How to sort stringlist with comments - delphi

Question

I have stringlist with comments (like Ini file section content):
;comment c
c=str1
;comment b
b=str2
;comment a
a=str3
Any ideas how to sort this list by names to:
;comment a
a=str3
;comment b
b=str2
;comment c
c=str1
Comment for pair should be linked with pair during sorting

Answer 1

One option would be to parse the TStringList content into a second list that separates and groups the name, value, and comment strings together, then sort that list on the names as needed, then repopulate the TStringList with the sorted groups. For example:
uses
...
System.Classes,
System.SysUtils,
System.Generics.Defaults,
System.Generics.Collections,
System.StrUtils,
System.Types;
type
ItemInfo = record
LeadingText,
Name,
Value: string;
end;
ItemInfoComparer = class(TComparer<ItemInfo>)
public
function Compare(const Left, Right: ItemInfo): Integer; override;
end;
function ItemInfoComparer.Compare(const Left, Right: ItemInfo): Integer;
begin
if (Left.Name <> '') and (Right.Name <> '') then
Result := AnsiCompareStr(Left.Name, Right.Name)
else if (Left.Name <> '') then
Result := -1
else
Result := 1;
end;
procedure SortMyList(List: TStringList);
var
Compare: IComparer<ItemInfo>;
Items: TList<ItemInfo>;
Info: ItemInfo;
I: Integer;
InText: Boolean;
S: String;
begin
Compare := ItemInfoComparer.Create;
Items := TList<ItemInfo>.Create(Compare);
try
Items.Capacity := List.Count;
InText := False;
for I := 0 to List.Count-1 do
begin
S := Trim(List[i]);
if (S = '') or (S[1] = ';') then
begin
if InText then
Info.LeadingText := Info.LeadingText + #13 + List[i]
else
begin
Info.LeadingText := List[i];
InText := True;
end;
end else
begin
Info.Name := List.Names[I];
Info.Value := List.ValueFromIndex[I];
Items.Add(Info);
Info := Default(ItemInfo);
InText := False;
end;
end;
if InText then
Items.Add(Info);
Items.Sort;
List.Clear;
for I := 0 to Items.Count-1 do
begin
Info := Items[I];
if Info.LeadingText <> '' then
begin
for S in SplitString(Info.LeadingText, #13) do
List.Add(S);
end;
if Info.Name <> '' then
List.Add(Info.Name + '=' + Info.Value);
end;
finally
Items.Free;
end;
end;

Answer 2

Here is a simple procedure that will sort and also deal with spaces as cargo. I also added code to handle comments at the end of the file.
This will work with older versions of Delphi that do not have generics or advanced types as in Remy's answer (provided as convenience for those using older versions)
function SortKeys(List: TStringList; Index1, Index2: Integer): Integer;
begin
result := CompareText(List.Names[Index1], List.Names[Index2]);
end;
Procedure SortStringListWithComments(AStrings: TStrings);
var
LCargoText: TStringList;
LSortedText : TStringList;
s: string;
i : integer;
begin
LCargoText := nil;
LSortedText := TStringList.Create;
try
for i := 0 to AStrings.count-1 do
begin
s := Trim(AStrings[i]);
if (s='') or (s[1] = ';') then //LCargoText and blank lines attached to sorted strings (Boolean short circuit assumed here)
begin
if LCargoText = nil then
LCargoText := TStringList.Create;
LCargoText.Add(AStrings[i]);
end
else
begin
LSortedText.AddObject(AStrings[i], LCargoText);
LCargoText := nil; //set nil to deal with cases where we have no comments for a following key value pair
end;
end;
LSortedText.CustomSort(SortKeys);
// LSortedText.sort - will cause a1=x to be sorted before a=x
AStrings.clear;
for i := 0 to LSortedText.count-1 do
begin
if LSortedText.objects[i] <> nil then
begin
AStrings.AddStrings(TStringList(LSortedText.Objects[i]));
LSortedText.Objects[i].Free;
end;
AStrings.Add(LSortedText[i]);
end;
if LCargoText <> nil then
begin
AStrings.AddStrings(LCargoText) ; //comments orphaned at the end of the file
LCargoText.Free;
end;
finally
LSortedText.Free;
end;
end;