=pod

=head1 NAME

ASN1_TYPE_get, ASN1_TYPE_set, ASN1_TYPE_set1, ASN1_TYPE_cmp, ASN1_TYPE_unpack_sequence, ASN1_TYPE_pack_sequence - ASN1_TYPE utility

functions

=head1 SYNOPSIS

 #include <openssl/asn1.h>

 int ASN1_TYPE_get(const 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);

 void *ASN1_TYPE_unpack_sequence(const ASN1_ITEM *it, const ASN1_TYPE *t);

 ASN1_TYPE *ASN1_TYPE_pack_sequence(const ASN1_ITEM *it, void *s,

                                    ASN1_TYPE **t);

=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.

ASN1_TYPE_set() sets the value of B 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 to B<type> a copy of B<value>.

ASN1_TYPE_cmp() compares ASN.1 types B and B and returns 0 if

they are identical and non-zero otherwise.

ASN1_TYPE_unpack_sequence() attempts to parse the SEQUENCE present in

B<t> using the ASN.1 structure B<it>. If successful it returns a pointer

to the ASN.1 structure corresponding to B<it> which must be freed by the

caller. If it fails it return NULL.

ASN1_TYPE_pack_sequence() attempts to encode the ASN.1 structure B<s>

corresponding to B<it> into an ASN1_TYPE. If successful the encoded

ASN1_TYPE is returned. If B<t> and B<*t> are not NULL the encoded type

is written to B<t> overwriting any existing data. If B<t> is not NULL

but B<*t> is NULL the returned ASN1_TYPE is written to B<*t>.

=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

unparsable 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 success and 0 for failure.

ASN1_TYPE_cmp() returns 0 if the types are identical and non-zero otherwise.

ASN1_TYPE_unpack_sequence() returns a pointer to an ASN.1 structure or

NULL on failure.

ASN1_TYPE_pack_sequence() return an ASN1_TYPE structure if it succeeds or

NULL on failure.

=head1 COPYRIGHT

Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the "License").  You may not use

this file except in compliance with the License.  You can obtain a copy

in the file LICENSE in the source distribution or at

L<https://www.openssl.org/source/license.html>.

=cut