Help with binary file c++

lucky_mutani · 05-27-2009, 02:44 PM

Ok what i'm trying to do in this program is first create an empty binary file of size 31 records. Records includes studid & gpa. and then I insert valid record into the binary file with h(k) = key% 29..and then read this binary file sequentially and write the records and their position into output file.....

sample input file
31 2.34
62 1.55
60
3.25
333 3.33
38 3.90
-1 //read upto -1

Code:

studBinaryFile.h

#include <iostream>
#include <fstream>
#include <iomanip>

using namespace std;

const int MIN_ID = 11;
const int MAX_ID = 99;
const float MIN_GPA = 0.00;
const float MAX_GPA = 4.00;

class StudBinaryFile
{
 public:

 void setId(int idVal);
 
 void setGpa(float gpaVal);

 void ReadRd(int i,ifstream& inFile);

 bool validRd();
 
 void writeBinary(StudBinaryFile rd, ofstream& outFile);

 void writeInvalidRd(ofstream& outFile2);

 void readBinary(StudBinaryFile rd, ifstream& inFile, ofstream&    outFile2);
 
 void printData(int count, const StudBinaryFile& record, ofstream&  outFile2);
 
private:
   int id;
   float gpa;
};

Code:

studBinaryFile.cxx

#include "studBinaryFile.h"

void StudBinaryFile::setId(int idVal)
{
	id = idVal;
}

void StudBinaryFile::setGpa(float gpaVal)
{
	gpa = gpaVal;
}

void StudBinaryFile::ReadRd(int i, ifstream& inFile)
{
	id = i;
	inFile >> gpa;
}


bool StudBinaryFile::validRd() 
{
	 return ((id >= MIN_ID)&&
                (id <= MAX_ID)&&
                (gpa >= MIN_GPA)&&
                (gpa <= MAX_GPA));

}

void StudBinaryFile::writeBinary(StudBinaryFile rd, ofstream& outFile)
{
	outFile.seekp((id % 29) * sizeof(rd));
	{outFile.write(reinterpret_cast<const char *> (&rd), sizeof(rd));}
}

void StudBinaryFile::readBinary(StudBinaryFile rd, ifstream& inFile, ofstream& outFile2)
{
	int count = 0;
	inFile.read(reinterpret_cast<char *> (&rd), sizeof(StudBinaryFile));
	while(inFile)
	{
		if (id != 0)
		{
			printData(count, rd, outFile2);
			count++;
		}
		inFile.read(reinterpret_cast<char *> (&rd), sizeof(StudBinaryFile));		
	}
} 

void StudBinaryFile::writeInvalidRd(ofstream& outFile2)
{
	outFile2 << id << setw(12) << gpa << endl;
}

void StudBinaryFile::printData(int count, const StudBinaryFile& record, ofstream& outFile2)
{
	if(record.id != 0)
		outFile2 << count << ".)  "  << record.id << setw(12) << record.gpa << endl;
	else
		outFile2 << count << ".)  " << "Empty record" << endl;

	count++;
}

Code:

run.cxx

#include "studBinaryFile.h"
int main()
{
	ifstream inFile, inFile2;
	ofstream outFile, outFile2;
	inFile.open("in.data");
	outFile.open("binrecords.bin",ios::out | ios::binary);

	outFile2.open("out.data");

	StudBinaryFile blankRd;
	for (int i = 1; i<=31; i++)
	{
		blankRd.setId(0);
		blankRd.setGpa(0.0);
		outFile.write(reinterpret_cast<const char *> (&blankRd), sizeof(blankRd));
	}

	StudBinaryFile rd;
	outFile.seekp(0L,ios::beg);
	int spliter;
	outFile2 << "*< Invalid Records Report >*" << endl;
	
	inFile >> spliter;
	while(spliter != -1)
	{
		rd.ReadRd(spliter,inFile);
		if(rd.validRd())
		{
			
			rd.writeBinary(rd, outFile);
		}
		else
			{rd.writeInvalidRd(outFile2);}
		inFile >> spliter;
	}
	outFile2 << "<* end >*" << endl << endl;
	inFile.close();
	outFile.close();

	outFile2 << "Reading random file sequentially" << endl;
	inFile.open("binrecords.bin", ios::in | ios::binary);
	rd.readBinary(rd, inFile, outFile2);

	inFile.close();
	return 0;
}

This is the output im getting

Code:

*< Invalid Records Report >*
333        3.33
<* end >*

Reading random file sequentially
0.)  Empty record
1.)  Empty record
2.)  60        3.25
3.)  Empty record
4.)  62        1.55
5.)  Empty record
6.)  Empty record
7.)  Empty record
8.)  Empty record
9.)  38         3.9
10.)  Empty record
11.)  Empty record
12.)  Empty record
13.)  Empty record
14.)  Empty record
15.)  Empty record
16.)  Empty record
17.)  Empty record
18.)  Empty record
19.)  Empty record
20.)  Empty record
21.)  Empty record
22.)  Empty record
23.)  Empty record
24.)  Empty record
25.)  Empty record
26.)  Empty record
27.)  Empty record
28.)  Empty record
29.)  Empty record
30.)  Empty record

This is the output i want

Code:

*< Invalid Records Report >*
333        3.33
<* end >*

Reading random file sequentially
0.)  Empty record
1.)  Empty record
2.)  31        2.34
3.)  60        3.25
4.)  62        1.55
5.)  Empty record
6.)  Empty record
7.)  Empty record
8.)  Empty record
9.)  38         3.9
10.)  Empty record
11.)  Empty record
12.)  Empty record
13.)  Empty record
14.)  Empty record
15.)  Empty record
16.)  Empty record
17.)  Empty record
18.)  Empty record
19.)  Empty record
20.)  Empty record
21.)  Empty record
22.)  Empty record
23.)  Empty record
24.)  Empty record
25.)  Empty record
26.)  Empty record
27.)  Empty record
28.)  Empty record
29.)  Empty record
30.)  Empty record

This program works fine except that its overriding some of the record because of collision problem ..someone please help me here

dwks · 05-27-2009, 03:27 PM

Well, when I change one of your functions to look like this,

Code:

void StudBinaryFile::writeBinary(StudBinaryFile rd, ofstream& outFile)
{
        std::cout << "Writing " << rd.get_id() << "," << rd.get_gpa()
            << " to " << (id % 29) << std::endl;
	outFile.seekp((id % 29) * sizeof(rd));
	{outFile.write(reinterpret_cast<const char *> (&rd), sizeof(rd));}
}

I get the following output:

Code:

Writing 31,2.34 to 2
Writing 62,1.55 to 4
Writing 60,3.25 to 2
Writing 38,3.9 to 9

If I change 60 to 61, I get the output

Code:

Writing 31,2.34 to 2
Writing 62,1.55 to 4
Writing 61,3.25 to 3
Writing 38,3.9 to 9

and the file output.data looks like this (which is what I think you wanted):

Code:

*< Invalid Records Report >*
333        3.33
<* end >*

Reading random file sequentially
0.)  Empty record
1.)  Empty record
2.)  31        2.34
3.)  61        3.25
4.)  62        1.55
5.)  Empty record
6.)  Empty record
7.)  Empty record
8.)  Empty record
9.)  38         3.9
10.)  Empty record
11.)  Empty record
12.)  Empty record
13.)  Empty record
14.)  Empty record
15.)  Empty record
16.)  Empty record
17.)  Empty record
18.)  Empty record
19.)  Empty record
20.)  Empty record
21.)  Empty record
22.)  Empty record
23.)  Empty record
24.)  Empty record
25.)  Empty record
26.)  Empty record
27.)  Empty record
28.)  Empty record
29.)  Empty record
30.)  Empty record

I think that's what you should expect, since 60%29 == 2 == 31%29.

Maybe you were intending to mod with 31 instead of with 29? At the moment, slots 29 and 30 in your pseudo-hash-table will never be used.

So I guess my question is, what's wrong with it? Why were you expecting the output you gave?

dwks · 05-27-2009, 03:42 PM

Unless . . . ah! It is a hash table, a hash table with open addressing -- am I right? So if you're writing something into the file, and the spot is already taken, you want it to e.g. go to the next spot instead. Brain freeze, sorry.

Well, here's my fix for it. I basically made the output file read as well as write, then before I wrote a record to the file, I would check to see if there was already a record there. If so, I'd advance to the next record and so on.

There may be other ways to do this, but that's what came to mind. With my code, and your original in.data, the out.data that you wanted gets produced.

Of course, this means that the table could get full, and I added some code to check for that too. Though I didn't handle it very well, just print a message and let it crash.

See my attached code. It's really a .zip file, just rename and extract. The crucial code I've reproduced here.

Code:

void StudBinaryFile::writeBinary(StudBinaryFile rd, fstream& outFile)
{
        //std::cout << "Writing " << rd.get_id() << "," << rd.get_gpa()
        //    << " to " << (id % 29) << std::endl;
        
        int original = id % 29;
        
        StudBinaryFile temp;
        for(;;) {
            //std::cout << "Checking " << id % 29 << std::endl;
            outFile.seekp((id % 29) * sizeof(rd));
            if(!outFile.read(reinterpret_cast<char *> (&temp), sizeof(temp))) break;
            //std::cout << "[existing data: " << temp.get_id() << "," << temp.get_gpa() << std::endl;
            if(temp.get_id() != 0) {
                id ++;
                
                if(id == original) {
                    std::cout << "Table full\n";
                    break;
                }
            }
            else break;
        }
        
	outFile.seekp((id % 29) * sizeof(rd));
	outFile.write(reinterpret_cast<const char *> (&rd), sizeof(rd));
        
}

lucky_mutani · 05-27-2009, 07:40 PM

Thank you so much for your help. I have another question...lets say in same program i have the input file
31 2.34
62 1.55
60 3.25
333 3.33
38 3.90
-1 // -1 seperates two kind of inputs. Next two input are for random access
62
38

In the same program how can I read the binary file randomely. So basically i want to read the next input from text file and compare it to binary file and then print it in outfile

Code:

This is the output I need
*< Invalid Records Report >*
333        3.33
<* end >*

Reading random file sequentially
0.)  Empty record
1.)  Empty record
2.)  31        2.34
3.)  61        3.25
4.)  62        1.55
5.)  Empty record
6.)  Empty record
7.)  Empty record
8.)  Empty record
9.)  38         3.9
10.)  Empty record
11.)  Empty record
12.)  Empty record
13.)  Empty record
14.)  Empty record
15.)  Empty record
16.)  Empty record
17.)  Empty record
18.)  Empty record
19.)  Empty record
20.)  Empty record
21.)  Empty record
22.)  Empty record
23.)  Empty record
24.)  Empty record
25.)  Empty record
26.)  Empty record
27.)  Empty record
28.)  Empty record
29.)  Empty record
30.)  Empty record

Reading Random Randomly
7.) 62           1.55
9.)  38          3.90

dwks · 06-05-2009, 09:24 AM

If you have the binary file already created, and you want to randomly access one record in it, you can use the seekg function of ifstream just as you have done. I think you should be able to figure it out.

05-27-2009, 03:27 PM	#2
dwks Frequently Quite Prolix Join Date: Apr 2005 Location: Canada Posts: 7,629	Well, when I change one of your functions to look like this, Code: void StudBinaryFile::writeBinary(StudBinaryFile rd, ofstream& outFile) { std::cout << "Writing " << rd.get_id() << "," << rd.get_gpa() << " to " << (id % 29) << std::endl; outFile.seekp((id % 29) * sizeof(rd)); {outFile.write(reinterpret_cast<const char > (&rd), sizeof(rd));} } I get the following output: Code: Writing 31,2.34 to 2 Writing 62,1.55 to 4 Writing 60,3.25 to 2 Writing 38,3.9 to 9 If I change 60 to 61, I get the output Code: Writing 31,2.34 to 2 Writing 62,1.55 to 4 Writing 61,3.25 to 3 Writing 38,3.9 to 9 and the file output.data looks like this (which is what I think you wanted): Code: < Invalid Records Report >* 333 3.33 <* end >* Reading random file sequentially 0.) Empty record 1.) Empty record 2.) 31 2.34 3.) 61 3.25 4.) 62 1.55 5.) Empty record 6.) Empty record 7.) Empty record 8.) Empty record 9.) 38 3.9 10.) Empty record 11.) Empty record 12.) Empty record 13.) Empty record 14.) Empty record 15.) Empty record 16.) Empty record 17.) Empty record 18.) Empty record 19.) Empty record 20.) Empty record 21.) Empty record 22.) Empty record 23.) Empty record 24.) Empty record 25.) Empty record 26.) Empty record 27.) Empty record 28.) Empty record 29.) Empty record 30.) Empty record I think that's what you should expect, since 60%29 == 2 == 31%29. Maybe you were intending to mod with 31 instead of with 29? At the moment, slots 29 and 30 in your pseudo-hash-table will never be used. So I guess my question is, what's wrong with it? Why were you expecting the output you gave? __________________ dwk Seek and ye shall find. quaere et invenies. "Simplicity does not precede complexity, but follows it." -- Alan Perlis "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra "The only real mistake is the one from which we learn nothing." -- John Powell Other boards: DaniWeb, TPS Unofficial Wiki FAQ: cpwiki.sf.net My website: http://dwks.theprogrammingsite.com/ Projects: codeform, xuni, atlantis, etc. New project: nort
dwks is offline

06-05-2009, 09:24 AM	#5
dwks Frequently Quite Prolix Join Date: Apr 2005 Location: Canada Posts: 7,629	If you have the binary file already created, and you want to randomly access one record in it, you can use the seekg function of ifstream just as you have done. I think you should be able to figure it out. __________________ dwk Seek and ye shall find. quaere et invenies. "Simplicity does not precede complexity, but follows it." -- Alan Perlis "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra "The only real mistake is the one from which we learn nothing." -- John Powell Other boards: DaniWeb, TPS Unofficial Wiki FAQ: cpwiki.sf.net My website: http://dwks.theprogrammingsite.com/ Projects: codeform, xuni, atlantis, etc. New project: nort
dwks is offline

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