[cBuffer] String Manipulation Helpers

[hnakamur]

I propose lev.string module.

It should be upper-compatible to lua's string module.

These are draft APIs for additional functions.

string.startsWith(s, prefix):boolean
string.endsWith(s, prefix):boolean
string.indexOf(s, predicate_func, startIndex):number or nil
string.lastIndexOf(s, predicate_func, startIndex):number or nil

string.ltrim(s, trimChars):string
string.rtrim(s, trimChars):string
string.trim(s, trimChars):string

string.lpad(s, resultLen, padding):string
string.rpad(s, resultLen, padding):string

[kristate]

Let's first implement this API into buffers.
I am also thinking about a better API for string transitions.

[hnakamur]

I realized these APIs should be implemented as a separate library because these does not depend on lev.
As for buffers, we should think of appropriate APIs for buffers.

[dvv]

+1 for not pulling this into the core. lua-nucleo has hard-tested and polished routines

[kristate]

It might be smart to modify the string library and add these additions. Reopening for cBuffer support

[dvv]

doesn't it contradict the initial goals? strings are generic lua, not fast and robust async io we've been trying to implement?

[kristate]

@dvv thank-you for your comment. All IO will go through cBuffers and having some of these functions added to buffers is fine. As for strings, they are still useful in certain places and it might be good to add these methods to the standard string library.

For example:

string.startsWith(s, prefix):boolean
string.endsWith(s, prefix):boolean

these are good functions to have because they only check the contents of memory -- there may be moments were it is important to use strings.