xref: /openssl/doc/man3/OSSL_ENCODER_CTX.pod (revision 981d129a) 
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>.
105If the argument is NULL, nothing is done.
106
107OSSL_ENCODER_CTX_add_encoder() populates the B<OSSL_ENCODER_CTX>
108I<ctx> with a encoder, to be used to encode an input object.
109
110OSSL_ENCODER_CTX_add_extra() finds encoders that further encodes output
111from already added encoders, and adds them as well.  This is used to build
112encoder chains.
113
114OSSL_ENCODER_CTX_set_output_type() sets the ending output type.  This must
115be specified, and determines if a complete encoder chain is available.
116
117OSSL_ENCODER_CTX_set_output_structure() sets the desired output structure.
118This may be used to determines what encoder implementations may be used.
119Depending on the type of object being encoded, the output structure may
120not be relevant.
121
122OSSL_ENCODER_CTX_get_num_encoders() gets the number of encoders currently
123added to the context I<ctx>.
124
125OSSL_ENCODER_CTX_set_construct() sets the constructor I<construct>.
126
127OSSL_ENCODER_CTX_set_construct_data() sets the constructor data that is
128passed to the constructor every time it's called.
129
130OSSL_ENCODER_CTX_set_cleanup() sets the constructor data I<cleanup>
131function.  This is called by L<OSSL_ENCODER_CTX_free(3)>.
132
133=head2 Constructor
134
135A B<OSSL_ENCODER_CONSTRUCT> gets the following arguments:
136
137=over 4
138
139=item I<encoder_inst>
140
141The B<OSSL_ENCODER_INSTANCE> for the encoder from which the constructor gets
142its data.
143
144=item I<construct_data>
145
146The pointer that was set with OSSL_ENCODE_CTX_set_construct_data().
147
148=back
149
150The constructor is expected to return a valid (non-NULL) pointer to a
151provider-native object that can be used as first input of an encoding chain,
152or NULL to indicate that an error has occurred.
153
154These utility functions may be used by a constructor:
155
156OSSL_ENCODER_INSTANCE_get_encoder() can be used to get the encoder
157implementation of the encoder instance I<encoder_inst>.
158
159OSSL_ENCODER_INSTANCE_get_encoder_ctx() can be used to get the encoder
160implementation's provider context of the encoder instance I<encoder_inst>.
161
162OSSL_ENCODER_INSTANCE_get_output_type() can be used to get the output type
163for the encoder implementation of the encoder instance I<encoder_inst>.
164This will never be NULL.
165
166OSSL_ENCODER_INSTANCE_get_output_structure() can be used to get the output
167structure for the encoder implementation of the encoder instance
168I<encoder_inst>.
169This may be NULL.
170
171=head1 RETURN VALUES
172
173OSSL_ENCODER_CTX_new() returns a pointer to a B<OSSL_ENCODER_CTX>, or NULL
174if the context structure couldn't be allocated.
175
176OSSL_ENCODER_settable_ctx_params() returns an L<OSSL_PARAM(3)> array, or
177NULL if none is available.
178
179OSSL_ENCODER_CTX_set_params() returns 1 if all recognised parameters were
180valid, or 0 if one of them was invalid or caused some other failure in the
181implementation.
182
183OSSL_ENCODER_CTX_add_encoder(), OSSL_ENCODER_CTX_add_extra(),
184OSSL_ENCODER_CTX_set_construct(), OSSL_ENCODER_CTX_set_construct_data() and
185OSSL_ENCODER_CTX_set_cleanup() return 1 on success, or 0 on failure.
186
187OSSL_ENCODER_CTX_get_num_encoders() returns the current number of encoders.
188It returns 0 if I<ctx> is NULL.
189
190OSSL_ENCODER_INSTANCE_get_encoder() returns an B<OSSL_ENCODER> pointer on
191success, or NULL on failure.
192
193OSSL_ENCODER_INSTANCE_get_encoder_ctx() returns a provider context pointer on
194success, or NULL on failure.
195
196OSSL_ENCODER_INSTANCE_get_output_type() returns a string with the name of the
197input type, if relevant.  NULL is a valid returned value.
198
199OSSL_ENCODER_INSTANCE_get_output_type() returns a string with the name of the
200output type.
201
202OSSL_ENCODER_INSTANCE_get_output_structure() returns a string with the name
203of the output structure.
204
205=head1 SEE ALSO
206
207L<provider(7)>, L<OSSL_ENCODER(3)>
208
209=head1 HISTORY
210
211The functions described here were added in OpenSSL 3.0.
212
213=head1 COPYRIGHT
214
215Copyright 2019-2022 The OpenSSL Project Authors. All Rights Reserved.
216
217Licensed under the Apache License 2.0 (the "License").  You may not use
218this file except in compliance with the License.  You can obtain a copy
219in the file LICENSE in the source distribution or at
220L<https://www.openssl.org/source/license.html>.
221
222=cut
223