OSSL_DECODER(3ossl)

💅 OSSL_DECODER — like, the decoder method routines (OpenSSL, `3ossl`, bestie)

okay so this page is your whole guide to OSSL_DECODER and its glam little friend group of functions. it's 3ossl documentation, meaning it's an OpenSSL manual page — yes we're being fancy today ✨

🦋 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. that's the whole squad, no one left behind 🫶

✨ 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[]);

like, just look at it. gorgeous. iconic. copy it exactly tho, don't be creative with the signatures 😭

💖 DESCRIPTION

OSSL_DECODER is a method for decoders — and a decoder is the thing that knows how to take encoded data and turn it into an object of some type that the rest of OpenSSL actually knows how to handle. it's giving translator energy, fr fr 🧚

OSSL_DECODER_fetch() — looks for an algorithm within the provider that's been loaded into the OSSL_LIB_CTX given by ctx, having the name given by name and the properties given by properties. the 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 the known properties and the values they may have, go peek at "Names and properties" in provider-encoder(7) 👀
OSSL_DECODER_up_ref() — increments the reference count for the given decoder. love a ref count going up, we stay winning 📈
OSSL_DECODER_free() — decrements the reference count for the given decoder, and when the count reaches zero, frees it. if the argument is NULL, nothing is done. she's chill like that 💅
OSSL_DECODER_get0_provider() — returns the provider of the given decoder.
OSSL_DECODER_get0_properties() — returns the property definition associated with the given decoder.
OSSL_DECODER_is_a() — checks if decoder is an implementation of an algorithm that's identifiable with name.
OSSL_DECODER_get0_name() — returns the name used to fetch the given decoder.
OSSL_DECODER_get0_description() — returns a description of the decoder, meant for display and human consumption. the description is totally at the discretion of the decoder implementation, so it's a vibes-based field ngl 🙈
OSSL_DECODER_names_do_all() — traverses all names for the given decoder, and calls fn with each name and data as arguments.
OSSL_DECODER_do_all_provided() — traverses all decoder implementations by all activated providers in the library context libctx, and for each of the implementations, calls fn with the implementation method and arg as arguments. it's a whole tour of the ecosystem 🌈
OSSL_DECODER_gettable_params() — returns an OSSL_PARAM(3) array of parameter descriptors.
OSSL_DECODER_get_params() — attempts to get parameters specified with an OSSL_PARAM(3) array params. parameters that the implementation doesn't recognise should be ignored. no drama, just skip 'em 🎀

👑 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. she just does her thing ✨
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 decoder was identifiable, otherwise 0.
OSSL_DECODER_get0_name() — returns the algorithm name from the provided implementation for the given decoder. note that the 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 decoder object and should not be freed by the caller. like, hands off, it's not yours 🫵
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. important distinction, don't misread it bestie 😭

🌸 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. so like, she might already be at the party and you didn't even send the invite 💀

🔥 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);

that's the whole thing, verbatim, don't touch a character 🔒

🎀 SEE ALSO

provider(7), OSSL_DECODER_CTX(3), OSSL_DECODER_from_bio(3), OSSL_DECODER_CTX_new_for_pkey(3), OSSL_LIB_CTX(3) — go read those next, they're all part of the lore 📚

💜 HISTORY

the functions described here were added in OpenSSL 3.0. vintage but make it fresh ⭐

🍓 COPYRIGHT

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 <https://www.openssl.org/source/license.html>.

okay that's the page!! this version of the docs is from 3.5.0, dated 2026-09-25 — mwah, go decode something cute, bestie 💖🦋✨

📦 where this page comes from

opensuse-leap 16.0: openssl-3-doc 3.5.0-160000.11.1 · Apache-2.0
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-04: a language model's rewrite of the original, under its terms