NAME

       ASN1_item_d2i_ex, ASN1_item_d2i, ASN1_item_d2i_bio_ex, ASN1_item_d2i_bio,
       ASN1_item_d2i_fp_ex, ASN1_item_d2i_fp, ASN1_item_i2d_mem_bio - decode and encode
       DER-encoded ASN.1 structures

SYNOPSIS

        #include <openssl/asn1.h>

        ASN1_VALUE *ASN1_item_d2i_ex(ASN1_VALUE **pval, const unsigned char **in,
                                     long len, const ASN1_ITEM *it,
                                     OSSL_LIB_CTX *libctx, const char *propq);
        ASN1_VALUE *ASN1_item_d2i(ASN1_VALUE **pval, const unsigned char **in,
                                  long len, const ASN1_ITEM *it);

        void *ASN1_item_d2i_bio_ex(const ASN1_ITEM *it, BIO *in, void *x,
                                   OSSL_LIB_CTX *libctx, const char *propq);
        void *ASN1_item_d2i_bio(const ASN1_ITEM *it, BIO *in, void *x);

        void *ASN1_item_d2i_fp_ex(const ASN1_ITEM *it, FILE *in, void *x,
                                  OSSL_LIB_CTX *libctx, const char *propq);
        void *ASN1_item_d2i_fp(const ASN1_ITEM *it, FILE *in, void *x);

        BIO *ASN1_item_i2d_mem_bio(const ASN1_ITEM *it, const ASN1_VALUE *val);

DESCRIPTION

       ASN1_item_d2i_ex() decodes the contents of the data stored in *in of length len which must
       be a DER-encoded ASN.1 structure, using the ASN.1 template it. It places the result in
       *pval unless pval is NULL. If *pval is non-NULL on entry then the ASN1_VALUE present there
       will be reused. Otherwise a new ASN1_VALUE will be allocated. If any algorithm fetches are
       required during the process then they will use the OSSL_LIB_CTXprovided in the libctx
       parameter and the property query string in propq. See "ALGORITHM FETCHING" in crypto(7)
       for more information about algorithm fetching.  On exit *in will be updated to point to
       the next byte in the buffer after the decoded structure.

       ASN1_item_d2i() is the same as ASN1_item_d2i_ex() except that the default OSSL_LIB_CTX is
       used (i.e. NULL) and with a NULL property query string.

       ASN1_item_d2i_bio_ex() decodes the contents of its input BIO in, which must be a DER-
       encoded ASN.1 structure, using the ASN.1 template it and places the result in *pval unless
       pval is NULL.  If in is NULL it returns NULL, else a pointer to the parsed structure. If
       any algorithm fetches are required during the process then they will use the OSSL_LIB_CTX
       provided in the libctx parameter and the property query string in propq. See "ALGORITHM
       FETCHING" in crypto(7) for more information about algorithm fetching.

       ASN1_item_d2i_bio() is the same as ASN1_item_d2i_bio_ex() except that the default
       OSSL_LIB_CTX is used (i.e. NULL) and with a NULL property query string.

       ASN1_item_d2i_fp_ex() is the same as ASN1_item_d2i_bio_ex() except that a FILE pointer is
       provided instead of a BIO.

       ASN1_item_d2i_fp() is the same as ASN1_item_d2i_fp_ex() except that the default
       OSSL_LIB_CTX is used (i.e. NULL) and with a NULL property query string.

       ASN1_item_i2d_mem_bio() encodes the given ASN.1 value val using the ASN.1 template it and
       returns the result in a memory BIO.

RETURN VALUES

       ASN1_item_d2i_bio() returns a pointer to an ASN1_VALUE or NULL.

       ASN1_item_i2d_mem_bio() returns a pointer to a memory BIO or NULL on error.

HISTORY

       The functions ASN1_item_d2i_ex(), ASN1_item_d2i_bio_ex(), ASN1_item_d2i_fp_ex() and
       ASN1_item_i2d_mem_bio() were added in OpenSSL 3.0.

COPYRIGHT

       Copyright 2021 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (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 <https://www.openssl.org/source/license.html>.