260 lines
10 KiB
Plaintext
260 lines
10 KiB
Plaintext
=pod
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=head1 NAME
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OSSL_DECODER_CTX,
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OSSL_DECODER_CTX_new,
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OSSL_DECODER_settable_ctx_params,
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OSSL_DECODER_CTX_set_params,
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OSSL_DECODER_CTX_free,
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OSSL_DECODER_CTX_set_selection,
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OSSL_DECODER_CTX_set_input_type,
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OSSL_DECODER_CTX_set_input_structure,
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OSSL_DECODER_CTX_add_decoder,
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OSSL_DECODER_CTX_add_extra,
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OSSL_DECODER_CTX_get_num_decoders,
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OSSL_DECODER_INSTANCE,
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OSSL_DECODER_CONSTRUCT,
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OSSL_DECODER_CLEANUP,
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OSSL_DECODER_CTX_set_construct,
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OSSL_DECODER_CTX_set_construct_data,
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OSSL_DECODER_CTX_set_cleanup,
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OSSL_DECODER_CTX_get_construct,
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OSSL_DECODER_CTX_get_construct_data,
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OSSL_DECODER_CTX_get_cleanup,
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OSSL_DECODER_export,
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OSSL_DECODER_INSTANCE_get_decoder,
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OSSL_DECODER_INSTANCE_get_decoder_ctx,
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OSSL_DECODER_INSTANCE_get_input_type,
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OSSL_DECODER_INSTANCE_get_input_structure
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- Decoder context routines
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=head1 SYNOPSIS
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#include <openssl/decoder.h>
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typedef struct ossl_decoder_ctx_st OSSL_DECODER_CTX;
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OSSL_DECODER_CTX *OSSL_DECODER_CTX_new(void);
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const OSSL_PARAM *OSSL_DECODER_settable_ctx_params(OSSL_DECODER *decoder);
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int OSSL_DECODER_CTX_set_params(OSSL_DECODER_CTX *ctx,
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const OSSL_PARAM params[]);
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void OSSL_DECODER_CTX_free(OSSL_DECODER_CTX *ctx);
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int OSSL_DECODER_CTX_set_selection(OSSL_DECODER_CTX *ctx, int selection);
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int OSSL_DECODER_CTX_set_input_type(OSSL_DECODER_CTX *ctx,
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const char *input_type);
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int OSSL_DECODER_CTX_set_input_structure(OSSL_DECODER_CTX *ctx,
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const char *input_structure);
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int OSSL_DECODER_CTX_add_decoder(OSSL_DECODER_CTX *ctx, OSSL_DECODER *decoder);
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int OSSL_DECODER_CTX_add_extra(OSSL_DECODER_CTX *ctx,
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OSSL_LIB_CTX *libctx,
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const char *propq);
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int OSSL_DECODER_CTX_get_num_decoders(OSSL_DECODER_CTX *ctx);
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typedef struct ossl_decoder_instance_st OSSL_DECODER_INSTANCE;
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OSSL_DECODER *
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OSSL_DECODER_INSTANCE_get_decoder(OSSL_DECODER_INSTANCE *decoder_inst);
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void *
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OSSL_DECODER_INSTANCE_get_decoder_ctx(OSSL_DECODER_INSTANCE *decoder_inst);
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const char *
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OSSL_DECODER_INSTANCE_get_input_type(OSSL_DECODER_INSTANCE *decoder_inst);
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OSSL_DECODER_INSTANCE_get_input_structure(OSSL_DECODER_INSTANCE *decoder_inst,
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int *was_set);
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typedef int OSSL_DECODER_CONSTRUCT(OSSL_DECODER_INSTANCE *decoder_inst,
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const OSSL_PARAM *object,
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void *construct_data);
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typedef void OSSL_DECODER_CLEANUP(void *construct_data);
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int OSSL_DECODER_CTX_set_construct(OSSL_DECODER_CTX *ctx,
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OSSL_DECODER_CONSTRUCT *construct);
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int OSSL_DECODER_CTX_set_construct_data(OSSL_DECODER_CTX *ctx,
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void *construct_data);
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int OSSL_DECODER_CTX_set_cleanup(OSSL_DECODER_CTX *ctx,
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OSSL_DECODER_CLEANUP *cleanup);
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OSSL_DECODER_CONSTRUCT *OSSL_DECODER_CTX_get_construct(OSSL_DECODER_CTX *ctx);
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void *OSSL_DECODER_CTX_get_construct_data(OSSL_DECODER_CTX *ctx);
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OSSL_DECODER_CLEANUP *OSSL_DECODER_CTX_get_cleanup(OSSL_DECODER_CTX *ctx);
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int OSSL_DECODER_export(OSSL_DECODER_INSTANCE *decoder_inst,
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void *reference, size_t reference_sz,
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OSSL_CALLBACK *export_cb, void *export_cbarg);
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=head1 DESCRIPTION
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The B<OSSL_DECODER_CTX> holds data about multiple decoders, as needed to
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figure out what the input data is and to attempt to unpack it into one of
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several possible related results. This also includes chaining decoders, so
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the output from one can become the input for another. This allows having
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generic format decoders such as PEM to DER, as well as more specialized
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decoders like DER to RSA.
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The chains may be limited by specifying an input type, which is considered a
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starting point. This is both considered by OSSL_DECODER_CTX_add_extra(),
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which will stop adding one more decoder implementations when it has already
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added those that take the specified input type, and functions like
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L<OSSL_DECODER_from_bio(3)>, which will only start the decoding process with
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the decoder implementations that take that input type. For example, if the
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input type is set to C<DER>, a PEM to DER decoder will be ignored.
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The input type can also be NULL, which means that the caller doesn't know
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what type of input they have. In this case, OSSL_DECODER_from_bio() will
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simply try with one decoder implementation after the other, and thereby
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discover what kind of input the caller gave it.
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For every decoding done, even an intermediary one, a constructor provided by
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the caller is called to attempt to construct an appropriate type / structure
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that the caller knows how to handle from the current decoding result.
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The constructor is set with OSSL_DECODER_CTX_set_construct().
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B<OSSL_DECODER_INSTANCE> is an opaque structure that contains data about the
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decoder that was just used, and that may be useful for the constructor.
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There are some functions to extract data from this type, described further
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down.
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=head2 Functions
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OSSL_DECODER_CTX_new() creates a new empty B<OSSL_DECODER_CTX>.
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OSSL_DECODER_settable_ctx_params() returns an L<OSSL_PARAM(3)> array of
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parameter descriptors.
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OSSL_DECODER_CTX_set_params() attempts to set parameters specified with an
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L<OSSL_PARAM(3)> array I<params>. These parameters are passed to all
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decoders that have been added to the I<ctx> so far. Parameters that an
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implementation doesn't recognise should be ignored by it.
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OSSL_DECODER_CTX_free() frees the given context I<ctx>.
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OSSL_DECODER_CTX_add_decoder() populates the B<OSSL_DECODER_CTX> I<ctx> with
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a decoder, to be used to attempt to decode some encoded input.
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OSSL_DECODER_CTX_add_extra() finds decoders that generate input for already
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added decoders, and adds them as well. This is used to build decoder
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chains.
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OSSL_DECODER_CTX_set_input_type() sets the starting input type. This limits
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the decoder chains to be considered, as explained in the general description
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above.
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OSSL_DECODER_CTX_set_input_structure() sets the name of the structure that
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the input is expected to have. This may be used to determines what decoder
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implementations may be used. NULL is a valid input structure, when it's not
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relevant, or when the decoder implementations are expected to figure it out.
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OSSL_DECODER_CTX_get_num_decoders() gets the number of decoders currently
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added to the context I<ctx>.
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OSSL_DECODER_CTX_set_construct() sets the constructor I<construct>.
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OSSL_DECODER_CTX_set_construct_data() sets the constructor data that is
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passed to the constructor every time it's called.
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OSSL_DECODER_CTX_set_cleanup() sets the constructor data I<cleanup>
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function. This is called by L<OSSL_DECODER_CTX_free(3)>.
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OSSL_DECODER_CTX_get_construct(), OSSL_DECODER_CTX_get_construct_data() and
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OSSL_DECODER_CTX_get_cleanup() return the values that have been set by
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OSSL_DECODER_CTX_set_construct(), OSSL_DECODER_CTX_set_construct_data() and
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OSSL_DECODER_CTX_set_cleanup() respectively.
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OSSL_DECODER_export() is a fallback function for constructors that cannot
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use the data they get directly for diverse reasons. It takes the same
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decode instance I<decoder_inst> that the constructor got and an object
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I<reference>, unpacks the object which it refers to, and exports it by
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creating an L<OSSL_PARAM(3)> array that it then passes to I<export_cb>,
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along with I<export_arg>.
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=head2 Constructor
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A B<OSSL_DECODER_CONSTRUCT> gets the following arguments:
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=over 4
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=item I<decoder_inst>
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The B<OSSL_DECODER_INSTANCE> for the decoder from which the constructor gets
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its data.
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=item I<object>
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A provider-native object abstraction produced by the decoder. Further
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information on the provider-native object abstraction can be found in
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L<provider-object(7)>.
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=item I<construct_data>
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The pointer that was set with OSSL_DECODE_CTX_set_construct_data().
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=back
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The constructor is expected to return 1 when the data it receives can be
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constructed, otherwise 0.
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These utility functions may be used by a constructor:
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OSSL_DECODER_INSTANCE_get_decoder() can be used to get the decoder
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implementation from a decoder instance I<decoder_inst>.
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OSSL_DECODER_INSTANCE_get_decoder_ctx() can be used to get the decoder
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implementation's provider context from a decoder instance I<decoder_inst>.
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OSSL_DECODER_INSTANCE_get_input_type() can be used to get the decoder
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implementation's input type from a decoder instance I<decoder_inst>.
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OSSL_DECODER_INSTANCE_get_input_structure() can be used to get the input
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structure for the decoder implementation from a decoder instance
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I<decoder_inst>.
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This may be NULL.
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=head1 RETURN VALUES
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OSSL_DECODER_CTX_new() returns a pointer to a B<OSSL_DECODER_CTX>, or NULL
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if the context structure couldn't be allocated.
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OSSL_DECODER_settable_ctx_params() returns an L<OSSL_PARAM(3)> array, or
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NULL if none is available.
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OSSL_DECODER_CTX_set_params() returns 1 if all recognised parameters were
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valid, or 0 if one of them was invalid or caused some other failure in the
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implementation.
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OSSL_DECODER_CTX_add_decoder(), OSSL_DECODER_CTX_add_extra(),
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OSSL_DECODER_CTX_set_construct(), OSSL_DECODER_CTX_set_construct_data() and
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OSSL_DECODER_CTX_set_cleanup() return 1 on success, or 0 on failure.
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OSSL_DECODER_CTX_get_construct(), OSSL_DECODER_CTX_get_construct_data() and
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OSSL_DECODER_CTX_get_cleanup() return the current pointers to the
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constructor, the constructor data and the cleanup functions, respectively.
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OSSL_DECODER_CTX_num_decoders() returns the current number of decoders. It
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returns 0 if I<ctx> is NULL.
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OSSL_DECODER_export() returns 1 on success, or 0 on failure.
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OSSL_DECODER_INSTANCE_decoder() returns an B<OSSL_DECODER> pointer on
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success, or NULL on failure.
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OSSL_DECODER_INSTANCE_decoder_ctx() returns a provider context pointer on
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success, or NULL on failure.
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=head1 SEE ALSO
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L<provider(7)>, L<OSSL_DECODER(3)>, L<OSSL_DECODER_from_bio(3)>
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=head1 HISTORY
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The functions described here were added in OpenSSL 3.0.
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=head1 COPYRIGHT
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Copyright 2020 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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