C++ I can not read .DAT file and output to screen ------- file2.read((char *)&temp, sizeof(Car)*x);

belhuang(wendy)

本文发表在 rolia.net 枫下论坛Do you have somebody tell me where I make mistake?
Car *temp = new Car[x];
for (int i=0;i<x; i++)
{ cout<<"read file";
file2.read((char *)&temp, sizeof(Car)*x);
cout<<(i+1)<<"Car="<<temp;
}

-----------------------------------------------------------------------------
void main()
{
int x;
cout<<"\n Number of Cars => ";
cin>>x;
Car *pcars = new Car[x];

if (!pcars)
{
cout<<"\nMemory Allocation Error!";
exit(1);
}

for (int i=0;i<x; i++)
cin>>pcars[i];

ofstream file1("CARS.DAT", ios::out);
if (!file1)
{
cerr<<"Error in opening file for output!";
exit(1);
}

file1.write((char *)pcars, sizeof(Car)*x);
file1.close();

ifstream file2("CARS.DAT");
//ifstream file2("CARS.DAT", ios::in);
if (!file2)
{
cerr<<"Error in opening file for input!";
exit(1);
}

//Car temp;
Car *temp = new Car[x];
for (int i=0;i<x; i++)
{ cout<<"read file";
file2.read((char *)&temp, sizeof(Car)*x);
cout<<(i+1)<<"Car="<<temp;
}更多精彩文章及讨论，请光临枫下论坛 rolia.net

(#8116284@0)
Last Updated: 2013-3-24
This post has been archived. It cannot be replied.

你的for loop是想循环x编，但你的file2.read（）一次就read了sizeof(Car)*x个data，这样你相当于read了x * x个car数据，超出文件范围了吧。 -haploidus(今剩叹); 2013-3-24 (#8116296@0)

cancel loop. Is it right? -belhuang(wendy); 2013-3-24 {166} (#8116368@0)
you mean don't use loop, like below,

Car *temp = new Car[x];
file2.read((char *)&temp, sizeof(Car)*x);
cout<<temp;

Can output all car information to screen
Help me change it. I don't have idea. -belhuang(wendy); 2013-3-24 {414} (#8116374@0)
How I change?
First-chance exception at 0x10306e6f (msvcp100d.dll) in file.exe: 0xC0000005: Access violation reading location 0xcdcdcdcd.
Unhandled exception at 0x10306e6f (msvcp100d.dll) in file.exe: 0xC0000005: Access violation reading location 0xcdcdcdcd.

//Car temp;
Car *temp = new Car[x];

cout<<"read file";
file2.read((char *)&temp, sizeof(Car));
cout<<"Car="<<temp;

两个方案。 -haploidus(今剩叹); 2013-3-24 {261} (#8116380@0)
1.
for (int i=0;i<x; i++)
{ cout<<"read file";
file2.read((char *)&temp[i++], sizeof(Car));
cout<<(i)<<"Car="<<temp;
}

2.
cout<<"read file";
file2.read((char *)temp, sizeof(Car)*x);

for (int i=0;i<x; i++) {
cout<<(i+1)<<"Car="<<temp[i];
}

why output to screen ....===>? Car=00504CC0. I think still have some wrong. see content text -belhuang(wendy); 2013-3-24 {310} (#8116388@0)
I change to below

Car *temp = new Car[x];

cout<<"read file";
for (int i=0;i<x; i++)
{
file2.read((char *)&temp[i++], sizeof(Car));
cout<<(i)<<"Car="<<temp;
}

-------------------output---------------------------------
Number of Cars => 1

Car Model => 111
read file1Car=00504CC0

注意指针 -haploidus(今剩叹); 2013-3-24 {127} (#8116402@0)
cout<<"read file";
for (int i=0;i<x; i++)
{
file2.read((char *)&temp[i], sizeof(Car));
cout<<(i+1)<<"Car="<<temp[i];
}

cout<<(i+1)<<"Car="<<temp[i]; -belhuang(wendy); 2013-3-24 {42} (#8116415@0)
temp[i] ---- Here wrong when I compiling
wrong sentence for cout<<....... Pls. get help -belhuang(wendy); 2013-3-24 (#8116418@0)

再帮下去，我就只能写出来，compile完了再说了，可是没环境啊。 -haploidus(今剩叹); 2013-3-24 (#8116495@0)

Run problem-------- do you understand void __CLR_OR_THIS_CALL gbump(int _Off) { // alter current position in read buffer by _Off *_IGcount -= _Off; *_IGnext += _Off; } -belhuang(wendy); 2013-3-24 {3323} (#8116552@0)
本文发表在 rolia.net 枫下论坛I give you whole code. try to compiler in your PC.

#include "StdAfx.h"
#include <iostream>
#include <fstream>
#include <cstring>
#include <stdio.h>
#include <conio.h>
using namespace std;

class Car
{
char model[30];
char name[20];
char phone[20];
char description[50];
//char date_recent[10];
int year_recent;
int month_recent;
int day_recent;
int number_service;
int year_next;
int month_next;
int day_next;
public:
Car()
{
strcpy(model, " ");
strcpy(name, " ");
strcpy(phone, " ");
strcpy(description, " ");
//strcpy(date_recent, " ");
year_recent=0;
month_recent=0;
day_recent=0;
year_next=0;
month_next=0;
day_next=0;
}

friend istream &operator>>(istream &in, Car &C)
{
fflush(stdin);
cout<<"\nCar Model => ";
in.getline(C.model,30);
/*
fflush(stdin);
cout<<"Owner's name => ";
in.getline(C.name,30);

fflush(stdin);
cout<<"Telephone Number => ";
in.getline(C.phone,30);

fflush(stdin);
cout<<"Service Descritption => ";
in.getline(C.description,30);

cout<<"Year of the most recent service => ";
in>>C.year_recent;
cout<<"Month of the most recent service => ";
in>>C.month_recent;
cout<<"Day of the most recent service => ";
in>>C.day_recent;

cout<<"Number of Services Per Year => ";
in>>C.number_service;

cout<<"Year of the next service => ";
in>>C.year_next;
cout<<"Month of the next service => ";
in>>C.month_next;
cout<<"Day of the next service => ";
in>>C.day_next;
*/
return in;
}

friend ostream &operator<<(ofstream &out, Car &C)
{
//out<<C.model<<" "<<C.name<<" "<<C.phone<<" "<<C.description<<" "<<C.year_recent<<" "<<C.month_recent<<" "<<C.day_recent<<" "<<C.number_service<<" "<<C.year_next<<" "<<C.month_next<<" "<<C.day_next<<endl;
out<<C.model<<" ";
return out;
}

}; //class

void main()
{
int x;
cout<<"\n Number of Cars => ";
cin>>x;
Car *pcars = new Car[x];

if (!pcars)
{
cout<<"\nMemory Allocation Error!";
exit(1);
}

for (int i=0; i<x; i++)
cin>>pcars[i];

//ofstream file1("CARS.DAT", ios::binary | ios::app);
ofstream file1("CARS.DAT", ios::app);
if (!file1)
{
cerr<<"Error in opening file for output!";
exit(1);
}

file1.write((char *)pcars, sizeof(Car)*x);
file1.close();

ifstream file2("CARS.DAT");
//ifstream file2("CARS.DAT", ios::in);
if (!file2)
{
cerr<<"Error in opening file for input!";
exit(1);
}

//Car temp;
Car *temp = new Car[x];
cout<<"read file";
for (int i=0; i<x; i++)
{
file2.read((char *)&temp, sizeof(Car));
cout<<(i+1)<<"Car="<<temp;
//temp++;
//cout<<*temp;
//cout<<(i+1)<<"Car=";
}

file2.close();
delete []pcars;
// delete []temp;
getch();
}更多精彩文章及讨论，请光临枫下论坛 rolia.net

家里电脑没有visual studio。 -haploidus(今剩叹); 2013-3-24 {171} (#8116567@0)
看了你的code, 你是先把pcars[i]写到文件里，在试图读文件把数据放在 temp[i]里，再输出到 cout。

作为试验，你可以在读文件前先试试

for (int i=0; i<x; i++)
cout<<pcars[i];

I give you whole code -belhuang(wendy); 2013-3-24 (#8116556@0)

you can download C++ software online -belhuang(wendy); 2013-3-24 (#8116581@0)

哎，好人做到底吧，进内 -haploidus(今剩叹); 2013-3-24 {3074} (#8116821@0)
本文发表在 rolia.net 枫下论坛#include <iostream>
#include <fstream>
#include <cstring>
#include <stdio.h>
using namespace std;

class Car
{
char model[30];
char name[20];
char phone[20];
char description[50];
//char date_recent[10];
int year_recent;
int month_recent;
int day_recent;
int number_service;
int year_next;
int month_next;
int day_next;

public:
Car()
{
strcpy(model, " ");
strcpy(name, " ");
strcpy(phone, " ");
strcpy(description, " ");
//strcpy(date_recent, " ");
year_recent=0;
month_recent=0;
day_recent=0;
year_next=0;
month_next=0;
day_next=0;
};

friend ostream &operator << (ostream &out, Car C)
{
//out<<C.model<<" "<<C.name<<" "<<C.phone<<" "<<C.description<<" "<<C.year_recent<<" "<<C.month_recent<<" "<<C.day_recent<<" "<<C.number_service<<" "<<C.year_next<<" "<<C.month_next<<" "<<C.day_next<<endl;
out << "Car " << C.model << " " << C.name << "\n";
return out;
};

friend istream &operator >> (istream &in, Car &C)
{
cout<<"\nCar Model => ";
//in.getline(C.model,30);
in>>C.model;

cout<<"Owner's name => ";
//in.getline(C.name,30);
in>>C.name;
fflush(stdin);
#if 0

fflush(stdin);
cout<<"Telephone Number => ";
in>>C.phon;

fflush(stdin);
cout<<"Service Descritption => ";
in>>C.description;

cout<<"Year of the most recent service => ";
in>>C.year_recent;
cout<<"Month of the most recent service => ";
in>>C.month_recent;
cout<<"Day of the most recent service => ";
in>>C.day_recent;

cout<<"Number of Services Per Year => ";
in>>C.number_service;

cout<<"Year of the next service => ";
in>>C.year_next;
cout<<"Month of the next service => ";
in>>C.month_next;
cout<<"Day of the next service => ";
in>>C.day_next;
#endif
return in;
};
}; //class

int
main()
{
int x;
cout<<"\n Number of Cars => ";
cin>>x;
Car *pcars = new Car[x];

if (!pcars)
{
cout<<"\nMemory Allocation Error!";
exit(1);
}

for (int i=0; i<x; i++)
cin>>pcars[i];

ofstream file1("CARS.DAT", ios::binary | ios::out);
//ofstream file1("CARS.DAT", ios::app);
if (!file1)
{
cerr<<"Error in opening file for output!";
exit(1);
}

file1.write((char *)pcars, sizeof(Car)*x);
file1.close();
//ifstream file2("CARS.DAT");
ifstream file2("CARS.DAT", ios::binary | ios::in);
if (!file2)
{
cerr<<"Error in opening file for input!";
exit(1);
}
#if 1

//Car temp;
Car *temp = new Car[x];
cout<<"read file"<<"\n";

file2.read((char *)temp, sizeof(Car)*x);

for (int i=0; i<x; i++) {
cout<< i+1 <<" : " << temp[i] << "\n";
}

delete []temp;
#endif
file2.close();

delete []pcars;

return 0;
}

运行结果

Administrator@MAX-20121108DXF ~/test
$ g++ test.cpp

Administrator@MAX-20121108DXF ~/test
$ ./a
Number of Cars => 2

Car Model => s
Owner's name => s

Car Model => d
Owner's name => d
read file
1 : Car s s

2 : Car d d更多精彩文章及讨论，请光临枫下论坛 rolia.net

今大虾原来是C++大拿啊。 -wincity(红卫兵); 2013-3-24 (#8116884@0)

不敢不敢，略知一二。 -haploidus(今剩叹); 2013-3-25 (#8117395@0)

You solve the problem for this time input record and output this time record information. If I want to append record to the previous file and output all records from the files(including old and new record )? How I modify the code? -belhuang(wendy); 2013-3-25 (#8117308@0)

免费帮你做整个作业，恐怕不太现实，你还得自己努力呀。你的问题其实很简单，注意用ifstream的fseek就行了。 -haploidus(今剩叹); 2013-3-25 (#8117402@0)

@Las Vegas

C++ I can not read .DAT file and output to screen ------- file2.read((char )&temp, sizeof(Car)x);

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