1 files changed, 108 insertions, 0 deletions
diff --git a/openssl/doc/crypto/BIO_set_callback.pod b/openssl/doc/crypto/BIO_set_callback.pod
new file mode 100644
index 000000000..475955624
--- /dev/null
+++ b/openssl/doc/crypto/BIO_set_callback.pod
@@ -0,0 +1,108 @@
+=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>
+
+ #define BIO_set_callback(b,cb)		((b)->callback=(cb))
+ #define BIO_get_callback(b)		((b)->callback)
+ #define BIO_set_callback_arg(b,arg)	((b)->cb_arg=(char *)(arg))
+ #define BIO_get_callback_arg(b)		((b)->cb_arg)
+
+ long BIO_debug_callback(BIO *bio,int cmd,const char *argp,int argi,
+	long argl,long ret);
+
+ typedef long (*callback)(BIO *b, int oper, const char *argp,
+			int argi, long argl, long retvalue);
+
+=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 if is interpreted as a BIO to send the information
+to, otherwise stderr is used.
+
+callback() is the callback function itself. The meaning of each
+argument is described below.
+
+The BIO the callback is attached to is passed in B<b>.
+
+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.
+
+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.
+
+B<retvalue> 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 retvalue, if
+the return value is not positive it will be immediately returned to
+the application and the BIO operation will not be performed.
+
+The callback should normally simply return B<retvalue> when it has
+finished processing, unless if specifically wishes to modify the
+value returned to the application.
+
+=head1 CALLBACK OPERATIONS
+
+=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 SEE ALSO
+
+TBA