gogzip

gogzip

An implementation of gzip in Go.

gzip was first publicly released in 31 October 1992. It was developed as part as free software under the GNU licence.

The algorithm was written to allow for decompression while streaming. I have not been able to do streaming (buffered) compression. It may be possible but I have not yet found the answer to this issue.

This is not finished. My goal with this is to improve my knowledge of i/o, readers, writers, files, and compression.

I have tried to implement buffered gzipping but so far the output produced by this has been invalid. This means that each file is read in fully then written out.

This implementation will handle compression and decompression. I will have to look closely at the original specification and decide what would make sense to implement.

Usage

• gogzip -h - print usage
• gogzip <file1> <file2> - gzip files and delete originals
• gogzip -k <file1> <file2> - do not delete original file
• gogzip -c - gzip standard input and send to standard output - with no files specified and with uncompressed stdin the -c flag is set to true
  • gogzip --stdout - gzip standard input and send to standard output
• gogzip -d <file1> <file2> - decompress instead of gzip
• gogzip -l <file1> <file2> - use compression level 0-9 with 0 being no compression
• gogzip -q <file1> <file2> - quiet output (no complaints for invalid input)
• gogzip -L <file1> <file2> - give summary information for listed files
• gogzip -t <file1> <file2> - test file list integrity
• gogzip -f <file1> <file2> - force overwrite etc. - implemented when file would be overriden

Notes

BSD gzip will forward to stdout if there is non-gzipped stdin. GNU gzip will not. I have implemented gogzip to behave like BSD in this way.

Building and Running

The app can be built by typing the command below. If you have an older version of Go installed you can change the version number in go.mod if there is a complaint on trying to compile. This should be compatible with earlier versions of Go like 1.14 and 1.15 though I have not checked. This app does not use embedding, which appeared in Go 1.16.

go build .

The app can be run without building by typing

go run gogzip.go

There are some tests which can be run by typing

go test -v .

Simple tests

As currently implemented, BSD gzip is faster.

$: time for i in {1..1000}; do ./gogzip -k sample/1.txt; done

real	0m4.684s
user	0m2.125s
sys	0m2.014s

$: time for i in {1..1000}; do gzip -k -f sample/1.txt; done

real	0m2.616s
user	0m0.943s
sys	0m1.517s

Notes

The argument parsing library used here does not deal with arguments such as -1, -2, -, etc. It may be that an argument will need to have a different identifier to work around this.

-- Ian Marsman