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add dns_name_hash

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Bob Halley 1999-01-28 23:52:00 +00:00
parent 54a58e494c
commit bcfcece57e
2 changed files with 48 additions and 0 deletions
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10
lib/dns/include/dns/name.h
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@ -243,6 +243,16 @@ isc_boolean_t dns_name_isabsolute(dns_name_t *name);
* FALSE The last label in 'name' is not the root label.
*/
unsigned int dns_name_hash(dns_name_t *name);
/*
* Provide a hash value for 'name'.
*
* Requires:
* 'name' is a valid name
*
* Returns:
* A hash value
*/
/***
*** Comparisons

38
lib/dns/name.c
View File

@ -294,6 +294,44 @@ dns_name_isabsolute(dns_name_t *name) {
return (ISC_FALSE);
}
unsigned int
dns_name_hash(dns_name_t *name) {
unsigned int length;
const char *s;
unsigned int h = 0;
unsigned int g;
/*
* Provide a hash value for 'name'.
*/
REQUIRE(VALID_NAME(name));
if (name->labels == 0)
return (0);
length = name->length;
if (length > 16)
length = 16;
/*
* P. J. Weinberger's hash function, adapted from p. 436 of
* _Compilers: Principles, Techniques, and Tools_, Aho, Sethi
* and Ullman, Addison-Wesley, 1986, ISBN 0-201-10088-6.
*/
s = name->ndata;
while (length > 0) {
h = ( h << 4 ) + *s;
if ((g = ( h & 0xf0000000 )) != 0) {
h = h ^ (g >> 24);
h = h ^ g;
}
s++;
length--;
}
return (h);
}
int
dns_name_compare(dns_name_t *name1, dns_name_t *name2) {
unsigned int l1, l2, l, count1, count2, count;