=pod

=head1 NAME

ossl_param_build_init,
ossl_param_build_to_param, ossl_param_build_push_int,
ossl_param_build_push_uint, ossl_param_build_push_long,
ossl_param_build_push_ulong, ossl_param_build_push_int32,
ossl_param_build_push_uint32, ossl_param_build_push_int64,
ossl_param_build_push_uint64, ossl_param_build_push_size_t,
ossl_param_build_push_double, ossl_param_build_push_BN,
ossl_param_build_push_utf8_string, ossl_param_build_push_utf8_ptr,
ossl_param_build_push_octet_string, ossl_param_build_push_octet_ptr
- functions to assist in the creation of OSSL_PARAM arrays

=head1 SYNOPSIS

=for comment generic

 #include "internal/params_template.h"

 #define OSSL_PARAM_BLD_MAX 10
 typedef struct { ... } OSSL_PARAM_BLD;

 void ossl_param_build_init(OSSL_PARAM_BLD *bld);
 OSSL_PARAM *ossl_param_build_to_param(OSSL_PARAM_BLD *bld, void **secure);
 OSSL_PARAM *ossl_param_build_to_param_ex(OSSL_PARAM_BLD *bld,
                                        OSSL_PARAM *params, size_t param_n,
                                        void *data, size_t data_n,
                                        void *secure, size_t secure_n);

 int ossl_param_build_push_TYPE(OSSL_PARAM_BLD *bld, const char *key, TYPE val);

 int ossl_param_build_push_BN(OSSL_PARAM_BLD *bld, const char *key,
                            const BIGNUM *bn);

 int ossl_param_build_push_utf8_string(OSSL_PARAM_BLD *bld, const char *key,
                                     char *buf, size_t bsize);
 int ossl_param_build_push_utf8_ptr(OSSL_PARAM_BLD *bld, const char *key,
                                  char *buf, size_t bsize);
 int ossl_param_build_push_octet_string(OSSL_PARAM_BLD *bld, const char *key,
                                      void *buf, size_t bsize);
 int ossl_param_build_push_octet_ptr(OSSL_PARAM_BLD *bld, const char *key,
                                   void *buf, size_t bsize);


=head1 DESCRIPTION

A collection of utility functions that simplify the creation of OSSL_PARAM
arrays.  The B<TYPE> names are as per L<OSSL_PARAM_int(3)>.

ossl_param_build_init() initialises the OSSL_PARAM_BLD structure so that values
can be added.
Any existing values are cleared.

ossl_param_build_to_param() converts a built up OSSL_PARAM_BLD structure
B<bld> into an allocated OSSL_PARAM array.
The pointer referenced by the B<secure> argument is set to point to an
allocated block of secure memory if required and to NULL it not. 
The OSSL_PARAM array and all associated storage can be freed by calling
OPENSSL_free() with the functions return value and OPENSSL_secure_free()
with the pointer referenced by B<secure>.

ossl_param_build_to_param_ex() behaves like ossl_param_build_to_param(), except that
no additional memory is allocated.
An OSSL_PARAM array of at least B<param_n> elements is passed in as B<params>.
The auxiliary storage for the parameters is a block of memory pointed to
by B<data> of at least B<data_n> bytes in size.
If required, secure memory for private BIGNUMs should be pointed to by
B<secure> of at least B<secure_n> bytes in size.

ossl_param_build_push_TYPE() are a series of functions which will create
OSSL_PARAM objects of the specified size and correct type for the B<val>
argument.
B<val> is stored by value and an expression or auto variable can be used.

ossl_param_build_push_BN() is a function that will create an OSSL_PARAM object
that holds the specified BIGNUM B<bn>.
If B<bn> is marked as being securely allocated, the secure flag is
set in the OSSL_PARAM_BLD structure.
The B<bn> argument is stored by reference and the underlying BIGNUM object
must exist until after ossl_param_build_to_param() has been called.

ossl_param_build_push_utf8_string() is a function that will create an OSSL_PARAM
object that references the UTF8 string specified by B<buf>.
If the length of the string, B<bsize>, is zero then it will be calculated.
The string that B<buf> points to is stored by reference and must remain in
scope until after ossl_param_build_to_param() has been called.

ossl_param_build_push_octet_string() is a function that will create an OSSL_PARAM
object that references the octet string specified by B<buf> and <bsize>.
The memory that B<buf> points to is stored by reference and must remain in
scope until after ossl_param_build_to_param() has been called.

ossl_param_build_push_utf8_ptr() is a function that will create an OSSL_PARAM
object that references the UTF8 string specified by B<buf>.
If the length of the string, B<bsize>, is zero then it will be calculated.
The string B<buf> points to is stored by reference and must remain in
scope until the OSSL_PARAM array is freed.

ossl_param_build_push_octet_ptr() is a function that will create an OSSL_PARAM
object that references the octet string specified by B<buf>.
The memory B<buf> points to is stored by reference and must remain in
scope until the OSSL_PARAM array is freed.

=head1 RETURN VALUES

ossl_param_build_to_param() and ossl_param_bld_to_param_ex() return the
allocated OSSL_PARAM array, or NULL on error.

All of the ossl_param_build_push_TYPE functions return 1 on success and 0
on error.

=head1 NOTES

The constant B<OSSL_PARAM_BLD_MAX> specifies the maximum number of parameters
that can be added.
Exceeding this will result in the push functions returning errors.

The structure B<OSSL_PARAM_BLD> should be considered opaque and subject to
change between versions.

=head1 EXAMPLES

Both examples creating an OSSL_PARAM array that contains an RSA key.
For both, the predefined key variables are:

    BIGNUM *p, *q;  /* both prime */
    BIGNUM *n;      /* = p * q */
    unsigned int e; /* exponent, usually 65537 */
    BIGNUM *d;      /* e^-1 */

=head2 Example 1

This example shows how to create an OSSL_PARAM array that contains an RSA
private key.

    OSSL_PARAM_BLD bld;
    OSSL_PARAM *params;
    void *secure;

    ossl_param_build_init(&bld, &secure);
    if (!ossl_param_build_push_BN(&bld, "p", p)
        || !ossl_param_build_push_BN(&bld, "q", q)
        || !ossl_param_build_push_uint(&bld, "e", e)
        || !ossl_param_build_push_BN(&bld, "n", n)
        || !ossl_param_build_push_BN(&bld, "d", d)
        || (params = ossl_param_build_to_param(&bld)) == NULL)
        goto err;
    /* Use params */
    ...
    OPENSSL_free(params);
    OPENSSL_secure_free(secure);

=head2 Example 2

This example shows how to create an OSSL_PARAM array that contains an RSA
public key.

    OSSL_PARAM_BLD bld;
    OSSL_PARAM *params;
    void *secure;

    ossl_param_build_init(&bld, &secure);
    if (!ossl_param_build_push_BN(&bld, "n", n)
        || !ossl_param_build_push_BN(&bld, "d", d)
        || (params = ossl_param_build_to_param(&bld)) == NULL)
        goto err;
    /* Use params */
    ...
    OPENSSL_free(params);
    OPENSSL_secure_free(secure);

=head1 SEE ALSO

L<OSSL_PARAM_int>, L<OSSL_PARAM>

=head1 HISTORY

The functions described here were all added in OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2019 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
L<https://www.openssl.org/source/license.html>.

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