LIBKECCAK_ZEROCOPY_UPDATE(3)

💖 NAME

Okay so this page is LIBKECCAK_...COPY_UPDATE(3) from the LIBKECCAK Library Functions Manual, and it’s all about libkeccak_zerocopy_update — partially hash a message without copying. (ADVANCED). Bestie, this one is giving low-level main character energy. 💅

📜 SYNOPSIS

#include <libkeccak.h>

void libkeccak_zerocopy_update(struct libkeccak_state *state, const void *msg, size_t msglen);

Link with -lkeccak.

✨ DESCRIPTION ✨

libkeccak_zerocopy_update() continues a hash — or starts one, no big deal — for a message. The current hashing state lives in *state, and it gets updated. The message you pass as msg, with the byte-size given by msglen, gets hashed. Slay. 🦋

Here’s the special restriction just for libkeccak_zerocopy_update(): msglen must be an integer multiple of the bitrate divided by eight. That number is returned by libkeccak_zerocopy_chunksize(3). If you need to dodge the restriction, libkeccak_update(3) or libkeccak_fast_update(3) can do it — but heads up, unlike libkeccak_zerocopy_update(), those will copy the message and move around copied data. Periodt.

🫶 RETURN VALUES

libkeccak_zerocopy_update() does not return a value. Like, nothing. Not a crumb. 💀

💀 ERRORS

libkeccak_zerocopy_update() cannot fail. Iconic behavior, honestly. 👑

🌸 NOTES

Neither parameter may be NULL or 0. That is not the vibe. 🙈

It is safe to call libkeccak_zerocopy_update() before libkeccak_update(3), libkeccak_fast_update(3), libkeccak_digest(3), and libkeccak_fast_digest(3) with the same state argument. However, calling libkeccak_zerocopy_update() after libkeccak_update(3) or libkeccak_fast_update(3) may cause the message to be misread. So don’t do that, fr fr. 😭

🌟 NOTES — cSHAKE edition 🌟

For cSHAKE, libkeccak_cshake_initialise(3) must be called, once, immediately after state initialisation; before the first call to libkeccak_zerocopy_update(). That’s the order, bestie. Periodt. 🧚

👀 SEE ALSO

• libkeccak_state_initialise(3)
• libkeccak_cshake_initialise(3)
• libkeccak_zerocopy_chunksize(3)
• libkeccak_fast_update(3)
• libkeccak_update(3)
• libkeccak_fast_digest(3)
• libkeccak_zerocopy_digest(3)
• libkeccak_digest(3)

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💖 cute sign-off: this gem is from the LIBKECCAK manual, page LIBKECCAK_...COPY_UPDATE(3), and the footer does not print a date — so here’s your source/version + date acknowledgement: LIBKECCAK, LIBKECCAK_...COPY_UPDATE(3), date not shown in the original footer. Bye bestie, go hash something beautiful. 🎀✨