xref: /openssl/doc/man3/OSSL_DECODER.pod (revision fecb3aae) 
1=pod
2
3=head1 NAME
4
5OSSL_DECODER,
6OSSL_DECODER_fetch,
7OSSL_DECODER_up_ref,
8OSSL_DECODER_free,
9OSSL_DECODER_get0_provider,
10OSSL_DECODER_get0_properties,
11OSSL_DECODER_is_a,
12OSSL_DECODER_get0_name,
13OSSL_DECODER_get0_description,
14OSSL_DECODER_do_all_provided,
15OSSL_DECODER_names_do_all,
16OSSL_DECODER_gettable_params,
17OSSL_DECODER_get_params
18- Decoder method routines
19
20=head1 SYNOPSIS
21
22 #include <openssl/decoder.h>
23
24 typedef struct ossl_decoder_st OSSL_DECODER;
25
26 OSSL_DECODER *OSSL_DECODER_fetch(OSSL_LIB_CTX *ctx, const char *name,
27                                  const char *properties);
28 int OSSL_DECODER_up_ref(OSSL_DECODER *decoder);
29 void OSSL_DECODER_free(OSSL_DECODER *decoder);
30 const OSSL_PROVIDER *OSSL_DECODER_get0_provider(const OSSL_DECODER *decoder);
31 const char *OSSL_DECODER_get0_properties(const OSSL_DECODER *decoder);
32 int OSSL_DECODER_is_a(const OSSL_DECODER *decoder, const char *name);
33 const char *OSSL_DECODER_get0_name(const OSSL_DECODER *decoder);
34 const char *OSSL_DECODER_get0_description(const OSSL_DECODER *decoder);
35 void OSSL_DECODER_do_all_provided(OSSL_LIB_CTX *libctx,
36                                   void (*fn)(OSSL_DECODER *decoder, void *arg),
37                                   void *arg);
38 int OSSL_DECODER_names_do_all(const OSSL_DECODER *decoder,
39                               void (*fn)(const char *name, void *data),
40                               void *data);
41 const OSSL_PARAM *OSSL_DECODER_gettable_params(OSSL_DECODER *decoder);
42 int OSSL_DECODER_get_params(OSSL_DECODER_CTX *ctx, const OSSL_PARAM params[]);
43
44=head1 DESCRIPTION
45
46B<OSSL_DECODER> is a method for decoders, which know how to
47decode encoded data into an object of some type that the rest
48of OpenSSL knows how to handle.
49
50OSSL_DECODER_fetch() looks for an algorithm within the provider that
51has been loaded into the B<OSSL_LIB_CTX> given by I<ctx>, having the
52name given by I<name> and the properties given by I<properties>.
53The I<name> determines what type of object the fetched decoder
54method is expected to be able to decode, and the properties are
55used to determine the expected output type.
56For known properties and the values they may have, please have a look
57in L<provider-encoder(7)/Names and properties>.
58
59OSSL_DECODER_up_ref() increments the reference count for the given
60I<decoder>.
61
62OSSL_DECODER_free() decrements the reference count for the given
63I<decoder>, and when the count reaches zero, frees it.
64
65OSSL_DECODER_get0_provider() returns the provider of the given
66I<decoder>.
67
68OSSL_DECODER_get0_properties() returns the property definition associated
69with the given I<decoder>.
70
71OSSL_DECODER_is_a() checks if I<decoder> is an implementation
72of an algorithm that's identifiable with I<name>.
73
74OSSL_DECODER_get0_name() returns the name used to fetch the given I<decoder>.
75
76OSSL_DECODER_get0_description() returns a description of the I<decoder>, meant
77for display and human consumption.  The description is at the discretion
78of the I<decoder> implementation.
79
80OSSL_DECODER_names_do_all() traverses all names for the given
81I<decoder>, and calls I<fn> with each name and I<data> as arguments.
82
83OSSL_DECODER_do_all_provided() traverses all decoder
84implementations by all activated providers in the library context
85I<libctx>, and for each of the implementations, calls I<fn> with the
86implementation method and I<arg> as arguments.
87
88OSSL_DECODER_gettable_params() returns an L<OSSL_PARAM(3)>
89array of parameter descriptors.
90
91OSSL_DECODER_get_params() attempts to get parameters specified
92with an L<OSSL_PARAM(3)> array I<params>.  Parameters that the
93implementation doesn't recognise should be ignored.
94
95=head1 RETURN VALUES
96
97OSSL_DECODER_fetch() returns a pointer to an OSSL_DECODER object,
98or NULL on error.
99
100OSSL_DECODER_up_ref() returns 1 on success, or 0 on error.
101
102OSSL_DECODER_free() doesn't return any value.
103
104OSSL_DECODER_get0_provider() returns a pointer to a provider object, or
105NULL on error.
106
107OSSL_DECODER_get0_properties() returns a pointer to a property
108definition string, or NULL on error.
109
110OSSL_DECODER_is_a() returns 1 if I<decoder> was identifiable,
111otherwise 0.
112
113OSSL_DECODER_get0_name() returns the algorithm name from the provided
114implementation for the given I<decoder>. Note that the I<decoder> may have
115multiple synonyms associated with it. In this case the first name from the
116algorithm definition is returned. Ownership of the returned string is retained
117by the I<decoder> object and should not be freed by the caller.
118
119OSSL_DECODER_get0_description() returns a pointer to a description, or NULL if
120there isn't one.
121
122OSSL_DECODER_names_do_all() returns 1 if the callback was called for all
123names. A return value of 0 means that the callback was not called for any names.
124
125=head1 NOTES
126
127OSSL_DECODER_fetch() may be called implicitly by other fetching
128functions, using the same library context and properties.
129Any other API that uses keys will typically do this.
130
131=head1 EXAMPLES
132
133To list all decoders in a provider to a bio_out:
134
135 static void collect_decoders(OSSL_DECODER *decoder, void *stack)
136 {
137     STACK_OF(OSSL_DECODER) *decoder_stack = stack;
138
139     sk_OSSL_DECODER_push(decoder_stack, decoder);
140     OSSL_DECODER_up_ref(decoder);
141 }
142
143 void print_name(const char *name, void *vdata)
144 {
145     BIO *bio = vdata;
146
147     BIO_printf(bio, "%s ", name);
148 }
149
150
151 STACK_OF(OSSL_DECODER) *decoders;
152 int i;
153
154 decoders = sk_OSSL_DECODER_new_null();
155
156 BIO_printf(bio_out, "DECODERs provided by %s:\n", provider);
157 OSSL_DECODER_do_all_provided(NULL, collect_decoders,
158                              decoders);
159
160 for (i = 0; i < sk_OSSL_DECODER_num(decoders); i++) {
161     OSSL_DECODER *decoder = sk_OSSL_DECODER_value(decoders, i);
162
163     if (strcmp(OSSL_PROVIDER_get0_name(OSSL_DECODER_get0_provider(decoder)),
164                provider) != 0)
165         continue;
166
167     if (OSSL_DECODER_names_do_all(decoder, print_name, bio_out))
168            BIO_printf(bio_out, "\n");
169 }
170 sk_OSSL_DECODER_pop_free(decoders, OSSL_DECODER_free);
171
172=head1 SEE ALSO
173
174L<provider(7)>, L<OSSL_DECODER_CTX(3)>, L<OSSL_DECODER_from_bio(3)>,
175L<OSSL_DECODER_CTX_new_for_pkey(3)>, L<OSSL_LIB_CTX(3)>
176
177=head1 HISTORY
178
179The functions described here were added in OpenSSL 3.0.
180
181=head1 COPYRIGHT
182
183Copyright 2020-2022 The OpenSSL Project Authors. All Rights Reserved.
184
185Licensed under the Apache License 2.0 (the "License").  You may not use
186this file except in compliance with the License.  You can obtain a copy
187in the file LICENSE in the source distribution or at
188L<https://www.openssl.org/source/license.html>.
189
190=cut
191