concatenate two char arrays into single char array using pointers - c++

Question

I am trying to take a text file with names (ex: john doe) and fin the first name and last name. Then, I want to take these two char arrays and concatenate them together using pointers. The code that is commented out is working code that takes the two char arrays and puts them into a single char array ie concatenating them together. This project requires that I use pointers, and that I use char arrays I am not asking for you to do it for me, but please help me realize what I am doing wrong. Thanks
EDIT: the error I am getting is a seg fault..so Im thining my playerPtr is going out of bounds somewhere??
void readPlayer(char *finName2, player *playerPtr)
{
player *playerHome = playerPtr;
ifstream fin;
char *tempfName= new char[20];
char *templName= new char[20];
char *tempName= new char[20];
char *tempNameHome = tempName;
fin.open(finName2);
if(!fin.good())
{
cout << "Error with player file!" << endl;
}
else
{
fin >> tempfName;
fin >> templName; //prime file
cout << tempfName << templName;
while(fin.good())
{
for(int i =0;i<5;i++)
{
//find the length
//int index =0, length=0;
while(*tempfName != '\0')
//while(tempfName[length] != '\0')
{
tempfName++;
}
strcopy(tempName,tempfName);
//now add space after first name
*tempName = ' ';
tempName++;
//tempfName[length] = ' ';
//tempfName++;
//length++;
while(*templName != '\0')
//while(templName[index] != '\0')
{
templName++;
//tempfName[length] = templName[index];
//length++;
//index++;
}
strcopy(tempName,templName);
//tempName++;
//tempfName[length]='\0';
strcopy((*playerPtr).name,tempName);
playerPtr++;
fin >> tempfName;
fin >> templName;
}
}
}
delete[] tempfName;
delete[] templName;
delete[]tempName;
}

Answer 1

Your tempfName & templName are incremented all the time and they move beyond their allocated memory. you need to reset their position.
Plus I can see that the
fin >> tempfName;
fin >> templName;
is inside the for loop, which means fin.Good is only checked once every 5 times.

Answer 2

Problems that I see (mentioned in comments too):
Incrementing tempFName and tempLName in loops
while(*tempfName != '\0')
{
tempfName++;
}
strcopy(tempName,tempfName);
At the end of the above loop, tempFName points to the end of the string - it points to the terminating null character. strcopy should copy nothing to tempName.
You have the same problem with the loop:
while(*templName != '\0')
{
templName++;
}
strcopy(tempName,templName);
Setting the value of *tempName after the first loop
//now add space after first name
*tempName = ' ';
tempName++;
This will be valid only if tempName points to the end of the copied string after the call to strcopy. If not, you are just setting the value of the first character in tempName to ' '. Incrementing tempName makes sense only of tempName points to the end of the copied string. Otherwise, it points to the second character.
As a result of the above errors, your code is subject to errors caused by out of bound memory access after the first iteration of the for loop. Nothing after that can be relied upon to behave in a reasonable manner.
I suggest the following changes to fix the above errors.
Don't increment the variables tempFName and tempLName at all
You don't need to at all.
Remove the lines:
while(*tempfName != '\0')
{
tempfName++;
}
just use:
strcopy(tempName,tempfName);
Use a temporary pointer to go to the end of tempName
After the first call to strcopy, use:
char* temp = tempName;
while ( *temp != '\0' ) ++temp;
*temp = ' ';
++temp;
*temp = '\0';
Use the temporary pointer for the second strcopy
Remove the lines:
while(*templName != '\0')
{
templName++;
}
Replace the line:
strcopy(tempName,templName);
with
strcopy(temp,tempfName);
Alternate strategy
If you implement your version of strcat, you can simply use:
tempName[0] = '\0';
strcat(tempName, tempFName);
strcat(tempName, " ");
strcat(tempName, tempLName);
That will remove much of the clutter in the for loop.