mutexSharedPtr.cpp

#include <iostream>
#include <mutex>
#include <map>
using namespace std;


// Map file paths to their respective files' mutexes
map<string, shared_ptr<mutex>> fileMutexes = {};
mutex fileMutexesAccess;

shared_ptr<mutex> getFileMutex(const string& filePath){
  unique_lock<mutex> lock(fileMutexesAccess);

  if(fileMutexes.count(filePath)){
    cout << "existed already for: " << filePath << endl;
    return fileMutexes[filePath];

  }else{
    shared_ptr<mutex> mut(new mutex());
    fileMutexes.insert(std::make_pair(filePath, mut));
    return fileMutexes[filePath];
  }
}

void testFileLocks(){
  string samplePathA = "some/path/";
  string samplePathB = "some/path/";
  string samplePathC = "diff/erent/";

  // A and B are the same (have similar addresses), but C is not
  auto mutexA = getFileMutex(samplePathA);
  auto mutexB = getFileMutex(samplePathB);
  auto mutexC = getFileMutex(samplePathC);

  // Shows how to use the mutex with unique_lock
  unique_lock<mutex> lck(*mutexA);

  // Print the addresses of the mutex pointers
  cout << mutexA << endl;
  cout << mutexB << endl;
  cout << mutexC << endl;
}

int main(){
  testFileLocks();
}