=pod

=head1 NAME

OSSL_PARAM_BLD, OSSL_PARAM_BLD_new, OSSL_PARAM_BLD_to_param,
OSSL_PARAM_BLD_free, OSSL_PARAM_BLD_push_int,
OSSL_PARAM_BLD_push_uint, OSSL_PARAM_BLD_push_long,
OSSL_PARAM_BLD_push_ulong, OSSL_PARAM_BLD_push_int32,
OSSL_PARAM_BLD_push_uint32, OSSL_PARAM_BLD_push_int64,
OSSL_PARAM_BLD_push_uint64, OSSL_PARAM_BLD_push_size_t,
OSSL_PARAM_BLD_push_time_t, OSSL_PARAM_BLD_push_double,
OSSL_PARAM_BLD_push_BN, OSSL_PARAM_BLD_push_BN_pad,
OSSL_PARAM_BLD_push_utf8_string, OSSL_PARAM_BLD_push_utf8_ptr,
OSSL_PARAM_BLD_push_octet_string, OSSL_PARAM_BLD_push_octet_ptr
- functions to assist in the creation of OSSL_PARAM arrays

=head1 SYNOPSIS

=for openssl generic

 #include <openssl/param_build.h>

 typedef struct OSSL_PARAM_BLD;

 OSSL_PARAM_BLD *OSSL_PARAM_BLD_new(void);
 OSSL_PARAM *OSSL_PARAM_BLD_to_param(OSSL_PARAM_BLD *bld);
 void OSSL_PARAM_BLD_free(OSSL_PARAM_BLD *bld);

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

 int OSSL_PARAM_BLD_push_BN(OSSL_PARAM_BLD *bld, const char *key,
                            const BIGNUM *bn);
 int OSSL_PARAM_BLD_push_BN_pad(OSSL_PARAM_BLD *bld, const char *key,
                                const BIGNUM *bn, size_t sz);

 int OSSL_PARAM_BLD_push_utf8_string(OSSL_PARAM_BLD *bld, const char *key,
                                     const char *buf, size_t bsize);
 int OSSL_PARAM_BLD_push_utf8_ptr(OSSL_PARAM_BLD *bld, const char *key,
                                  char *buf, size_t bsize);
 int OSSL_PARAM_BLD_push_octet_string(OSSL_PARAM_BLD *bld, const char *key,
                                      const void *buf, size_t bsize);
 int OSSL_PARAM_BLD_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<I<TYPE>> names are as per L<OSSL_PARAM_int(3)>.

OSSL_PARAM_BLD_new() allocates and initialises a new OSSL_PARAM_BLD structure
so that values can be added.
Any existing values are cleared.

OSSL_PARAM_BLD_free() deallocates the memory allocates by OSSL_PARAM_BLD_new().

OSSL_PARAM_BLD_to_param() converts a built up OSSL_PARAM_BLD structure
I<bld> into an allocated OSSL_PARAM array.
The OSSL_PARAM array and all associated storage must be freed by calling
OSSL_PARAM_free() with the functions return value.
OSSL_PARAM_BLD_free() can safely be called any time after this function is.

=begin comment

POD is pretty good at recognising function names and making them appropriately
bold...  however, when part of the function name is variable, we have to help
the processor along

=end comment

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

OSSL_PARAM_BLD_push_BN() is a function that will create an OSSL_PARAM object
that holds the specified BIGNUM I<bn>.
If I<bn> is marked as being securely allocated, its OSSL_PARAM representation
will also be securely allocated.
The I<bn> argument is stored by reference and the underlying BIGNUM object
must exist until after OSSL_PARAM_BLD_to_param() has been called.

OSSL_PARAM_BLD_push_BN_pad() is a function that will create an OSSL_PARAM object
that holds the specified BIGNUM I<bn>.
The object will be padded to occupy exactly I<sz> bytes, if insufficient space
is specified an error results.
If I<bn> is marked as being securely allocated, its OSSL_PARAM representation
will also be securely allocated.
The I<bn> argument is stored by reference and the underlying BIGNUM object
must exist until after OSSL_PARAM_BLD_to_param() has been called.

OSSL_PARAM_BLD_push_utf8_string() is a function that will create an OSSL_PARAM
object that references the UTF8 string specified by I<buf>.
The length of the string I<bsize> should not include the terminating NUL byte.
If it is zero then it will be calculated.
The string that I<buf> points to is stored by reference and must remain in
scope until after OSSL_PARAM_BLD_to_param() has been called.

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

OSSL_PARAM_BLD_push_utf8_ptr() is a function that will create an OSSL_PARAM
object that references the UTF8 string specified by I<buf>.
The length of the string I<bsize> should not include the terminating NUL byte.
If it is zero then it will be calculated.
The string I<buf> points to is stored by reference and must remain in
scope until the OSSL_PARAM array is freed.

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

=head1 RETURN VALUES

OSSL_PARAM_BLD_new() returns the allocated OSSL_PARAM_BLD structure, or NULL
on error.

OSSL_PARAM_BLD_to_param() returns the allocated OSSL_PARAM array, or NULL
on error.

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

=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_BLD_new();
    OSSL_PARAM *params = NULL;

    if (bld == NULL
        || !OSSL_PARAM_BLD_push_BN(bld, "p", p)
        || !OSSL_PARAM_BLD_push_BN(bld, "q", q)
        || !OSSL_PARAM_BLD_push_uint(bld, "e", e)
        || !OSSL_PARAM_BLD_push_BN(bld, "n", n)
        || !OSSL_PARAM_BLD_push_BN(bld, "d", d)
        || (params = OSSL_PARAM_BLD_to_param(bld)) == NULL)
        goto err;
    OSSL_PARAM_BLD_free(bld);
    /* Use params */
    ...
    OSSL_PARAM_free(params);

=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_BLD_new();
    OSSL_PARAM *params = NULL;

    if (nld == NULL
        || !OSSL_PARAM_BLD_push_BN(bld, "n", n)
        || !OSSL_PARAM_BLD_push_BN(bld, "d", d)
        || (params = OSSL_PARAM_BLD_to_param(bld)) == NULL)
        goto err;
    OSSL_PARAM_BLD_free(bld);
    /* Use params */
    ...
    OSSL_PARAM_free(params);

=head1 SEE ALSO

L<OSSL_PARAM_int(3)>, L<OSSL_PARAM(3)>, L<OSSL_PARAM_free(3)>

=head1 HISTORY

The functions described here were all added in OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2019-2021 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
L<https://www.openssl.org/source/license.html>.

=cut