Fix DSA parameter generation control error

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

diff --git a/doc/crypto/OBJ_nid2obj.pod b/doc/crypto/OBJ_nid2obj.pod
index 50650bdbcefae59fc7b99da85bd291edbdadad18..b8d289673deedc16306bea8d99f502819010e325 100644 (file)
--- a/doc/crypto/OBJ_nid2obj.pod
+++ b/doc/crypto/OBJ_nid2obj.pod
@@ -8,6 +8,8 @@ functions
 
 =head1 SYNOPSIS
 
+ #include <openssl/objects.h>
+
  ASN1_OBJECT * OBJ_nid2obj(int n);
  const char *  OBJ_nid2ln(int n);
  const char *  OBJ_nid2sn(int n);
@@ -31,6 +33,12 @@ functions
 
 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,
@@ -94,6 +102,16 @@ 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
+corresponding ASN.1 OBJECT IDENTIFIER encoding (for example no OID currently
+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>:
@@ -101,15 +119,16 @@ Create an object for B<commonName>:
  ASN1_OBJECT *o;
  o = OBJ_nid2obj(NID_commonName);
 
-Check is an object is B<commonName>
+Check if an object is B<commonName>
 
  if (OBJ_obj2nid(obj) == NID_commonName)
-       /* Do something */
+        /* 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);
@@ -129,14 +148,16 @@ than enough to handle any OID encountered in practice.
 
 =head1 RETURN VALUES
 
-OBJ_nid2obj() returns an ASN1_OBJECT structure or B<NULL> is an
+OBJ_nid2obj() returns an B<ASN1_OBJECT> structure or B<NULL> is an
 error occurred.
+It returns a pointer to an internal table and does not
+allocate memory; ASN1_OBJECT_free() will have no effect.
 
 OBJ_nid2ln() and OBJ_nid2sn() returns a valid string or B<NULL>
 on error.
 
 OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() and OBJ_txt2nid() return
-a NID or NID_undef on error.
+a NID or B<NID_undef> on error.
 
 =head1 SEE ALSO