std::basic_streambuf<CharT,Traits>:: pubsetbuf, std::basic_streambuf<CharT,Traits>:: setbuf
From cppreference.com
<
cpp
|
io
|
basic streambuf
|
public
:
basic_streambuf < CharT, Traits > * pubsetbuf ( char_type * s, std:: streamsize n ) |
(1) | |
|
protected
:
virtual basic_streambuf < CharT, Traits > * setbuf ( char_type * s, std:: streamsize n ) |
(2) | |
1)
Calls
setbuf
(
s, n
)
of the most derived class.
2)
The base class version of this function has no effect. The derived classes may override this function to allow removal or replacement of the controlled character sequence (the buffer) with a user-provided array, or for any other implementation-specific purpose.
Parameters
| s | - |
pointer to the first
CharT
in the user-provided buffer
|
| n | - |
the number of
CharT
elements in the user-provided buffer
|
Return value
1)
The return value of
setbuf
(
s, n
)
.
2)
this
Example
Provides a 10k buffer for reading. On linux, the strace utility may be used to observe the actual number of bytes read.
Run this code
#include <fstream> #include <iostream> #include <string> int main() { int cnt = 0; std::ifstream file; char buf[1024 * 10 + 1]; file.rdbuf()->pubsetbuf(buf, sizeof buf); file.open("/usr/share/dict/words"); for (std::string line; getline(file, line);) ++cnt; std::cout << cnt << '\n'; }
Possible output:
356010
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 158 | C++98 |
the default behavior of
setbuf
was only specified
if gptr() is not null and not equal to egptr() |
specified as no-op
for all cases |
See also
|
[virtual]
|
attempts to replace the controlled character sequence with an array
(virtual protected member function of
std::basic_stringbuf<CharT,Traits,Allocator>
)
|
|
[virtual]
|
provides user-supplied buffer or turns this filebuf unbuffered
(virtual protected member function of
std::basic_filebuf<CharT,Traits>
)
|
|
[virtual]
|
attempts to replace the controlled character sequence with an array
(virtual protected member function of
std::strstreambuf
)
|
|
sets the buffer for a file stream
(function) |