# Can Blosc.jl only decompress content that it has compressed?

**URL:** https://discourse.julialang.org/t/can-blosc-jl-only-decompress-content-that-it-has-compressed/31141
**Category:** General Usage
**Created:** [November 16, 2019, 1:07am UTC](https://discourse.julialang.org/t/can-blosc-jl-only-decompress-content-that-it-has-compressed/31141 "2019-11-16T01:07:11Z")
**Posts on this page:** 4
**Page:** 1

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### Author: ![xiaodai](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/xiaodai/32/15937_2.png) [@xiaodai](https://discourse.julialang.org/u/xiaodai)
#### Post date: [November 16, 2019, 1:07am UTC](https://discourse.julialang.org/t/can-blosc-jl-only-decompress-content-that-it-has-compressed/31141/1 "2019-11-16T01:07:11Z")

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I have been using Blocs.jl and it’s quite awesome. I am trying to make passing compressed data between Python, Julia, and R easier so I was looking for compression format that can used in all of them.

I tried to compress something using LZ4 in R

```r
xc = sample(10:20, 1e6, replace = TRUE)
x <- writeBin(xc, raw())

xc1= qs::lz4_compress_raw(x, 1)
writeBin(xc1, "c:/data/ok.io")

qs::lz4_decompress_raw(xc1)

```

As you can see, I can read them in R fine. However, I can’t read them using CodecLz4.jl as the particular lz format isn’t supported yet, see [https://github.com/invenia/CodecLz4.jl/issues/25](https://github.com/invenia/CodecLz4.jl/issues/25)

So I tried Blosc.jl as the comment seems to suggest

```julia
using Blosc
comp = open("c:/data/ok.io", "r") do io
	read(io)
end

Blosc.set_compressor("lz4")
Blosc.decompress(UInt8, comp) # returns 0 length array

Blosc.set_compressor("lz4hc")
Blosc.decompress(UInt8, comp) # return 0 length arrray

```

So I want to know if Blosc.jl can only read content that it has compressed? How do I change the inptu content so that Blosc.jl can decompress the lz4 content produced by other lz4 compressors in other languages?

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<div class="post-metadata">

### Author: ![davidanthoff](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/davidanthoff/32/223493_2.png) [@davidanthoff](https://discourse.julialang.org/u/davidanthoff)
#### Post date: [November 16, 2019, 1:49am UTC](https://discourse.julialang.org/t/can-blosc-jl-only-decompress-content-that-it-has-compressed/31141/2 "2019-11-16T01:49:52Z")

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You could also look at [https://github.com/bicycle1885/Snappy.jl](https://github.com/bicycle1885/Snappy.jl). Not sure whether it supports the particular format you need, but in general it has worked well for parquet.

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### Author: ![stevengj](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stevengj/32/71_2.png) [@stevengj](https://discourse.julialang.org/u/stevengj)
#### Post date: [November 16, 2019, 2:52am UTC](https://discourse.julialang.org/t/can-blosc-jl-only-decompress-content-that-it-has-compressed/31141/3 "2019-11-16T02:52:03Z")

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Even you set a different compressor to use under the hood, IIRC blosc expects the data to use its own header format.

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<div class="post-metadata">

### Author: ![xiaodai](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/xiaodai/32/15937_2.png) [@xiaodai](https://discourse.julialang.org/u/xiaodai)
#### Post date: [November 16, 2019, 2:55am UTC](https://discourse.julialang.org/t/can-blosc-jl-only-decompress-content-that-it-has-compressed/31141/4 "2019-11-16T02:55:06Z")

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> [@stevengj](#):
>
> own header format.

Would appreciate pointers to the documentation, my google-fu isn’t turning up much on that.

I guess solution is for a Julia LZ4 implementation that works for all LZ4 formats.