iOS Question [Almost SOLVED] DEFLATE Compression

Star-Dust · Mar 16, 2021

I should compress strings specifically with the Deflate compression algorithm.
You know how it can be done on B4i or Obj-C

P.S: I anticipate the questions ... unfortunately I just need the deflate algorithm and nothing else

Star-Dust · Mar 16, 2021

B4X:

Dim Deflate As CompressedStreams
Dim CompressData() As Byte
CompressData=Deflate.CompressBytes(Data(),"zlib")

Star-Dust · Mar 18, 2021

It seems that ZLib doesn't exactly match the deflate algorithm
Is there another solution?

Erel · Mar 18, 2021

Please upload a file with the compressed data and a file with the uncompressed data.

Star-Dust · Mar 19, 2021

This is the data compressed in bytes expressed in Hex

c1 45 aa 56 4a 49 2c 49 54 b2 8a ae 56 ca 4c 51 b2 52 4a 2a c9 2b 4e cd 4b 51 d2 51 4a 2d 4b cd 2b 01 8a 24 e7 64 26 67 2b d5 c6 02 45 4a 2a 0b 52 81 22 c5 a9 25 8e a5 25 f9 b9 89 25 99 c9 ae 20 55 c5 4a b5 00 00

So they are expressed in decimals

(170,86,74,73,44,73,84,178,138,174,86,202,76,81,178,82,74,42,201,43,78,205,75,81,210,81,74,45,75,205,43,1,138,36,231,100,38,103,43,213,198,2,69,74,42,11,82,129,34,197,169,37,142,165,37,249,185,137,37,153,201,174,32,85,197,74,181,0,0)

So is the uncompressed string

{"data":[{"id":"btnsend","event":"click"}],"etype":"setAutomaticEvents"}

Using this code:

B4X:

Dim DecData() As Byte=CompressedStreams1.DecompressBytes(DataDeflate,"zlib")

I get this error:

Errore nella linea: 114
java.util.zip.ZipException: incorrect header check
at java.util.zip.InflaterInputStream.read(InflaterInputStream.java:164)
at java.io.FilterInputStream.read(FilterInputStream.java:107)
at anywheresoftware.b4a.objects.streams.File.Copy2(File.java:349)
at anywheresoftware.b4a.randomaccessfile.CompressedStreams.DecompressBytes(CompressedStreams.java:152)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at anywheresoftware.b4a.shell.Shell.runMethod(Shell.java:632)
at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:234)
at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:167)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:91)
at anywheresoftware.b4a.shell.ShellBA.raiseEvent2(ShellBA.java:98)
at anywheresoftware.b4a.debug.Debug.delegate(Debug.java:64)
at b4j.example.main._elaboratewebsocket(main.java:136)
at b4j.example.main._buttondec_click(main.java:128)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at anywheresoftware.b4a.shell.Shell.runMethod(Shell.java:632)
at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:237)
at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:167)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:91)
at anywheresoftware.b4a.shell.ShellBA.raiseEvent2(ShellBA.java:98)
at anywheresoftware.b4a.BA$1.run(BA.java:216)
at com.sun.javafx.application.PlatformImpl.lambda$null$177(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$178(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$152(WinApplication.java:177)
at java.lang.Thread.run(Thread.java:748)
No dec: (Exception) java.lang.Exception: java.util.zip.ZipException: incorrect header check

Star-Dust · Mar 21, 2021

If it helps, this site allows you to examine data packets expressed in either hexadecimal, decimal or otherwise and apply different compression algorithms, encoding, etc ...

CyberChef

The Cyber Swiss Army Knife - a web app for encryption, encoding, compression and data analysis

gchq.github.io

Erel · Mar 21, 2021

Using this nice tool, I'm getting different results than you:

How did you compress the string?

Star-Dust · Mar 21, 2021

Erel said:
Using this nice tool, I'm getting different results than you:

View attachment 110164

How did you compress the string?

This string is the response from a browser compressed with Deflate.

I'm sure it's Deflate because that's how it is specified in the response handshake

Using a network sniffer I can unzip it and the resulting string is the one I entered.

But there seem to be different versions of Deflate, zlib, lz77, lzw etc ...

Star-Dust · Mar 21, 2021

I found some more details in RFC 2616

deflate
The "zlib" format defined in RFC 1950 in combination with the "deflate" compression mechanism described in RFC 1951.

So CompressedStreams's zlib is not enough

Star-Dust · Mar 22, 2021

Studying the examples on GitHub in Java it would be the java.util.zip.Deflater class. Is there a correspondent in objective-c?

Deleted member 103 · Mar 22, 2021

Star-Dust said:
Studying the examples on GitHub in Java it would be the java.util.zip.Deflater class. Is there a correspondent in objective-c?

Maybe this thread can help you.

Native zlib inflate/deflate for Swift 3 on iOS

I'd like to be able to inflate/deflate Swift 3 data structs. I found GzipSwift, but it's not clear how I make that available to my iOS app. The naive things I've tried include: Copying the Data+Gzip.

stackoverflow.com

Star-Dust · Mar 22, 2021

Filippo said:
Maybe this thread can help you.

Native zlib inflate/deflate for Swift 3 on iOS

I'd like to be able to inflate/deflate Swift 3 data structs. I found GzipSwift, but it's not clear how I make that available to my iOS app. The naive things I've tried include: Copying the Data+Gzip.

stackoverflow.com

I don't think I will be able to use it because I use the hosted builder

Deleted member 103 · Mar 22, 2021

Star-Dust said:
I don't think I will be able to use it because I use the hosted builder

Maybe Erel can help?

Star-Dust · Mar 22, 2021

Filippo said:
Maybe Erel can help?

I have already asked Erel for help many times in relation to the work I am doing, I would not like to take on all the thorny problems of my library.

Erel · Mar 22, 2021

Star-Dust said:
Studying the examples on GitHub in Java it would be the java.util.zip.Deflater class. Is there a correspondent in objective-c?

I'm unable to uncompress the input you posted with java.util.zip.Inflater (B4J):

B4X:

Dim h As String = "c1 45 aa 56 4a 49 2c 49 54 b2 8a ae 56 ca 4c 51 b2 52 4a 2a c9 2b 4e cd 4b 51 d2 51 4a 2d 4b cd 2b 01 8a 24 e7 64 26 67 2b d5 c6 02 45 4a 2a 0b 52 81 22 c5 a9 25 8e a5 25 f9 b9 89 25 99 c9 ae 20 55 c5 4a b5 00 00"
Dim bc As ByteConverter
Dim b() As Byte = bc.HexToBytes(h.Replace(" ", ""))
Dim Inflater As JavaObject
Inflater.InitializeNewInstance("java.util.zip.Inflater", Null)
Inflater.RunMethod("setInput", Array(b))
Dim raw(100) As Byte
Inflater.RunMethod("inflate", Array(raw))

Waiting for debugger to connect...
Program started.
Error occurred on line: 19 (Main)
java.lang.reflect.InvocationTargetException
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at anywheresoftware.b4j.object.JavaObject.RunMethod(JavaObject.java:132)
at b4j.example.main._appstart(main.java:88)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at anywheresoftware.b4a.shell.Shell.runMethod(Shell.java:632)
at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:234)
at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:167)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:91)
at anywheresoftware.b4a.shell.ShellBA.raiseEvent2(ShellBA.java:98)
at anywheresoftware.b4a.BA.raiseEvent(BA.java:78)
at b4j.example.main.main(main.java:29)
Caused by: java.util.zip.DataFormatException: incorrect header check
at java.base/java.util.zip.Inflater.inflateBytesBytes(Native Method)
at java.base/java.util.zip.Inflater.inflate(Inflater.java:378)
at java.base/java.util.zip.Inflater.inflate(Inflater.java:464)
... 21 more
Program terminated (StartMessageLoop was not called).

Star-Dust · Mar 22, 2021

It's strange. that string is sniffed by a connection between jServer and the browser.

The sniffer manages to decompress and displays the original byte sequence that you decompressed.

jServer uses java.util.zip.Inflater and java.util.zip.Deflater for websocket communications.

Star-Dust · Mar 22, 2021

Unfortunately, I am out of the office and cannot do any further tests. Perhaps the explanation lies in a suggestion I read on a site this morning. That is, delete the first 2 bytes from the sequence to be decompressed.

Yesterday all afternoon I researched the Huffman (Deflate) algorithm and it doesn't seem complex to implement. But from what we understand is that depending on the implementation and how the frequency tree is composed the resulting sequence of bytes can be different even if of the same length.
So comparing two compressed Arrays of the same string is not necessarily the same even if compressed with Deflate.

But the decompression on the other hand must obviously be identical

OliverA · Mar 22, 2021

Could it be related to WebSocket inflate/deflate?
Pertinent RFC: https://tools.ietf.org/html/rfc7692
Code that may pertain to this: https://github.com/AnywhereSoftware...on/extensions/compress/CompressExtension.java

Erel · Mar 22, 2021

OliverA said:
Could it be related to WebSocket inflate/deflate?

I don't know. It is managed by Jetty. You will need to do some research.

Star-Dust · Mar 22, 2021

OliverA said:
Could it be related to WebSocket inflate/deflate?
Pertinent RFC: https://tools.ietf.org/html/rfc7692
Code that may pertain to this: https://github.com/AnywhereSoftware...on/extensions/compress/CompressExtension.java

Yes, I am the same, but as @Erel found it generates an error because the Header is incorrect:

Caused by: java.util.zip.DataFormatException: incorrect header check

iOS Question [Almost SOLVED] DEFLATE Compression

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