std::strstream::strstream
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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.
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[edit] 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):
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[edit] 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'
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
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LWG 115 | C++98 | overload (2) only considered the case mode & app == 0 ( == has higher precedence than & )
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considers cases (mode & app) == 0 and (mode & app) != 0 |
[edit] See also
constructs a strstreambuf object (public member function of std::strstreambuf )
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constructs an istrstream object, optionally allocating the buffer (public member function of std::istrstream )
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constructs an ostrstream object, optionally allocating the buffer (public member function of std::ostrstream )
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