llHash
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Summary
Function: integer llHash( string val );| ? | Function ID |
| 0.0 | Forced Delay |
| 10.0 | Energy |
Returns a 32bit hash for the provided string.
Returns an integer
| • string | val | – | String to hash. |
Specification
The SDBM algorithm provides a good general purpose hash function with a fairly even distribution across the 32 bit space in the general case. The characters fed into the hash function are 32bit wide.
U32 SDBMHash(const std::wstring &val)
{
U32 hash(0);
for(const wchar_t &c: val)
{
hash = c + (hash << 6) + (hash << 16) - hash;
}
return hash;
}
In LSL:
integer llSDBMHash(string value)
{
integer hash = 0;
integer index = 0;
for (index = 0; index < llStringLength(value); ++index)
{
hash = llOrd(value, index) + (hash << 6) + (hash << 16) - hash;
}
return hash;
}
Caveats
This hash value is not cryptographically secure and should not be used as part of any security protocol. SDBM provides a good distribution of hash values across its range, however with only 32 bits the chance of a collision is unacceptably high.(with 1000 entries, the odds for a collision are about 1 in 10000.)
Examples
See Also
Functions
| • llOrd | Convert a character into an ordinal | |||
| • llChar | Convert an ordinal into a character |
Articles
| • |  List of Hash Functions
|
|||
| • | Hash Collision Probabilities |