Use libdeflate [de]compressor under conditional compilation

[wqweto]

Pros

• better compression ratio
• better decompression speed

Cons

• additional dependency
• official release is a cdecl only .dll

[tannerhelland]

A few additional thoughts...

Pros

• better compression speed (even at minimum comp. levels)
• faster crc32

Cons

• libdeflate only implements "one-shot" deflate/inflate API. There is no streaming API. Probably not a deal-breaker for most users, but this would prevent future Zip64 support (via libdeflate, anyway).

Misc

• as noted in the libdeflate README, compiling via VS is "supported" but the perf hit is large. The recommended MinGW toolchain further complicates custom stdcall building (which is why I just stick with official binaries and DispCallFunc wrappers... it's ugly, but the perf benefits are worth it IMO)
• if conditional compilation introduces too many complexities, another implementation option could be a public sub like...

Public Sub SetLibDeflatePath(pathToDll As String)
  mhLibDeflate = LoadLibrary(pathToDll)
  If (mhLibDeflate <> 0) Then
    'Cache proc addresses for relevant functions
  End If
End Sub

...with relevant deflate/inflate code gently modified...

If (mhLibDeflate <> 0) Then
   'Use libdeflate
Else
   'Use thunk
End If

Hard to know what is "best" for the average VB6 consumer of the class :/

[wqweto]

10x for input, Tanner.

I think gcc/mingw must support stdcall on x86 targets. Although still have to weight in benefits of using official release dlls against custom built stdcall ones.

[tannerhelland]

Yes, GCC does support stdcall exports, but I am fuzzy on "best practices" for handling things like name-mangling with it...

tbh I have moved more and more toward p/invoke-style DispCallFunc wrapping of official 3rd-party release builds in recent years, mostly because maintaining custom stdcall builds is tedious and I find few repo owners are interested in merging patches to simplify cross-building. But it's also entirely possible that I am just getting lazier... :)

Either way, thank you for investigating this feature! (And sorry for popping into this repo so often; it's one of the few I watch on GitHub as I've deployed it to quite a few client projects - across many production environments, it works excellently.)