std::basic_streambuf<CharT,Traits>::pubsetbuf, std::basic_streambuf<CharT,Traits>::
From cppreference.com
< cpp | io | basic streambuf
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public
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basic_streambuf<CharT, Traits> * pubsetbuf( char_type* s, std::streamsize n ) |
(1) | |
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protected
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virtual basic_streambuf<CharT, Traits> * setbuf( char_type* s, std::streamsize n ) |
(2) | |
1) Calls setbuf(s, n) of the most derived class.
2)
Parameters
| s | - | pointer to the first CharT in the user-provided buffer
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| n | - | the number of CharT elements in the user-provided buffer
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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 specifiedif gptr() is not null and not equal to egptr() |
specified as no-op for all cases |
See also
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[virtual]
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attempts to replace the controlled character sequence with an array (virtual protected member function of std::basic_stringbuf<CharT,Traits,Allocator>) |
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[virtual]
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provides user-supplied buffer or turns this filebuf unbuffered (virtual protected member function of std::basic_filebuf<CharT,Traits>) |
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[virtual]
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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) |