141 lines
4.0 KiB
C
141 lines
4.0 KiB
C
#ifndef BLOOM_H
|
|
#define BLOOM_H
|
|
|
|
struct commit;
|
|
struct repository;
|
|
struct commit_graph;
|
|
|
|
struct bloom_filter_settings {
|
|
/*
|
|
* The version of the hashing technique being used.
|
|
* The newest version is 2, which is
|
|
* the seeded murmur3 hashing technique implemented
|
|
* in bloom.c. Bloom filters of version 1 were created
|
|
* with prior versions of Git, which had a bug in the
|
|
* implementation of the hash function.
|
|
*/
|
|
uint32_t hash_version;
|
|
|
|
/*
|
|
* The number of times a path is hashed, i.e. the
|
|
* number of bit positions that cumulatively
|
|
* determine whether a path is present in the
|
|
* Bloom filter.
|
|
*/
|
|
uint32_t num_hashes;
|
|
|
|
/*
|
|
* The minimum number of bits per entry in the Bloom
|
|
* filter. If the filter contains 'n' entries, then
|
|
* filter size is the minimum number of 8-bit words
|
|
* that contain n*b bits.
|
|
*/
|
|
uint32_t bits_per_entry;
|
|
|
|
/*
|
|
* The maximum number of changed paths per commit
|
|
* before declaring a Bloom filter to be too-large.
|
|
*
|
|
* Not written to the commit-graph file.
|
|
*/
|
|
uint32_t max_changed_paths;
|
|
};
|
|
|
|
#define DEFAULT_BLOOM_MAX_CHANGES 512
|
|
#define DEFAULT_BLOOM_FILTER_SETTINGS { 1, 7, 10, DEFAULT_BLOOM_MAX_CHANGES }
|
|
#define BITS_PER_WORD 8
|
|
#define BLOOMDATA_CHUNK_HEADER_SIZE 3 * sizeof(uint32_t)
|
|
|
|
/*
|
|
* A bloom_filter struct represents a data segment to
|
|
* use when testing hash values. The 'len' member
|
|
* dictates how many entries are stored in
|
|
* 'data'.
|
|
*/
|
|
struct bloom_filter {
|
|
unsigned char *data;
|
|
size_t len;
|
|
int version;
|
|
|
|
void *to_free;
|
|
};
|
|
|
|
/*
|
|
* A bloom_key represents the k hash values for a
|
|
* given string. These can be precomputed and
|
|
* stored in a bloom_key for re-use when testing
|
|
* against a bloom_filter. The number of hashes is
|
|
* given by the Bloom filter settings and is the same
|
|
* for all Bloom filters and keys interacting with
|
|
* the loaded version of the commit graph file and
|
|
* the Bloom data chunks.
|
|
*/
|
|
struct bloom_key {
|
|
uint32_t *hashes;
|
|
};
|
|
|
|
int load_bloom_filter_from_graph(struct commit_graph *g,
|
|
struct bloom_filter *filter,
|
|
uint32_t graph_pos);
|
|
|
|
/*
|
|
* Calculate the murmur3 32-bit hash value for the given data
|
|
* using the given seed.
|
|
* Produces a uniformly distributed hash value.
|
|
* Not considered to be cryptographically secure.
|
|
* Implemented as described in https://en.wikipedia.org/wiki/MurmurHash#Algorithm
|
|
*/
|
|
uint32_t murmur3_seeded_v2(uint32_t seed, const char *data, size_t len);
|
|
|
|
void fill_bloom_key(const char *data,
|
|
size_t len,
|
|
struct bloom_key *key,
|
|
const struct bloom_filter_settings *settings);
|
|
void clear_bloom_key(struct bloom_key *key);
|
|
|
|
void add_key_to_filter(const struct bloom_key *key,
|
|
struct bloom_filter *filter,
|
|
const struct bloom_filter_settings *settings);
|
|
|
|
void init_bloom_filters(void);
|
|
void deinit_bloom_filters(void);
|
|
|
|
enum bloom_filter_computed {
|
|
BLOOM_NOT_COMPUTED = (1 << 0),
|
|
BLOOM_COMPUTED = (1 << 1),
|
|
BLOOM_TRUNC_LARGE = (1 << 2),
|
|
BLOOM_TRUNC_EMPTY = (1 << 3),
|
|
BLOOM_UPGRADED = (1 << 4),
|
|
};
|
|
|
|
struct bloom_filter *get_or_compute_bloom_filter(struct repository *r,
|
|
struct commit *c,
|
|
int compute_if_not_present,
|
|
const struct bloom_filter_settings *settings,
|
|
enum bloom_filter_computed *computed);
|
|
|
|
/*
|
|
* Find the Bloom filter associated with the given commit "c".
|
|
*
|
|
* If any of the following are true
|
|
*
|
|
* - the repository does not have a commit-graph, or
|
|
* - the repository disables reading from the commit-graph, or
|
|
* - the given commit does not have a Bloom filter computed, or
|
|
* - there is a Bloom filter for commit "c", but it cannot be read
|
|
* because the filter uses an incompatible version of murmur3
|
|
*
|
|
* , then `get_bloom_filter()` will return NULL. Otherwise, the corresponding
|
|
* Bloom filter will be returned.
|
|
*
|
|
* For callers who wish to inspect Bloom filters with incompatible hash
|
|
* versions, use get_or_compute_bloom_filter().
|
|
*/
|
|
struct bloom_filter *get_bloom_filter(struct repository *r, struct commit *c);
|
|
|
|
int bloom_filter_contains(const struct bloom_filter *filter,
|
|
const struct bloom_key *key,
|
|
const struct bloom_filter_settings *settings);
|
|
|
|
#endif
|