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Formatting a string into multiple lines of a certain length in C / C ++

Is there a common C / C ++ library (or a common technique) for entering line (s) of input text and word splitting on separate lines. Where each line of output has a maximum width and the words are not separated by lines. Spaces that are collapsed or saved are in order. Punctuation must be maintained. A small and compact library is preferred.

I could easily spend the day putting something together that works, but would like to know if there is something in common, so I am not reinventing the wheel. Bonus points if the input line may contain a format specifier to indicate the level of indentation for the output lines.

Example input: "Beef with a gang of beef and chicken, chicken beef with a chicken of chicken with chicken, chicken and pork lamb chicken with beef chicken with short tail. Short loin andouille.

Output Example (Target Width = 60)

123456789012345678901234567890123456789012345678901234567890   Line added to show where 60 is
Shankle drumstick corned beef, chuck turkey chicken pork
chop venison beef strip steak cow sausage. Tail short loin
shoulder ball tip, jowl drumstick rump. Tail tongue ball tip
meatloaf, bresaola short loin tri-tip fatback pork loin
sirloin shank flank biltong. Venison short loin andouille.
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8 answers

Here my approach is, of course, not the fastest, but I tried to make it as readable as possible. The result is the same as your example.

#include <iostream>
#include <string>


std::string splitInLines(std::string source, std::size_t width, std::string whitespace = " \t\r")
{
    std::size_t  currIndex = width - 1;
    std::size_t  sizeToElim;
    while ( currIndex < source.length() )
    {
        currIndex = source.find_last_of(whitespace,currIndex + 1); 
        if (currIndex == std::string::npos)
            break;
        currIndex = source.find_last_not_of(whitespace,currIndex);
        if (currIndex == std::string::npos)
            break;
        sizeToElim = source.find_first_not_of(whitespace,currIndex + 1) - currIndex - 1;
        source.replace( currIndex + 1, sizeToElim , "\n");
        currIndex += (width + 1); //due to the recently inserted "\n"
    }
    return source;
}

int main() {
    std::string source = "Shankle drumstick corned beef, chuck turkey chicken pork chop venison beef strip steak cow sausage. Tail short loin shoulder ball tip, jowl drumstick rump. Tail tongue ball tip meatloaf, bresaola short loin tri-tip fatback pork loin sirloin shank flank biltong. Venison short loin andouille.";
    std::string result = splitInLines(source , 60);
    std::cout << result;
    return 0;
}
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, , . list . std::, , using namespace std; using std::list; using std::string; using std::size_t;, , .

list<string> wraptext(string input, size_t width) {
    size_t curpos = 0;
    size_t nextpos = 0;

    list<string> lines;
    string substr = input.substr(curpos, width + 1);

    while (substr.length() == width + 1 && (nextpos = substr.rfind(' ')) != input.npos) {
        lines.push_back(input.substr(curpos, nextpos));
        curpos += nextpos + 1;
        substr = input.substr(curpos, width + 1);
    }

    if (curpos != input.length())
        lines.push_back(input.substr(curpos, input.npos));

    return lines;
}

, :

int main() {
    string input = "Shankle drumstick corned beef, chuck turkey chicken pork chop venison beef strip steak cow sausage. Tail short loin shoulder ball tip, jowl drumstick rump. Tail tongue ball tip meatloaf, bresaola short loin tri-tip fatback pork loin sirloin shank flank biltong. Venison short loin andouille.";

    list<string> l = wraptext(input, 60);

    for (auto i = l.begin(); i != l.end(); ++i)
        cout << *i << endl;

    cin.get();
}

:

Shankle drumstick corned beef, chuck turkey chicken pork
chop venison beef strip steak cow sausage. Tail short loin
shoulder ball tip, jowl drumstick rump. Tail tongue ball tip
meatloaf, bresaola short loin tri-tip fatback pork loin
sirloin shank flank biltong. Venison short loin andouille.
+1

, :

char temp[60];
int cnt, x = 0;
do
{
    cnt = 59;
    strncpy(temp, src + x, 60); //Assuming the original is stored in src
    while(temp[cnt] != ' ') cnt --;
    temp[cnt] = (char) 0;
    x += cnt + 1;
    printf("%s\n", temp);
}while (x < strlen(src));
+1

C, w_wrap.c w_wrap.h, Fidonet C_ECHO 20 .

++, , :

#include <sstream>
#include <string>
#include <iostream>

void wrap(std::string const &input, size_t width, std::ostream &os, size_t indent = 0)
{ 
    std::istringstream in(input);

    os << std::string(indent, ' '); 
    size_t current = indent;
    std::string word;

    while (in >> word) {
        if (current + word.size() > width) {
            os << "\n" << std::string(indent, ' ');
            current = indent;
        }
        os << word << ' ';
        current += word.size() + 1;
    }
}

#ifdef TEST 
int main() { 
    char *in = "Shankle drumstick corned beef, chuck turkey chicken pork chop"
               " venison beef strip steak cow sausage. Tail short loin shoulder"
               " ball tip, jowl drumstick rump. Tail tongue ball tip meatloaf,"
               " bresaola short loin tri-tip fatback pork loin sirloin shank"
               " flank biltong. Venison short loin andouille.";

    wrap(in, 60, std::cout);
    return 0;
}
#endif

, - :

wrap(in, 60, std::cout, 5);

, I/O, , , , , . , , , , . , , - 3 , , () 60 . , - C, .

+1

Ya, , strtok, , seperator.

0

, :

void put_multiline(const char *s,int width)
{
  int n,i=0;
  char t[100];
  while( 1==sscanf(s,"%99s%n",t,&n) )
  {
    if( i+strlen(t)>width ) puts(""),i=0;
    printf("%s%s",i?++i," ":"",t);i+=strlen(t);
    s+=n;
  }
}

strtok , . /.

0

, : /(.*){,60}? +/ $1\n, ( : ? ).

, .

0

Here is a regex based approach. Unlike the approaches in other answers, it also correctly processes newlines in the input string.

#include <regex>
#include <iostream>
#include <string>

int main() {
  auto test = std::string{"Shankle drumstick corned beef, chuck turkey chicken pork chop venison beef strip steak cow sausage. Tail short loin shoulder ball tip, jowl drumstick rump. Tail tongue ball tip meatloaf, bresaola short loin tri-tip fatback pork loin sirloin shank flank biltong. Venison short loin andouille."};

  // Consume 60 characters that are followed by a space or the end of the input string
  auto line_wrap = std::regex{"(.{1,60})(?: +|$)"};

  // Replace the space or the end of the input string with a new line
  test = regex_replace(test, line_wrap, "$1\n");

  // Trim the new line added for the end of the input string
  test.resize(test.size() - 1);

  std::cout << test << std::endl;
}
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