reading strings from a binary .txt file

My program saves customer data to a .txt file in binary. Fields such as name and address are typed in as a C++ string, converted to a C style char array, and saved to disk (since the compiler will not let me save a c++string, only a char array). These same fields can also be loaded into a C style char array and converted back to a string (for the ease of manipulation). I am using stringstreams to do the conversions but I am getting no results.

Code:

//  save customer profile to disk

int saveprof()
{
    ofstream fcust(c:\\cust_data.txt",ios::binary | ios::app);
    if (fcust.fail()) 
    { cout<<"\nCannot open library file!\a"; }
    else
    {
        string temp;
        temp.assign(custinfo.cust_name, 0, 26);
        fcust.write(temp.c_str(),26);
        temp.assign(custinfo.cust_address, 0, 26);
        fcust.write(temp.c_str(),26);
        temp.assign(custinfo.cust_city, 0, 16);
        fcust.write(temp.c_str(),16);
        temp.assign(custinfo.cust_state, 0, 3);
        fcust.write(temp.c_str(),3);
        fcust.write(reinterpret_cast<char*>(&custinfo.cust_zip), sizeof(int));
        temp.assign(custinfo.cust_contact, 0, 26);
        fcust.write(temp.c_str(),26);
        temp.assign(custinfo.cust_phone, 0, 13);
        fcust.write(temp.c_str(),13);
        cout<<"\nFile saved";
        fcust.close();
    }
    return 0;
}


//  load customer profile from disk

int findprof()
{
    ifstream fcust("c:\\cust_data.txt", ios::binary);
    if (fcust.fail())
    { cout<<"\nCannot open library file!\a"; }
    else
    {
        istringstream sstream(ctemp);
        getline(sstream, custinfo.cust_name);
        sstream.str("");
        fcust.read(ctemp,26);
        sstream.str(ctemp);
        getline(sstream, custinfo.cust_address);
        sstream.str("");
        fcust.read(ctemp,16);
        sstream.str(ctemp);
        getline(sstream, custinfo.cust_city);
        sstream.str("");
        fcust.read(ctemp,3);
        sstream.str(ctemp);
        getline(sstream, custinfo.cust_state);
        sstream.str("");        
        fcust.read(reinterpret_cast<char*>(&custinfo.cust_zip), sizeof(int));
        fcust.close();
    }
    return 0;
}

The customer name comes up just fine but all the other string fields come up blank. (the zip code works fine, also)

Using DEV-C++ Under Windows XP

Try the FAQ under such subjects as "getting a line from the user (C++)".

If your 'customer' or whatever class is just 'plain old data', or something like this:

Code:

struct customer
{
	char cust_name[26];
	char cust_address[26];
	char cust_state[3];
	char cust_contact[26];
	char cust_phone[13];
	int cust_zip;
}

Then you can just:

Code:

	// write

	std::ofstream o("test.txt", std::ios::binary);

	customer c(...);

	o.write(reinterpret_cast<char*>(&c), sizeof(c));

	// read

	std::ifstream i("test.txt", std::ios::binary);

	customer c;

	i.read(reinterpret_cast<char*>(&c), sizeof(c));

Why are you using "binary" files when handling text? Wouldn't it be way easier using text methods from the beginning?

Code:

struct CInfo
{
  std::string Name;
  std::string Address;
  std::string Phone;
};

void Save(const CInfo& Info)
{
  std::ofstream File("SomeFile.txt");

  File << Info.Name << std::endl;
  File << Info.Address << std::endl;
  File << Info.Phone << std::endl;
}

void Load(CInfo& Info)
{
  std::ifstream File("SomeFile.txt");

  std::getline(File, Info.Name);
  std::getline(File, Info.Address);
  std::getline(File, Info.Phone);
}

(this, of course, assumes that each string field occupies no more than 1 line)

And why are you giving binary files a .txt extension?

Why are you using "binary" files when handling text? Wouldn't it be way easier using text methods from the beginning?

Yes, it would be easier to use text methods, but then I would not learn how to work with binary methods.

The point is I have heard that you can use stringstreams to convert from a char array to a string, but everything I have tried just produces an empty string. Is it possible to do this or is there an easier way? I have searched and googled until I was blue in the face and could not come up with anything.....

No need for stringstreams, std::string has a constructor that takes a char pointer:

Code:

char CharArray[32];
std::string String = CharArray;

Make sure the array ends with a NULL terminator ( '\0' ).
If this is not the case, you could use a temporary buffer:

Code:

char CharArrayWithNoNullTerminator[32];
std::vector<char> TempBuffer;
TempBuffer.resize(32 + 1);
std::memcpy(&TempBuffer[0], CharArrayWithNoNullTerminator, 32);
TempBuffer[32] = '\0';
std::string String = &TempBuffer[0];

Now, I could swear I did that before and it did not work.... Now it does....

Maybe I just THOUGHT I did that... Oh well, Thanks for the help! I knew there was an easier way... Maybe I just need to get some sleep..........

Originally Posted by Magos

std::string has a constructor that takes a char pointer...Make sure the array ends with a NULL terminator ( '\0' ). If this is not the case, you could use a temporary buffer

Code:

char CharArrayWithNoNullTerminator[32];
std::vector<char> TempBuffer;
TempBuffer.resize(32 + 1);
std::memcpy(&TempBuffer[0], CharArrayWithNoNullTerminator, 32);
TempBuffer[32] = '\0';
std::string String = &TempBuffer[0];

No need for all that. There is a string constructor that can handle non null terminated char arrays, as well:

Code:

const int size = 3;
char NoNullTerminator[size] = {'y', 'e', 's'};
	
string myString(NoNullTerminator, size);
cout<<myString.c_str()<<endl;

...and you can do more straight forward things like this as well:

Code:

string myString1;
myString.assign(NoNullTerminator, size);
cout<<myString.c_str()<<endl;

string myString2;
myString2.append(NoNullTerminator, size);
cout<<myString2.c_str()<<endl;

string myString3;
myString3.insert(myString3.end(), NoNullTerminator, NoNullTerminator + size);
cout<<myString2.c_str()<<endl;