DragonFly On-Line Manual Pages

BIO(3)		      DragonFly Library Functions Manual		BIO(3)

NAME
     BIO -- I/O abstraction

SYNOPSIS
     #include <openssl/bio.h>

DESCRIPTION
     A BIO is an I/O abstraction, it hides many of the underlying I/O details
     from an application.  If an application uses a BIO for its I/O, it can
     transparently handle SSL connections, unencrypted network connections and
     file I/O.

     There are two types of BIO, a source/sink BIO and a filter BIO.

     As its name implies, a source/sink BIO is a source and/or sink of data,
     examples include a socket BIO and a file BIO.

     A filter BIO takes data from one BIO and passes it through to another, or
     to the application.  The data may be left unmodified (for example a mes-
     sage digest BIO) or translated (for example an encryption BIO).  The
     effect of a filter BIO may change according to the I/O operation it is
     performing: for example an encryption BIO will encrypt data if it is
     being written to and decrypt data if it is being read from.

     BIOs can be joined together to form a chain (a single BIO is a chain with
     one component).  A chain normally consist of one source/sink BIO and one
     or more filter BIOs.  Data read from or written to the first BIO then
     traverses the chain to the end (normally a source/sink BIO).

SEE ALSO
     BIO_ctrl(3), BIO_f_base64(3), BIO_f_buffer(3), BIO_f_cipher(3),
     BIO_f_md(3), BIO_f_null(3), BIO_f_ssl(3), BIO_find_type(3), BIO_new(3),
     BIO_new_bio_pair(3), BIO_push(3), BIO_read(3), BIO_s_accept(3),
     BIO_s_bio(3), BIO_s_connect(3), BIO_s_fd(3), BIO_s_file(3), BIO_s_mem(3),
     BIO_s_null(3), BIO_s_socket(3), BIO_set_callback(3), BIO_should_retry(3)

DragonFly 4.7			 July 17, 2014			 DragonFly 4.7
BIO_set_callback(3)                 OpenSSL                BIO_set_callback(3)

NAME
       BIO_set_callback, BIO_get_callback, BIO_set_callback_arg,
       BIO_get_callback_arg, BIO_debug_callback - BIO callback functions

SYNOPSIS
        #include <openssl/bio.h>

        #define BIO_set_callback(b,cb)         ((b)->callback=(cb))
        #define BIO_get_callback(b)            ((b)->callback)
        #define BIO_set_callback_arg(b,arg)    ((b)->cb_arg=(char *)(arg))
        #define BIO_get_callback_arg(b)                ((b)->cb_arg)

        long BIO_debug_callback(BIO *bio,int cmd,const char *argp,int argi,
               long argl,long ret);

        typedef long (*callback)(BIO *b, int oper, const char *argp,
                               int argi, long argl, long retvalue);

DESCRIPTION
       BIO_set_callback() and BIO_get_callback() set and retrieve the BIO
       callback, they are both macros. The callback is called during most high
       level BIO operations. It can be used for debugging purposes to trace
       operations on a BIO or to modify its operation.

       BIO_set_callback_arg() and BIO_get_callback_arg() are macros which can
       be used to set and retrieve an argument for use in the callback.

       BIO_debug_callback() is a standard debugging callback which prints out
       information relating to each BIO operation. If the callback argument is
       set if is interpreted as a BIO to send the information to, otherwise
       stderr is used.

       callback() is the callback function itself. The meaning of each
       argument is described below.

       The BIO the callback is attached to is passed in b.

       oper is set to the operation being performed. For some operations the
       callback is called twice, once before and once after the actual
       operation, the latter case has oper or'ed with BIO_CB_RETURN.

       The meaning of the arguments argp, argi and argl depends on the value
       of oper, that is the operation being performed.

       retvalue is the return value that would be returned to the application
       if no callback were present. The actual value returned is the return
       value of the callback itself. In the case of callbacks called before
       the actual BIO operation 1 is placed in retvalue, if the return value
       is not positive it will be immediately returned to the application and
       the BIO operation will not be performed.

       The callback should normally simply return retvalue when it has
       finished processing, unless if specifically wishes to modify the value
       returned to the application.

CALLBACK OPERATIONS
       BIO_free(b)
           callback(b, BIO_CB_FREE, NULL, 0L, 0L, 1L) is called before the
           free operation.

       BIO_read(b, out, outl)
           callback(b, BIO_CB_READ, out, outl, 0L, 1L) is called before the
           read and callback(b, BIO_CB_READ|BIO_CB_RETURN, out, outl, 0L,
           retvalue) after.

       BIO_write(b, in, inl)
           callback(b, BIO_CB_WRITE, in, inl, 0L, 1L) is called before the
           write and callback(b, BIO_CB_WRITE|BIO_CB_RETURN, in, inl, 0L,
           retvalue) after.

       BIO_gets(b, out, outl)
           callback(b, BIO_CB_GETS, out, outl, 0L, 1L) is called before the
           operation and callback(b, BIO_CB_GETS|BIO_CB_RETURN, out, outl, 0L,
           retvalue) after.

       BIO_puts(b, in)
           callback(b, BIO_CB_WRITE, in, 0, 0L, 1L) is called before the
           operation and callback(b, BIO_CB_WRITE|BIO_CB_RETURN, in, 0, 0L,
           retvalue) after.

       BIO_ctrl(BIO *b, int cmd, long larg, void *parg)
           callback(b,BIO_CB_CTRL,parg,cmd,larg,1L) is called before the call
           and callback(b,BIO_CB_CTRL|BIO_CB_RETURN,parg,cmd, larg,ret) after.

EXAMPLE
       The BIO_debug_callback() function is a good example, its source is in
       crypto/bio/bio_cb.c

SEE ALSO
       TBA

1.0.2h                            2016-05-03               BIO_set_callback(3)