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add hash_equ_any

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simon 2019-07-20 20:30:08 -04:00
parent 53841ab679
commit 95749d6a28
1 changed files with 38 additions and 3 deletions
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41
hamming.c
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@ -74,7 +74,7 @@ Datum hash_distance(PG_FUNCTION_ARGS) {
);
distance += __builtin_popcount(
*((uint16 *) h1 + 8) ^ *((uint16 *) h2 + 8)
);
);
PG_RETURN_INT32(distance);
}
@ -87,14 +87,14 @@ PG_FUNCTION_INFO_V1(hash_is_within_distance_any);
hashes among an array of hashes
*
* It is assumed that: the first array is exactly 18 bytes long, the
second array is a multiple of 18 bytes
second array length is a multiple of 18 bytes
*
* Import with
CREATE OR REPLACE FUNCTION hash_is_within_distance_any(bytea, bytea, integer) RETURNS bool
AS '/path/to/libhamming.so', 'hash_is_within_distance_any'
LANGUAGE C STRICT;'
*
* @return the hamming distance between the two arrays
* @return true if at least 1 hash matches
*/
Datum hash_is_within_distance_any(PG_FUNCTION_ARGS) {
@ -132,3 +132,38 @@ Datum hash_is_within_distance_any(PG_FUNCTION_ARGS) {
PG_RETURN_BOOL(false);
}
PG_FUNCTION_INFO_V1(hash_equ_any);
/**
* Check if the first argument exactly matches any hashes among an array of hashes
*
* It is assumed that: the first array is exactly 18 bytes long, the
second array length is a multiple of 18 bytes
*
* Import with
* CREATE OR REPLACE FUNCTION hash_equ_any(bytea, bytea) RETURNS bool
AS '/path/to/libhamming.so', 'hash_equ_any'
LANGUAGE C STRICT;
* @return true if at least 1 hash is equal
*/
Datum hash_equ_any(PG_FUNCTION_ARGS) {
char *h = VARDATA(PG_GETARG_BYTEA_P(0));
bytea *h_bytea = PG_GETARG_BYTEA_P(1);
char *h_arr = VARDATA(h_bytea);
for (int i = VARSIZE(h_bytea); i >= 0; i -= 18) {
// This is a bit faster than __builtin_memcmp
if (*((uint64 *) h) == *((uint64 *) h_arr) &&
*((uint64 *) h + 1) == *((uint64 *) h_arr + 1) &&
*((uint16 *) h + 8) == *((uint16 *) h_arr + 8)) {
PG_RETURN_BOOL(true);
}
h_arr += 18;
}
PG_RETURN_BOOL(false);
}