Like this article? We recommend
Like this article? We recommend
Like this article? We recommend
C++ Design Issues
Using Python as a glue logic facility necessarily imposes a number of design requirements on your C++ code:
- Good error-handling and exception management
- Correct memory management
- Correct disk I/O management
In other words, if you call bad C++ code from within Python glue logic, the result won't be any better than calling the C++ code directly! Listing 5 illustrates the C++ code used earlier.
Listing 5—The C++ code invoked using Python.
#include <iostream>
#include <string.h>
#define MEMORY_BLOCK_SIZE 30
#include "Person.h"
using namespace std;
void printABlock(string blockName, char *block, int size) {
cout << blockName << " = ";
for (int i = 0; i < size; i++) {
cout << block[i];
}
cout << endl;
}
void doSomeMemoryWork()
{
cout << endl << "Function name: "<< __func__ << "()"<< endl;
char* a = (char*)malloc(MEMORY_BLOCK_SIZE);
memset(a, 'a', MEMORY_BLOCK_SIZE);
char* b = (char*)malloc(MEMORY_BLOCK_SIZE);
memset(b, 'b', MEMORY_BLOCK_SIZE);
char* c = (char*)malloc(MEMORY_BLOCK_SIZE);;
memset(c, 'c', MEMORY_BLOCK_SIZE);
cout << "Before memory assignment" << endl;
printABlock("a", a, MEMORY_BLOCK_SIZE);
printABlock("b", b, MEMORY_BLOCK_SIZE);
printABlock("c", c, MEMORY_BLOCK_SIZE);
// Before re-assignment of a, free its allocated memory
free(a);
a = b;
cout << "After memory assignment" << endl;
printABlock("a", a, MEMORY_BLOCK_SIZE);
printABlock("b", b, MEMORY_BLOCK_SIZE);
printABlock("c", c, MEMORY_BLOCK_SIZE);
free (b);
free (c);
}
unique_ptr<Person> createPerson()
{
unique_ptr<Person> p(new Person("John Doe", 100));
cout << "Person just created is: " << p->getName() << endl;
return p;
}
void getPersonDetails()
{
unique_ptr<Person> person = createPerson();
cout << "Person name = " << person->getName(); // Get the person's name
// The person object is now destroyed on exit
}
int main() {
cout << endl << "Now calling doSomeMemoryWork()" << endl;
doSomeMemoryWork();
cout << "Now calling getPersonDetails()" << endl;
getPersonDetails();
return 0;
}
Listing 5 calls two functions:
doSomeMemoryWork();
and
getPersonDetails();
The first function (doSomeMemoryWork) makes some C calls to malloc(), memset(), and free(). This function also does a little bit of pointer reassignment and prints the results.
Inside getPersonDetails(), I use a unique_ptr to create an object that then gets deleted automatically.
Not much happens inside the C++ code. However, there's no real limit to the complexity that can be added to the invoked C++ program. In other words, any legacy C++ program can be run in this way. As with all software, the better the code quality, the better the experience!