BIOpush(3) OpenSSL BIOpush(3)

NAME
       BIOpush, BIOpop - add and remove BIOs from a chain.

SYNOPSIS
        #include 

        BIO *  BIOpush(BIO *b,BIO *append);
        BIO *  BIOpop(BIO *b);

DESCRIPTION
       The BIOpush() function appends the BIO aappppeenndd to bb, it returns bb.

       BIOpop() removes the BIO bb 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.

NNOOTTEESS
       The names of these functions are perhaps a little misleading.
       BIOpush() joins two BIO chains whereas BIOpop() 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 BIOpush() and BIOpop() 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.

EEXXAAMMPPLLEESS
       For these examples suppose mmdd11 and mmdd22 are digest BIOs, bb6644 is a base64
       BIO and ff is a file BIO.

       If the call:

        BIOpush(b64, f);

       is made then the new chain will be bb6644-cchhaaiinn. After making the calls

        BIOpush(md2, b64);
        BIOpush(md1, md2);

       the new chain is mmdd11-mmdd22-bb6644-ff. Data written to mmdd11 will be digested by
       mmdd11 and mmdd22, bbaassee6644 encoded and written to ff.

       It should be noted that reading causes data to pass in the reverse
       direction, that is data is read from ff, base64 ddeeccooddeedd and digested by
       mmdd11 and mmdd22. If the call:

        BIOpop(md2);

       The call will return bb6644 and the new chain will be mmdd11-bb6644-ff data can
       be written to mmdd11 as before.

RETURN VALUES
       BIOpush() returns the end of the chain, bb.

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

SEE ALSO
       TBA



0.9.7l                            2000-09-14                       BIOpush(3)