New src/gzip.c implements DEFLATE (RFC 1951) plus the gzip wrapper
(RFC 1952) from the RFC text only. Single-pass inflate, no allocations:
the output buffer doubles as the LZ77 sliding window, so back-references
read from out[out_pos - distance]. Canonical Huffman decode using
counts[] / symbols[] tables, ~10x smaller code than fast lookup tables
which matters in the bootloader. CRC32 + ISIZE verified against the
gzip trailer. Gated by WOLFBOOT_GZIP.
include/gzip.h carries the public entry point plus the RFC-canonical
constants (magic bytes, CM=DEFLATE, fixed Huffman boundaries, EOB
symbol, dynamic block field widths, run-length repeat metadata, CRC32
init/final-XOR, header/trailer sizes, alphabet sizes) so future
maintainers can cross-reference the RFC sections by name instead of
chasing literal numbers.
Tests in tools/unit-tests/unit-gzip.c round-trip 6 corpora through host
gzip(1) and back through wolfBoot_gunzip (empty, short text, all-zeros,
structured text, pseudo-random, ~2 MB kernel-sized). 9 negative cases
cover bad magic, bad CM, reserved FLG bits, truncated header,
truncated DEFLATE body, CRC32 mismatch, ISIZE mismatch, output overflow,
and NULL parameters. All 15 pass under libcheck.
David Garske