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{
Some handly UTF8 function copied from the Lazarus LCL. Surely we can move
this into FPC?
}
unit fpUTF8Utils;
{$ifdef FPC}
{$mode objfpc}{$H+}
{$endif}
interface
uses
Classes, SysUtils;
function UTF8Pos(const SearchForText, SearchInText: string): integer;
function UTF8Copy(const s: string; StartCharIndex, CharCount: integer): string;
function UTF8Length(const s: string): integer;
function UTF8Length(p: PChar; ByteCount: integer): integer;
function UTF8CharStart(UTF8Str: PChar; Len, Index: integer): PChar;
function UTF8CharacterLength(p: PChar): integer;
implementation
function UTF8Pos(const SearchForText, SearchInText: string): integer;
// returns the character index, where the SearchForText starts in SearchInText
var
p: LongInt;
begin
p:=System.Pos(SearchForText,SearchInText);
if p>0 then
Result:=UTF8Length(PChar(SearchInText),p-1)+1
else
Result:=0;
end;
function UTF8Copy(const s: string; StartCharIndex, CharCount: integer): string;
// returns substring
var
StartBytePos: PChar;
EndBytePos: PChar;
MaxBytes: PtrInt;
begin
StartBytePos:=UTF8CharStart(PChar(s),length(s),StartCharIndex-1);
if StartBytePos=nil then
Result:=''
else begin
MaxBytes:=PtrInt(PChar(s)+length(s)-StartBytePos);
EndBytePos:=UTF8CharStart(StartBytePos,MaxBytes,CharCount);
if EndBytePos=nil then
Result:=copy(s,StartBytePos-PChar(s)+1,MaxBytes)
else
Result:=copy(s,StartBytePos-PChar(s)+1,EndBytePos-StartBytePos);
end;
end;
function UTF8Length(const s: string): integer;
begin
Result := UTF8Length(PChar(s),length(s));
end;
function UTF8Length(p: PChar; ByteCount: integer): integer;
var
CharLen: LongInt;
begin
Result:=0;
while (ByteCount>0) do begin
inc(Result);
CharLen:=UTF8CharacterLength(p);
inc(p,CharLen);
dec(ByteCount,CharLen);
end;
end;
function UTF8CharStart(UTF8Str: PChar; Len, Index: integer): PChar;
var
CharLen: LongInt;
begin
Result:=UTF8Str;
if Result<>nil then begin
while (Index>0) and (Len>0) do begin
CharLen:=UTF8CharacterLength(Result);
dec(Len,CharLen);
dec(Index);
inc(Result,CharLen);
end;
if (Index>0) or (Len<0) then
Result:=nil;
end;
end;
function UTF8CharacterLength(p: PChar): integer;
begin
if p<>nil then begin
if ord(p^)<%11000000 then begin
// regular single byte character (#0 is a character, this is pascal ;)
Result:=1;
end
else if ((ord(p^) and %11100000) = %11000000) then begin
// could be 2 byte character
if (ord(p[1]) and %11000000) = %10000000 then
Result:=2
else
Result:=1;
end
else if ((ord(p^) and %11110000) = %11100000) then begin
// could be 3 byte character
if ((ord(p[1]) and %11000000) = %10000000)
and ((ord(p[2]) and %11000000) = %10000000) then
Result:=3
else
Result:=1;
end
else if ((ord(p^) and %11111000) = %11110000) then begin
// could be 4 byte character
if ((ord(p[1]) and %11000000) = %10000000)
and ((ord(p[2]) and %11000000) = %10000000)
and ((ord(p[3]) and %11000000) = %10000000) then
Result:=4
else
Result:=1;
end
else
Result:=1
end else
Result:=0;
end;
end.
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