如何在C ++中的pthread_create中正确传递具有函数成员的结构指针

Question

I'm working on an image processing project, where my job is to speed up the processing of a thinning algorithm.

This is the snippet of initial code:-

#include <iostream>
#include <stdlib.h>
#include <deque>
#include <opencv2/imgproc/imgproc.hpp>

#define ROWS 10
#define COLS 10
class Thinner
{
protected:
    typedef bool (*Thinner_Function)(uchar*  skeletal_data, int iter, int col,
            int row, int cols);
    bool thin_customize(Thinner_Function thin_fn);
    std::deque<int> cols_to_set;
    std::deque<int> rows_to_set;
};

bool Thinner::thin_customize(Thinner_Function thin_fn)
{
    uchar *skelcontour_data; //some data...
    for (unsigned short iter = 0; iter < 2; ++iter)
    {
        // for each point, check if it needs to be changed
        for (int row = 0; row < ROWS; ++row)
        {
            for (int col = 0; col < COLS; ++col)
            {
                if (thin_fn(skelcontour_data, iter, col, row, COLS))
                {
                    cols_to_set.push_back(col);
                    rows_to_set.push_back(row);
                }
            } // end for (col)
        } // end for (row)
    }
}

I want to split the

cols_to_set.push_back(col);
rows_to_set.push_back(row);

into 2 separate threads to see if it helps speed things up.

So here's what I tried:-

class Thinner
{
protected:
    typedef bool (*Thinner_Function)(uchar*  skeldata, int iter, int col, int row, int cols);
    typedef bool (*My_Thinner_Function)(uchar*  skeldata, int iter, int col, int row, int cols);
    void *push_rows(void *args);
    void push_cols(void *args)
    bool thin_customize();
    std::deque<int> cols_to_set;
    std::deque<int> rows_to_set;
    struct thread_struct
    {
        unsigned short iter;
        Thinner_Function thin_fn;
    };

};

void Thinner:: *push_cols(void *args)
        {
    Thinner::thread_struct *thread_data = args;
    //unsigned short iter = thread_data->iter;

    //Thinner::Thinner_Function thin_fn = thread_data->thin_fn;
    //this is incorrect...gives seg faults.
    //how to pass a function via struct in pthread_create()?

    for (int row = 0; row < ROWS; ++row)
    {
        for (int col = 0; col < COLS; ++col)
        {
            if (thin_fn(skelcontour_data, iter, col, row, COLS))
            {
                cols_to_set.push_back(col);
            }
        }
    }
        }

// similar for rows...

bool Thinner::thin_customize()
{
    pthread_t thread1, thread2;
    thread_struct thread_data = {0, My_Thinner_Function};
    for (unsigned short iter = 0; iter < 2; ++iter)
    {
        rows_to_set.clear();
        cols_to_set.clear();
        int  iret1, iret2;
        // for each point in skelcontour, check if it needs to be changed
        iret1 = pthread_create(&thread1, NULL, push_cols, &thread_data);
        if (iret1)
        {
            fprintf(stderr,"Error - pthread_create() return code: %d\n",iret1);
            exit(EXIT_FAILURE);
        }
        iret2 = pthread_create(&thread2, NULL, push_rows, &thread_data);
        if (iret2)
        {
            fprintf(stderr,"Error - pthread_create() return code: %d\n",iret2);
            exit(EXIT_FAILURE);
        }
        pthread_join(thread1, NULL);
        pthread_join(thread2, NULL);
    }
}


 but I'm stuck at not being able to properly pass the 

    typedef bool (*Thinner_Function)(uchar*  skeletal_data, int iter, int col, int row, int cols)

function via a struct through `pthread_create()`


    EDIT: based on suggestions by @G.M. and @Shadowigor:-

I tried to initialize the function inside `thin_customize()`, but I'm not sure how to do that. Sorry for the delay in response. Have been trying to init. the `Thinner_Function()` all day today, to no avail.

Answer 1

对于程序本身，您永远不会初始化thread_data ，这就是为什么thread_data->thin_fn将无效，从而导致段错误的原因。