main: add quick path for looking up too long strings in the keyword table

[techee]

Parser code like

vString *str = vStringNew();
while (someCondition)
{
    int c = getcFromInputFile();
    vStringPut(str, c);
    if (lookupCaseKeyword (vStringValue(str), some_lang))
    {
        do_stuff();
        vStringClear(str);
    }
}

is prone to quadratic complexity because when someCondition isn't satisfied in the parsed file, the string str grows by one in each iteration and in each iteration lookupCaseKeyword() has to go through strlen(str) characters to compute the hash.

Since we know the maximum length of the strings inside the keyword hash table, we can store this value and if the queried string is longer than this value, we can be sure it isn't present in the hash table and return quickly without having to compute the full hash of the string.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (bca2e86) 82.83% compared to head (9a02e92) 82.83%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3664   +/-   ##
=======================================
  Coverage   82.83%   82.83%           
=======================================
  Files         223      223           
  Lines       54508    54518   +10     
=======================================
+ Hits        45149    45159   +10     
  Misses       9359     9359           

Impacted Files	Coverage Δ
main/keyword.c	78.67% <100.00%> (+1.69%)	⬆️

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[masatake]

Thank you,

[masatake]

Now we can add

int lookupKeywordVString (const vString *string, langType language);

:-)