-
July 21st, 2013, 04:45 AM
#1
Problem With read Function
Here is My Code:
Code:
#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
#include <cstdlib>
using namespace std;
class Student
{
public:
Student(string name = "", int num = 0, int unit = 0)
{
setName(name);
this->num = num;
this->unit = unit;
}
void set(string name = "", int num = 0, int unit = 0)
{
setName(name);
this->num = num;
this->unit = unit;
}
void setName(string n)
{
int len = n.length();
len = (len < 15) ? len : 14;
n.copy(this->name, len);
name[len] = '\0';
}
char * getName()
{
return name;
}
int getNum()
{
return num;
}
int getUnit()
{
return unit;
}
private:
char name[15];
int num, unit;
};
int main()
{
ofstream o("test.bin", ios::out| ios::binary);
ifstream f("test.bin", ios::in| ios::binary);
Student s;
Student st;
Student stu;
if(!f || !o)
{
cerr << "Error!";
exit(1);
}
string name;
int num, unit;
for(int i = 0;i < 50;i++)
{
o.write(reinterpret_cast<const char *>(&s), sizeof(Student));
}
cin >> name >> num >> unit;
while(num > 0 && num <= 50)
{
st.set(name, num, unit);
o.seekp((st.getNum() - 1) * sizeof(Student));
o.write(reinterpret_cast<const char *>(&st), sizeof(Student));
cin >> name >> num >> unit;
}
f.read(reinterpret_cast<char *>(&stu), sizeof(Student));
while(f.good())
{
if(stu.getNum() != 0 )
{
cout << "Name : " << stu.getName() << endl;
}
f.read(reinterpret_cast<char *>(&stu), sizeof(Student));
}
f.close();
return 0;
}
My Problem is When I Write n Student's information in file, Read Function only read n - 1 information from file! for example if I enter this input:
1 1 1
2 2 2
-1 -1 -1
Output is :
Name : 1
Last edited by N@R!MAN; July 21st, 2013 at 04:50 AM.
-
July 21st, 2013, 05:14 AM
#2
Re: Problem With read Function
Originally Posted by N@R!MAN
My Problem is When I Write n Student's information in file, Read Function only read n - 1 information from file! for example if I enter this input:
1 1 1
2 2 2
-1 -1 -1
Output is :
Name : 1
Which "Output" do you mean? Where is it in your code?
Did you debug your code?
Victor Nijegorodov
-
July 21st, 2013, 06:52 AM
#3
Re: Problem With read Function
Which "Output" do you mean? Where is it in your code?
Did you debug your code?
of Course!
after I read information from file :
Code:
if(stu.getNum() != 0 )
{
cout << "Name : " << stu.getName() << endl;
}
-
July 21st, 2013, 07:06 AM
#4
Re: Problem With read Function
I used o.flush() after writing process and mu problem is solved now!!! it was not read function problem!
tnx
-
July 22nd, 2013, 06:06 AM
#5
Re: Problem With read Function
Just as a comment. Why open the same file twice - once as an input stream, and once as an output stream? Why not open the same file just once for both input and output? You then haven't got to remember to flush the contents of the write stream to make the contents available to the read stream?
Code:
fstream io("test.bin", ios:: out | ios:: in | ios:: binary);
All advice is offered in good faith only. All my code is tested (unless stated explicitly otherwise) with the latest version of Microsoft Visual Studio (using the supported features of the latest standard) and is offered as examples only - not as production quality. I cannot offer advice regarding any other c/c++ compiler/IDE or incompatibilities with VS. You are ultimately responsible for the effects of your programs and the integrity of the machines they run on. Anything I post, code snippets, advice, etc is licensed as Public Domain https://creativecommons.org/publicdomain/zero/1.0/ and can be used without reference or acknowledgement. Also note that I only provide advice and guidance via the forums - and not via private messages!
C++23 Compiler: Microsoft VS2022 (17.6.5)
Posting Permissions
- You may not post new threads
- You may not post replies
- You may not post attachments
- You may not edit your posts
-
Forum Rules
|
Click Here to Expand Forum to Full Width
|