Encoding can't be set as intended

[Muffexx]

Steps to reproduce

Encode ZipFile using 7Zip (including non ASCII characters like "ä", "ü")
Try to unzip using SharpZipLib with CodePage set to "850".

Expected behavior

Characters should be decoded correctly (including non ASCII characters).

Actual behavior

Non ASCII characters aren't decoded correctly.

Version of SharpZipLib

1.0.0

Obtained from (place an x between the brackets for all that apply)

• Package installed using:
  • NuGet

Comment

when looking at (in ZipStrings)

private static Encoding EncodingFromFlag(int flags)
			=> ((flags & (int)GeneralBitFlags.UnicodeText) != 0)
				? Encoding.UTF8
                                : Encoding.GetEncoding(_SystemDefaultCodePage_)

I'm not sure whether this is as intended - since the Codepage Property could be used instead of SystemDefaultCodePage.

The only way to get the characters decoded correctly is to encrypt via 7Zip with the cu-flag set to on (7-Zip uses UTF-8 for file names that contain non-ASCII symbols)
or setting the SystemDefaultCodePage via reflection to a suitable codepage.

Maybe a setter for SystemDefaultCodePage can be added
or Codepage can be used in the mentioned code part?

Hope I didn't overlook anything.
regards

[piksel]

Setting a custom encoding is not currently supported for extracting an archive, but it should be kind of trivial to add. Like adding a CustomEncoding property that, if set, is used instead of SystemDefaultCodePage.

A PR would be welcomed!

Also: I am a bit confused about your description, perhaps you could clarify this?

First in steps to reproduce:

Encode ZipFile using 7Zip (including non ASCII characters like "ä", "ü")
Try to unzip using SharpZipLib with CodePage set to "850".

But later on:

(7-Zip uses UTF-8 for file names that contain non-ASCII symbols)

Why do you try to extract it with another encoding then?

[Muffexx]

Yes, a custom encoding would be very helpful.

When using 7-Zip with default parameters it won't encode in UTF-8 by default (at least on my system).
Then when unzipping, UTF-8 is used by SharpZipLib since my local codepage won't support the special characters.
To resolve my issue I have three options:

• encode via 7-Zip and set codepage 850
• encode via 7-Zip and set UTF-8 to "on"
• decode via SharpZipLib using a custom codepage (which I did via reflection)

Maybe there is a smarter approach.