C ++ function using the BinarySearch algorithm (.bin file)

Question

I have to create a function that checks if a specific word exists in the .bin file. I want to use the binary search algorithm. The thing is, I have to read from a .bin file, so I got confused (like there are no lines, right?). Function does not work for me. It states that the “specific word” (entered by the user) does not exist, although it does exist. Any help would be enjoyable.

#include <iostream>
#include <string>
#include <fstream>
#include <cstring>
#include <algorithm>

using namespace std;
const int buffer_size = 30;

void Create_Bin_File ()
{
ifstream fin ("example.txt");  
ofstream fout ("Binary.bin", ios::binary); 
const unsigned int RECORD_SIZE = 30; // was BUFFER_SIZE
char buffer[RECORD_SIZE] = {0}; // zero init buffer

while (fin.getline (buffer, RECORD_SIZE))
{
fout.write (buffer, RECORD_SIZE);
// refill buffer with zeroes for next time round
fill_n (buffer, RECORD_SIZE, 0);
}
fin.close ();
fout.close ();
}

void Binary_Search (const string& filename, string SearchVal)
{
ifstream file (filename.c_str(), ios::binary);
if (file.is_open())
{
    cout << "The file is opened"<< endl;
    cout << "\n";
}
else
{
    cout << "Error opening file"<< endl;
    cout << "\n";
    return; // no point continuing Binary_Search() if file failed to open!
}
const unsigned int RECORD_SIZE = 30; // was BUFFER_SIZE
char buffer[RECORD_SIZE] = {0}; // zero init buffer
int recordCount  =  0;
int recordWanted = -1;
while (file.read(buffer, RECORD_SIZE))
{
    if(SearchVal == buffer)
    {

        recordWanted = recordCount;
        // if this was just a naive search loop could bail out now...
    }
    cout << recordCount << " : " << buffer << "\n";

    // refill buffer with zeroes for next time round
    fill_n (buffer, RECORD_SIZE, 0);
    ++recordCount;
}

cout << "\n";
cout << "file contains " << recordCount << " records\n";
cout << "\n";
if (recordWanted == -1)

    cout << "record wanted could not be found\n";
else

    cout << "record wanted is at index " << recordWanted << " records\n";
cout << "\n";
} 




int main()
{

Create_Bin_File();  
string word;
cout << "Enter word, that you want to find in a file: " << endl;
cin >> word;

Binary_Search("Binary.bin", word);


return 0;
}

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---

grek40 BinarySearch:

, :

std::string GetRecord(std::ifstream& inFile, int pos)
{
char buffer[RECORD_SIZE];
// clear possible flags like EOF, before moving the read position
inFile.clear();
// set the file read position to the requested record position
inFile.seekg(pos * RECORD_SIZE, std::ios::beg);
inFile.read(buffer, RECORD_SIZE);
// note: automatic conversion from char[] to std::string
return buffer;
}

: ( - !)

void Binary_Search (const string& filename, string SearchVal)
{
ifstream file (filename.c_str(), ios::binary);
if (file.is_open())
{
cout << "The file is opened"<< endl;
cout << "\n";
}
else
{
cout << "Error opening file"<< endl;
cout << "\n";
return; // no point continuing Binary_Search() if file failed to open!
}
int pos = 0;
int lowerLimit = 0;
int recordCount = 73; // Calculated before[I'll change this part, when I get      this function working]
                  // At this point, there exactly 73 records in .bin file
 char buffer[RECORD_SIZE] = {0}; // zero init buffer (while loop will overwrite with record values)
 int upperLimit = recordCount;
 while ( (lowerLimit < upperLimit) ) // Searching as long as it doesn't find it
 {
    pos = (lowerLimit + upperLimit) / 2;
    std::string buffer = GetRecord(file, pos);

    if (buffer == SearchVal)
    {
        cout << "Found!";
        lowerLimit = 1; // For stopping (If found!)
        upperLimit = 0; // For stopping
    }
    else if (SearchVal > buffer)
    {
        lowerLimit = pos + 1;
    }
    else if (SearchVal < buffer)
    {
     upperLimit = pos;
    }

}
}

Answer 1

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, (30), .

, :

std::string GetRecord(std::ifstream& inFile, int pos)
{
    char buffer[RECORD_SIZE];
    // clear possible flags like EOF, before moving the read position
    inFile.clear();
    // set the file read position to the requested record position
    inFile.seekg(pos * RECORD_SIZE, std::ios::beg);
    inFile.read(buffer, RECORD_SIZE);
    // note: automatic conversion from char[] to std::string
    return buffer;
}

. , lastItemPosition + 1, .

int lowerLimit = 0;
int upperLimit = recordCount; // count when reading the lines in .txt

, , lowerLimit < upperLimit.

position = (lowerLimit + upperLimit) / 2;.

. .

, , , . lowerLimit = position + 1

, , , , . upperLimit = position

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