#include "pch.h"
#include <stdlib.h>
#include <stdio.h>
#include <Windows.h>
#include <string.h>

/**************************************************************************
 * Authors: Gary Fleming, Amber McCloughan
 * Class: CIS452 - Operating Systems Concepts
 * Professor: Dr. Greg Wolffe
 * Date: 4/11/2019
 * 
 * A mini programming assignment where we do some memory operations in
 * Windows. We get the page size of the system, allocate memory,
 * check the state of that memory, deallocate the memory, and then check 
 * the state of the memory again.
 ***************************************************************************/

// See function implementation for details.
const char *checkMemState(DWORD);

/**
 * Main function for driving the program.
 */
int main()
{
    // Buffer for holding system info.
    SYSTEM_INFO sysInf;

    // Grabbing system info.
    GetSystemInfo(&sysInf);

    // Figuring out the size of a page and printing it.
    printf("The size of a page is: %lu\n", sysInf.dwPageSize);

    // Allocating a large sum of memory (1M).
    printf("Allocating memory...\n");
    int *bigboy = (int *)malloc(1048576);

    // Buffer for holding memory information.
    MEMORY_BASIC_INFORMATION buf;

    // Querying memory information about the memory we allocated.
    VirtualQuery(bigboy, &buf, sizeof(MEMORY_BASIC_INFORMATION));

    // Printing out the memory's state.
    printf("The state of the memory is: %s\n", checkMemState(buf.State));

    // Freeing the allocated memory.
    printf("Freeing memory...\n");
    free(bigboy);

    // Querying memory information about the memory location again.
    VirtualQuery(bigboy, &buf, sizeof(MEMORY_BASIC_INFORMATION));

    // Printing out the memory's state again.
    printf("The state of the memory is: %s\n", checkMemState(buf.State));

    // Goodbye.
    return 0;
}

/**
 * Function that takes the memory state and
 * turns it into a user-readable string.
 *
 * @param DWORD state, the raw value for the
 * memory state.
 */
const char *checkMemState(DWORD state)
{
    // Committed state (0x1000)
    if (state == 4096)
    {
        return "COMMITTED";
    }
    // Free state (0x10000)
    else if (state == 65536)
    {
        return "FREE";
    }
    // Reserved state (0x2000)
    else if (state == 8192)
    {
        return "RESERVED";
    }
    // Catch-all for any issues.
    else
    {
        return "UNKNOWN";
    }
}