BIO_push (3)
Leading comments
Automatically generated by Pod::Man 4.07 (Pod::Simple 3.32) Standard preamble: ========================================================================
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 theBIO
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 twoBIO
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 base64BIO
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:
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