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std::strstream::strstream(3)  C++ Standard Libary std::strstream::strstream(3)

NAME
       std::strstream::strstream - std::strstream::strstream

Synopsis
	  strstream();						 (1)
	  strstream(char* s, int n, std::ios_base::openmode mode (2)
	  = std::ios_base::in |	std::ios_base::out);

	  Constructs   new   input/output   strstream	and   its   underlying
       std::strstreambuf.

	  1) Default-constructs	the underlying std::strstreambuf,  which  cre-
       ates a dynamically
	  growing  buffer,  and	initializes the	base class with	the address of
       the strstreambuf
	  member.
	  2) Initialized the base class	with the  address  of  the  underlying
       std::strstreambuf
	  member,  which  is initialized in one	of the two possible ways, both
       of which	use a
	  user-provided	fixed-size array:
	  a) if	the app	bit is not set in mode,	constructs the buffer by call-
       ing
	  strstreambuf(s, n, s). The behavior is undefined if there  are  less
       than n elements
	  in the array whose first element is pointed to by s
	  b)  if  the app bit is set in	mode, constructs the buffer by calling
       strstreambuf(s,
	  n, s + std::strlen(s)). The behavior is undefined if there are  less
       than n elements
	  in  the array	whose first element is pointed to by s or if the array
       does not	contain
	  a valid null-terminated character sequence.

Parameters
	  s    - char array to use as the output buffer
	  n    - size of the array to be used for output
		 specifies stream open mode. It	is a bitmask type, the follow-
       ing constants are
		 defined (although only	app is used):

		 Constant Explanation
	  mode - app	  seek to the end of stream before each	write
		 binary	  open in binary mode
		 in	  open for reading
		 out	  open for writing
		 trunc	  discard the contents of the stream when opening
		 ate	  seek to the end of stream immediately	after open

Example
       // Run this code

	#include <iostream>
	#include <strstream>
	#include <string>

	int main()
	{
	    // dynamic buffer
	    std::strstream s1; // dynamic buffer
	    s1 << 1 << ' ' << 3.14 << "	example" << std::ends;
	    std::cout << "buffer holds '" << s1.str() << "'\n";
	    s1.freeze(false);

	    int	n; double d;
	    std::string	w;
	    s1 >> n >> d >> w;
	    std::cout << "Read back: n = " << n
		      << " d = " << d
		      << " w = '" << w << "'\n";

	    // static buffer
	    char arr[20] = "-1 -3.14 ";
	    std::strstream s2(arr, sizeof arr, std::ios_base::app);
	    s2 << "another" << std::ends;
	    std::cout << "buffer holds:	'" << s2.str() << "'\n";
	    s2 >> n >> d >> w;
	    std::cout << "Read back: n = " << n
		      << " d = " << d
		      << " w = '" << w << "'\n";
	}

Output:
	buffer holds '1	3.14 example'
	Read back: n = 1 d = 3.14 w = 'example'
	buffer holds: '-1 -3.14	another'
	Read back: n = -1 d = -3.14 w =	'another'

See also
	  constructor	constructs a strstreambuf object
			(public	member function	of std::strstreambuf)
	  constructor	constructs an  strstream,  optionally  allocating  the
       buffer
			(public	member function	of std::istrstream)
	  constructor	 constructs  an	 strstream,  optionally	allocating the
       buffer
			(public	member function	of std::ostrstream)

http://cppreference.com		  2022.07.31	  std::strstream::strstream(3)

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