Chapter 26. Input and Output

Chapter 26. Input and Output
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Derived filebufs

+ Extensions allowing filebufs to be constructed from + "C" types like FILE*s and file descriptors. +

Derived filebufs

The v2 library included non-standard extensions to construct + std::filebufs from C stdio types such as + FILE*s and POSIX file descriptors. + Today the recommended way to use stdio types with libstdc++ + IOStreams is via the stdio_filebuf class (see below), + but earlier releases provided slightly different mechanisms. +

3.0.x filebufs have another ctor with this signature: + basic_filebuf(__c_file_type*, ios_base::openmode, int_type); + + This comes in very handy in a number of places, such as + attaching Unix sockets, pipes, and anything else which uses file + descriptors, into the IOStream buffering classes. The three + arguments are as follows: +
+ For those wanting to use file descriptors instead of FILE*'s, I + invite you to contemplate the mysteries of C's fdopen(). +
In library snapshot 3.0.95 and later, filebufs bring + back an old extension: the fd() member function. The + integer returned from this function can be used for whatever file + descriptors can be used for on your platform. Naturally, the + library cannot track what you do on your own with a file descriptor, + so if you perform any I/O directly, don't expect the library to be + aware of it. +
Beginning with 3.1, the extra filebuf constructor and + the fd() function were removed from the standard + filebuf. Instead, <ext/stdio_filebuf.h> contains + a derived class called + __gnu_cxx::stdio_filebuf. + This class can be constructed from a C FILE* or a file + descriptor, and provides the fd() function. +

If you want to access a filebuf's file descriptor to + implement file locking (e.g. using the fcntl() system + call) then you might be interested in Henry Suter's RWLock class. + +

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