custom socket-like file descriptors

[gkgoat1]

This adds custom socket-like FDs to w2c2, which is useful for virtualization.

This code has been reformatted, but there was no clang-format file. In addition, I do not know if the code is still C89; Please comment if any of those issues come up.

[turbolent]

@gkgoat1 Thank you for this contribution! I like this idea 👍

The PR is currently really hard to review, because it's almost impossible to see what was actually changed. Could you please avoid /revert the irrelevant re-formatting?

[gkgoat1]

@gkgoat1 Thank you for this contribution! I like this idea 👍

The PR is currently really hard to review, because it's almost impossible to see what was actually changed. Could you please avoid /revert the irrelevant re-formatting?

Do you have a .clang-format file or similar I can use to restore the formatting?

[turbolent]

@gkgoat1 No, I don't use clang format, it might be worth investigating.

Thank you for removing the re-formatting, it's now clear what you're trying to add. I'll open a follow up PR to improve the API a bit and address some of the problems.

[gkgoat1]

Are you still looking at this PR? You mentioned a follow-up PR, so I assumed this would be merged.

[turbolent]

I had a look through all places where the descriptor's fd, path, and dir fields are accessed and it looks like the following functions still need to handle non-native descriptors:

• wasiFdFdstatGet
• wasiPathFilestatGet
• wasiPathRename
• wasiPathUnlinkFile
• wasiPathRemoveDirectory
• wasiPathCreateDirectory
• wasiPathSymlink
• wasiPathReadlink
• wasiFDReaddir
• wasiDirectorySet

What if there is no distinction between native and non-native descriptors, and the callback are only used if they are set (e.g. when reading, writing, etc.)?

[turbolent]

It looks like this is duplicating the last part of wasiFileDescriptorsAdd, adding the descriptor to the descriptors.

Maybe refactor the existing code a bit more:

• Rename this function to wasiFileDescriptorsAdd
• Rename the existing wasiFileDescriptorsAdd to something that indicates it is adding a native descriptor. Maybe wasiFileDescriptorAddNative?
• Rename this new function to something that indicates it is adding the non-native/callbacks descriptor

[turbolent]

What is the magic number -2 here? Is the idea that wasiFileDescriptorAddStruct is called with fd = -2 when the callbacks are set?

[gkgoat1]

It is a tag indicating the descriptor is non-native

[gkgoat1]

What if there is no distinction between native and non-native descriptors, and the callback are only used if they are set (e.g. when reading, writing, etc.)?

The goal of this PR is to create streaming file descriptors without a native file backing it, so either we distinguish native and non-native descriptors, or implement a complete VFS all in one PR--a hard-to-review almost-full refactor. That may be something we consider later on, but right now having this distinction would enforce the stream-like nature of non-native descriptors.