path: root/secure/lib/libcrypto/man/OBJ_nid2obj.3

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.IX Title "OBJ_nid2obj 3"
.TH OBJ_nid2obj 3 "0.9.7" "2003-02-03" "OpenSSL"
.UC
.SH "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 \- \s-1ASN1\s0 object utility
functions
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 3
\& ASN1_OBJECT * OBJ_nid2obj(int n);
\& const char *  OBJ_nid2ln(int n);
\& const char *  OBJ_nid2sn(int n);
.Ve
.Vb 3
\& int OBJ_obj2nid(const ASN1_OBJECT *o);
\& int OBJ_ln2nid(const char *ln);
\& int OBJ_sn2nid(const char *sn);
.Ve
.Vb 1
\& int OBJ_txt2nid(const char *s);
.Ve
.Vb 2
\& 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);
.Ve
.Vb 2
\& int OBJ_cmp(const ASN1_OBJECT *a,const ASN1_OBJECT *b);
\& ASN1_OBJECT * OBJ_dup(const ASN1_OBJECT *o);
.Ve
.Vb 2
\& int OBJ_create(const char *oid,const char *sn,const char *ln);
\& void OBJ_cleanup(void);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \s-1ASN1\s0 object utility functions process \s-1ASN1_OBJECT\s0 structures which are
a representation of the \s-1ASN1\s0 \s-1OBJECT\s0 \s-1IDENTIFIER\s0 (\s-1OID\s0) type.
.PP
\&\fIOBJ_nid2obj()\fR, \fIOBJ_nid2ln()\fR and \fIOBJ_nid2sn()\fR convert the \s-1NID\s0 \fBn\fR to 
an \s-1ASN1_OBJECT\s0 structure, its long name and its short name respectively,
or \fB\s-1NULL\s0\fR is an error occurred.
.PP
\&\fIOBJ_obj2nid()\fR, \fIOBJ_ln2nid()\fR, \fIOBJ_sn2nid()\fR return the corresponding \s-1NID\s0
for the object \fBo\fR, the long name <ln> or the short name <sn> respectively
or NID_undef if an error occurred.
.PP
\&\fIOBJ_txt2nid()\fR returns \s-1NID\s0 corresponding to text string <s>. \fBs\fR can be
a long name, a short name or the numerical respresentation of an object.
.PP
\&\fIOBJ_txt2obj()\fR converts the text string \fBs\fR into an \s-1ASN1_OBJECT\s0 structure.
If \fBno_name\fR is 0 then long names and short names will be interpreted
as well as numerical forms. If \fBno_name\fR is 1 only the numerical form
is acceptable.
.PP
\&\fIOBJ_obj2txt()\fR converts the \fB\s-1ASN1_OBJECT\s0\fR \fBa\fR into a textual representation.
The representation is written as a null terminated string to \fBbuf\fR
at most \fBbuf_len\fR bytes are written, truncating the result if necessary.
The total amount of space required is returned. If \fBno_name\fR 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 \fBno_name\fR is 1 then the numerical
form will always be used.
.PP
\&\fIOBJ_cmp()\fR compares \fBa\fR to \fBb\fR. If the two are identical 0 is returned.
.PP
\&\fIOBJ_dup()\fR returns a copy of \fBo\fR.
.PP
\&\fIOBJ_create()\fR adds a new object to the internal table. \fBoid\fR is the 
numerical form of the object, \fBsn\fR the short name and \fBln\fR the
long name. A new \s-1NID\s0 is returned for the created object.
.PP
\&\fIOBJ_cleanup()\fR cleans up OpenSSLs internal object table: this should
be called before an application exits if any new objects were added
using \fIOBJ_create()\fR.
.SH "NOTES"
.IX Header "NOTES"
Objects in OpenSSL can have a short name, a long name and a numerical
identifier (\s-1NID\s0) associated with them. A standard set of objects is
represented in an internal table. The appropriate values are defined
in the header file \fBobjects.h\fR.
.PP
For example the \s-1OID\s0 for commonName has the following definitions:
.PP
.Vb 3
\& #define SN_commonName                   "CN"
\& #define LN_commonName                   "commonName"
\& #define NID_commonName                  13
.Ve
New objects can be added by calling \fIOBJ_create()\fR.
.PP
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.
.PP
Objects which are not in the table have the \s-1NID\s0 value NID_undef.
.PP
Objects do not need to be in the internal tables to be processed,
the functions \fIOBJ_txt2obj()\fR and \fIOBJ_obj2txt()\fR can process the numerical
form of an \s-1OID\s0.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
Create an object for \fBcommonName\fR:
.PP
.Vb 2
\& ASN1_OBJECT *o;
\& o = OBJ_nid2obj(NID_commonName);
.Ve
Check if an object is \fBcommonName\fR
.PP
.Vb 2
\& if (OBJ_obj2nid(obj) == NID_commonName)
\&        /* Do something */
.Ve
Create a new \s-1NID\s0 and initialize an object from it:
.PP
.Vb 3
\& int new_nid;
\& ASN1_OBJECT *obj;
\& new_nid = OBJ_create("1.2.3.4", "NewOID", "New Object Identifier");
.Ve
.Vb 1
\& obj = OBJ_nid2obj(new_nid);
.Ve
Create a new object directly:
.PP
.Vb 1
\& obj = OBJ_txt2obj("1.2.3.4", 1);
.Ve
.SH "BUGS"
.IX Header "BUGS"
\&\fIOBJ_obj2txt()\fR is awkward and messy to use: it doesn't follow the 
convention of other OpenSSL functions where the buffer can be set
to \fB\s-1NULL\s0\fR to determine the amount of data that should be written.
Instead \fBbuf\fR must point to a valid buffer and \fBbuf_len\fR should
be set to a positive value. A buffer length of 80 should be more
than enough to handle any \s-1OID\s0 encountered in practice.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fIOBJ_nid2obj()\fR returns an \fB\s-1ASN1_OBJECT\s0\fR structure or \fB\s-1NULL\s0\fR is an
error occurred.
.PP
\&\fIOBJ_nid2ln()\fR and \fIOBJ_nid2sn()\fR returns a valid string or \fB\s-1NULL\s0\fR
on error.
.PP
\&\fIOBJ_obj2nid()\fR, \fIOBJ_ln2nid()\fR, \fIOBJ_sn2nid()\fR and \fIOBJ_txt2nid()\fR return
a \s-1NID\s0 or \fBNID_undef\fR on error.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
ERR_get_error(3)
.SH "HISTORY"
.IX Header "HISTORY"
\&\s-1TBA\s0