Skiasharp: Native crash when opening files with special characters in path

[LukePulverenti]

Reproduced on Windows 10 using 1.59.2
Example:
c:\albums\上田雅美\folder.jpg

Try to open this using
var skFileStream = new SKFileStream(path);

This causes a native crash which in turn crashes the entire application.

[LukePulverenti]

A couple more observations. This also applies to diacritics, e.g. accent characters.

Additionally, trying to open a file that doesn't exist will also cause a native crash that will bring down the managed process. So I guess the root cause is that if the native layer is unable to open a file, there is currently no way to recover gracefully from that.

[mattleibow]

I am not able to reproduce the crash... Could you attach a stack trace?

However, I can confirm that there is an issue with special characters. The stream is not null (nor crashes), but it has no length. Somewhere the stream is failing to load. I will investigate - it may just be that the skia file stream is not that bright.

In any case, you can use a managed stream:

var stream = new SKManagedStream(File.OpenRead("images/上田雅美/CMYK.jpg"), true);

SkiaSharpDemo.zip

[mattleibow]

At this point, I am going to close this issue as it cannot be solved from SkiaSharp. This is a limitation in native skia and they even have a TODO:

https://github.com/google/skia/blob/chrome/m59/src/ports/SkOSFile_stdio.cpp#L68-L69

I would recommend wrapping the managed stream as this will further avoid any platform differences. The native streams aren't really meant to be used - they are rather for use by skia.

[mattleibow]

What the heck was I doing... I am reopening because I am going to fix this.
@LukePulverenti thanks for bringing this up - I have no idea what came over me to close this.

In the meantime, use a managed stream as I mentioned, I will ensure that it is fixed in the next release.

[LukePulverenti]

Thanks for the info, and that is what I'm doing, although correct me if I'm wrong but that will incur some overhead. Therefore I have some decision making to try and limit it to only when necessary.

[solabc16]

Luke, for reference, attached is the information we collated from our development work on Synology.

All reported failures generated the same stack trace, so it seems to be a reasonably specific scenario.

We're still defaulting to Skia support for x86/x64 based h/w, as the combination of the latest native library with release 1.58 of the managed code has proved stable; in the context of Emby Server at least.

skia_stacktrace.txt

[mattleibow]

@LukePulverenti I did the work for you. In the next release, the path system will be clever and try to use the fastest method. Because this is only a bug on Windows, iOS, Android, macOS, etc are not affected in the least. On Windows, this is a specific case where the path contains non-ASCII characters, and thus I first check the path. If the path contains non-ASCII character, then open in .NET and wrap it, otherwise continue with the native file stream.

[mattleibow]

The current logic is pretty simple:

public static bool IsPathSupported (string path)
{
    if (PlatformConfiguration.IsWindows) {
        for (int i = 0; i < path.Length; i++) {
            if (path [i] >= byte.MaxValue)
                return false;
        }
    }

    return true;
}

public static SKStreamAsset OpenStream (string path)
{
    if (!IsPathSupported (path)) {
        return new SKManagedStream (File.OpenRead (path), true);
    } else {
        return new SKFileStream (path);
    }
}

[LukePulverenti]

Excellent, thanks. Just for reference, this is the check I have been using
` private static bool HasDiacritics(string text)
{
return !String.Equals(text, text.RemoveDiacritics(), StringComparison.Ordinal);
}

    public bool HasUnicodeCategory(string value, UnicodeCategory category)
    {
        foreach (var chr in value)
        {
            if (char.GetUnicodeCategory(chr) == category)
            {
                return true;
            }
        }

        return false;
    }

    private static bool RequiresSpecialCharacterHack(string path)
    {
        if (HasUnicodeCategory(path, UnicodeCategory.OtherLetter))
        {
            return true;
        }

        if (HasDiacritics(path))
        {
            return true;
        }

        return false;
    }

`