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BIO_push.pod 1.8 KB

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  1. =pod
  2. =head1 NAME
  3. BIO_push, BIO_pop - add and remove BIOs from a chain.
  4. =head1 SYNOPSIS
  5. #include <openssl/bio.h>
  6. BIO * BIO_push(BIO *b,BIO *append);
  7. BIO * BIO_pop(BIO *b);
  8. =head1 DESCRIPTION
  9. The BIO_push() function appends the BIO B<append> to B<b>, it returns
  10. B<b>.
  11. BIO_pop() removes the BIO B<b> from a chain and returns the next BIO
  12. in the chain, or NULL if there is no next BIO. The removed BIO then
  13. becomes a single BIO with no association with the original chain,
  14. it can thus be freed or attached to a different chain.
  15. =head1 NOTES
  16. The names of these functions are perhaps a little misleading. BIO_push()
  17. joins two BIO chains whereas BIO_pop() deletes a single BIO from a chain,
  18. the deleted BIO does not need to be at the end of a chain.
  19. The process of calling BIO_push() and BIO_pop() on a BIO may have additional
  20. consequences (a control call is made to the affected BIOs) any effects will
  21. be noted in the descriptions of individual BIOs.
  22. =head1 EXAMPLES
  23. For these examples suppose B<md1> and B<md2> are digest BIOs, B<b64> is
  24. a base64 BIO and B<f> is a file BIO.
  25. If the call:
  26. BIO_push(b64, f);
  27. is made then the new chain will be B<b64-f>. After making the calls
  28. BIO_push(md2, b64);
  29. BIO_push(md1, md2);
  30. the new chain is B<md1-md2-b64-f>. Data written to B<md1> will be digested
  31. by B<md1> and B<md2>, B<base64> encoded and written to B<f>.
  32. It should be noted that reading causes data to pass in the reverse
  33. direction, that is data is read from B<f>, base64 B<decoded> and digested
  34. by B<md1> and B<md2>. If the call:
  35. BIO_pop(md2);
  36. The call will return B<b64> and the new chain will be B<md1-b64-f> data can
  37. be written to B<md1> as before.
  38. =head1 RETURN VALUES
  39. BIO_push() returns the end of the chain, B<b>.
  40. BIO_pop() returns the next BIO in the chain, or NULL if there is no next
  41. BIO.
  42. =head1 SEE ALSO
  43. TBA