/usr/man/cat.3/BIO_push.3

BIO_push(3)                  OpenSSL                  BIO_push(3)

NAME

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

SYNOPSIS

      #include <openssl/bio.h>

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

DESCRIPTION

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

     BIO_pop() removes the BIO b from a chain and returns the
     next BIO in the chain, or NULL if there is no next BIO. The
     removed BIO then becomes a single BIO with no association
     with the original chain, it can thus be freed or attached to
     a different chain.

NOTES

     The names of these functions are perhaps a little
     misleading. BIO_push() joins two BIO chains whereas
     BIO_pop() 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 BIO_push() and BIO_pop() on a BIO may
     have additional consequences (a control call is made to the
     affected BIOs) any effects will be noted in the descriptions
     of individual BIOs.

EXAMPLES

     For these examples suppose 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-f. After making the
     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.

     It should be noted that reading causes data to pass in the
     reverse direction, that is data is read from f, base64
     decoded and digested by md1 and md2. If the call:

1.0.2t               Last change: 2019-09-10                    1

BIO_push(3)                  OpenSSL                  BIO_push(3)

      BIO_pop(md2);

     The call will return b64 and the new chain will be md1-b64-f
     data can be written to md1 as before.

RETURN VALUES

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

     BIO_pop() returns the next BIO in the chain, or NULL if
     there is no next BIO.

SEE ALSO

     TBA

1.0.2t               Last change: 2019-09-10                    2

See also BIO_pop(3)