问题
I compressed a file in a terminal with compress file.txt and got (as expected) file.txt.Z
When I pass that file to ioutil.ReadFile in Go,
buf0, err := ioutil.ReadFile("file.txt.Z")
I get the error (the line above is 116):
finder_test.go:116: lzw: invalid code
I found that Go would accept the file if I compress it using the compress/lzw package, I just used code from a website that does that. I only modified the line
outputFile, err := os.Create("file.txt.lzw")
I changed the .lzw to .Z. then used the resulting file.txt.Z in the Go code at the top, and it worked fine, no error.
Note: file.txt is 16.0 kB, unix-compressed file.txt.Z is 7.8 kB, and go-compressed file.txt.Z is 8.2 kB
Now, I was trying to understand why this happened. So, I tried to run
uncompress.real file.txt.Z
and it did not work. I got
file.txt.Z: not in compressed format
I need to use a compressor (preferably unix-compress) to compress files using lzw-compression then use the same compressed files on two different algorithms, one written in C and the other in Go, because I intend to compare the performance of the two algorithms. The C program will only accept the files compressed with unix-compress and the Go program will only accept the files compressed with Go's compress/lzw.
Can someone explain why that happened? Why are the two .Z files not equivalent? How can I overcome this?
Note: I am working on Ubuntu installed in VirtualBox on a Mac.
回答1:
A .Z file does not only contain LZW compressed data, there is also a 3-bytes header that the Go LZW code does not generate because it is meant to compress data, not generate a Z file.
回答2:
Presumably you only want to test the performance of two of your/some third party algorithms (& not the compression algorithms themselves), you may want to write a shell script which calls the compress command passing the files/dir's required and then call this script from your C / GO program. This is one way you can overcome this, but leaves open other parts of your queries on the correct way to use the compression libraries.
来源：https://stackoverflow.com/questions/42889664/why-using-unix-compress-and-go-compress-lzw-produce-different-files-not-readabl