Detect newline byte from filestream

问题

I'm trying to collect information from a textfile which contains names of organisations (without spaces) and floating integers. I want to store this information in an array structure.

The problem I'm having so far is collecting the information. Here is a sample of the textfile:

CBA 12.3 4.5 7.5 2.9 4.1

TLS 3.9 1 8.6 12.8 4.9

I can have up to 128 different numbers for each organisation, and up to 200 organisations in the textfile.

This is what my structure looks like so far:

struct callCentre
{
char name[256];
float data[20];
};

My main:

int main()
{
callCentre aCentre[10];
getdata(aCentre);
calcdata(aCentre);
printdata(aCentre);
return 0;
}

And the getdata function:

void getdata(callCentre aCentre[])
{
ifstream ins;
char dataset[20];

cout << "Enter the name of the data file: ";
cin >> dataset;

ins.open(dataset);

if(ins.good())
{
    while(ins.good())
    {
        ins >> aCentre[c].name;
        for(int i = 0; i < MAX; i++)
        {
            ins >> aCentre[c].data[i];
            if(ins == '\n')
                break;
        }
        c++;
    }
}
else
{
    cout << "Data files couldnt be found." << endl;
}
ins.close();
}

What I'm trying to achieve in my getdata function is this: store the organisation name first into the structure, then read each float into the data array until the program detects a newline byte. However, so far my check for the newline byte isn't working.

Assume that variables c and MAX are already defined.

How should I go about this properly?

回答1:

char byte = ins.peek();

if(ins.peek() == '\n') break;

(Edit): You'll want to also check for an eof after your peek(), because some files may not have a ending newline.

I'd like to point out that you might want to consider using a vector<callCentre> instead of a static array. If your input file length exceeds the capacity of the array, you'll walk all over the stack.

回答2:

The >> operator treats whitespace as a delimiter, and that includes newlines, so it just eats those and you never see them.

回答3:

You need to read lines and then chop the lines up. The following bit of hackery illustrates the basic idea:

#include <iostream>
#include <string>
#include <sstream>
using namespace std;

int main() {
    string line;
    while( getline( cin, line ) ) {
        istringstream is( line );
        string cs;
        is >> cs;
        double vals[10];
        int i = 0;
        while( is >> vals[i] ) {
            i++;
        }

        cout << "CS: " << cs;
        for ( int j = 0; j < i; j++ ) {
            cout << " " << vals[j];
        }
        cout << endl;
    }
}

回答4:

I would read the file, one line after another and parse each line individually for the values:

std::string line;
while (std::getline(ins, line)) {
  std::istringstream sline(line);
  sline >> aCentre[c].name;
  int i = 0;
  while (sline >> aCentre[c].data[i])
    i++;
  c++;
}

来源：https://stackoverflow.com/questions/640983/detect-newline-byte-from-filestream

标签

c++

newline

text-files

fstream