compress

gzip, zlib and raw DEFLATE, over zlib (-lz, added only when a program imports compress).

import "compress";

let gr = compress.gzip(body);
guard let gz = gr else let e = err_of(gr) { log.error(e); return; }

// decompression ALWAYS takes a ceiling -- see below
let ur = compress.gunzip(payload, 4194304);        // 4 MiB
guard let plain = ur else let e = err_of(ur) {
    log.warn("rejected: " + e);                     // names the limit
    return;
}

Decompression takes a mandatory output limit. max_out is a required argument, not an optional one with a generous default. The expansion ratio is unbounded — 65 KB of gzip holds 64 MB of output, and that ratio goes much further — so a program that decompresses anything it did not itself produce is one hostile input away from the OOM killer. The ceiling is enforced before the allocation that would cross it, not by inspecting the result afterwards: rejecting a 64 MB bomb was measured at 3.9 MB peak RSS against a 0.86 MB baseline. A default here would be a number nobody chose, applied at every call site that never thought about it.

Three containers, because HTTP needs all three. They are the same compressed bits under different headers: gzip (RFC 1952) is what servers send; zlib (RFC 1950) is what the deflate content-coding is supposed to mean; raw (RFC 1951, no header) is what the servers that get it wrong send instead — which is why inflate_raw exists rather than being a purist's omission. They are not interchangeable, and each decoder says so rather than producing garbage.

Backed by zlib rather than written here, unlike regex. That package was written in-house because a backtracking engine has a catastrophic input class and being immune to it by construction was the point. DEFLATE has no equivalent argument — what it has is thirty years of hostile input and a reference implementation on every platform slang targets. A hand-written inflate would be a memory-safety surface with no upside, since every bug in one is a buffer overrun driven by attacker-controlled input.

API#