std::strstream::strstream

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

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

1) Default-constructs the underlying std::strstreambuf, which creates 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 calling 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

mode

specifies stream open mode. It is a bitmask type, the following constants are defined (although only app is used):

Constant	Explanation
`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

#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'

(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`)

std::strstream::strstream

Parameters

Example

See also