CODEWITHSUNDEEP
c++
Jono_2007
Jono_2007

Reputation: 1046

Outputting a whole array at once

I have a large 1D array of chars and I'm looking for a way to output the whole array without using the usual for-loop and doing this in a single output rather then thousands of outputs, the reason being performance and execution time reduction.

Is there anyway to be able to achieve this?

Upvotes: 3

Views: 19528

Answers (7)

user15939950
user15939950

Reputation:

You can copy from the container to standard output.

For instance

using std::ostream_iterator;
using std::cout;
using std::begin;
using std::end;
using std::copy;


copy(arr.begin(), arr.end(), ostream_iterator<Type>(cout,”\n”)) ;

std::ostream_iterator constructs output iterator tied to given ostream.

Upvotes: 0

rcollyer
rcollyer

Reputation: 10695

An alternative is to use ostream::write which accepts a char array and the array size. The array is copied directly to the streambuffer, so it skips the formatting steps.

Edit

//since, std::cout is an ostream ...
std::cout.write( array, 8 );

Upvotes: 9

sehe
sehe

Reputation: 393064

If you don't mind taking a copy,

std::cout << std::string(a, a+N) << std::endl;

wrapping it into a generic function:

template <typename T, size_t N>
std::ostream& dump(std::ostream& os, const T (&a)[N])
{
    return os << std::basic_string<T>(a, a+N) << std::endl;
}

// ....

wchar_t[] whello = L"Hello world";
dump(std::wcerr, whello) << std::endl;

unsigned char[] hello = "Hello world";
dump(std::cout, hello) << std::endl;

char buf[2048];
std::ofstream ofs("out.bin", std::ios::binary);
dump(ofs, buf);

Upvotes: 0

Luca Martini
Luca Martini

Reputation: 1474

To decrease execution time, if the characters have to be formatted, I would buffer the output to a std::ostringstream and then copy the resulting string to the output.

Upvotes: 0

Sarfaraz Nawaz
Sarfaraz Nawaz

Reputation: 361462

As a general case, use std::copy as:

T a[N]; //N is some constant!
//...
std::copy(a, a + N, std::ostream_iterator<T>(std::cout, " "));

Replace T with char, int, std::string or any type, it should work, as long as operator<< is overloaded for T, either as member function of std::ostream or free function which takes std::ostream& as first argument, and const T& as second argument.

Upvotes: 5

John Dibling
John Dibling

Reputation: 101456

You can use the copy algorithm from the Standard Library. If you want to output to the standard output, you send the contents to an ostream_iterator on cout:

#include <string>
#include <iostream>
#include <algorithm>
#include <iterator>
using namespace std;

int main()
{
    char my_chars[] = {'a','b','c'};

    copy( &my_chars[0], &my_chars[sizeof(my_chars)], ostream_iterator<char>(cout, "\t"));
}

You can also send the output to another stream, and then when that is done, dump the whole thing to cout in one shot:

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

int main()
{
    char my_chars[] = {'a','b','c'};

    stringstream ss;
    copy( &my_chars[0], &my_chars[sizeof(my_chars)], ostream_iterator<char>(ss, "\t"));

    cout << ss.str() << endl;
}

Upvotes: 0

Andy Balaam
Andy Balaam

Reputation: 6671

// If it's null-terminated
#include <stdio.h>
printf( "%s\n", myarray );

Upvotes: 0

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