Use zlib.js to decompress python zlib compress

Question

On the server side I use python zlib to compress a string as follows:

import zlib

s = '{"foo": "bar"}'
compress = zlib.compress(s)
print compress

The result of the previous code is the following

xœ«VJËÏW²RPJJ,Rª

On the client side I use zlib.js to decompress

var s = "xœ«VJËÏW²RPJJ,Rª"
var data = new Array(s.length);
for (i = 0, il = s.length; i < il; ++i) {
    data[i] = s.charCodeAt(i);
}
var inflate = new Zlib.Inflate(data);

I get the following error

zlib_and_gzip.min.js:1 Uncaught Error: invalid fcheck flag:28
    at new tb (zlib_and_gzip.min.js:48)
    at <anonymous>:1:15

what am I doing wrong?

Double-check your encoding? using a string might change byte-order or add unexpected bits? You might consider using base64 for transmission to reduce such errors. — theGleep
– theGleep, Commented Nov 1, 2017 at 15:09
Definately an encoding problem. The string should be var s = 'x\x9c\xabVJ\xcb\xcfW\xb2RPJJ,R\xaa\x05\x00 \x98\x04T' — Artyer
– Artyer, Commented Nov 1, 2017 at 15:26

Blasito · Accepted Answer · 2021-04-22 13:28:37Z

7

The problem was coding. in python I used base64 to encode.

>>> import zlib

>>> s = '{"foo": "bar"}'
>>> compress = zlib.compress(s)
>>> print compress.encode('base64')

>>> "eJyrVkrLz1eyUlBKSixSqgUAIJgEVA=="

On the client side:

var s = atob("eJyrVkrLz1eyUlBKSixSqgUAIJgEVA==");

var data = new Array(s.length);
for (i = 0, il = s.length; i < il; ++i) {
    data[i] = s.charCodeAt(i);
}

var inflate = new Zlib.Inflate(data);
var decompress = inflate.decompress();
var plain = new TextDecoder("utf-8").decode(decompress);

plain 
'{"foo": "bar"}'

Thank you very much for the help

edited Apr 22, 2021 at 13:28

answered Nov 1, 2017 at 16:28

Blasito

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