y_stringhash allows you to make compile-time hashes of simple strings. What's a hash? It's a semi-unique number assigned to a string, so you can see if two different strings are the same just by comparing the numbers instead of the whole strings. For large numbers of string comparisons (such as a dictionary search) this can greatly save time over always using strcmp. More importantly, because y_stringhash does this at compile-time, you can use the results in places which only take constants, such as switch.
_H<> is the basic interface. To get the unique number for a string, simply use:
new hash = _H<string goes here>;The string must be a literal without ""s:
new hash1 = _H<Hello world>; // Correct.
new hash2 = _H<"Hello world">; // Won't compile.
new string[] = "Hello world";
new hash3 = _H<string>; // Will return the hash for `"string"` not `"Hello world"`.The most common use is in switch:
YCMD:buy(playerid, const params[], help)
{
if (help)
{
SendClientMessage(playerid, COLOUR_HELP, "/buy command to demonstrate `_H<>`.");
return 1;
}
switch (YHash(params))
{
case _H<gun>: // Give them a gun.
case _H<health>: // Give them some health.
case _H<car>: // Give them a car.
}
return 1;
}YHash(string) is the run-time equivalent to _H<>. The default hash used is called djb2, and is used all over YSI (referenced as "Bernstein"). There is a highly optimised implementation in y_utils, called Bernstein().