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=pod
=head1 NAME
OBJ_nid2obj, OBJ_nid2ln, OBJ_nid2sn, OBJ_obj2nid, OBJ_txt2nid, OBJ_ln2nid,
OBJ_sn2nid, OBJ_cmp, OBJ_dup, OBJ_txt2obj, OBJ_obj2txt, OBJ_create, OBJ_cleanup
- ASN1 object utility functions
=head1 SYNOPSIS
#include <openssl/objects.h>
ASN1_OBJECT * OBJ_nid2obj(int n);
const char * OBJ_nid2ln(int n);
const char * OBJ_nid2sn(int n);
int OBJ_obj2nid(const ASN1_OBJECT *o);
int OBJ_ln2nid(const char *ln);
int OBJ_sn2nid(const char *sn);
int OBJ_txt2nid(const char *s);
ASN1_OBJECT * OBJ_txt2obj(const char *s, int no_name);
int OBJ_obj2txt(char *buf, int buf_len, const ASN1_OBJECT *a, int no_name);
int OBJ_cmp(const ASN1_OBJECT *a,const ASN1_OBJECT *b);
ASN1_OBJECT * OBJ_dup(const ASN1_OBJECT *o);
int OBJ_create(const char *oid,const char *sn,const char *ln);
void OBJ_cleanup(void);
=head1 DESCRIPTION
The ASN1 object utility functions process ASN1_OBJECT structures which are
a representation of the ASN1 OBJECT IDENTIFIER (OID) type.
OBJ_nid2obj(), OBJ_nid2ln() and OBJ_nid2sn() convert the NID B<n> to
an ASN1_OBJECT structure, its long name and its short name respectively,
or B<NULL> is an error occurred.
OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() return the corresponding NID
for the object B<o>, the long name <ln> or the short name <sn> respectively
or NID_undef if an error occurred.
OBJ_txt2nid() returns NID corresponding to text string <s>. B<s> can be
a long name, a short name or the numerical respresentation of an object.
OBJ_txt2obj() converts the text string B<s> into an ASN1_OBJECT structure.
If B<no_name> is 0 then long names and short names will be interpreted
as well as numerical forms. If B<no_name> is 1 only the numerical form
is acceptable.
OBJ_obj2txt() converts the B<ASN1_OBJECT> B<a> into a textual representation.
The representation is written as a null terminated string to B<buf>
at most B<buf_len> bytes are written, truncating the result if necessary.
The total amount of space required is returned. If B<no_name> is 0 then
if the object has a long or short name then that will be used, otherwise
the numerical form will be used. If B<no_name> is 1 then the numerical
form will always be used.
OBJ_cmp() compares B<a> to B<b>. If the two are identical 0 is returned.
OBJ_dup() returns a copy of B<o>.
OBJ_create() adds a new object to the internal table. B<oid> is the
numerical form of the object, B<sn> the short name and B<ln> the
long name. A new NID is returned for the created object.
OBJ_cleanup() cleans up OpenSSLs internal object table: this should
be called before an application exits if any new objects were added
using OBJ_create().
=head1 NOTES
Objects in OpenSSL can have a short name, a long name and a numerical
identifier (NID) associated with them. A standard set of objects is
represented in an internal table. The appropriate values are defined
in the header file B<objects.h>.
For example the OID for commonName has the following definitions:
#define SN_commonName "CN"
#define LN_commonName "commonName"
#define NID_commonName 13
New objects can be added by calling OBJ_create().
Table objects have certain advantages over other objects: for example
their NIDs can be used in a C language switch statement. They are
also static constant structures which are shared: that is there
is only a single constant structure for each table object.
Objects which are not in the table have the NID value NID_undef.
Objects do not need to be in the internal tables to be processed,
the functions OBJ_txt2obj() and OBJ_obj2txt() can process the numerical
form of an OID.
=head1 EXAMPLES
Create an object for B<commonName>:
ASN1_OBJECT *o;
o = OBJ_nid2obj(NID_commonName);
Check if an object is B<commonName>
if (OBJ_obj2nid(obj) == NID_commonName)
/* Do something */
Create a new NID and initialize an object from it:
int new_nid;
ASN1_OBJECT *obj;
new_nid = OBJ_create("1.2.3.4", "NewOID", "New Object Identifier");
obj = OBJ_nid2obj(new_nid);
Create a new object directly:
obj = OBJ_txt2obj("1.2.3.4", 1);
=head1 BUGS
OBJ_obj2txt() is awkward and messy to use: it doesn't follow the
convention of other OpenSSL functions where the buffer can be set
to B<NULL> to determine the amount of data that should be written.
Instead B<buf> must point to a valid buffer and B<buf_len> should
be set to a positive value. A buffer length of 80 should be more
than enough to handle any OID encountered in practice.
=head1 RETURN VALUES
OBJ_nid2obj() returns an B<ASN1_OBJECT> structure or B<NULL> is an
error occurred.
OBJ_nid2ln() and OBJ_nid2sn() returns a valid string or B<NULL>
on error.
OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() and OBJ_txt2nid() return
a NID or B<NID_undef> on error.
=head1 SEE ALSO
L<ERR_get_error(3)|ERR_get_error(3)>
=head1 HISTORY
TBA
=cut
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