/xlv3/openssl/0.9.7e-sgipl1/work/0.9.7e-sgipl1/openssl-
0.9.7e/doc/crypto
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NAME
RSA_get_ex_new_index, RSA_set_ex_data, RSA_get_ex_data - add
application specific data to RSA structures
SYNOPSIS
#include <openssl/rsa.h>
int RSA_get_ex_new_index(long argl, void *argp,
CRYPTO_EX_new *new_func,
CRYPTO_EX_dup *dup_func,
CRYPTO_EX_free *free_func);
int RSA_set_ex_data(RSA *r, int idx, void *arg);
void *RSA_get_ex_data(RSA *r, int idx);
typedef int new_func(void *parent, void *ptr, CRYPTO_EX_DATA *ad,
int idx, long argl, void *argp);
typedef void free_func(void *parent, void *ptr, CRYPTO_EX_DATA *ad,
int idx, long argl, void *argp);
typedef int dup_func(CRYPTO_EX_DATA *to, CRYPTO_EX_DATA *from, void *from_d,
int idx, long argl, void *argp);
DESCRIPTION
Several OpenSSL structures can have application specific
data attached to them. This has several potential uses, it
can be used to cache data associated with a structure (for
example the hash of some part of the structure) or some
additional data (for example a handle to the data in an
external library).
Since the application data can be anything at all it is
passed and retrieved as a void * type.
The RSA_get_ex_new_index() function is initially called to
"register" some new application specific data. It takes
three optional function pointers which are called when the
parent structure (in this case an RSA structure) is
initially created, when it is copied and when it is freed
up. If any or all of these function pointer arguments are
not used they should be set to NULL. The precise manner in
which these function pointers are called is described in
more detail below. RSA_get_ex_new_index() also takes
additional long and pointer parameters which will be passed
to the supplied functions but which otherwise have no
special meaning. It returns an index which should be stored
(typically in a static variable) and passed used in the idx
parameter in the remaining functions. Each successful call
to RSA_get_ex_new_index() will return an index greater than
any previously returned, this is important because the
optional functions are called in order of increasing index
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value.
RSA_set_ex_data() is used to set application specific data,
the data is supplied in the arg parameter and its precise
meaning is up to the application.
RSA_get_ex_data() is used to retrieve application specific
data. The data is returned to the application, this will be
the same value as supplied to a previous RSA_set_ex_data()
call.
new_func() is called when a structure is initially allocated
(for example with RSA_new(). The parent structure members
will not have any meaningful values at this point. This
function will typically be used to allocate any application
specific structure.
free_func() is called when a structure is being freed up.
The dynamic parent structure members should not be accessed
because they will be freed up when this function is called.
new_func() and free_func() take the same parameters. parent
is a pointer to the parent RSA structure. ptr is a the
application specific data (this wont be of much use in
new_func(). ad is a pointer to the CRYPTO_EX_DATA structure
from the parent RSA structure: the functions
CRYPTO_get_ex_data() and CRYPTO_set_ex_data() can be called
to manipulate it. The idx parameter is the index: this will
be the same value returned by RSA_get_ex_new_index() when
the functions were initially registered. Finally the argl
and argp parameters are the values originally passed to the
same corresponding parameters when RSA_get_ex_new_index()
was called.
dup_func() is called when a structure is being copied.
Pointers to the destination and source CRYPTO_EX_DATA
structures are passed in the to and from parameters
respectively. The from_d parameter is passed a pointer to
the source application data when the function is called,
when the function returns the value is copied to the
destination: the application can thus modify the data
pointed to by from_d and have different values in the source
and destination. The idx, argl and argp parameters are the
same as those in new_func() and free_func().
RETURN VALUES
RSA_get_ex_new_index() returns a new index or -1 on failure
(note 0 is a valid index value).
RSA_set_ex_data() returns 1 on success or 0 on failure.
RSA_get_ex_data() returns the application data or 0 on
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failure. 0 may also be valid application data but currently
it can only fail if given an invalid idx parameter.
new_func() and dup_func() should return 0 for failure and 1
for success.
On failure an error code can be obtained from
ERR_get_error(3).
BUGS
dup_func() is currently never called.
The return value of new_func() is ignored.
The new_func() function isn't very useful because no
meaningful values are present in the parent RSA structure
when it is called.
SEE ALSO
rsa(3), CRYPTO_set_ex_data(3)
HISTORY
RSA_get_ex_new_index(), RSA_set_ex_data() and
RSA_get_ex_data() are available since SSLeay 0.9.0.
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