| I/O manipulators | ||||
| Print functions(C++23) | ||||
| C-style I/O | ||||
| Buffers | ||||
(C++23) | ||||
(C++98/26*) | ||||
(C++20) | ||||
| Streams | ||||
| Abstractions | ||||
| File I/O | ||||
| String I/O | ||||
| Array I/O | ||||
(C++23) | ||||
(C++23) | ||||
(C++23) | ||||
(C++98/26*) | ||||
(C++98/26*) | ||||
(C++98/26*) | ||||
| Synchronized Output | ||||
(C++20) | ||||
| Types | ||||
| Error category interface | ||||
(C++11) | ||||
(C++11) |
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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) | |
Contents |
| s | - | pointer to the firstCharT in the user-provided buffer |
| n | - | the number ofCharT elements in the user-provided buffer |
Provides a 10k buffer for reading. On linux, the strace utility may be used to observe the actual number of bytes read.
#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
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 ofsetbuf was only specifiedifgptr() is not null and not equal toegptr() | specified as no-op for all cases |
[virtual] | attempts to replace the controlled character sequence with an array (virtual protected member function of std::basic_stringbuf<CharT,Traits,Allocator>)[edit] |
[virtual] | provides user-supplied buffer or turns this filebuf unbuffered (virtual protected member function of std::basic_filebuf<CharT,Traits>)[edit] |
[virtual] | attempts to replace the controlled character sequence with an array (virtual protected member function of std::strstreambuf)[edit] |
| sets the buffer for a file stream (function)[edit] |
