/usr/man2/cat.3/OBJ_cmp.3.Z(/usr/man2/cat.3/OBJ_cmp.3.Z)

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.  For
       convenience, OIDs are usually represented in source code as numeric
       identifiers, or NIDs.  OpenSSL has an internal table of OIDs that are
       generated when the library is built, and their corresponding NIDs are
       available as defined constants.  For the functions below, application
       code should treat all returned values -- OIDs, NIDs, or names -- as
       constants.

       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 if 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> respec-
       tively 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 numer-
       ical 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.

       Some objects are used to represent algorithms which do not have a cor-
       responding ASN.1 OBJECT IDENTIFIER encoding (for example no OID cur-
       rently exists for a particular algorithm). As a result they cannot be
       encoded or decoded as part of ASN.1 structures. Applications can deter-
       mine if there is a corresponding OBJECT IDENTIFIER by checking
       OBJ_length() is not zero.

       These functions cannot return const because an ASN1_OBJECT can repre-
       sent both an internal, constant, OID and a dynamically-created one.
       The latter cannot be constant because it needs to be freed after use.

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 con-
       vention 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.  It returns a pointer to an internal table and does not allo-
       cate memory; ASN1_OBJECT_free() will have no effect.

       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)

HISTORY

       TBA

1.0.2t                            2019-09-10                    OBJ_nid2obj(3)
See also OBJ_cleanup(3)
See also OBJ_create(3)
See also OBJ_dup(3)
See also OBJ_ln2nid(3)
See also OBJ_nid2ln(3)
See also OBJ_nid2obj(3)
See also OBJ_nid2sn(3)
See also OBJ_obj2nid(3)
See also OBJ_obj2txt(3)
See also OBJ_sn2nid(3)
See also OBJ_txt2nid(3)
See also OBJ_txt2obj(3)