OSSL_DISPATCH(3ossl)

💖 NAME 💖

okay so bestie, this page is OSSL_DISPATCH(3ossl) — the OpenSSL Core type that defines a dispatchable function table — and it also covers OSSL_DISPATCH_END, the macro that says “we’re done here, periodt.”

✨ SYNOPSIS ✨

#include <openssl/core.h>

typedef struct ossl_dispatch_st OSSL_DISPATCH;
struct ossl_dispatch_st {
    int function_id;
    void (*function)(void);
};

#define OSSL_DISPATCH_END

🦋 DESCRIPTION 🦋

This type is literally a tuple of function identity and function pointer. Arrays of this type get passed between the OpenSSL libraries and the providers to describe what functionality one side provides to the other.

⚠️ No cap: arrays of this type must be terminated with the OSSL_DISPATCH_END macro.

🌸 OSSL_DISPATCH fields 🌸

• function_id — the OpenSSL-defined function identity of the implemented function.
• function — pointer to the implemented function itself. Even though this field has a generic definition, the function it points to must have a function signature that corresponds to the function_id.

Available function identities and corresponding function signatures are defined in openssl-core_dispatch.h(7). Furthermore, the chosen function identities and associated function signature must be chosen specifically for the operation that it’s intended for, as determined by the intended OSSL_ALGORITHM(3) array.

Any function identity not recognised by the recipient of this type will be ignored. This ensures that providers built with one OpenSSL version in mind will work together with any other OpenSSL version that supports this mechanism. slay for compatibility 💅

👀 SEE ALSO 👀

crypto(7), openssl-core_dispatch.h(7), OSSL_ALGORITHM(3)

🎀 HISTORY 🎀

OSSL_DISPATCH was added in OpenSSL 3.0.

💜 COPYRIGHT 💜

Copyright 2022-2023 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 https://www.openssl.org/source/license.html.

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Signing off from OpenSSL 3.5.0, dated 2026-09-25 — OSSL_DISPATCH(3ossl) out 💅✨