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copied!<p>A toy program on how to use some C++0x threading and synchronization facilities. No idea on what the performance of this (I recommend Matt's answer), my focus is on clarity and correctness for the sake of making an example.</p> <p>The files are read separately, as you requested. They're not converted to a sequence of <code>int</code> however, as I feel this is more related to processing rather than strict I/O. So the files are dumped into a plain <code>std::string</code>.</p> <pre><code>#include <fstream> #include <sstream> #include <string> #include <vector> #include <deque> #include <future> #include <mutex> #include <condition_variable> int main() { // this is shared std::mutex mutex; std::condition_variable condition; bool more_to_process = true; std::deque<std::string> to_process; /* Reading the files is done asynchronously */ std::vector<std::string> filenames = /* initialize */ auto process = std::async(std::launch::async, [&](std::vector<std::string> filenames) { typedef std::lock_guard<std::mutex> lock_type; for(auto&& filename: filenames) { std::ifstream file(filename); if(file) { std::ostringstream stream; stream << file.rdbuf(); if(stream) { lock_type lock(mutex); to_process.push_back(stream.str()); condition.notify_one(); } } } lock_type lock(mutex); more_to_process = false; condition.notify_one(); }, std::move(filenames)); /* processing is synchronous */ for(;;) { std::string file; { std::unique_lock<std::mutex> lock(mutex); condition.wait(lock, [&] { return !more_to_process || !to_process.empty(); }); if(!more_to_process && to_process.empty()) break; else if(to_process.empty()) continue; file = std::move(to_process.front()); to_process.pop_front(); } // use file here } process.get(); } </code></pre> <p>Some notes:</p> <ul> <li>the mutex, condition variable, stop flag and <code>std::string</code> container are all logically related. You may as well replace them with a thread-safe container/channel</li> <li>I use <code>std::async</code> instead of <code>std::thread</code> because it has better exception-safety characteristics</li> <li>there is no error handling to speak of; if a file can't be read for some reason, it is silently skipped. You have several options: signal that there is no more to process and throw to handle as soon as possible; or use a <code>boost::variant<std::string, std::exception_ptr></code> to pass the error on to the processing side of things (here the error is passed as an exception but you can use an <code>error_code</code> or anything you fancy). Not an exhaustive list by any means.</li> </ul>

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