/xlv3/openssl/0.9.7e-sgipl1/work/0.9.7e-sgipl1/openssl-
0.9.7e/doc/crypto
Page 1 (printed 10/20/05)
BIO_push(3) 14/Sep/2000 (0.9.7e) 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-chain. 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:
Page 1 (printed 10/20/05)
BIO_push(3) 14/Sep/2000 (0.9.7e) 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
Page 2 (printed 10/20/05)
