std::strstreambuf::str
(removed in C++26)
Calls freeze() , then returns a copy of start pointer of the get area, std::streambuf::eback() .
The start of the get area, for all writeable std::strstreambuf objects constructed through the interface provided by std::strstream , is also the start of the put area.
Contents
[edit] Parameters
(none)
[edit] Return value
A copy of eback() , which may be a null pointer.
[edit] Notes
This function is typically called through the std::strstream interface.
The call to freeze() guarantees that the returned pointer remains valid until the next explicit call to freeze (false): otherwise (on a dynamic buffer) any output operation could trigger buffer reallocation which would invalidate the pointer. It also causes a memory leak in the destructor of std::strstreambuf, unless freeze(false) is called before the buffer (or, more commonly, the std::strstream that manages it) is destroyed.
[edit] Example
#include <iostream> #include <strstream> int main() { std::strstream dyn; // dynamically-allocated read/write buffer dyn << "Test: " << 1.23 << std::ends ; std::strstreambuf * buf = dyn.rdbuf(); std::cout << "R/W buffer holds [" << buf->str() // or dyn.str() << "]\n"; dyn.freeze(false); // after calling .str() on a dynamic strstream char arr[10]; std::ostrstream user(arr, 10); // fixed-size write-only buffer buf = user.rdbuf(); user << 1.23 << std::ends ; std::cout << "Write-only buffer holds [" << buf->str() // or user.str() << "]\n"; std::istrstream lit("1 2 3"); // fixed-size read-only buffer buf = lit.rdbuf(); std::cout << "Read-only buffer holds [" << buf->str() // or lit.str() << "]\n"; }
Output:
R/W buffer holds [Test: 1.23] Write-only buffer holds [1.23] Read-only buffer holds [1 2 31 2 3]