proposal: compress: add Compress and Decompress convenience functions

[dsnet]

Filing on behalf of an internal user, who requests that we add convenience wrappers of Compress and Decompress:

func Decompress(b []byte) ([]byte, error) {
    rd, err := NewReader(bytes.NewReader(b))
    if err != nil {
        return nil, err
    }
    d, err := ioutil.ReadAll(rd)
    if cerr := rd.Close(); err == nil {
        err = cerr
    }
    return d, err
}

What are people's thoughts?

[nhooyr]

If we do this, we should use a sync.Pool for the readers.

[bradfitz]

Maybe things have changed, but I would expect pushback for sync.Pool use.

[odeke-em]

Just like net/http has:

• Get.
• Post.
• Head.
• PostForm

etc
that underlyingly use the default client's methods perhaps each compress package could have its own Compress and Decompress convenience functions, instead of a default of zlib?

• compress/zlib.[Compress, Decompress]
• compress/lzw.[Compress, Decompress]
• compress/gzip.[Compress, Decompress]
• compress/bzip2.[Compress, Decompress]

Apologies if am preaching to the choir but it wasn't straight forward for me from your example if the convenience functions would be in the top level compress or in each package.

[dsnet]

@odeke-em, the suggestion in the original post is for exactly what you listed out. Thanks for the asking to clarify.

[ulikunitz]

If convenience functions are required for compression packages I suggest the alternatives:

func Compress(w io.Writer, data []byte) error
func Decompress(r io.Reader) (data []byte, err error)

These functions would have more use cases and are very easy to use with a bytes.Buffer or a bytes.Reader.

var buf bytes.Buffer
err := Compress(&buf, data)

data, err := Decompress(bytes.NewReader(compressedData))

BTW Decompression doesn't need the Close call. It doesn't do anything useful. Depending on the compression package Close for a reader either sets the reader to closed or returns the last returned error if its not io.EOF. IMHO returning a io.ReadCloser for a decompressor is a design error. The bzip2 package does the right thing and returns only an io.Reader.

[bradfitz]

Yeah, I don't think helpers which slurp everything to memory are helpful. You're compressing it in the first place because it's large, so pulling it all into memory when it's almost certainly large is not a good idea.

I think the existing Reader- & Writer-based interfaces are the right answer.

Maybe we just need more documentation?

[bradfitz]

Sorry, going to close this one. We already have @ulikunitz's func Decompress in the form of ioutil.ReadAll anyway.