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- =pod
- =head1 NAME
- OSSL_DECODER,
- OSSL_DECODER_fetch,
- OSSL_DECODER_up_ref,
- OSSL_DECODER_free,
- OSSL_DECODER_get0_provider,
- OSSL_DECODER_get0_properties,
- OSSL_DECODER_is_a,
- OSSL_DECODER_get0_name,
- OSSL_DECODER_get0_description,
- OSSL_DECODER_do_all_provided,
- OSSL_DECODER_names_do_all,
- OSSL_DECODER_gettable_params,
- OSSL_DECODER_get_params
- - Decoder method routines
- =head1 SYNOPSIS
- #include <openssl/decoder.h>
- typedef struct ossl_decoder_st OSSL_DECODER;
- OSSL_DECODER *OSSL_DECODER_fetch(OSSL_LIB_CTX *ctx, const char *name,
- const char *properties);
- int OSSL_DECODER_up_ref(OSSL_DECODER *decoder);
- void OSSL_DECODER_free(OSSL_DECODER *decoder);
- const OSSL_PROVIDER *OSSL_DECODER_get0_provider(const OSSL_DECODER *decoder);
- const char *OSSL_DECODER_get0_properties(const OSSL_DECODER *decoder);
- int OSSL_DECODER_is_a(const OSSL_DECODER *decoder, const char *name);
- const char *OSSL_DECODER_get0_name(const OSSL_DECODER *decoder);
- const char *OSSL_DECODER_get0_description(const OSSL_DECODER *decoder);
- void OSSL_DECODER_do_all_provided(OSSL_LIB_CTX *libctx,
- void (*fn)(OSSL_DECODER *decoder, void *arg),
- void *arg);
- int OSSL_DECODER_names_do_all(const OSSL_DECODER *decoder,
- void (*fn)(const char *name, void *data),
- void *data);
- const OSSL_PARAM *OSSL_DECODER_gettable_params(OSSL_DECODER *decoder);
- int OSSL_DECODER_get_params(OSSL_DECODER_CTX *ctx, const OSSL_PARAM params[]);
- =head1 DESCRIPTION
- B<OSSL_DECODER> is a method for decoders, which know how to
- decode encoded data into an object of some type that the rest
- of OpenSSL knows how to handle.
- OSSL_DECODER_fetch() looks for an algorithm within the provider that
- has been loaded into the B<OSSL_LIB_CTX> given by I<ctx>, having the
- name given by I<name> and the properties given by I<properties>.
- The I<name> determines what type of object the fetched decoder
- method is expected to be able to decode, and the properties are
- used to determine the expected output type.
- For known properties and the values they may have, please have a look
- in L<provider-encoder(7)/Names and properties>.
- OSSL_DECODER_up_ref() increments the reference count for the given
- I<decoder>.
- OSSL_DECODER_free() decrements the reference count for the given
- I<decoder>, and when the count reaches zero, frees it.
- OSSL_DECODER_get0_provider() returns the provider of the given
- I<decoder>.
- OSSL_DECODER_get0_properties() returns the property definition associated
- with the given I<decoder>.
- OSSL_DECODER_is_a() checks if I<decoder> is an implementation
- of an algorithm that's identifiable with I<name>.
- OSSL_DECODER_get0_name() returns the name used to fetch the given I<decoder>.
- OSSL_DECODER_get0_description() returns a description of the I<decoder>, meant
- for display and human consumption. The description is at the discretion
- of the I<decoder> implementation.
- OSSL_DECODER_names_do_all() traverses all names for the given
- I<decoder>, and calls I<fn> with each name and I<data> as arguments.
- OSSL_DECODER_do_all_provided() traverses all decoder
- implementations by all activated providers in the library context
- I<libctx>, and for each of the implementations, calls I<fn> with the
- implementation method and I<arg> as arguments.
- OSSL_DECODER_gettable_params() returns an L<OSSL_PARAM(3)>
- array of parameter descriptors.
- OSSL_DECODER_get_params() attempts to get parameters specified
- with an L<OSSL_PARAM(3)> array I<params>. Parameters that the
- implementation doesn't recognise should be ignored.
- =head1 RETURN VALUES
- OSSL_DECODER_fetch() returns a pointer to an OSSL_DECODER object,
- or NULL on error.
- OSSL_DECODER_up_ref() returns 1 on success, or 0 on error.
- OSSL_DECODER_free() doesn't return any value.
- OSSL_DECODER_get0_provider() returns a pointer to a provider object, or
- NULL on error.
- OSSL_DECODER_get0_properties() returns a pointer to a property
- definition string, or NULL on error.
- OSSL_DECODER_is_a() returns 1 if I<decoder> was identifiable,
- otherwise 0.
- OSSL_DECODER_get0_name() returns the algorithm name from the provided
- implementation for the given I<decoder>. Note that the I<decoder> may have
- multiple synonyms associated with it. In this case the first name from the
- algorithm definition is returned. Ownership of the returned string is retained
- by the I<decoder> object and should not be freed by the caller.
- OSSL_DECODER_get0_description() returns a pointer to a description, or NULL if
- there isn't one.
- OSSL_DECODER_names_do_all() returns 1 if the callback was called for all
- names. A return value of 0 means that the callback was not called for any names.
- =head1 NOTES
- OSSL_DECODER_fetch() may be called implicitly by other fetching
- functions, using the same library context and properties.
- Any other API that uses keys will typically do this.
- =head1 EXAMPLES
- To list all decoders in a provider to a bio_out:
- static void collect_decoders(OSSL_DECODER *decoder, void *stack)
- {
- STACK_OF(OSSL_DECODER) *decoder_stack = stack;
- sk_OSSL_DECODER_push(decoder_stack, decoder);
- OSSL_DECODER_up_ref(decoder);
- }
- void print_name(const char *name, void *vdata)
- {
- BIO *bio = vdata;
- BIO_printf(bio, "%s ", name);
- }
- STACK_OF(OSSL_DECODER) *decoders;
- int i;
- decoders = sk_OSSL_DECODER_new_null();
- BIO_printf(bio_out, "DECODERs provided by %s:\n", provider);
- OSSL_DECODER_do_all_provided(NULL, collect_decoders,
- decoders);
- for (i = 0; i < sk_OSSL_DECODER_num(decoders); i++) {
- OSSL_DECODER *decoder = sk_OSSL_DECODER_value(decoders, i);
- if (strcmp(OSSL_PROVIDER_get0_name(OSSL_DECODER_get0_provider(decoder)),
- provider) != 0)
- continue;
- if (OSSL_DECODER_names_do_all(decoder, print_name, bio_out))
- BIO_printf(bio_out, "\n");
- }
- sk_OSSL_DECODER_pop_free(decoders, OSSL_DECODER_free);
- =head1 SEE ALSO
- L<provider(7)>, L<OSSL_DECODER_CTX(3)>, L<OSSL_DECODER_from_bio(3)>,
- L<OSSL_DECODER_CTX_new_for_pkey(3)>, L<OSSL_LIB_CTX(3)>
- =head1 HISTORY
- The functions described here were added in OpenSSL 3.0.
- =head1 COPYRIGHT
- Copyright 2020-2022 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
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