std::strstream:: strstream
From cppreference.com
|
strstream
(
)
;
|
(1) |
(deprecated in C++98)
(removed in C++26) |
|
strstream
(
char
*
s,
int
n,
std::
ios_base
::
openmode
mode
=
std:: ios_base :: in | std:: ios_base :: out ) ; |
(2) |
(deprecated in C++98)
(removed in C++26) |
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
(
mode
&
app
)
==
0
(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
(
mode
&
app
)
!
=
0
(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):
|
Example
Run this code
#include <iostream> #include <string> #include <strstream> int main() { // dynamic buffer std::strstream s1; 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'
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 115 | C++98 |
overload (2) only considered the case
mode & app == 0 (
==
has higher precedence than
&
)
|
considers cases
(
mode
&
app
)
==
0
and ( mode & app ) ! = 0 |
See also
constructs a
strstreambuf
object
(public member function of
std::strstreambuf
)
|
|
constructs an
istrstream
object, optionally allocating the buffer
(public member function of
std::istrstream
)
|
|
constructs an
ostrstream
object, optionally allocating the buffer
(public member function of
std::ostrstream
)
|