Uncompress gzip from byte array in golang

Question

I have a bunch of files that come from some web requests, and some are gziped, i need to unpack them and print them as a string. This is the first time I try using golang, I tried some examples I found online but can't get it working.

Here's the last test I was trying:

package main

import (
    "bytes"
    "compress/gzip"
    "fmt"
    "io/ioutil"
)

func main() {
    content := []byte{72,84,84,80,47,49,46,49,32,50,48,48,32,79,75,13,10,84,114,97,110,115,102,101,114,45,69,110,99,111,100,105,110,103,58,32,99,104,117,110,107,101,100,13,10,67,111,110,110,101,99,116,105,111,110,58,32,75,101,101,112,45,65,108,105,118,101,13,10,67,111,110,116,101,110,116,45,69,110,99,111,100,105,110,103,58,32,103,122,105,112,13,10,67,111,110,116,101,110,116,45,84,121,112,101,58,32,116,101,120,116,47,104,116,109,108,13,10,68,97,116,101,58,32,83,117,110,44,32,49,52,32,65,112,114,32,50,48,49,57,32,48,53,58,49,50,58,50,51,32,71,77,84,13,10,75,101,101,112,45,65,108,105,118,101,58,32,116,105,109,101,111,117,116,61,53,44,32,109,97,120,61,49,48,48,13,10,83,101,114,118,101,114,58,32,65,112,97,99,104,101,47,50,46,52,46,49,48,32,40,68,101,98,105,97,110,41,13,10,86,97,114,121,58,32,65,99,99,101,112,116,45,69,110,99,111,100,105,110,103,13,10,13,10,54,98,100,13,10,31,139,8,0,0,0,0,0,0,3,236,89,235,111,218,72,16,255,156,254,21,83,127,1,36,108,243,200,163,215,0,82,66,104,19,53,205,85,133,94,85,157,78,104,177,7,188,141,189,246,237,174,33,180,234,255,126,179,182,73,8,143,132,180,167,83,117,106,68,204,122,119,231,249,155,89,123,134,103,123,173,231,103,191,119,7,159,222,245,32,208,81,216,121,214,202,191,0,90,1,50,223,12,104,168,185,14,177,211,239,95,2,116,121,18,160,132,126,202,53,42,250,74,146,88,106,244,225,116,14,159,226,84,194,169,140,103,10,101,203,205,105,114,250,231,182,221,138,80,51,16,44,194,182,53,229,56,51,100,22,120,177,208,40,116,219,154,113,95,7,109,31,167,220,67,59,187,169,2,23,92,115,22,218,202,99,33,182,235,78,205,234,216,118,193,241,135,185,85,33,98,55,60,74,163,197,132,117,167,43,156,198,177,86,90,178,4,110,5,134,92,92,67,32,113,220,182,60,165,220,209,98,135,19,113,225,208,140,5,18,195,182,165,244,60,68,21,32,146,58,17,250,156,209,148,39,17,133,181,204,39,219,202,73,93,171,96,25,104,157,168,151,174,235,121,142,239,41,244,156,84,112,59,96,66,196,83,148,142,143,46,143,38,238,152,77,29,34,178,64,207,19,178,155,71,108,130,238,141,157,241,201,16,115,23,144,181,70,177,63,47,4,250,124,10,220,39,159,144,178,214,210,156,23,50,165,200,24,242,25,227,2,101,177,182,186,158,144,16,219,240,189,183,99,111,121,11,33,190,180,68,139,247,86,85,194,68,157,160,107,5,245,44,130,150,3,8,206,8,70,30,42,136,199,43,209,67,155,91,46,113,121,152,111,131,216,178,220,133,165,133,11,103,179,153,179,193,131,165,78,139,124,8,74,122,237,146,113,230,89,183,143,158,125,25,79,226,161,23,205,175,157,68,76,104,139,203,54,136,93,153,89,189,189,211,169,68,218,151,54,59,169,148,187,161,212,25,4,92,193,12,71,42,203,159,9,159,210,117,30,167,20,158,227,88,70,76,243,88,0,125,116,128,96,188,229,229,222,82,121,186,205,141,143,70,185,143,104,46,203,61,5,68,8,100,113,42,185,152,192,249,96,240,174,111,50,65,160,103,152,41,103,69,223,117,173,72,229,189,189,91,115,216,74,72,234,25,215,154,92,232,197,145,171,2,38,209,90,32,80,172,216,217,172,61,74,181,54,1,237,51,205,236,84,134,59,4,181,23,160,119,93,80,104,188,161,196,237,154,25,136,83,189,226,128,45,166,59,5,177,226,95,40,33,66,38,39,88,204,4,76,5,154,77,140,150,161,202,121,88,157,193,140,242,210,96,76,246,82,48,81,98,242,68,119,158,143,83,145,185,170,236,87,85,149,251,149,175,83,38,225,179,170,142,63,171,182,239,76,80,247,66,140,232,92,81,167,243,1,155,92,209,161,83,86,149,63,107,127,29,243,113,249,249,242,134,211,249,133,95,38,6,149,175,25,37,229,61,211,88,172,17,201,241,103,229,80,38,114,223,12,76,32,90,174,155,132,76,27,224,157,101,55,211,137,69,76,149,243,89,89,199,164,132,147,144,127,133,190,138,125,116,184,32,251,245,41,18,13,150,115,29,43,199,223,190,149,253,216,75,141,152,170,149,91,101,85,111,225,153,17,155,202,113,203,45,204,93,10,132,173,113,221,26,73,183,211,74,22,81,18,82,250,151,204,33,82,34,103,14,77,164,150,58,219,158,3,163,251,207,1,40,199,146,142,142,124,33,161,192,162,177,240,176,242,178,229,38,157,181,212,217,16,154,45,58,101,99,49,233,244,19,244,200,134,252,38,87,117,117,247,254,221,238,123,135,140,65,236,17,210,37,65,111,112,14,125,138,167,71,40,14,239,40,206,48,119,45,133,208,42,209,26,233,54,51,203,94,173,218,24,85,182,26,214,235,158,157,247,108,186,246,79,236,147,94,191,222,120,97,191,238,190,181,251,231,39,141,131,195,173,54,209,54,56,229,122,171,5,198,86,188,241,40,39,39,248,18,214,142,82,20,206,140,95,243,196,60,199,156,88,78,92,115,231,246,194,208,24,235,13,233,196,153,226,240,140,143,199,28,237,115,12,195,136,137,18,104,147,133,186,93,26,142,66,38,174,115,205,77,206,85,129,128,151,243,204,77,59,203,58,241,167,140,194,197,31,246,110,105,135,125,205,132,207,164,191,46,138,28,147,75,122,123,210,221,89,4,185,208,38,31,174,115,91,248,150,117,156,239,66,243,232,49,52,223,223,97,249,11,199,159,22,199,102,109,71,28,73,200,34,39,155,47,246,183,98,73,219,126,97,185,3,150,228,195,141,88,102,190,253,78,44,235,251,79,192,146,100,253,2,241,7,65,172,111,132,176,254,125,0,214,106,213,223,252,237,0,254,4,105,72,42,12,203,44,156,196,146,235,32,170,172,27,79,27,126,118,200,254,245,188,35,216,154,7,59,193,246,159,103,220,255,1,175,157,83,108,219,59,253,56,149,84,108,201,226,189,254,85,126,183,92,143,238,246,174,222,44,117,62,208,11,191,125,50,161,50,228,229,102,156,94,148,58,111,227,47,60,12,153,123,224,212,160,252,145,11,159,202,4,184,26,64,189,230,212,142,129,38,14,247,143,225,230,112,191,2,39,73,18,226,71,28,189,225,218,61,104,30,57,205,67,40,191,57,31,188,189,172,66,200,175,17,94,83,169,24,87,160,27,200,56,66,247,168,233,212,104,203,139,166,83,175,53,161,207,198,76,242,130,236,73,17,75,102,188,203,202,20,83,179,80,1,234,14,46,251,64,245,170,202,161,223,102,22,237,154,214,157,198,83,69,237,138,51,210,3,65,14,77,33,51,188,16,62,247,50,92,54,0,127,117,97,112,191,7,222,118,157,183,213,229,79,53,194,148,233,74,51,42,220,233,193,101,42,85,208,60,194,135,156,69,181,189,113,107,78,20,143,239,23,247,62,247,65,196,26,20,10,31,88,198,11,166,44,76,113,67,56,155,81,214,81,185,107,120,64,170,168,32,45,240,0,170,129,3,216,242,186,13,44,19,80,188,92,195,53,157,32,166,149,114,151,234,206,35,153,35,25,57,228,61,155,237,150,32,141,82,231,143,71,227,168,233,52,225,73,254,111,44,74,113,245,16,210,181,198,168,74,151,35,186,52,107,116,169,239,211,163,148,142,229,39,203,234,221,104,20,198,134,135,196,213,232,175,74,255,7,230,194,204,101,100,46,126,117,60,174,213,105,84,111,60,89,238,123,140,98,42,229,7,255,81,96,61,91,52,71,158,45,53,249,76,23,53,73,85,96,45,247,8,139,225,222,237,142,113,76,138,222,245,74,31,237,181,46,226,202,138,82,211,63,241,232,220,225,218,202,163,154,180,54,45,108,160,97,34,227,41,247,243,62,138,233,141,173,245,233,182,244,61,173,181,67,226,172,219,239,117,179,99,66,162,66,38,189,0,38,50,78,19,96,122,51,215,213,182,221,58,203,75,228,35,193,191,192,7,193,179,163,82,207,225,188,32,200,158,67,134,111,65,99,229,52,171,141,239,45,218,187,60,74,72,75,149,70,142,249,93,194,234,92,208,61,23,89,19,47,239,82,193,69,134,50,4,108,138,148,208,115,58,9,162,172,89,7,148,202,127,167,168,178,38,40,208,163,132,41,204,126,33,96,222,138,157,15,136,31,179,32,44,36,247,153,162,183,11,120,69,51,121,155,56,185,133,120,61,26,104,144,183,224,41,142,242,31,84,246,254,1,0,0,255,255,3,0,8,20,73,242,107,25,0,0,13,10,48,13,10,13,10}
    buf := bytes.NewBuffer(content)
    reader, err := gzip.NewReader(buf)
    if err != nil {
        panic(err)
    }
    defer reader.Close()


    s, err := ioutil.ReadAll(reader)
    if err != nil {
        panic(err)
    }

    fmt.Println("decompressed:\t", string(s))
}

But it shows the error: panic: gzip: invalid header, same as a few other examples.

How can I ungzip the byte array content?

Answer 1

content := []byte{72,84,84,80,47,49,46,49,32,50,48,48,32,79,75, ...

This is no gzip data at all. Proper gzip data start with the magic sequence 0x1f 0x8b, i.e. []byte{31,139,...}. Insofar it rightly complains about gzip: invalid header.

So lets have a closer look of what this byte sequence actually is. When printing it as string it gives:

HTTP/1.1 200 OK
Transfer-Encoding: chunked
Connection: Keep-Alive
Content-Encoding: gzip
Content-Type: text/html
Date: Sun, 14 Apr 2019 05:12:23 GMT
Keep-Alive: timeout=5, max=100
Server: Apache/2.4.10 (Debian)
Vary: Accept-Encoding

6bd
... binary data ..
0

Thus, this is a HTTP response where the body is first compressed with gzip and then encoded with chunked transfer encoding. To extract the data you need to first remove the HTTP header, then decode from chunked transfer encoding and then you'll can take the result and decompress it with gzip.