Client file streaming (WoW.mfil)

Tools for the 3.3.5 client's built-in streaming downloader. The client can pull missing data files over HTTP at runtime instead of shipping them all up front. It is driven by a plain-text manifest named WoW.mfil in the client root.

How it works:

• At launch the client runs StartupStreaming("WoW.mfil"). If the file exists, streaming starts while the client reads it. No DLL hook is needed to start it.
• The manifest is key=value lines. Reserved keys: version, source, manifest, transportmanifest, sourcemanifest, isTrial, bgpreloadsleep. Every other line is a file entry whose value is path;size;md5;flags.
• source=http://example.com/streaming tells the client where to fetch from. Each file is requested as http://example.com/streaming/<relpath> using HTTP byte-range requests, so the server layout must mirror the in-game relative paths. The transport is http only, https is rejected.

Generate the manifest

python generate_mfil.py CONTENT_DIR \
    --url http://example.com/streaming \
    --serve-root ./serve

• CONTENT_DIR is a tree mirroring client-relative paths, e.g. CONTENT_DIR/Data/enUS/patch-3.MPQ -> in-game Data/enUS/patch-3.MPQ.
• --serve-root (required) stages a copy of every included file under ./serve/<relpath> plus the server manifest, so that directory can be served directly as the streaming root.
• --include / --exclude take glob patterns (repeatable) to filter the tree.

This always writes a two-file layout: a tiny stub on the client that redirects to a full manifest hosted on the server, which the client then reads. That lets you update the file list server-side without re-touching clients. It produces:

• ./serve/streaming.mfil - the server-hosted manifest (version + source + full list), staged in the serve root so it is reachable at <source>/streaming.mfil. This is the one the client actually reads.
• ./WoW.mfil - the client stub, just version=1 and manifest=<source>/streaming.mfil. The client follows that redirect to the hosted manifest. Put this on the client.

MPQ archives are streamed whole, like any other file. List a .MPQ in CONTENT_DIR and the client downloads byte ranges of it on demand, then everything inside becomes available through normal MPQ mounting. Streaming only fires for files the client cannot already resolve from a mounted MPQ or from disk, so an installed copy always wins. Loose files override MPQ contents.

Serve the files

Put WoW.mfil in the client root (next to Wow.exe) and serve the staged files with HTTP range support so that <source>/<relpath> resolves.

Local test server (single-range 206 support built in):

python serve_streaming.py ./serve --port 80 --prefix /streaming

In production any range-capable static host works (nginx serves ranges by default, also Caddy, S3, a CDN). Point it so that example.com/streaming/<relpath> returns the file.