`deflate.gzip`

gzip (RFC 1952) framing over the raw DEFLATE in raw.mojo.

gunzip decodes a whole .gz file: every member of a concatenated stream, each one's header (all five flags: FTEXT, FHCRC, FEXTRA, FNAME, FCOMMENT) parsed and skipped, and each one's CRC-32 and ISIZE checked against what it decoded to. gunzip_at decodes one member and reports where it ended, as inflate_at does for raw streams. gzip writes a single member.

The CRC-32 is the zlib/gzip one (reflected polynomial 0xEDB88320), slice-by-8 as in hashes.mojo's crc32. It is repeated here rather than imported so the tin keeps no sibling dependency: a consumer still needs nothing but -I deflate.mojo/src.

Functions

`crc32_backend`

def crc32_backend() -> String

armv8-crc or slice-by-8: which CRC-32 this build uses.

`gunzip`

def gunzip(data: Span[UInt8]) -> List[UInt8]

Decompress a gzip file: all of its members, concatenated.

Each member's CRC-32 and length are verified. Zero bytes after the last member are padding (as gzip(1) and Python's gzip accept); anything else there raises, as does an empty input.

`gunzip_at`

def gunzip_at(data: Span[UInt8], mut end: Int) -> List[UInt8]

Decompress the one gzip member at the start of data, verifying its CRC-32 and length, and set end to the offset just past its trailer.

For walking a multi-member file one member at a time, so only one member's output is held at once:

var pos = 0
while pos < len(data):
    var end = 0
    var part = gunzip_at(Span(data)[pos:], end)
    pos += end

`gzip`

def gzip(data: Span[UInt8], level: Int = Int(6)) -> List[UInt8]

Compress data into a single gzip member.

level 0 writes stored (uncompressed) DEFLATE blocks; 1 to 9 all use deflate's one fixed-Huffman strategy, so they produce the same bytes. The header carries no name, comment or timestamp (MTIME 0, OS 255).