) 
 

#ifndef _MAIN_H
#define _MAIN_H

#include "main.h"
#include <iostream>
#include "shrmm.hpp"

using namespace std;

int initial_memory();

typedef struct Features {
  int Image_X;
  int Image_Y;
  float Image_Z;
  int Class_Id;
}Features;

TestLib m_sh_cmd_features;
Features *pStatus_feature;


// share_memory m_sh_cmd_feature;

#endif

#include "main.h"
#include <iostream>
#include "stdio.h"

using namespace std;

int main(int argc, char *argv[]) {
  initial_memory();
  pStatus_feature->Class_Id = 0;
  pStatus_feature->Image_X = 1;
  pStatus_feature->Image_Y = 2;
  pStatus_feature->Image_Z = 3;
  while(1) {
    cout<< "the image features xxxxxxx:"<< pStatus_feature->Image_X<< endl;
    cout<< "the image features yyyyyyy:"<< pStatus_feature->Image_Y<< endl;
    cout<< "the image features zzzzzzz:"<< pStatus_feature->Image_Z<< endl;
    cout<< "the image features iiiiiii:"<< pStatus_feature->Class_Id<< endl;
  }
  cout << "exit " << endl;
  return 0;
}
// open the share memory
int initial_memory() {
  int i = shmget(4600, 1024, 0666|IPC_CREAT);;
  if(i == 0) {
    cout<< "error"<< endl;
    return 0;
  }
  void* addr = NULL;
  addr = shmat(i, (void *)0, 0);
  pStatus_feature = (Features*)addr;
  memset(pStatus_feature, 0, sizeof(Features));

  return 1;
}

cmake_minimum_required(VERSION 2.8)
project(calibControl)

include(CheckCXXCompilerFlag)
CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
CHECK_CXX_COMPILER_FLAG("-std=c++0x" COMPILER_SUPPORTS_CXX0X)

# 使用变量设置编译标志
if(COMPILER_SUPPORTS_CXX11)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
elseif(COMPILER_SUPPORTS_CXX0X)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x")
else()
message(STATUS "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support. Please use a different C++ compiler.")
endif()

SET(CMAKE_BUILD_TYPE "Release")

SET(CMAKE_CXX_FLAGS_DEBUG "$ENV{CXXFLAGS} -O0 -Wall -g -ggdb")
SET(CMAKE_CXX_FLAGS_RELEASE "$ENV{CXXFLAGS} -O3 -Wall")

include_directories("./include/")
include_directories("./")
aux_source_directory(./src SRC_FILES)
set(SRC_LIST ${SRC_FILES})
#add_executable(memoryTest main.cpp ./src/shrmm.cpp)
add_executable(memoryTest main.cpp ${SRC_LIST})
target_link_libraries(memoryTest  ${PROJECT_SOURCE_DIR}/lib/libm_sharmMem.so)

import os
import ctypes
from ctypes import *
import sys
import struct
#import posix_ipc
from configparser import ConfigParser
# def initShm():
#ll = ctypes.cdll.LoadLibrary


var = []
lib = cdll.LoadLibrary('./lib/libm_sharmMem.so')
class image_show_struct (ctypes.Structure):
    _fields_ = [("image_x", ctypes.c_int),
                ("image_y", ctypes.c_int),
                ("image_z", ctypes.c_float),
                ("class_id", ctypes.c_int)]
#config = ConfigParser()
#config.read("./config.ini")
#SHM_KEY = config.getint("shareM", "id")
SHM_KEY = 4600
SHM_SIZE = 1024

# this part is used to define shmget and shmat in python
shmget = lib.shmget
shmget.argtypes = [c_int, c_size_t, c_int]
shmget.restype = c_int
shmat = lib.shmat
shmat.argtypes = [c_int, POINTER(c_void_p), c_int]
shmat.restype = POINTER(image_show_struct)

shmid = shmget(SHM_KEY, SHM_SIZE, 0o666)
print(shmid)
if shmid < 0:
    print ("System not infected")
else:
    addr = shmat(shmid, None, 0)
print(addr)

# use the parameters in C++
for x in range(1, 10):
    addr.contents.image_x=x
    addr.contents.image_y=2*x
    addr.contents.image_z=3*x
    var = [addr.contents.image_x, addr.contents.image_y, addr.contents.image_z]
    print(var)
    addr.contents.class_id = 4*x
    cls_id = addr.contents.class_id
    print(cls_id)

if id == 0:
    print("error")
else:
    print("ok")

print("end")