char* str(); |
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.
(none).
A copy of eback(), which may be a null pointer.
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.
#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]
| accesses the output buffer (public member function of std::strstream) |
|
| accesses the output buffer (public member function of std::ostrstream) |
|
| accesses the output buffer (public member function of std::istrstream) |
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