2000-09-07 00:22:31 +00:00
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=pod
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=head1 NAME
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2000-09-14 12:14:41 +00:00
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BIO_push, BIO_pop - add and remove BIOs from a chain.
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2000-09-07 00:22:31 +00:00
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=head1 SYNOPSIS
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#include <openssl/bio.h>
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BIO * BIO_push(BIO *b,BIO *append);
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BIO * BIO_pop(BIO *b);
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=head1 DESCRIPTION
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The BIO_push() function appends the BIO B<append> to B<b>, it returns
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B<b>.
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BIO_pop() removes the BIO B<b> from a chain and returns the next BIO
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in the chain, or NULL if there is no next BIO. The removed BIO then
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becomes a single BIO with no association with the original chain,
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it can thus be freed or attached to a different chain.
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=head1 NOTES
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The names of these functions are perhaps a little misleading. BIO_push()
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joins two BIO chains whereas BIO_pop() deletes a single BIO from a chain,
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the deleted BIO does not need to be at the end of a chain.
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The process of calling BIO_push() and BIO_pop() on a BIO may have additional
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consequences (a control call is made to the affected BIOs) any effects will
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be noted in the descriptions of individual BIOs.
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=head1 EXAMPLES
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For these examples suppose B<md1> and B<md2> are digest BIOs, B<b64> is
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a base64 BIO and B<f> is a file BIO.
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If the call:
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BIO_push(b64, f);
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2014-06-29 12:38:55 +00:00
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is made then the new chain will be B<b64-f>. After making the calls
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2000-09-07 00:22:31 +00:00
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BIO_push(md2, b64);
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BIO_push(md1, md2);
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the new chain is B<md1-md2-b64-f>. Data written to B<md1> will be digested
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by B<md1> and B<md2>, B<base64> encoded and written to B<f>.
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It should be noted that reading causes data to pass in the reverse
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direction, that is data is read from B<f>, base64 B<decoded> and digested
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by B<md1> and B<md2>. If the call:
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BIO_pop(md2);
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The call will return B<b64> and the new chain will be B<md1-b64-f> data can
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be written to B<md1> as before.
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=head1 RETURN VALUES
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BIO_push() returns the end of the chain, B<b>.
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BIO_pop() returns the next BIO in the chain, or NULL if there is no next
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BIO.
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=head1 SEE ALSO
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TBA
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