Manual Pages for UNIX Operating System command usage for man BIO_set_callback_arg

OpenSSL                                BIO_set_callback(3openssl)



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

SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS
      #include 

      #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);


DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
     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 bbbb.

     ooooppppeeeerrrr 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 ooooppppeeeerrrr
     or'ed with BIO_CB_RETURN.

     The meaning of the arguments aaaarrrrggggpppp, aaaarrrrggggiiii and aaaarrrrggggllll depends on
     the value of ooooppppeeeerrrr, that is the operation being performed.

     rrrreeeettttvvvvaaaalllluuuueeee 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



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OpenSSL                                BIO_set_callback(3openssl)



     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 rrrreeeettttvvvvaaaalllluuuueeee when it
     has finished processing, unless if specifically wishes to
     modify the value returned to the application.

CCCCAAAALLLLLLLLBBBBAAAACCCCKKKK OOOOPPPPEEEERRRRAAAATTTTIIIIOOOONNNNSSSS
     BBBBIIIIOOOO_ffffrrrreeeeeeee((((bbbb))))
         callback(b, BIO_CB_FREE, NULL, 0L, 0L, 1L) is called
         before the free operation.

     BBBBIIIIOOOO_rrrreeeeaaaadddd((((bbbb,,,, oooouuuutttt,,,, oooouuuuttttllll))))
         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.

     BBBBIIIIOOOO_wwwwrrrriiiitttteeee((((bbbb,,,, iiiinnnn,,,, iiiinnnnllll))))
         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.

     BBBBIIIIOOOO_ggggeeeettttssss((((bbbb,,,, oooouuuutttt,,,, oooouuuuttttllll))))
         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.

     BBBBIIIIOOOO_ppppuuuuttttssss((((bbbb,,,, iiiinnnn))))
         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.

     BBBBIIIIOOOO_ccccttttrrrrllll((((BBBBIIIIOOOO ****bbbb,,,, iiiinnnntttt ccccmmmmdddd,,,, lllloooonnnngggg llllaaaarrrrgggg,,,, vvvvooooiiiidddd ****ppppaaaarrrrgggg))))
         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.

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

SSSSEEEEEEEE AAAALLLLSSSSOOOO
     TBA






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OpenSSL                                BIO_set_callback(3openssl)























































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