Constify i2t_ASN1_OBJECT, i2d_ASN1_OBJECT, i2a_ASN1_OBJECT.

[openssl.git] / doc / crypto / OBJ_nid2obj.pod

diff --git a/doc/crypto/OBJ_nid2obj.pod b/doc/crypto/OBJ_nid2obj.pod
index 9fa9e664250cbbcd832d9414cf779adeccc97a15..3ada6679cf92b7d47e68e1532a562cdaa7a4ebbb 100644 (file)
--- a/doc/crypto/OBJ_nid2obj.pod
+++ b/doc/crypto/OBJ_nid2obj.pod
@@ -25,7 +25,7 @@ OBJ_dup, OBJ_txt2obj, OBJ_obj2txt, OBJ_create, OBJ_cleanup
  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 i2t_ASN1_OBJECT(char *buf, int buf_len, ASN1_OBJECT *a);
+ int i2t_ASN1_OBJECT(char *buf, int buf_len, const ASN1_OBJECT *a);
 
  int OBJ_cmp(const ASN1_OBJECT *a, const ASN1_OBJECT *b);
  ASN1_OBJECT *OBJ_dup(const ASN1_OBJECT *o);
@@ -45,6 +45,12 @@ Deprecated:
 
 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 B<NID>s.  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 B<n> to
 an ASN1_OBJECT structure, its long name and its short name respectively,
@@ -123,6 +129,10 @@ exists for a particular algorithm). As a result they B<cannot> be encoded or
 decoded as part of ASN.1 structures. Applications can determine if there
 is a corresponding OBJECT IDENTIFIER by checking OBJ_length() is not zero.
 
+These functions cannot return B<const> because an B<ASN1_OBJECT> can
+represent both an internal, constant, OID and a dynamically-created one.
+The latter cannot be constant because it needs to be freed after use.
+
 =head1 EXAMPLES
 
 Create an object for B<commonName>:
@@ -139,6 +149,7 @@ 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);