Data structures and functions for streaming trees.
Copyright (C) 2011-2025 Free Software Foundation, Inc.
Contributed by Diego Novillo <dnovillo@google.com>
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Cache of pickled nodes. Used to avoid writing the same node more
than once. The first time a tree node is streamed out, it is
entered in this cache. Subsequent references to the same node are
resolved by looking it up in this cache.
This is used in two ways:
- On the writing side, the first time T is added to STREAMER_CACHE,
a new reference index is created for T and T is emitted on the
stream. If T needs to be emitted again to the stream, instead of
pickling it again, the reference index is emitted.
- On the reading side, the first time T is read from the stream, it
is reconstructed in memory and a new reference index created for
T. The reconstructed T is inserted in some array so that when
the reference index for T is found in the input stream, it can be
used to look up into the array to get the reconstructed T.