1=pod
2
3=head1 NAME
4
5OBJ_nid2obj, OBJ_nid2ln, OBJ_nid2sn, OBJ_obj2nid, OBJ_txt2nid, OBJ_ln2nid, OBJ_sn2nid,
6OBJ_cmp, OBJ_dup, OBJ_txt2obj, OBJ_obj2txt, OBJ_create, OBJ_cleanup - ASN1 object utility
7functions
8
9=head1 SYNOPSIS
10
11 ASN1_OBJECT * OBJ_nid2obj(int n);
12 const char *  OBJ_nid2ln(int n);
13 const char *  OBJ_nid2sn(int n);
14
15 int OBJ_obj2nid(const ASN1_OBJECT *o);
16 int OBJ_ln2nid(const char *ln);
17 int OBJ_sn2nid(const char *sn);
18
19 int OBJ_txt2nid(const char *s);
20
21 ASN1_OBJECT * OBJ_txt2obj(const char *s, int no_name);
22 int OBJ_obj2txt(char *buf, int buf_len, const ASN1_OBJECT *a, int no_name);
23
24 int OBJ_cmp(const ASN1_OBJECT *a,const ASN1_OBJECT *b);
25 ASN1_OBJECT * OBJ_dup(const ASN1_OBJECT *o);
26
27 int OBJ_create(const char *oid,const char *sn,const char *ln);
28 void OBJ_cleanup(void);
29
30=head1 DESCRIPTION
31
32The ASN1 object utility functions process ASN1_OBJECT structures which are
33a representation of the ASN1 OBJECT IDENTIFIER (OID) type.
34
35OBJ_nid2obj(), OBJ_nid2ln() and OBJ_nid2sn() convert the NID B<n> to 
36an ASN1_OBJECT structure, its long name and its short name respectively,
37or B<NULL> is an error occurred.
38
39OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() return the corresponding NID
40for the object B<o>, the long name <ln> or the short name <sn> respectively
41or NID_undef if an error occurred.
42
43OBJ_txt2nid() returns NID corresponding to text string <s>. B<s> can be
44a long name, a short name or the numerical respresentation of an object.
45
46OBJ_txt2obj() converts the text string B<s> into an ASN1_OBJECT structure.
47If B<no_name> is 0 then long names and short names will be interpreted
48as well as numerical forms. If B<no_name> is 1 only the numerical form
49is acceptable.
50
51OBJ_obj2txt() converts the B<ASN1_OBJECT> B<a> into a textual representation.
52The representation is written as a null terminated string to B<buf>
53at most B<buf_len> bytes are written, truncating the result if necessary.
54The total amount of space required is returned. If B<no_name> is 0 then
55if the object has a long or short name then that will be used, otherwise
56the numerical form will be used. If B<no_name> is 1 then the numerical
57form will always be used.
58
59OBJ_cmp() compares B<a> to B<b>. If the two are identical 0 is returned.
60
61OBJ_dup() returns a copy of B<o>.
62
63OBJ_create() adds a new object to the internal table. B<oid> is the 
64numerical form of the object, B<sn> the short name and B<ln> the
65long name. A new NID is returned for the created object.
66
67OBJ_cleanup() cleans up OpenSSLs internal object table: this should
68be called before an application exits if any new objects were added
69using OBJ_create().
70
71=head1 NOTES
72
73Objects in OpenSSL can have a short name, a long name and a numerical
74identifier (NID) associated with them. A standard set of objects is
75represented in an internal table. The appropriate values are defined
76in the header file B<objects.h>.
77
78For example the OID for commonName has the following definitions:
79
80 #define SN_commonName                   "CN"
81 #define LN_commonName                   "commonName"
82 #define NID_commonName                  13
83
84New objects can be added by calling OBJ_create().
85
86Table objects have certain advantages over other objects: for example
87their NIDs can be used in a C language switch statement. They are
88also static constant structures which are shared: that is there
89is only a single constant structure for each table object.
90
91Objects which are not in the table have the NID value NID_undef.
92
93Objects do not need to be in the internal tables to be processed,
94the functions OBJ_txt2obj() and OBJ_obj2txt() can process the numerical
95form of an OID.
96
97=head1 EXAMPLES
98
99Create an object for B<commonName>:
100
101 ASN1_OBJECT *o;
102 o = OBJ_nid2obj(NID_commonName);
103
104Check if an object is B<commonName>
105
106 if (OBJ_obj2nid(obj) == NID_commonName)
107	/* Do something */
108
109Create a new NID and initialize an object from it:
110
111 int new_nid;
112 ASN1_OBJECT *obj;
113 new_nid = OBJ_create("1.2.3.4", "NewOID", "New Object Identifier");
114
115 obj = OBJ_nid2obj(new_nid);
116 
117Create a new object directly:
118
119 obj = OBJ_txt2obj("1.2.3.4", 1);
120
121=head1 BUGS
122
123OBJ_obj2txt() is awkward and messy to use: it doesn't follow the 
124convention of other OpenSSL functions where the buffer can be set
125to B<NULL> to determine the amount of data that should be written.
126Instead B<buf> must point to a valid buffer and B<buf_len> should
127be set to a positive value. A buffer length of 80 should be more
128than enough to handle any OID encountered in practice.
129
130=head1 RETURN VALUES
131
132OBJ_nid2obj() returns an B<ASN1_OBJECT> structure or B<NULL> is an
133error occurred.
134
135OBJ_nid2ln() and OBJ_nid2sn() returns a valid string or B<NULL>
136on error.
137
138OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() and OBJ_txt2nid() return
139a NID or B<NID_undef> on error.
140
141=head1 SEE ALSO
142
143L<ERR_get_error(3)|ERR_get_error(3)>
144
145=head1 HISTORY
146
147TBA
148
149=cut
150