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Diffstat (limited to 'doc/man3/BIO_set_callback.pod')
-rw-r--r-- | doc/man3/BIO_set_callback.pod | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/doc/man3/BIO_set_callback.pod b/doc/man3/BIO_set_callback.pod new file mode 100644 index 0000000000..113b416488 --- /dev/null +++ b/doc/man3/BIO_set_callback.pod @@ -0,0 +1,131 @@ +=pod + +=head1 NAME + +BIO_set_callback, BIO_get_callback, BIO_set_callback_arg, BIO_get_callback_arg, +BIO_debug_callback - BIO callback functions + +=head1 SYNOPSIS + + #include <openssl/bio.h> + + + typedef long (*BIO_callback_fn)(BIO *b, int oper, const char *argp, int argi, + long argl, long ret); + + void BIO_set_callback(BIO *b, BIO_callack_fn cb); + BIO_callack_fn BIO_get_callback(BIO *b); + void BIO_set_callback_arg(BIO *b, char *arg); + char *BIO_get_callback_arg(const BIO *b); + + long BIO_debug_callback(BIO *bio, int cmd, const char *argp, int argi, + long argl, long ret); + +=head1 DESCRIPTION + +BIO_set_callback() and BIO_get_callback() set and retrieve the BIO callback, +they are both macros. The callback is called during most high level BIO +operations. It can be used for debugging purposes to trace operations on +a BIO or to modify its operation. + +BIO_set_callback_arg() and BIO_get_callback_arg() are macros which can be +used to set and retrieve an argument for use in the callback. + +BIO_debug_callback() is a standard debugging callback which prints +out information relating to each BIO operation. If the callback +argument is set it is interpreted as a BIO to send the information +to, otherwise stderr is used. + +BIO_callback_fn() is the type of the callback function. The meaning of each +argument is described below: + +=over + +=item B<b> + +The BIO the callback is attached to is passed in B<b>. + +=item B<oper> + +B<oper> is set to the operation being performed. For some operations +the callback is called twice, once before and once after the actual +operation, the latter case has B<oper> or'ed with BIO_CB_RETURN. + +=item B<argp> B<argi> B<argl> + +The meaning of the arguments B<argp>, B<argi> and B<argl> depends on +the value of B<oper>, that is the operation being performed. + +=item B<ret> + +B<ret> is the return value that would be returned to the +application if no callback were present. The actual value returned +is the return value of the callback itself. In the case of callbacks +called before the actual BIO operation 1 is placed in B<ret>, if +the return value is not positive it will be immediately returned to +the application and the BIO operation will not be performed. + +=back + +The callback should normally simply return B<ret> when it has +finished processing, unless it specifically wishes to modify the +value returned to the application. + +=head1 CALLBACK OPERATIONS + +In the notes below, B<callback> defers to the actual callback +function that is called. + +=over 4 + +=item B<BIO_free(b)> + +callback(b, BIO_CB_FREE, NULL, 0L, 0L, 1L) is called before the +free operation. + +=item B<BIO_read(b, out, outl)> + +callback(b, BIO_CB_READ, out, outl, 0L, 1L) is called before +the read and callback(b, BIO_CB_READ|BIO_CB_RETURN, out, outl, 0L, retvalue) +after. + +=item B<BIO_write(b, in, inl)> + +callback(b, BIO_CB_WRITE, in, inl, 0L, 1L) is called before +the write and callback(b, BIO_CB_WRITE|BIO_CB_RETURN, in, inl, 0L, retvalue) +after. + +=item B<BIO_gets(b, out, outl)> + +callback(b, BIO_CB_GETS, out, outl, 0L, 1L) is called before +the operation and callback(b, BIO_CB_GETS|BIO_CB_RETURN, out, outl, 0L, retvalue) +after. + +=item B<BIO_puts(b, in)> + +callback(b, BIO_CB_WRITE, in, 0, 0L, 1L) is called before +the operation and callback(b, BIO_CB_WRITE|BIO_CB_RETURN, in, 0, 0L, retvalue) +after. + +=item B<BIO_ctrl(BIO *b, int cmd, long larg, void *parg)> + +callback(b, BIO_CB_CTRL, parg, cmd, larg, 1L) is called before the call and +callback(b, BIO_CB_CTRL|BIO_CB_RETURN, parg, cmd, larg, ret) after. + +=back + +=head1 EXAMPLE + +The BIO_debug_callback() function is a good example, its source is +in crypto/bio/bio_cb.c + +=head1 COPYRIGHT + +Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved. + +Licensed under the OpenSSL license (the "License"). You may not use +this file except in compliance with the License. You can obtain a copy +in the file LICENSE in the source distribution or at +L<https://www.openssl.org/source/license.html>. + +=cut |