BIO_push (3)

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(The comments found at the beginning of the groff file "man3/BIO_push.3ssl".)

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 append to b, it returns b.

BIO_pop() removes the

b from a chain and returns the next in the chain, or if there is no next The removed then becomes a single 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 chains whereas BIO_pop() deletes a single from a chain, the deleted does not need to be at the end of a chain.

The process of calling BIO_push() and BIO_pop() on a

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 and f is a file

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

in the chain, or if there is no next

SEE ALSO