1=pod
2
3=head1 NAME
4
5OSSL_ENCODER_CTX,
6OSSL_ENCODER_CTX_new,
7OSSL_ENCODER_settable_ctx_params,
8OSSL_ENCODER_CTX_set_params,
9OSSL_ENCODER_CTX_free,
10OSSL_ENCODER_CTX_set_selection,
11OSSL_ENCODER_CTX_set_output_type,
12OSSL_ENCODER_CTX_set_output_structure,
13OSSL_ENCODER_CTX_add_encoder,
14OSSL_ENCODER_CTX_add_extra,
15OSSL_ENCODER_CTX_get_num_encoders,
16OSSL_ENCODER_INSTANCE,
17OSSL_ENCODER_INSTANCE_get_encoder,
18OSSL_ENCODER_INSTANCE_get_encoder_ctx,
19OSSL_ENCODER_INSTANCE_get_output_type,
20OSSL_ENCODER_INSTANCE_get_output_structure,
21OSSL_ENCODER_CONSTRUCT,
22OSSL_ENCODER_CLEANUP,
23OSSL_ENCODER_CTX_set_construct,
24OSSL_ENCODER_CTX_set_construct_data,
25OSSL_ENCODER_CTX_set_cleanup
26- Encoder context routines
27
28=head1 SYNOPSIS
29
30 #include <openssl/encoder.h>
31
32 typedef struct ossl_encoder_ctx_st OSSL_ENCODER_CTX;
33
34 OSSL_ENCODER_CTX *OSSL_ENCODER_CTX_new();
35 const OSSL_PARAM *OSSL_ENCODER_settable_ctx_params(OSSL_ENCODER *encoder);
36 int OSSL_ENCODER_CTX_set_params(OSSL_ENCODER_CTX *ctx,
37                                 const OSSL_PARAM params[]);
38 void OSSL_ENCODER_CTX_free(OSSL_ENCODER_CTX *ctx);
39
40 int OSSL_ENCODER_CTX_set_selection(OSSL_ENCODER_CTX *ctx, int selection);
41 int OSSL_ENCODER_CTX_set_output_type(OSSL_ENCODER_CTX *ctx,
42                                      const char *output_type);
43 int OSSL_ENCODER_CTX_set_output_structure(OSSL_ENCODER_CTX *ctx,
44                                           const char *output_structure);
45
46 int OSSL_ENCODER_CTX_add_encoder(OSSL_ENCODER_CTX *ctx, OSSL_ENCODER *encoder);
47 int OSSL_ENCODER_CTX_add_extra(OSSL_ENCODER_CTX *ctx,
48                                OSSL_LIB_CTX *libctx, const char *propq);
49 int OSSL_ENCODER_CTX_get_num_encoders(OSSL_ENCODER_CTX *ctx);
50
51 typedef struct ossl_encoder_instance_st OSSL_ENCODER_INSTANCE;
52 OSSL_ENCODER *
53 OSSL_ENCODER_INSTANCE_get_encoder(OSSL_ENCODER_INSTANCE *encoder_inst);
54 void *
55 OSSL_ENCODER_INSTANCE_get_encoder_ctx(OSSL_ENCODER_INSTANCE *encoder_inst);
56 const char *
57 OSSL_ENCODER_INSTANCE_get_output_type(OSSL_ENCODER_INSTANCE *encoder_inst);
58 const char *
59 OSSL_ENCODER_INSTANCE_get_output_structure(OSSL_ENCODER_INSTANCE *encoder_inst);
60
61 typedef const void *OSSL_ENCODER_CONSTRUCT(OSSL_ENCODER_INSTANCE *encoder_inst,
62                                            void *construct_data);
63 typedef void OSSL_ENCODER_CLEANUP(void *construct_data);
64
65 int OSSL_ENCODER_CTX_set_construct(OSSL_ENCODER_CTX *ctx,
66                                    OSSL_ENCODER_CONSTRUCT *construct);
67 int OSSL_ENCODER_CTX_set_construct_data(OSSL_ENCODER_CTX *ctx,
68                                         void *construct_data);
69 int OSSL_ENCODER_CTX_set_cleanup(OSSL_ENCODER_CTX *ctx,
70                                  OSSL_ENCODER_CLEANUP *cleanup);
71
72=head1 DESCRIPTION
73
74Encoding an input object to the desired encoding may be done with a chain of
75encoder implementations, which means that the output from one encoder may be
76the input for the next in the chain.  The B<OSSL_ENCODER_CTX> holds all the
77data about these encoders.  This allows having generic format encoders such
78as DER to PEM, as well as more specialized encoders like RSA to DER.
79
80The final output type must be given, and a chain of encoders must end with
81an implementation that produces that output type.
82
83At the beginning of the encoding process, a constructor provided by the
84caller is called to ensure that there is an appropriate provider-side object
85to start with.
86The constructor is set with OSSL_ENCODER_CTX_set_construct().
87
88B<OSSL_ENCODER_INSTANCE> is an opaque structure that contains data about the
89encoder that is going to be used, and that may be useful for the
90constructor.  There are some functions to extract data from this type,
91described in L</Constructor> below.
92
93=head2 Functions
94
95OSSL_ENCODER_CTX_new() creates a B<OSSL_ENCODER_CTX>.
96
97OSSL_ENCODER_settable_ctx_params() returns an L<OSSL_PARAM(3)>
98array of parameter descriptors.
99
100OSSL_ENCODER_CTX_set_params() attempts to set parameters specified
101with an L<OSSL_PARAM(3)> array I<params>.  Parameters that the
102implementation doesn't recognise should be ignored.
103
104OSSL_ENCODER_CTX_free() frees the given context I<ctx>.
105
106OSSL_ENCODER_CTX_add_encoder() populates the B<OSSL_ENCODER_CTX>
107I<ctx> with a encoder, to be used to encode an input object.
108
109OSSL_ENCODER_CTX_add_extra() finds encoders that further encodes output
110from already added encoders, and adds them as well.  This is used to build
111encoder chains.
112
113OSSL_ENCODER_CTX_set_output_type() sets the ending output type.  This must
114be specified, and determines if a complete encoder chain is available.
115
116OSSL_ENCODER_CTX_set_output_structure() sets the desired output structure.
117This may be used to determines what encoder implementations may be used.
118Depending on the type of object being encoded, the output structure may
119not be relevant.
120
121OSSL_ENCODER_CTX_get_num_encoders() gets the number of encoders currently
122added to the context I<ctx>.
123
124OSSL_ENCODER_CTX_set_construct() sets the constructor I<construct>.
125
126OSSL_ENCODER_CTX_set_construct_data() sets the constructor data that is
127passed to the constructor every time it's called.
128
129OSSL_ENCODER_CTX_set_cleanup() sets the constructor data I<cleanup>
130function.  This is called by L<OSSL_ENCODER_CTX_free(3)>.
131
132=head2 Constructor
133
134A B<OSSL_ENCODER_CONSTRUCT> gets the following arguments:
135
136=over 4
137
138=item I<encoder_inst>
139
140The B<OSSL_ENCODER_INSTANCE> for the encoder from which the constructor gets
141its data.
142
143=item I<construct_data>
144
145The pointer that was set with OSSL_ENCODE_CTX_set_construct_data().
146
147=back
148
149The constructor is expected to return a valid (non-NULL) pointer to a
150provider-native object that can be used as first input of an encoding chain,
151or NULL to indicate that an error has occurred.
152
153These utility functions may be used by a constructor:
154
155OSSL_ENCODER_INSTANCE_get_encoder() can be used to get the encoder
156implementation of the encoder instance I<encoder_inst>.
157
158OSSL_ENCODER_INSTANCE_get_encoder_ctx() can be used to get the encoder
159implementation's provider context of the encoder instance I<encoder_inst>.
160
161OSSL_ENCODER_INSTANCE_get_output_type() can be used to get the output type
162for the encoder implementation of the encoder instance I<encoder_inst>.
163This will never be NULL.
164
165OSSL_ENCODER_INSTANCE_get_output_structure() can be used to get the output
166structure for the encoder implementation of the encoder instance
167I<encoder_inst>.
168This may be NULL.
169
170=head1 RETURN VALUES
171
172OSSL_ENCODER_CTX_new() returns a pointer to a B<OSSL_ENCODER_CTX>, or NULL
173if the context structure couldn't be allocated.
174
175OSSL_ENCODER_settable_ctx_params() returns an L<OSSL_PARAM(3)> array, or
176NULL if none is available.
177
178OSSL_ENCODER_CTX_set_params() returns 1 if all recognised parameters were
179valid, or 0 if one of them was invalid or caused some other failure in the
180implementation.
181
182OSSL_ENCODER_CTX_add_encoder(), OSSL_ENCODER_CTX_add_extra(),
183OSSL_ENCODER_CTX_set_construct(), OSSL_ENCODER_CTX_set_construct_data() and
184OSSL_ENCODER_CTX_set_cleanup() return 1 on success, or 0 on failure.
185
186OSSL_ENCODER_CTX_get_num_encoders() returns the current number of encoders.
187It returns 0 if I<ctx> is NULL.
188
189OSSL_ENCODER_INSTANCE_get_encoder() returns an B<OSSL_ENCODER> pointer on
190success, or NULL on failure.
191
192OSSL_ENCODER_INSTANCE_get_encoder_ctx() returns a provider context pointer on
193success, or NULL on failure.
194
195OSSL_ENCODER_INSTANCE_get_output_type() returns a string with the name of the
196input type, if relevant.  NULL is a valid returned value.
197
198OSSL_ENCODER_INSTANCE_get_output_type() returns a string with the name of the
199output type.
200
201OSSL_ENCODER_INSTANCE_get_output_structure() returns a string with the name
202of the output structure.
203
204=head1 SEE ALSO
205
206L<provider(7)>, L<OSSL_ENCODER(3)>
207
208=head1 HISTORY
209
210The functions described here were added in OpenSSL 3.0.
211
212=head1 COPYRIGHT
213
214Copyright 2019-2023 The OpenSSL Project Authors. All Rights Reserved.
215
216Licensed under the Apache License 2.0 (the "License").  You may not use
217this file except in compliance with the License.  You can obtain a copy
218in the file LICENSE in the source distribution or at
219L<https://www.openssl.org/source/license.html>.
220
221=cut
222