pthread_create passing in dynamic vector array into argument - c++

Question

how do I cast a void pointer vector array into a vector array?
vector<string>* vArray = new vector<string[numThreads];
p_thread_create(&my_thread[1], NULL, &function, (void)* vArray[1]);
void* function (vector<string> vArray[])
{
//?? casting?
}
when passed in as argument (void)* vArray[1] it says invalid cast...
And can pthread create take in more arguments, say 2, if the function takes 2 parameters? Thanks
Here's my complete code
#include <iostream>
#include <iomanip>
#include <iterator>
#include <sstream>
#include <fstream>
#include <string>
#include <vector>
#include <pthread.h>
#include <queue>
using namespace std;
int array[5] = { 0, 0, 0, 0, 0 };
void* readData(void* arg)
{
string fileName = "Wisconsin.txt";
cout << "HERE!"<< endl;
ifstream cities(fileName.c_str());
string line;
while(!cities.eof()){
getline(cities, line);
if(line != "") {
int commaPos = line.find(',');
int popul = atoi(line.substr(commaPos + 2).c_str());
int x = popul;
if (x >= 1 && x <= 999)
{
array[0]++;
} else
if (x >= 1000 && x <= 9999)
{
array[1]++;
} else
if (x >= 10000 && x <= 99999)
{
array[2]++;
} else
if (x >= 100000 && x <= 999999)
{
array[3]++;
} else
if (x >= 1000000)
{
array[4]++;
}
} // end of IF
} // end of while
}
int main()
{
int numThreads;
ifstream ifs("states.txt");
std::string str((std::istreambuf_iterator<char>(ifs)),
std::istreambuf_iterator<char>());
stringstream ss(str);
int fileCount = 0;
string fileName;
while (ss >> fileName)
{
fileCount++;
}
cout << fileCount;
string* filesArr = new string[fileCount];
ss.clear();
ss.seekg(0, std::ios::beg);
for (int i = 0; i < fileCount; i++)
{
ss >> filesArr[i];
}
cout << "Enter number of threads: ";
cin >> numThreads;
vector<string>* vArray = new vector<string>[numThreads];
for (int i = 0; i < fileCount; i++)
{
vArray[i % numThreads].insert(vArray[i % numThreads].begin(), filesArr[i]);
}
//queue<string>* queueArr = new queue<string>[numThreads];
//for (int i = 0; i < fileCount; i++)
// queueArr[i % numThreads].push(filesArr[i]);
for(int i = 0; i < numThreads; i ++)
{
cout << endl;
cout << "FOR THREAD " << i + 1 << ":" << endl;
for (std::vector<string>::iterator it = vArray[i].begin(); it != vArray[i].end(); it++)
{
cout << *it << endl;
}
}
pthread_t my_thread[numThreads];
int ret = pthread_create(&my_thread[1], NULL, &readData, (void*)(vArray+1));
/////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////
///////////// ERROR HERE!
pthread_join(my_thread[1], ret);
// for (int id = 0; id < numThreads; id++)
// {
//}
pthread_join(my_thread[1]);
cout << endl;
printf("%-20s", "1-999:");
cout << array[0] << endl;
printf("%-20s", "1,000 - 9,999:");
cout << array[1] << endl;
printf("%-20s", "10,000-99,999:");
cout << (array[2]) << endl;
printf("%-20s", "100,000-999,999:");
cout << (array[3]) << endl;
printf("%-20s", "1,000,000+:");
cout << (array[4]) << endl;
//int pos;
//string token;
//while ((pos = s.find(delimiter))
cin.get();
return 0;
}
pthread join doesn't seem to be working now.. compiling it return me: too few arguments to function 'int pthread_join(pthread_t, void**)

Answer 1

After cleaning up your code:
#include <iostream>
#include <vector>
using namespace std;
const int numThreads = 10;
void * thread_body (void * param)
{
// retrieve parameter
string& prm = *(string *)param;
// use it
cout << prm << endl;
return NULL;
}
int main() {
vector<string >threadPrm(numThreads);
vector<pthread_t>threadId (numThreads);
threadPrm[1] = "Hello";
pthread_create(&threadId[1], NULL, thread_body, &threadPrm[1]);
pthread_join (threadId[1], NULL);
return 0;
}
You don't seem to be comfortable with
vectors
pointers and references
variable naming
Also, trying to shut the compiler up with static casts is a sure way to produce silly code.
The point is usually to make the code run, not to compile it at all cost.
Lastly, you can answer your own question about the number of parameters a posix thread can take by reading the manual