OBJ_NID2OBJ(3)

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

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);

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 n to an ASN1_OBJECT structure, its long name and its short name respectively, or NULL is an error occurred.

OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() return the corresponding NID for the object 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>. s can be a long name, a short name or the numerical respresentation of an object.

OBJ_txt2obj() converts the text string s into an ASN1_OBJECT structure. If no_name is 0 then long names and short names will be interpreted as well as numerical forms. If no_name is 1 only the numerical form is acceptable.

OBJ_obj2txt() converts the ASN1_OBJECT a into a textual representation. The representation is written as a null terminated string to buf at most buf_len bytes are written, truncating the result if necessary. The total amount of space required is returned. If 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 no_name is 1 then the numerical form will always be used.

OBJ_cmp() compares a to b. If the two are identical 0 is returned.

OBJ_dup() returns a copy of o.

OBJ_create() adds a new object to the internal table. oid is the numerical form of the object, sn the short name and 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().

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 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.

EXAMPLES
Create an object for commonName:

 ASN1_OBJECT *o;
 o = OBJ_nid2obj(NID_commonName);

Check if an object is 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);

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 NULL to determine the amount of data that should be written. Instead buf must point to a valid buffer and 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.

RETURN VALUES
OBJ_nid2obj() returns an ASN1_OBJECT structure or NULL is an error occurred.

OBJ_nid2ln() and OBJ_nid2sn() returns a valid string or NULL on error.

OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() and OBJ_txt2nid() return a NID or NID_undef on error.

SEE ALSO
ERR_get_error(3)