# llHash

*LSL function*

```lsl
integer integer llHash(string val);
```

- `string val`: String to hash.

- Returns: `integer`
- Energy: 10

Returns an integer representing the 32-bit hash value of the string val (returns 0 if the string is empty).

Returns a 32bit hash for the provided string. Returns 0 if the input string is empty.

```lsl title="How to use" frame="terminal"
integer result = llHash("");
```

## 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.

```lsl
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:

```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

<details open>
<summary>Given the combination of the object name and the owner's key generate a unique number. This number could be used for things</summary>

like selecting a chat channel that has a low probability of colliding with another object.

```lsl
integer pickIDForObject()
{
    /* Generate an arbitrary integer ID for the combination of the
     * object name and the ower's key.  This value could be used
     * for selecting a chat/listen channel.
     */
    string obj_name = llGetObjectName();
    key obj_owner = llGetOwner();

    integer hash = llHash(obj_name + (string)obj_owner);

    return hash;
}
```

</details>

## See also

### Functions

- [llOrd](/functions/llOrd/) — Convert a character into an ordinal
- [llChar](/functions/llChar/) — Convert an ordinal into a character

### Articles

- [List of hash functions](https://en.wikipedia.org/wiki/List_of_hash_functions)
- [Hash Collision Probabilities](https://preshing.com/20110504/hash-collision-probabilities/)

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*Source: [LlHash](https://wiki.secondlife.com/wiki/LlHash) on the Second Life Wiki. Content from the Second Life Wiki article LlHash (revision 1210062, 2021-05-21), CC BY-SA 3.0.*

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From lsl.dev: https://lsl.dev/functions/llHash/