#!/bin/sh
# Ensure that reference compressed files are still decompressible, and
# that their corresponding inputs still compress to precisely the same bytes.
# For a "normal" compression program, one must not require that the encoded
# bytes remain the same. The compression algorithm may change. What normally
# matters is solely that the decompressed result is the same as the input
# to the compressor. However, here, with gzip's current moribund state,
# it is fine to require that. In particular, this test ensures that
# a CRC-perf change doesn't accidentally cause trouble. It's not enough
# that gzip decompress files the compressor has just created: it must
# continue to decompress old compressed outputs, too.

# Copyright 2024-2026 Free Software Foundation, Inc.

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.
# limit so don't run it by default.

. "${srcdir=.}/init.sh"; path_prepend_ ..

od -An -tx1 </dev/null || skip_ "od does not support -An and -tx1"

fail=0

cat <<EOF > exp || framework_failure_
: 1f 8b 08 00 00 00 00 00 00 03 03 00 00 00 00 00 00 00 00 00
a: 1f 8b 08 00 00 00 00 00 00 03 4b 04 00 43 be b7 e8 01 00 00 00
b: 1f 8b 08 00 00 00 00 00 00 03 4b 02 00 f9 ef be 71 01 00 00 00
c: 1f 8b 08 00 00 00 00 00 00 03 4b 06 00 6f df b9 06 01 00 00 00
yyy: 1f 8b 08 00 00 00 00 00 00 03 ab ac ac 04 00 ea 81 45 73 03 00 00 00
zzzzzzzzzzz: 1f 8b 08 00 00 00 00 00 00 03 ab aa 82 03 00 55 97 5b a7 0b 00 00 00
EOF

# Ensure that compressing these simple strings always produces the same bytes.
for i in '' a b c yyy zzzzzzzzzzz; do
  echo $i: $(printf %s "$i" | gzip | od -An -tx1)
done > out || framework_failure_

compare exp out || fail=1

# Each output stream must inflate the original input.
for i in '' a b c yyy zzzzzzzzzzz; do
  in=$(printf %s "$i" | gzip | gzip -d)
  test "$i" = "$in" || fail=1
done

Exit $fail