incremental string backoff

Question

Using Delphi XE-5 Firemonkey mobile

I have a string (Path) that looks like this

host domain and node here\\something1\\something2\\something3\\something4\\something5

I need a function that removes each portion with each call. e.g., when call the function the first time, it would remove "\something5" leaving the string as

something1\\something2\\something3\\something4

function CountOccurences( const SubText: string;
                          const Text: string): Integer;
begin
  if (SubText = '') OR (Text = '') OR (Pos(SubText, Text) = 0) then
    Result := 0
  else
    Result := (Length(Text) - Length(StringReplace(Text, SubText, '', [rfReplaceAll]))) div  Length(subtext);
end; {Robert Frank}

 function IncrementalBackOff(aPath: String): String;
 var
  I: Integer;
  Found: Boolean;
 begin
  result:= aPath;
  if (CountOccurences('\\', result) > 1) then
  begin
   for I:= Length(result) downto 1 do
   begin
    if (result[I] <> '\') then
     Delete(result, I, 1)
    else
    begin
     Delete(result, I, 1);
     Delete(result, I-1, 1);
    end;
   end;
  end;
 end;

NOTE: I need to always keep the first section (i.e. never delete '\\something1'

host domain and node here\\something1

So, the function must return the remainng string each time

Do you really have double backslashes? Did you consider using a split function? — David Heffernan, Dec 19 '13 at 16:07
[LastDelimiter](http://docwiki.embarcadero.com/Libraries/XE5/en/System.SysUtils.LastDelimiter) would work nicely here. — Merlin W., Dec 19 '13 at 16:11

Andreas Rejbrand · Accepted Answer · 2013-12-19T16:19:54.280

3

This is not the shortest version, but it is still quite short and rather readable:

function ReducePath(const Path: string): string;
var
  i: Integer;
begin
  result := Path;
  if PosEx('\\', Path, Pos('\\', Path) + 2) = 0 then Exit;
  for i := Length(result) - 1 downto 1 do
    if Copy(result, i, 2) = '\\' then
    begin
      Delete(result, i, Length(result));
      break;
    end;
end;

Shorter code but inefficient:

function ReducePath(const Path: string): string;
begin
  result := Path;
  if PosEx('\\', Path, Pos('\\', Path) + 2) = 0 then Exit;
  Result := Copy(Result, 1, Length(Result) - Pos('\\', ReverseString(Result)) - 1);
end;

edited Dec 19 '13 at 16:19

answered Dec 19 '13 at 16:14

Andreas Rejbrand

105,602
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Interesting, thanks for responding! Let me try that out. – JakeSays Dec 19 '13 at 16:24
@sholmes: [Are you sure?](http://docwiki.embarcadero.com/Libraries/XE5/en/System.StrUtils.PosEx) – Andreas Rejbrand Dec 19 '13 at 16:29
Sorry, mobile (android) development always flags things wrong until you compile it - my bad – JakeSays Dec 19 '13 at 16:31

Remy Lebeau · Answer 2 · 2013-12-19T18:35:47.453

1

The RTL has an ExtractFileDir() function for this exact purpose. There is also ExtractFilePath(), though it leaves the trailing delimiter intact, whereas ExtractFileDir() removes it.

edited Dec 19 '13 at 18:35

answered Dec 19 '13 at 16:48

Remy Lebeau

555,201
31
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770

It does not help here, but `ExtractFileDir` would do. A `Path` always include a trailing path delimiter. If not it is a directory or a file – Sir Rufo Dec 19 '13 at 17:56
Both of these functions only remove a single backslash. @Remy, are you reading this as C++ with escaped backslashes? – David Heffernan Dec 19 '13 at 19:44

incremental string backoff

2 Answers2