BIO_s_file() returns the BIO file method. As its name implies it is a wrapper round the stdio FILE structure and it is a source/sink BIO.Calls to BIO_read() and BIO_write() read and write data to the underlying stream. BIO_gets() and BIO_puts() are supported on file BIOs.
BIO_flush() on a file BIO calls the fflush() function on the wrapped stream.
BIO_reset() attempts to change the file pointer to the start of file using fseek(stream, 0, 0).
BIO_seek() sets the file pointer to position ofs from start of file using fseek(stream, ofs, 0).
BIO_eof() calls feof().
Setting the BIO_CLOSE flag calls fclose() on the stream when the BIO is freed.
BIO_new_file() creates a new file BIO with mode mode the meaning of mode is the same as the stdio function fopen(). The BIO_CLOSE flag is set on the returned BIO.
BIO_new_fp() creates a file BIO wrapping stream. Flags can be: BIO_CLOSE, BIO_NOCLOSE (the close flag) BIO_FP_TEXT (sets the underlying stream to text mode, default is binary: this only has any effect under Win32).
BIO_set_fp() set the fp of a file BIO to fp. flags has the same meaning as in BIO_new_fp(), it is a macro.
BIO_get_fp() retrieves the fp of a file BIO, it is a macro.
BIO_seek() is a macro that sets the position pointer to offset bytes from the start of file.
BIO_tell() returns the value of the position pointer.
BIO_read_filename(), BIO_write_filename(), BIO_append_filename() and BIO_rw_filename() set the file BIO b to use file name for reading, writing, append or read write respectively.