/*
* Borrow HAMMER1's directory hash algorithm #1 with a few modifications.
* The filename is split into fields which are hashed separately and then
* added together.
*
* Differences include: bit 63 must be set to 1 for HAMMER2 (HAMMER1 sets
* it to 0), this is because bit63=0 is used for hidden hardlinked inodes.
* (This means we do not need to do a 0-check/or-with-0x100000000 either).
*
* Also, the iscsi crc code is used instead of the old crc32 code.
*/
hammer2_key_t
hammer2_dirhash(const unsigned char *name, size_t len)
{
const unsigned char *aname = name;
uint32_t crcx;
uint64_t key;
size_t i;
size_t j;
key = 0;
/*
* m32
*/
crcx = 0;
for (i = j = 0; i < len; ++i) {
if (aname[i] == '.' ||
aname[i] == '-' ||
aname[i] == '_' ||
aname[i] == '~') {
if (i != j)
crcx += hammer2_icrc32(aname + j, i - j);
j = i + 1;
}
}
if (i != j)
crcx += hammer2_icrc32(aname + j, i - j);
/*
* The directory hash utilizes the top 32 bits of the 64-bit key.
* Bit 63 must be set to 1.
*/
crcx |= 0x80000000U;
key |= (uint64_t)crcx << 32;
/*
* l16 - crc of entire filename
*
* This crc reduces degenerate hash collision conditions
*/
crcx = hammer2_icrc32(aname, len);
crcx = crcx ^ (crcx << 16);
key |= crcx & 0xFFFF0000U;
/*
* Set bit 15. This allows readdir to strip bit 63 so a positive
* 64-bit cookie/offset can always be returned, and still guarantee
* that the values 0x0000-0x7FFF are available for artificial entries.
* ('.' and '..').
*/
key |= 0x8000U;
return (key);
}
hammer2_key_t
dirhash(const unsigned char *name, size_t len)
{
const unsigned char *aname = name;
uint32_t crcx;
uint64_t key;
size_t i;
size_t j;
/*
* Filesystem version 6 or better will create directories
* using the ALG1 dirhash. This hash breaks the filename
* up into domains separated by special characters and
* hashes each domain independently.
*
* We also do a simple sub-sort using the first character
* of the filename in the top 5-bits.
*/
key = 0;
/*
* m32
*/
crcx = 0;
for (i = j = 0; i < len; ++i) {
if (aname[i] == '.' ||
aname[i] == '-' ||
aname[i] == '_' ||
aname[i] == '~') {
if (i != j)
crcx += hammer2_icrc32(aname + j, i - j);
j = i + 1;
}
}
if (i != j)
crcx += hammer2_icrc32(aname + j, i - j);
/*
* The directory hash utilizes the top 32 bits of the 64-bit key.
* Bit 63 must be set to 1.
*/
crcx |= 0x80000000U;
key |= (uint64_t)crcx << 32;
/*
* l16 - crc of entire filename
*
* This crc reduces degenerate hash collision conditions
*/
crcx = hammer2_icrc32(aname, len);
crcx = crcx ^ (crcx << 16);
key |= crcx & 0xFFFF0000U;
/*
* Set bit 15. This allows readdir to strip bit 63 so a positive
* 64-bit cookie/offset can always be returned, and still guarantee
* that the values 0x0000-0x7FFF are available for artificial entries.
* ('.' and '..').
*/
key |= 0x8000U;
return (key);
}
