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=pod
=head1 NAME
ASN1_TYPE_get, ASN1_TYPE_set, ASN1_TYPE_set1, ASN1_TYPE_cmp - ASN1_TYPE utility
functions
=head1 SYNOPSIS
#include <openssl/asn1.h>
int ASN1_TYPE_get(ASN1_TYPE *a);
void ASN1_TYPE_set(ASN1_TYPE *a, int type, void *value);
int ASN1_TYPE_set1(ASN1_TYPE *a, int type, const void *value);
int ASN1_TYPE_cmp(const ASN1_TYPE *a, const ASN1_TYPE *b);
=head1 DESCRIPTION
These functions allow an ASN1_TYPE structure to be manipulated. The
ASN1_TYPE structure can contain any ASN.1 type or constructed type
such as a SEQUENCE: it is effectively equivalent to the ASN.1 ANY type.
ASN1_TYPE_get() returns the type of B<a>.
ASN1_TYPE_set() sets the value of B<a> to B<type> and B<value>. This
function uses the pointer B<value> internally so it must B<not> be freed
up after the call.
ASN1_TYPE_set1() sets the value of B<a> to B<type> a copy of B<value>.
ASN1_TYPE_cmp() compares ASN.1 types B<a> and B<b> and returns 0 if
they are identical and non-zero otherwise.
=head1 NOTES
The type and meaning of the B<value> parameter for ASN1_TYPE_set() and
ASN1_TYPE_set1() is determined by the B<type> parameter.
If B<type> is V_ASN1_NULL B<value> is ignored. If B<type> is V_ASN1_BOOLEAN
then the boolean is set to TRUE if B<value> is not NULL. If B<type> is
V_ASN1_OBJECT then value is an ASN1_OBJECT structure. Otherwise B<type>
is and ASN1_STRING structure. If B<type> corresponds to a primitive type
(or a string type) then the contents of the ASN1_STRING contain the content
octets of the type. If B<type> corresponds to a constructed type or
a tagged type (V_ASN1_SEQUENCE, V_ASN1_SET or V_ASN1_OTHER) then the
ASN1_STRING contains the entire ASN.1 encoding verbatim (including tag and
length octets).
ASN1_TYPE_cmp() may not return zero if two types are equivalent but have
different encodings. For example the single content octet of the boolean TRUE
value under BER can have any non-zero encoding but ASN1_TYPE_cmp() will
only return zero if the values are the same.
If either or both of the parameters passed to ASN1_TYPE_cmp() is NULL the
return value is non-zero. Technically if both parameters are NULL the two
types could be absent OPTIONAL fields and so should match, however passing
NULL values could also indicate a programming error (for example an
unparseable type which returns NULL) for types which do B<not> match. So
applications should handle the case of two absent values separately.
=head1 RETURN VALUES
ASN1_TYPE_get() returns the type of the ASN1_TYPE argument.
ASN1_TYPE_set() does not return a value.
ASN1_TYPE_set1() returns 1 for sucess and 0 for failure.
ASN1_TYPE_cmp() returns 0 if the types are identical and non-zero otherwise.
=cut
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