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This is similar to many of our uses of sha1-array, but it overcomes one limitation of a sha1-array: when you are de-duplicating a large input with relatively few unique entries, sha1-array uses 20 bytes per non-unique entry. Whereas this set will use memory linear in the number of unique entries (albeit a few more than 20 bytes due to hashmap overhead). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
45 lines
1.2 KiB
C
45 lines
1.2 KiB
C
#ifndef OIDSET_H
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#define OIDSET_H
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/**
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* This API is similar to sha1-array, in that it maintains a set of object ids
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* in a memory-efficient way. The major differences are:
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*
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* 1. It uses a hash, so we can do online duplicate removal, rather than
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* sort-and-uniq at the end. This can reduce memory footprint if you have
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* a large list of oids with many duplicates.
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*
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* 2. The per-unique-oid memory footprint is slightly higher due to hash
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* table overhead.
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*/
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/**
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* A single oidset; should be zero-initialized (or use OIDSET_INIT).
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*/
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struct oidset {
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struct hashmap map;
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};
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#define OIDSET_INIT { { NULL } }
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/**
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* Returns true iff `set` contains `oid`.
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*/
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int oidset_contains(const struct oidset *set, const struct object_id *oid);
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/**
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* Insert the oid into the set; a copy is made, so "oid" does not need
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* to persist after this function is called.
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*
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* Returns 1 if the oid was already in the set, 0 otherwise. This can be used
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* to perform an efficient check-and-add.
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*/
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int oidset_insert(struct oidset *set, const struct object_id *oid);
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/**
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* Remove all entries from the oidset, freeing any resources associated with
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* it.
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*/
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void oidset_clear(struct oidset *set);
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#endif /* OIDSET_H */
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