Anyone got a faster way of doing this?

so I have this code... which seems long and cumbersome, and not all that fun to type out, and so far I have thought of using tables to get things up and running, but I wanted to see if anyone had something better it would go something like this

I am trying to find the bits borrowed out of an ip address and the bits remaining

Code:

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void bitsborrowed(int ip[], int subnet[], char addressclass,  int *bitsborrowed, int *bitsremaning)
{
    if(addressclass == 'c')
    {
        //for class c use the last octet
        if(subnet[3] == 252)
        {
              *bitsremaining = 2;
              *bitsborrowed = 6;
        }
        else if(subnet[3] == 248)
        {
              *bitsremaining = 3;
              *bitsborrowed = 5;
        }
   

  //etc...
  if(addressclass == 'b')
  {
      if(subnet[3] === 252 && subnet[2] == 255)
      {
            *bitsremaining = 2;
            *bitsborrowed = 14;
      }



  // and so forth...

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as you can see there are a lot of cases to check... any help would be great, thanks!

One solution is to implement all cases in their own functions and use a map.

Kuphryn

Hmmm, well thats possible, I was thinking would it be possible to use it as such? I know the total range of values, would it be easier to create sort of a hash. That is, create an array that has values which represent the differences between the octets? Like I could figure things based on that? I have no idea, just more ideas would be awesome... partially because a lot of you have good ideas and I like to see as many as I can.

Wow

Is that repetitve or what?

Perhaps you may want to look at using switch and increment or decrement your bits...

Based on the octet value

First, represent the ip as an unsigned char array since the max value of any # is 255 (or 0xFF). Next, do this exercise which will help solve your problem:

Write a function to count the number of bits in an unsigned char:

Code:

---

int count_bits(usigned char b);

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Hint: you'll want to do something in a loop with a counter from 1 to 8 using the bitshift operator (<<). Write something up, and if you're still stuck, post that code and we'll continue from there.

gg

Well I got one part of the code implemented, but for some reason I am getting segmentation faults everytime I run the code in a specific function... I've isolated it to this place



(header provided for reference)

Code:

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void dtob(int oc3[], int oc2[], int oc1[], int third, int second, int first, int numoc)

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when I run this code (the arrays are predefined as being arrays of 8 zeros)

Code:

---

int oc1[] = {0,0,0,0,0,0,0,0};
int oc2[] = {0,0,0,0,0,0,0,0};
int oc3[] = {0,0,0,0,0,0,0,0};

dtob(oc1,oc2,oc3,sn[3],sn[2],sn[1], 3);

---

it gets a segmentation fault before it hits the function...
sn[3], sn[2], and sn[1] are defined and have the values of 0, 0, and 240

anyone see something obvious?? I apparently can't see it, and don't understand why it is doing this...


any help would be awesome, thanks again.

doh, to clarify as soon as that function call takes place there is a segmentation fault...

The code location of the seg fault and the cause are rarely the same. Most likely, something is wrong upstream. You are going to have to narrow it down some more and post more code.
Also, know that a seg fault means you are accessing memory that don't belong to you.

gg

Is the code as above, or have you changed it since posting that?
[edit]Oh, I see its a different function, better post it.

Ok here's the code... forgive the horrid coding style I am just typing it quick :( was gonna clean it up later once I got the code plastered out...and yes I should use things like reading in chars and whatnot... I know :)

getting minimal sleep and trying to do this just ain't cutting it :(

Code:

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void input(int a[], int b[], char *);
//void printstep(int);
void bitsborrowed(int [], int *, int *, char);
void conversion(int [], int *, int *, int);
void dtob(int [], int [], int [], int, int, int, int);

int main(void)
{
        int ipaddress[MAX_OCTECT];
        int subnetmask[MAX_OCTECT];
        int bitsborrow = 0;
        int bitsremain = 0;
        char addressclass;

        input(ipaddress, subnetmask, &addressclass);

        if(addressclass == 'n')
        {
            cout << "This is a class I do not support." << endl;
            return 0;
        }

        cout << endl << addressclass << endl;
        bitsborrowed(subnetmask, &bitsborrow, &bitsremain, addressclass);
        cout << endl << endl << "bitsborrowed " << bitsborrow << " bitsremain " << bi
tsremain;
        cout << endl << "These are the numbers for this subnet mask." << endl;
        return 0;
}



void input(int ip[], int subnet[], char *adcl)
{

        cout << "Please enter an ip address, using spaces between each octet. : ";
        cin >> ip[0] >> ip[1] >> ip[2] >> ip[3];

        cout << endl;

        cout << "You entered: ";
        for(int i = 0; i < 4; i++)
        {
                cout << ip[i];
        if( i < 3)
                        cout << ".";
        }
        cout << endl;
        cout << "Please enter the subnet mask using spaces between each octet. : ";
        cin >> subnet[0] >> subnet[1] >> subnet[2] >> subnet[3];

        cout << endl;

        for(int j = 0; j < 4; j++)
        {
                cout << subnet[j];
                if(j < 3)
                        cout << ".";
        }

        if(0 < ip[0] && 127 >= ip[0])
        {
          *adcl = 'a';
        }
        else if(128 <= ip[0] && ip[0] <= 191)
        {
            *adcl = 'b';
        }
        else if(192 <= ip[0] && 223 >= ip[0])
        {
            *adcl = 'c';
        }
        else
        {
            *adcl = 'n';
        }

}

void bitsborrowed(int subnet[], int *bitsborrowed, int *bitsremaining, char aclass)
{
    int octet = 0;
    if(aclass == 'c')
    {
        conversion(subnet, bitsborrowed, bitsremaining, 1);
    }

    else if(aclass == 'b')
    {
        conversion(subnet, bitsborrowed, bitsremaining, 2);
    }
    else
    {
        conversion(subnet, bitsborrowed, bitsremaining, 3);
    }
}



void conversion(int sn[], int *bb, int *br, int octets)
{
    /*int oc1[] = {0,0,0,0,0,0,0,0};
    int oc2[] = {0,0,0,0,0,0,0,0};
    int oc3[] = {0,0,0,0,0,0,0,0};
    */
    int oc1[8];
    int oc2[8];
    int oc3[8];

    int tempbr = 0;
    int tempr = 0;

    if(octets == 1)
    {
        dtob(oc1,oc2,oc3,sn[3],0,0,1);

        int i = 7;
        while(oc1[i] == 1)
        {
            tempbr++;
            i--;
        }
        tempr = 8 - tempbr;

        *bb = tempbr;
        *br = tempr;
    }
    if(octets == 2)
    {
        dtob(oc1,oc2,oc3,sn[3],sn[2],0,2);
        int i = 7;
        while(oc2[i] == 1)
        {
            tempbr++;
            i--;
        }
        if(i == 0)
        {

            i = 7;
            while(oc1[i] == 1)
            {
                tempbr++;
                i--;
            }
tempr = 16 - tempbr;
            *bb = tempbr;
            *br = tempr;
        }
        else
        {
            tempr = 16-tempbr;
            *bb = tempbr;
            *br = tempr;
        }
    }

    if(octets == 3)
    {
        cout << "Made it." << endl;
        cout << sn[3] << " " << sn[2] << " " << sn[1] << " " << endl;
        for(int j = 0; j < 7; j++)
        {
            cout << oc1[j] << " " << oc2[j] << " " << oc3[j] << endl;
        }
        dtob(oc3, oc2, oc1, sn[3], sn[2], sn[1], 3);
        cout << "Made it again." << endl;
        int i = 7;
        while(oc3[i] == 1)
        {
            tempbr++;
            i--;
        }
        if(i == 0)
        {
            i = 7;
            while(oc2[i] == 1)
            {
                tempbr++;
                i--;
            }

        }
        else
        {
            tempr = 16-tempbr;
            *bb = tempbr;
            *br = tempr;
        }
        if(i == 0)
        {
            i = 7;
            while(oc1[i] == 1)
            {
                tempbr++;
i--;
            }

            tempr = 24 - tempbr;
            *bb = tempbr;
            *br = tempr;
        }

    }
}

void dtob(int oc3[], int oc2[], int oc1[], int third, int second, int first, int numo
c)
{
    int remainder = 0;
    int count = 0;

    cout << "123";
    if(numoc >= 1)
    {
        cout << "OK!" << third;
        if(third != 0)
        {
        while(third != 1)
        {
            remainder = third % 2;      //calculate the remainder
            third = (int)(third / 2);
            oc3[count++] = remainder;
        }
        oc3[count] = third;
        cout << "First!";
        }
        else
        {
            for(int i = 0; i < 7; i++)
            {
                oc3[i] = 0;
            }
            cout << "FIRST!";
        }
    }
    if(numoc >= 2)
    {
        count = 0;
        while(second != 1)
        {
            remainder = second % 2;      //calculate the remainder
            second = (int)(second / 2);
            oc2[count++] = remainder;
 }
        oc2[count] = second;
        cout << "Second!";
    }
    if(numoc == 3)
    {
        count = 0;
        while(first != 1)
        {
            remainder = first % 2;
            first = (int)(first / 2);
            oc1[count++] = remainder;
        }
        oc1[count] = first;
        cout << "Third!";
    }
}

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