support decompressing concatenated gzip files

[sisong]

ref ebiggers#335 (comment)

[sisong]

@ghuls
it's ok

[ghuls]

It does not work for all concatenated gzip files. For example compressing the pgzip binary and creating a gzip file with multiple concatenated gzip files, does not work after appending it for the third time.

$ gzip -c pgzip/pgzip > compressed_pgzip_multiple.gz
$ gzip -c pgzip/pgzip >> compressed_pgzip_multiple.gz

# Decompress gzip file with 2 gzip archives.
$ zcat compressed_pgzip_multiple.gz | wc -c
339424

$ pgzip/pgzip -cd compressed_pgzip_multiple.gz | wc -c
339424

$ gzip -c pgzip/pgzip >> compressed_pgzip_multiple.gz

# Decompress gzip file with 3 gzip archives.
$ zcat compressed_pgzip_multiple.gz | wc -c
509136

$ pgzip/pgzip -cd compressed_pgzip_multiple.gz | wc -c
pgzip: 
ERROR: gzips_decompress_by_stream_mt() error code 1


262144

$ build/programs/libdeflate-gzip -cd compressed_pgzip_multiple.gz | wc -c
509136

Another example:

echo 1 | gzip -c > multiple_gzip_header.gz
echo 2 | gzip -c >> multiple_gzip_header.gz
echo 3 | gzip -c >> multiple_gzip_header.gz

$ pgzip/pgzip -cd multiple_gzip_header.gz 
1
2
3

$ echo 4 | gzip -c >> multiple_gzip_header.gz

$ pgzip/pgzip -cd multiple_gzip_header.gz 
pgzip: 
ERROR: gzips_decompress_by_stream_mt() error code 1

[sisong]

you updated source code to last commit?

[ghuls]

you updated source code to last commit?

Yes: 0603f39cf2b003b8e928d11ee27ffd8b8f42de5b

compressed_pgzip_multiple.gz

[sisong]

Thank you, I fixed this bug