I need three fast-on-large-strings functions: fast search, fast search and replace, and fast count of substrings in a string.
I have run into Boyer-Moore string searches in C++ and Python, but the only Delphi Boyer-Moore algorithm used to implement fast search and replace that I have found is part of the FastStrings by Peter Morris, formerly of DroopyEyes software, and his website and email are no longer working.
I have already ported FastStrings forward to work great for AnsiStrings in Delphi 2009/2010, where a byte is equal to one AnsiChar, but making them also work with the String (UnicodeString) in Delphi 2010 appears non-trivial.
Using this Boyer-Moore algorithm, it should be possible to easily do case insensitive searches, as well as case-insensitive search and replace, without any temporary string (using StrUpper etc), and without calling Pos() which is slower than Boyer-Moore searching when repeated searches over the same text are required.
(Edit: I have a partial solution, written as an answer to this question, it is almost 100% complete, it even has a fast string replace function. I believe it MUST have bugs, and especially think that since it pretends to be Unicode capable that it must be that there are glitches due to unfulfilled Unicode promises. )
(Edit2: Interesting and unexpected result; The large stack size of a unicode code-point table on the stack - SkipTable in the code below puts a serious damper on the amount of win-win-optimization you can do here in a unicode string boyer-moore string search. Thanks to Florent Ouchet for pointing out what I should have noticed immediately.)