able to get chunk Index from Index, fix writer

[helinwang]

No description provided.

[wangkuiyi]

dummyCloser ==> noopCompressor ?

[helinwang]

Done.

[wangkuiyi]

I think the function should be somehow like the following:

func compressData(src io.Reader, compressorIndex int) (*bytes.Buffer, error) {
        var compressed bytes.Buffer
	var compressor io.WriteCloser

	switch compressorIndex {
	case NoCompression:
		compressor = &noopCompressor{compressed}
	case Snappy:
		compressor = snappy.NewBufferedWriter(compressed)
	case Gzip:
		compressor = gzip.NewWriter(compressed)
	default:
		return nil, fmt.Errorf("Unknown compression algorithm: %d", compressorIndex)
	}

        defer compressor.Close()
	if _, e := io.Copy(compressor, src); e != nil {
		return nil, fmt.Errorf("Failed to compress chunk data: %v", e)
	}

	return &compressed, nil
}

The point is that compressed is still of type bytes.Buffer, and we just create a noopCompressor which works like snappy.Writer and gzip.Writer.

[helinwang]

Much better, thanks! Done.

[wangkuiyi]

Can we merge this const group with the previous one?

[helinwang]

Done.

[wangkuiyi]

Is this snippet for debugging? Should we remove it?

[helinwang]

Yes, done.

[wangkuiyi]

== -1 ==> < 0 ?

[helinwang]

Done.