FA-27619 / HTTP ranges / Member archive

A parallel downloader splits a representation into worker ranges and rebalances idle workers: the thief copies the victim end before the victim is shortened · case 04

A parallel downloader splits a representation into worker ranges and rebalances idle workers: the thief copies the victim end before the victim is shortened.

Member previewVariant 4 · 3 implementations · 15 checks per implementation

Case contract

x has total length, worker count and events. Initial segments follow array-split sizing: base=total//workers, the first total%workers workers get one extra byte; zero-size segments are dropped and later worker indices refer to the surviving list. Each segment is [cursor,end]. data(i,n) advances worker i by n>=0 accepted bytes; an invalid or negative index, negative n or overrun past its end returns null. steal(i) is ignored unless i is a valid finished worker; the victim is the worker with the most remaining bytes (lowest index on ties); a victim with fewer than2 remaining bytes is left alone; otherwise the victim keeps the first ceil(rem/2) bytes and the thief takes the rest. Return Range header values for unfinished workers in worker order. workers<=0 or negative total returns null.

Why this case matters

Range responses combine representation identity, conditional requests, framing, and partial-object state.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
steal-assignment-order fixture 7	`["bytes=5-7"]`	`["bytes=8-9", "bytes=5-7"]`	Failed

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