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BIO_tell (3)
  • >> BIO_tell (3) ( Разные man: Библиотечные вызовы )
  •  

    NAME

    BIO_ctrl, BIO_callback_ctrl, BIO_ptr_ctrl, BIO_int_ctrl, BIO_reset,
    BIO_seek, BIO_tell, BIO_flush, BIO_eof, BIO_set_close, BIO_get_close,
    BIO_pending, BIO_wpending, BIO_ctrl_pending, BIO_ctrl_wpending,
    BIO_get_info_callback, BIO_set_info_callback - BIO control operations
     
    

    SYNOPSIS

     #include <openssl/bio.h>
    
    

     long BIO_ctrl(BIO *bp,int cmd,long larg,void *parg);
     long BIO_callback_ctrl(BIO *b, int cmd, void (*fp)(struct bio_st *, int, const char *, int, long, long));
     char * BIO_ptr_ctrl(BIO *bp,int cmd,long larg);
     long BIO_int_ctrl(BIO *bp,int cmd,long larg,int iarg);
    
    

     int BIO_reset(BIO *b);
     int BIO_seek(BIO *b, int ofs);
     int BIO_tell(BIO *b);
     int BIO_flush(BIO *b);
     int BIO_eof(BIO *b);
     int BIO_set_close(BIO *b,long flag);
     int BIO_get_close(BIO *b);
     int BIO_pending(BIO *b);
     int BIO_wpending(BIO *b);
     size_t BIO_ctrl_pending(BIO *b);
     size_t BIO_ctrl_wpending(BIO *b);
    
    

     int BIO_get_info_callback(BIO *b,bio_info_cb **cbp);
     int BIO_set_info_callback(BIO *b,bio_info_cb *cb);
    
    

     typedef void bio_info_cb(BIO *b, int oper, const char *ptr, int arg1, long arg2, long arg3);
    
    
     

    DESCRIPTION

    BIO_ctrl(), BIO_callback_ctrl(), BIO_ptr_ctrl() and BIO_int_ctrl() are BIO ``control'' operations taking arguments of various types. These functions are not normally called directly, various macros are used instead. The standard macros are described below, macros specific to a particular type of BIO are described in the specific BIOs manual page as well as any special features of the standard calls.

    BIO_reset() typically resets a BIO to some initial state, in the case of file related BIOs for example it rewinds the file pointer to the start of the file.

    BIO_seek() resets a file related BIO's (that is file descriptor and FILE BIOs) file position pointer to ofs bytes from start of file.

    BIO_tell() returns the current file position of a file related BIO.

    BIO_flush() normally writes out any internally buffered data, in some cases it is used to signal EOF and that no more data will be written.

    BIO_eof() returns 1 if the BIO has read EOF, the precise meaning of ``EOF'' varies according to the BIO type.

    BIO_set_close() sets the BIO b close flag to flag. flag can take the value BIO_CLOSE or BIO_NOCLOSE. Typically BIO_CLOSE is used in a source/sink BIO to indicate that the underlying I/O stream should be closed when the BIO is freed.

    BIO_get_close() returns the BIOs close flag.

    BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending() return the number of pending characters in the BIOs read and write buffers. Not all BIOs support these calls. BIO_ctrl_pending() and BIO_ctrl_wpending() return a size_t type and are functions, BIO_pending() and BIO_wpending() are macros which call BIO_ctrl().  

    RETURN VALUES

    BIO_reset() normally returns 1 for success and 0 or -1 for failure. File BIOs are an exception, they return 0 for success and -1 for failure.

    BIO_seek() and BIO_tell() both return the current file position on success and -1 for failure, except file BIOs which for BIO_seek() always return 0 for success and -1 for failure.

    BIO_flush() returns 1 for success and 0 or -1 for failure.

    BIO_eof() returns 1 if EOF has been reached 0 otherwise.

    BIO_set_close() always returns 1.

    BIO_get_close() returns the close flag value: BIO_CLOSE or BIO_NOCLOSE.

    BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending() return the amount of pending data.  

    NOTES

    BIO_flush(), because it can write data may return 0 or -1 indicating that the call should be retried later in a similar manner to BIO_write(). The BIO_should_retry() call should be used and appropriate action taken is the call fails.

    The return values of BIO_pending() and BIO_wpending() may not reliably determine the amount of pending data in all cases. For example in the case of a file BIO some data may be available in the FILE structures internal buffers but it is not possible to determine this in a portably way. For other types of BIO they may not be supported.

    Filter BIOs if they do not internally handle a particular BIO_ctrl() operation usually pass the operation to the next BIO in the chain. This often means there is no need to locate the required BIO for a particular operation, it can be called on a chain and it will be automatically passed to the relevant BIO. However this can cause unexpected results: for example no current filter BIOs implement BIO_seek(), but this may still succeed if the chain ends in a FILE or file descriptor BIO.

    Source/sink BIOs return an 0 if they do not recognize the BIO_ctrl() operation.  

    BUGS

    Some of the return values are ambiguous and care should be taken. In particular a return value of 0 can be returned if an operation is not supported, if an error occurred, if EOF has not been reached and in the case of BIO_seek() on a file BIO for a successful operation.  

    SEE ALSO

    TBA


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    RETURN VALUES
    NOTES
    BUGS
    SEE ALSO


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