Memory Pager

#define WINVER _WIN32_WINNT_WIN7
#include <iostream>
#include <list>
#include <windows.h>
#include <psapi.h>




class Process
{
    private:
    void* hndl = INVALID_HANDLE_VALUE;

    public:
    void* get() const noexcept
    { return hndl; }

    bool invalid() const noexcept
    { return get() == nullptr; }

    bool valid() const noexcept
    { return !invalid(); }

    // Operators
    HANDLE& operator=(HANDLE& h) noexcept
    {
        if (hndl != INVALID_HANDLE_VALUE) CloseHandle(hndl);
        hndl = h;
        return hndl;
    }

    operator void*() const noexcept
    { return get(); }

    explicit operator bool() const noexcept
    { return valid(); }

    // Constructors
    Process() = default;
    Process(HANDLE h) : hndl(h){};

    ~Process()
    { CloseHandle(hndl); }
};


bool PSAPI_EnumProcesses(
    std::list<unsigned int>& listProcessIDs,
    unsigned int dwMaxProcessCount)
{ // stolen from stackoverflow
    DWORD dwRet = NO_ERROR;
    listProcessIDs.clear();
    DWORD *pProcessIds = new DWORD[dwMaxProcessCount];
    DWORD cb = dwMaxProcessCount * sizeof(DWORD);
    DWORD dwBytesReturned = 0;

    if (::EnumProcesses(pProcessIds, cb, &dwBytesReturned))
    {
        const int nSize = dwBytesReturned / sizeof(DWORD);
        for(int nIndex = 0; nIndex < nSize; nIndex++)
        { listProcessIDs.push_back(pProcessIds[nIndex]); }
    } else dwRet = ::GetLastError();
    delete[]pProcessIds;

    return dwRet == NO_ERROR;
}


bool flush(unsigned int pid)
{
    Process hndl(OpenProcess(
            PROCESS_QUERY_INFORMATION | PROCESS_SET_QUOTA | PROCESS_VM_READ,
            false,
            pid));

    if (hndl)
    {
        if (EmptyWorkingSet(hndl))
        {
            char name[MAX_PATH];
            std::cout
                << " Success: "
                << (GetModuleFileNameEx(hndl,0,name,MAX_PATH) ? name : "???")
                << " (" << pid << ")"
                << std::endl;
            return true;
        } else std::cout << " FAILURE: EmptyWorkingSet() " << pid << std::endl;
    } else std::cout << " FAILURE: OpenProcess() " << pid << std::endl;
    return false;
}


void flush_all()
{
    std::list<unsigned int> listProcessIDs;
    const unsigned int MaxProcessCount = 1024;

    if (PSAPI_EnumProcesses(listProcessIDs, MaxProcessCount))
    { for (const unsigned int& pid : listProcessIDs) flush(pid); }
    else std::cout << "PSAPI_EnumProcesses() failed." << std::endl;
}


int main()
{
    using namespace std;

    cout
        << "Emptying the working sets of all open processes.\n"
        << "This may cause some weirdness...\n"
        << endl;

    flush_all();

    cout << "\n\n\nFlushing Complete." << endl;

    return 0;
}




/* ------------ Dylan's C code for "reference" (read: stealing)
#define WINVER 0x0600
#include <stdio.h>
#include <windows.h>
#include <psapi.h>
#include <stdint.h>

int main()
{
    uint32_t pid;

    do
    {
        HANDLE pidHandle;

        fprintf(stderr, "Enter the PID to flush pages: ");
        scanf("%u", &pid);

        if ((pidHandle = OpenProcess(PROCESS_QUERY_INFORMATION | PROCESS_SET_QUOTA, 0, pid)) != NULL)
        {
            if (EmptyWorkingSet(pidHandle))
                fprintf(stderr, "Pages flushed successfully.\n");
            else
                fprintf(stderr, "Pages couldn't be flushed...access permissions?\n");
        }
        else
            fprintf(stderr, "nope.jpg...probably invalid pid.\n");

        CloseHandle(pidHandle);
    } while (pid != 0);

    return 0;

}
*/