feat: add CompoundFile::copy_to for writing a compacted copy - #92
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A compound file never shrinks in place: sectors freed by removing or shrinking streams stay in the file. copy_to writes the same storages and streams, with their CLSIDs, state bits and timestamps, into a fresh file of the same version, which is how Windows compacts a file as well.
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Closes #55.
A compound file never shrinks in place: sectors freed by removing or shrinking streams stay in the file. This is also how Windows and Wine behave; Microsoft's guidance for compacting is to copy the root storage into a new file with
IStorage::CopyTo, which is what this adds.copy_towrites the same storages and streams, with their CLSIDs, state bits and timestamps, into a fresh file of the same version and returns it. It is available on any readable source, so a read-only file can be compacted into a new writer, and callers who want in-place semantics can copy to a temporary file and rename it over the original.This sidesteps the truncation problem from the issue thread: no trait for resizing the underlying writer is needed, and space freed in the middle of the file is reclaimed too, which trimming the tail never could.