hmac_sha256_update(9)

💅 hmac_sha256_update — bestie's field guide

okay so this is hmac_sha256_update(9) from the Kernel API Manual, and honestly? she's a little icon. lowkey one of the hardest-working functions in the whole crypto family and she doesn't even need a big speech. let's get into it 🎀

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✨ NAME ✨

hmac_sha256_update — the girlies who feed message data into an HMAC-SHA256 context. that's literally her whole job. update an HMAC-SHA256 context with message data, periodt 💅

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🌸 SYNOPSIS 🌸

void hmac_sha256_update (struct hmac_sha256_ctx *ctx , const u8 *data ,
size_t data_len );

look at her. three params, no drama, void return because she's not here to give you results, she's here to do the work. main character energy fr ✨

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🦋 ARGUMENTS 🦋

• ctx — the HMAC context you're updating. and listen, bestie, this one is non-negotiable: it must have been initialized first. no initializing, no updating. that's the rule 🙈
• data — the message data itself. the actual content. the payload. the moment 💖
• data_len — how long data is, measured in bytes. don't guess, don't vibe-check it, just tell her the length 🌸

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⭐ DESCRIPTION ⭐

This can be called any number of times.

that's it. that's the whole description. she's confident, she doesn't over-explain, she just lets you call her as many times as you need 🔥 like okay versatility queen!!

no cap, "any number of times" is doing a lot of heavy lifting here — you can keep feeding her chunks of data over and over and she'll just keep updating the context like the absolute icon she is 👑

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🌈 CONTEXT 🌈

Any context. all of them. every single one. she does not discriminate, she does not gatekeep, she is welcome everywhere 🫶✨

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👑 SEE ALSO 👑

Kernel file ./include/crypto/sha2.h — plus a whole extended family, because the sha2 crew is large and they all show up to the group chat:

• struct sha224_ctx(9)
• sha224_init(9)
• sha224_update(9)
• sha224_final(9)
• sha224(9)
• struct hmac_sha224_key(9)
• struct hmac_sha224_ctx(9)
• hmac_sha224_preparekey(9)
• hmac_sha224_init(9)
• hmac_sha224_init_usingrawkey(9)
• hmac_sha224_update(9)
• hmac_sha224_final(9)
• hmac_sha224(9)
• hmac_sha224_usingrawkey(9)
• struct sha256_ctx(9)
• sha256_init(9)
• sha256_update(9)
• sha256_final(9)
• sha256(9)
• sha256_finup_2x(9)
• sha256_finup_2x_is_optimized(9)
• struct hmac_sha256_key(9)
• struct hmac_sha256_ctx(9)
• hmac_sha256_preparekey(9)
• hmac_sha256_init(9)
• hmac_sha256_init_usingrawkey(9)
• hmac_sha256_final(9)
• hmac_sha256(9)
• hmac_sha256_usingrawkey(9)
• struct sha384_ctx(9)
• sha384_init(9)
• sha384_update(9)
• sha384_final(9)
• sha384(9)
• struct hmac_sha384_key(9)
• struct hmac_sha384_ctx(9)
• hmac_sha384_preparekey(9)
• hmac_sha384_init(9)
• hmac_sha384_init_usingrawkey(9)
• hmac_sha384_update(9)
• hmac_sha384_final(9)
• hmac_sha384(9)
• hmac_sha384_usingrawkey(9)
• struct sha512_ctx(9)
• sha512_init(9)
• sha512_update(9)
• sha512_final(9)
• sha512(9)
• struct hmac_sha512_key(9)
• struct hmac_sha512_ctx(9)
• hmac_sha512_preparekey(9)
• hmac_sha512_init(9)
• hmac_sha512_init_usingrawkey(9)
• hmac_sha512_update(9)
• hmac_sha512_final(9)
• hmac_sha512(9)
• hmac_sha512_usingrawkey(9)

like i said. large family. iykyk 🧚

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💀 friendly reminder before you go: ctx must have been initialized. that's not a suggestion, that's the whole vibe check. do not skip it, do not pass go, do not collect $200.

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and that's the page, bestie!! brought to you by the source at ./include/crypto, dated October 2026, and of course our girl hmac_sha256_update(9) herself. slay, ate, no crumbs. 💖✨🎀