Shortest code to split std::string into std::pair

Question

I have a text, in "key:value" format. The actual text may look like, "Server: nginx" or "Server:nginx" ignoring the whitespaces between the key, : and value.

What could be the fastest and shortest way to split this into a std::pair<std::string, std::string>?

possible duplicate of [Split a string in C++?](http://stackoverflow.com/questions/236129/split-a-string-in-c) — StenSoft, Jul 08 '15 at 11:54
Not really, this is about pushing directly into the pair, much is about tokenizing — quarks, Jul 08 '15 at 11:56
Requirements vastly underspecified, as discovered below. Please be clearer and more precise next time. — Lightness Races in Orbit, Jul 08 '15 at 12:21

score 6 · Accepted Answer · answered Jul 08 '15 at 12:23

David was close, but he didn't actually test his code.

Here's a working version.

auto index = str.find(':');
std::pair<std::string,std::string> keyVal;
if (index != std::string::npos) {

   // Split around ':' character
   keyVal = std::make_pair(
      str.substr(0,index),
      str.substr(index+1)
   );

   // Trim any leading ' ' in the value part
   // (you may wish to add further conditions, such as '\t')
   while (!keyVal.second.empty() && keyVal.second.front() == ' ') {
      keyVal.second.erase(0,1);
   } 
}

(live demo)

NathanOliver · Answer 2 · 2015-07-08T12:31:39.277

1

I would use a stringstream and use:

string str = "Server: nginx with more stuff";
std::string key, val;
std::stringstream ss(str);
std::getline(ss, key, ':');
std::getline(ss, val);
auto p = make_pair(key, val);
if (p.second.front() = ' ') // get rid of leading space if it exist
    p.second.erase(0, 1);

edited Jul 08 '15 at 12:31

answered Jul 08 '15 at 12:04

NathanOliver

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@xybrek: Pretty pointless link since we have no idea what your input data are – Lightness Races in Orbit Jul 08 '15 at 12:11
1

@xybrek This works with the sample data you included in your post. If you have different constraints then you should add that to the question. – NathanOliver Jul 08 '15 at 12:13
1

@xybrek and can you show how that should be parsed? Does everything after `Response Headers:` need to be in value of that key? Please edit your question with the relevant information. It is not fair to ask for X and then comment that hey it doesn't work on Y which is actually what I want. – NathanOliver Jul 08 '15 at 12:17
@xybrek So only the date one got cut. Maybe just replace `ss >> val` with another std::getline? – KABoissonneault Jul 08 '15 at 12:17
Yes, I'd do that. Getline with the default delimiter the second time. – Lightness Races in Orbit Jul 08 '15 at 12:20
@LightnessRacesinOrbit using `getline()` again will still leave any leading whitespace in the second part. I am trying to figure out a way to get rid of it. – NathanOliver Jul 08 '15 at 12:23
Isn't there an istream manipulator to skip over any whitespace in the stream? – celticminstrel Jul 08 '15 at 13:26

score 0 · Answer 3 · edited Jul 08 '15 at 12:22

0

I'd say

auto index = str.find(":");
std::pair<std::string,std::string> keyVal
if (index != std::string::npos){
 keyVal = std::make_pair( str.substr(0,str.size()-index),
 str.substr(index+1, std::string::npos));
 if (keyVal.second.front() == ' ') {keyVal.second.erase(0,1); } 
}

this will remove the whitespace if the seperator is ": " instead of ":"

of course , you can make the code spaggetier and remove even more line and use str.find(":") directly instead of 'index'.

edited Jul 08 '15 at 12:22

Lightness Races in Orbit

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answered Jul 08 '15 at 11:55

David Haim

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missed that, one second . – David Haim Jul 08 '15 at 11:57
@xybrek: Pretty pointless link since we have no idea what your input data are – Lightness Races in Orbit Jul 08 '15 at 12:10
@xybrek: You're right; this is broken. David it would be great if you actually _tried_ your proposed solution before handing it to the OP, instead of rushing to be the "frist"! – Lightness Races in Orbit Jul 08 '15 at 12:18

score 0 · Answer 4 · answered Jul 08 '15 at 12:21

0

I would recommend the usage of regular expressions (if the pattern of your values won't change at runtime): http://www.cplusplus.com/reference/regex/

But in concern of performance you should make speed tests for all the possibilities which are showed above (string parsing manually, using stringstreams, regular expressions,....

answered Jul 08 '15 at 12:21

mbed_dev

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Why on earth would you use regular expressions for this?! The OP even specifically stated he wanted it to be fast.... – Lightness Races in Orbit Jul 08 '15 at 12:22

Shortest code to split std::string into std::pair

4 Answers4

(live demo)