Re: Suggestion : Use unique string type instead of two (short and long)

[Roberto Ierusalimschy <roberto@...>]

> Lua has unique string type before 5.2.1 , all the strings is interning
> for fast comparison .
> 
> [...]
> attack , but short string is still interning. I guess the reason is
> the performance of string comparison is very important to lua , string
> interning can reduce the string comparison from O(n) to O(1).
> 
> I think if we can find another way to compare strings with O(1) , we
> can use only one string type without interning.
> 
> We can add an unique 64bit id into TString struct , every time we push
> a string into lua VM , allocate a new id to it . When we need compare
> two strings, compare the id first. If id are the same, they are
> equality, otherwise we compare the hash. If hash is also the same, use
> memcmp.  And if the strings are equality, we can change the lower id
> to the higher one.

It is a nice idea. One drawback to keep in mind is the addition of eight
bytes to the memory overhead of all strings. Another is that Lua does
not demand platforms to have a 64-bit integer type.

-- Roberto