// Requires Int64 type. Earliest versions of Delphi may lack it.
type
a8ch = array[1..8] of char;
PA8C = ^a8ch; // pointer type, to above array of characters
PI64 = ^Int64; // pointer type, for Int64 numbers
// converts short strings (8 chars max) to a number holding ASCII bytes
function StrToAsc(s: string): Int64;
begin
SetLength(s, 8); // increase or decrease to length of 8
Result := PI64(Pointer(PA8C(@(s[1]))))^;
end;
// Intermediate use of generic Pointer yields no compiler warnings
// The compiler translates the characters in the string
// first into the array-of-chars type, and then into the numeric type.
// The 8 character-bytes is essentially an array of ASCII codes, and
// since they ARE a group of adjacent memory cells holding numbers,
// they can be directly interpreted as the 8 bytes of an Int64 in one
// swoop. So, no time-wasting byte-at-a-time copying loop is needed!
// WITH THE PRECEDING PREPARATION, HERE IS THE COMPARER FUNCTION:
// Result: positive: s1 is larger
// negative: s2 is larger
// zero: first 8 characters of strings are the same
function CmpShortS(s1, s2: string): Int64;
begin
Result := StrToAsc(s1) - StrToAsc(s2);
end;
// The two swoops are the two lower-level function calls :)
// Yes, the Result is a C-language kind of value. Useful...
//(included for sake of completeness)
// interprets a 64-bit number as a sequence of characters
function AscToStr(a: Int64): string;
begin
SetLength(Result, 8);
Result := string(PA8C(Pointer(@a))^);
end;