Namespaces
Variants
Views
Actions

std::strstreambuf::str

From cppreference.com
< cpp‎ | io‎ | strstreambuf
Revision as of 13:31, 26 August 2013 by Cubbi (Talk | contribs)

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
char* str() const;

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 <strstream>
#include <iostream>
 
int main()
{
    std::strstream dyn; // dynamically-allocated read/write buffer
    dyn << "Test: " << 1.23;
    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"

[edit] See also

accesses the output buffer
(public member function of std::strstream) [edit]
accesses the output buffer
(public member function of std::ostrstream) [edit]
accesses the output buffer
(public member function of std::istrstream) [edit]