Welcome to OStack Knowledge Sharing Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
634 views
in Technique[技术] by (71.8m points)

reading until the end of file in C++

I'm trying to read till the end of a file for a phonebook app that im converting from C to C++. When I print the the results from the file i get this:

johnny smith
(Home)3
(Cell)4
x?> x?>
(Home)4
(Cell)4

it should print:

johnny smith
(Home)3
(Cell)4

Right now I'm using while(!infile.eof()) which i've read is a poor practice, but when I use infile.getline() I get a repeat of the first and last name, and the format is all jacked up. Is there anyway(or another way) to get rid of the junk at the end of the input or another way to read till the end of file in C++ that fixes this. I've been reading about different solutions, but the one a lot of sites seem to agree on is fgets, which is what I had with the original C version, but obviously fgets doesn't work with ifstream which is what I'm using. here is the code:

void contacts:: readfile(contacts*friends ,int* counter, int i,char buffer[],char    user_entry3[])
{
   ifstream read;
   read.open(user_entry3,ios::in);
   int len;
   contacts temp;
   *counter=0;
   i=0; 

     while (!read.eof()) { 
       temp.First_Name=(char*)malloc(36); 
       temp.Last_Name=(char*)malloc(36); 

       read>>temp.First_Name>>temp.Last_Name;

       read>>buffer;
       len=strlen(buffer);
       if(buffer[len-1]=='
')
          buffer[len-1]='';

       temp.home=(char*)malloc(20); 
       strcpy(temp.home, buffer);

       read>>buffer;
       len=strlen(buffer);
       if(buffer[len-1]=='
')
       buffer[len-1]='';


       temp.cell=(char*)malloc(20); 
       strcpy(temp.cell, buffer); 

      friends[i].First_Name=(char*)malloc(MAXNAME);
      friends[i].Last_Name=(char*)malloc(MAXNAME);
      friends[i].home=(char*)malloc(MAXPHONE);
      friends[i].cell=(char*)malloc(MAXPHONE);


  //adds file content to the structure
      strcpy(friends[*counter].First_Name,temp.First_Name);
      strcpy(friends[*counter].Last_Name,temp.Last_Name);
      strcpy(friends[*counter].home,temp.home);
      strcpy(friends[*counter].cell,temp.cell);


     (*counter)++;
     i++; 

   }
   //closes file and frees memory
    read.close();
    free(temp.Last_Name);
    free(temp.First_Name);
    free(temp.home);
    free(temp.cell);
}
See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Answer

0 votes
by (71.8m points)

Do not use eof() to determine if you reached end of file. Instead, read what you want to read and then check if you successfully read the data. Obce reading failed you may use eof() to determine if the error is down to having reached the end of the file before producing an error report about a format error.

Since you mentioned that you read that using !infile.eof() is good practice: Can you point us at the source of this wrong information? This information need correction.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome to OStack Knowledge Sharing Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...