Current archive nesting depth (1 for the top-level archive, incremented on each nested archive).
Maximum allowed nesting depth from Tuning.MaxArchiveDepth.
Remaining uncompressed bytes the archive tree may unpack. Decremented as bytes are read.
Remaining members the archive tree may unpack. Decremented before each member is read.
Mutable tree-wide budget shared across a top-level archive and any nested archives unpacked inside it.