NAME    [Toc]    [Back]

       BIO_push, BIO_pop - Add and remove BIOs from a chain.

SYNOPSIS    [Toc]    [Back]

       #include <openssl/bio.h>

       BIO * BIO_push(
               BIO *b,
               BIO *append ); BIO * BIO_pop(
               BIO *b );

DESCRIPTION    [Toc]    [Back]

       The  BIO_push()  function  appends the BIO append to b. It
       returns b.

       The BIO_pop() function removes the BIO b from a chain  and
       returns  the  next BIO in the chain. The return is NULL if
       there are no more BIOs in the chain. The removed BIO  then
       becomes  a  single BIO with no association to the original
       chain. It can be freed or attached to a different chain.

NOTES    [Toc]    [Back]

       The names of these functions are somewhat misleading.  The
       BIO_push()  function  joins  two  BIO  chains, whereas the
       BIO_pop() function deletes a single BIO from a chain.  The
       deleted BIO does not need to be at the end of a chain.

       The  process of calling the BIO_push() and BIO_pop() functions
 on a BIO may have additional consequences (a control
       call  is made to the affected BIOs). Any effects are noted
       in the descriptions of individual BIOs.

RETURN VALUES    [Toc]    [Back]

       The BIO_push() function returns the end of the chain, b.

       The BIO_pop() function returns the next BIO in the  chain.
       If  there  are  no  more  BIOs in the chain, the return is
       NULL.

EXAMPLES    [Toc]    [Back]

       For these examples, md1 and md2 are digest BIOs, b64 is  a
       base64 BIO, and f is a file BIO.

       If the call: BIO_push(b64, f);

       is made then the new chain will be b64-chain. After making
       the  following  calls  BIO_push(md2,  b64);  BIO_push(md1,
       md2);

       the  new  chain is md1-md2-b64-f. Data written to md1 will
       be digested by md1 and md2, base64 encoded and written  to
       f.

                                  Note

       Reading causes data to pass in the reverse direction. Data
       is read from f, base64 decoded and  digested  by  md1  and
       md2.

       If the call:
        BIO_pop(md2);

       is  made, the call will return b64, and the new chain will
       be md1-b64-f. Data can be written to md1 as before.

SEE ALSO    [Toc]    [Back]

       TBA



                                                      BIO_push(3)