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std::quoted - cppreference.com

Allows insertion and extraction of quoted strings, such as the ones found in CSV or XML.

When used in an expression

, where

is an output stream with

equal to

and, for overloads (2,3),

equal to

, behaves as a

, which inserts into

a sequence of characters

constructed as follows:

a) First, the character delim is added to the sequence.

b) Then every character from s, except if the next character to output equals delim or equals escape (as determined by the stream's traits_type::eq), then first appends an extra copy of escape.

c) In the end, delim is appended to seq once more.

Then, if seq.size() < out.width(), adds out.width()-seq.size() copies of the fill character out.fill() either at the end of the sequence (if ios_base::left is set in out.flags()) or at the beginning of the sequence (in all other cases).

Finally, outputs each character from the resulting sequence as if by calling out.rdbuf()->sputn(seq, n), where n=std::max(out.width(), seq.size()) and out.width(0) to cancel the effects of std::setw, if any.

When used in an expression

, where

is an input stream with

equal to

and

equal to

, extracts characters from

, using

, according to the following rules:

a) If the first character extracted does not equal delim (as determined by the stream's traits_type::eq), then simply performs in >> s.

b) Otherwise (if the first character is the delimiter):

1) Turns off the skipws flag on the input stream.

2) Empties the destination string by calling s.clear().

3) Extracts successive characters from in and appends them to s, except that whenever an escape character is extracted, it is ignored and the next character is appended to s. Extraction stops when !in == true or when an unescaped delim character is found.

4) Discards the final (unescaped) delim character.

5) Restores the skipws flag on the input stream to its original value.

Returns an object of unspecified type such that the described behavior takes place.

Throws std::ios_base::failure if operator>> or operator<< throws.

#include <iomanip>
#include <iostream>
#include <sstream>
 
void default_delimiter()
{
    const std::string in = "std::quoted() quotes this string and embedded \"quotes\" too";
    std::stringstream ss;
    ss << std::quoted(in);
    std::string out;
    ss >> std::quoted(out);
 
    std::cout << "Default delimiter case:\n"
                 "read in     [" << in << "]\n"
                 "stored as   [" << ss.str() << "]\n"
                 "written out [" << out << "]\n\n";
}
 
void custom_delimiter()
{
    const char delim{'$'};
    const char escape{'%'};
 
    const std::string in = "std::quoted() quotes this string and embedded $quotes$ $too";
    std::stringstream ss;
    ss << std::quoted(in, delim, escape);
    std::string out;
    ss >> std::quoted(out, delim, escape);
 
    std::cout << "Custom delimiter case:\n"
                 "read in     [" << in << "]\n"
                 "stored as   [" << ss.str() << "]\n"
                 "written out [" << out << "]\n\n";
}
 
int main()
{
    default_delimiter();
    custom_delimiter();
}

Output:

Default delimiter case:
read in     [std::quoted() quotes this string and embedded "quotes" too]
stored as   ["std::quoted() quotes this string and embedded \"quotes\" too"]
written out [std::quoted() quotes this string and embedded "quotes" too]
 
Custom delimiter case:
read in     [std::quoted() quotes this string and embedded $quotes$ $too]
stored as   [$std::quoted() quotes this string and embedded %$quotes%$ %$too$]
written out [std::quoted() quotes this string and embedded $quotes$ $too]

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