openpyxl.preserve.zipio

Zip-layer machinery for the preserve-mode save.

• Deterministic output: every entry gets a fixed timestamp and uniform attributes, so part payloads (and, on the raw-copy path, compressed streams) are reproducible run-to-run.
• Raw compressed-stream copy: untouched parts are copied without recompression (measured 235x faster and byte-identical); guarded by the the raw-copy guards, with transparent fallback to recompression.
• Atomic targets: path targets are written temp-file-then-os.replace (in-place truncation is the measured corruption hazard); in-memory targets must be exact io.BytesIO instances or verified path-backed io.BufferedRandom handles (the form pandas uses for append mode).

FIXED_DATE_TIME

RAW_COPY_AVAILABLE