compression

问题 So, this is a seemingly simple question, but I'm apparently very very dull. I have a little script that downloads all the .bz2 files from a webpage, but for some reason the decompressing of that file is giving me a MAJOR headache. I'm quite a Python newbie, so the answer is probably quite obvious, please help me. In this bit of the script, I already have the file, and I just want to read it out to a variable, then decompress that? Is that right? I've tried all sorts of way to do this, I

问题 Let me clarify, I'm not talking about perfect compression in the sense of an algorithm that is able to compress any given source material, I realize that is impossible. What I'm trying to get at is an algorithm that is able to encode any source string of bits to it's absolute maximum compressed state, as determined by it's Shannon entropy. I believe I have heard some things about Huffman Coding being in some sense optimal, so I believe that this encryption scheme might be based off that, but

问题 I am told that Huffman coding is used as loseless data compression algorithm , but I am also told that real data compress software do not employ Huffman coding, because if the keys are not distributed decentralized enough, the compressed file could be even larger than the orignal file. This leaves me wondering are there any real-world application of Huffman coding? 回答1: Huffman is widely used in all the mainstream compression formats that you might encounter - from GZIP, PKZIP (winzip etc)

问题 How to use tar and filter the archive through LZ4? Or any available tools? It looks cumbersome to use tar cvf folderABC.tar folderABC && lz4c -c0 folderABC.tar . PS: *nix environment 回答1: lz4 has a command line structure similar to gzip. Therefore, something like this will work : tar cvf - folderABC | lz4 > folderABC.tar.lz4 or tar cvf - folderABC | lz4 - folderABC.tar.lz4 First one compresses silently, like gzip. Second one is a bit more lz4-specific, and will also display summarized

问题 I have this uncompressed byte array: 0E 7C BD 03 6E 65 67 6C 65 63 74 00 00 00 00 00 00 00 00 00 42 52 00 00 01 02 01 00 BB 14 8D 37 0A 00 00 01 00 00 00 00 05 E9 05 E9 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00 00 00 81 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 05 00 00 01 00 00 00 And I need to compress it using the deflate algorithm (implemented in zlib), from what I searched the equivalent in C# would be using GZipStream but I can't match the compressed

问题 I need to send voluminous data in a http post request to a server supporting gziped encoded requests. Starting from a simple public async Task<string> DoPost(HttpContent content) { HttpClient client = new HttpClient(); HttpResponseMessage response = await client.PostAsync("http://myUri", content); response.EnsureSuccessStatusCode(); return await response.Content.ReadAsStringAsync(); } I've just added a pre compression public async Task<string> DoPost(HttpContent content, bool compress) { if

问题 I'm trying to speed up my website. Google insights (https://developers.google.com/speed/pagespeed/insights) tells me that a critical problem is to enable GZip compression. The address of the site is http://user2.net It's based on codeigniter framework. I have enabled gzip compression with folowing changes to my .htaccess file: AddOutputFilterByType DEFLATE text/plain AddOutputFilterByType DEFLATE text/html AddOutputFilterByType DEFLATE text/xml AddOutputFilterByType DEFLATE text/css

问题 I have managed to enable inbound HTTP compression on ASP.NET (ie compression of HTTP requests , not just responses) but I am now struggling on the client side (C# / .NET 4.0 app). I would like to: add the HTTP header Content-Encoding: gzip compress HTTP body with GZip to all outbound HTTP requests emitted by a WCF channel. Solutions that do not work so far: with IClientMessageInspector I can compress the message, but it does not account for the whole HTTP body as the envelop is not compressed

问题 I am looking to gzip multiple files (into multiple .gz files) in a directory while keeping the originals. I can do individual files using these commands: find . -type f -name "*cache.html" -exec gzip {} \; or gzip *cache.html but neither preserves the original. I tried find . -type f -name "*cache.html" -exec gzip -c {} > {}.gz but that only made a {}.gz file. Is there a simple way to do this? 回答1: Your > in the last command gets parsed by the same shell which runs find . Use a nested shell:

问题 Looking at the node in a Web.config, I see that it allows both httpCompression and urlCompression elements. What's the difference between the two? I just want to do standard gzip, which one should I use? 回答1: urlCompression specifies what to compress and httpCompression indicates how to do the compression. If you're running on IIS7.5, you don't need to specify anything, both dynamic and static compression are enabled by default, both use gzip; here are some links on urlCompression and