std::strstreambuf::str (3) - Linux Manuals

std::strstreambuf::str: std::strstreambuf::str

NAME

std::strstreambuf::str - std::strstreambuf::str

Synopsis

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.

Parameters

(none)

Return value

A copy of eback(), which may be a null pointer.

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.

Example

// Run this code

  #include <strstream>
  #include <iostream>

  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"