bytevector-fill!(3scm)

💖 bytevector-fill!(3scm) 💖

okay so bestie, welcome to the Scheme Programmer's Manual — yes that's the actual manual name, she's fancy, we love her — and today's main character is bytevector-fill!. Buckle up 🎀

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✨ NAME ✨

bytevector-fill! — fill a bytevector with a value. that's it. that's the whole gig. and she ate 💅

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📚 LIBRARY 📚

import her like this, depending on your era:

(import (rnrs))                     ;R6RS
(import (rnrs bytevectors))         ;R6RS

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🦋 SYNOPSIS 🦋

(bytevector-fill! bytevector fill)

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🌸 DESCRIPTION 🌸

so what she does is: this procedure stores fill in every single element of bytevector. every one. no cap. 💯

the fill value has to be an exact integer living in the interval [-128, 255]. and the negative fill values? they get interpreted as bytes, viz.:

(bytevector-fill! bytevector (bitwise-and fill #xff))

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🫶 RETURN VALUES 🫶

returns unspecified values. she gives you nothing back, she's mysterious like that 🙈

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⭐ EXAMPLES ⭐

(let ((a (u8-list->bytevector '(1 2 3))))
  (bytevector-fill! a 0)
  a)
   => #vu8(0 0 0)

see how she just zeroed the whole thing out? iconic 🎀

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👑 APPLICATION USAGE 👑

ok so this one's kinda the "responsible bestie" move: this procedure is sometimes useful to clear sensitive parts of memory, like bytevectors holding cryptographic keys. 🔐

but bestie listen — this is optimistic but is not in any way guaranteed to wipe the data from memory. 😭 so like, don't @ me if your keys are still lurking, fr fr.

also, heads up: a bytevector that contains the specified value would normally be created from scratch with make-bytevector(3scm).

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🌈 COMPATIBILITY 🌈

the only difference in behavior between implementations should be in how fast it runs. that's it. that's the drama. and just so you know — this procedure is not present in R7RS-small. 🫠

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💀 ERRORS 💀

she can raise exceptions with the following condition types:

• &assertion (R6RS) — the wrong number of arguments was passed or an argument was outside its domain. basically: you fumbled the input, bestie 🤷‍♀️

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🔥 SEE ALSO 🔥

• vector-fill!(3scm)
• make-bytevector(3scm)

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💜 STANDARDS 💜

R6RS ⭐

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🧚 AUTHORS 🧚

This page is part of the scheme-manpages project. It includes materials from the RnRS documents. More information can be found at https://github.com/schemedoc/manpages/.

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and that's the whole vibe check, bestie 💖 mwah, go fill those bytevectors responsibly — this page is from 2021-02-23 and it's bytevector-fill!(3scm) all day, every day 🍓✨