LZ4_compress_default(9)

📦 version 7.3.1, in nixpkgs unstable

💜 LZ4_compress_default(9) — like, the Kernel API Manual page, bestie

okay so picture this: you're in the kernel, your data is way too chunky, and this little icon is here to squeeze it down. welcome to LZ4_compress_default(9). it's glorious, it's fast, and it's lowkey the main character of the LZ4 lineup ✨

🌸 NAME 🌸

LZ4_compress_default — compress data from source to dest. that's it, that's the vibe 💅

🎀 SYNOPSIS 🎀

int LZ4_compress_default (const char *source , char *dest , int
inputSize , int maxOutputSize , void *wrkmem );

yeah. five arguments. don't panic, we're gonna go through each one together 🫶

🦋 ARGUMENTS 🦋

  • source — the source address of the original data. i.e. the raw, un-smooshed stuff you're trying to shrink 💖
  • dest — output buffer address of the compressed data. this is where the glow-up lands ✨
  • inputSize — size of the input data. max supported value is LZ4_MAX_INPUT_SIZE — go past that and it's giving "no ❤️" 😭
  • maxOutputSize — the full or partial size of buffer dest. be so fr when you set this, because the buffer must be already allocated — no take-backs, no auto-growing 🙈
  • wrkmem — address of the working memory. this one requires 'workmem' of LZ4_MEM_COMPRESS (yes, the page spells it 'workmem' there and wrkmem in the parameter — she contains multitudes 🌈). think of it as the little backstage area where the compression gets ready 😌

🔥 DESCRIPTION 🔥

so here's the tea: it compresses 'sourceSize' bytes from buffer 'source' into the already-allocated 'dest' buffer of size 'maxOutputSize'. 💫

and here's a line straight from the page, word for word, because she's iconic and also a little bit of a sentence-fragment queen: Compression is guaranteed to succeed if It also runs faster, so it's a recommended setting. like, yes ma'am, we love a confident queen 💅 (that's literally how it's written — not me, blame the source 🫶)

now the dramatic part: if the function cannot compress 'source' into a more limited 'dest' budget, compression stops *immediately*, and the function result is zero. periodt. 💀

and as a consequence — this matters, bestie — 'dest' content is not valid in that case. do not go reading it, do not go trusting it, do not go passing it to your friends. it is not the moment. 🙅‍♀️

⭐ RETURN ⭐

it hands you back the number of bytes written into buffer 'dest' — necessarily <= maxOutputSize, so it never overstays its welcome — or 0 if compression fails. zero means "we don't have the budget for this, conversation over" 😭

🌈 SEE ALSO 🌈

the kernel file: ./include/linux/lz4.h — that's the mothership 👑

and the whole extended friend group:

twenty of them. i counted. go read them, iykyk 📚💖

and that's the whole page, bestie 🧚 from ./include/linux, dated October 2026, sitting pretty at version LZ4_compress_default(9). slay, bye 🎀💜

📦 where this page comes from