How does FastDL achieve multi-connection segmented downloading over HTTP/2 and HTTP/1.1?

[amasen03]

How does FastDL partition a file across parallel worker threads, and how does it verify server Range header support?

[amasen02]

FastDL issues an initial HEAD request to inspect Accept-Ranges: bytes and Content-Length. It then divides the byte range across N worker channels, downloading chunks directly into pre-allocated memory-mapped file segments (MemoryMappedFile).